Annual report 2011 SINTEF Offshore Blowout Database Final_tcm109-486730.pdf

SINTEF REPORT TITLE

Blowout and Well Release Characteristics and Frequencies,

2011

SINTEF Technology and Society Safety Research

Address: NO-7465 Trondheim, NORWAY Location: S P Andersens veg 5 Telephone: +47 73 59 27 56 Fax: +47 73 59 28 96 Enterprise No.: NO 948 007 029 MVA

AUTHOR(S)

Per Holand, ExproSoft

CLIENT(S)

Multiclient

REPORT NO. CLASSIFICATION CLIENTS REF.

SINTEF F21297 Confidential Espen Fyhn Nilsen, Statoil

CLASS. THIS PAGE ISBN PROJECT NO. NO. OF PAGES/APPENDICES

Open 60S067 85/1

ELECTRONIC FILE CODE PROJECT MANAGER (NAME, SIGN.) CHECKED BY (NAME, SIGN.)

\\Bombay\es201016\BLOWOUT\Tekst 2011\Annual report 2011 SINTEF Offshore Blowout Database Final.docx

Per Holand Lars Bodsberg

FILE CODE DATE APPROVED BY (NAME, POSITION, SIGN.)

2011-12-29 Lars Bodsberg, Research Director

ABSTRACT

This report is based on the 2011 Version of the SINTEF Offshore Blowout Database. The report gives

an overview of offshore blowout and well release characteristics and frequencies.

Blowout data from the US Gulf of Mexico Outer Continental Shelf, the Norwegian waters, and the UK

waters from the period 1980-01-01 until 2009-12-31 have been focused on.

KEYWORDS ENGLISH NORWEGIAN

GROUP 1

Marine Technology

Marin Teknikk

GROUP 2

Offshore

Offshore

SELECTED BY AUTHOR

Risk

Risiko

Blowout

Utblåsning

Frequencies

Frekvenser

Blowout and Well Release Characteristics and Frequencies, 2011 version Page: 3

PREFACE

This report is based on the SINTEF Offshore Blowout Database, version 2011. The intention

of the report is to give an overview of blowout/well release characteristics and frequencies,

and not to analyse and evaluate the different blowout types. The format of the report is

similar to the report that was issued last year.

Three new tables concerning drilling rig type vs. water depth have been added. Table 2.8,

page 19 (concerning incident occurrences), and Table 6.7 and Table 6.8 on page 68 and 69

(concerning exposure data).

A new Phase of operation has been defined. The new phase is “other”. This phase was

defined because a couple of incidents have been observed were abandoned wells having

developed leaks after many years.

A new Installation type has been defined. The new installation type is “other”. This

installation type was defined because one incident occurred during well intervention with a

service vessel.

Appendix 1 to this report lists criteria used for the database fields in general.

Some key updates from 2010 version

Software

Some minor bug fixes have been carried out.

Exposure data

The exposure data has been updated also to include the 2009 exposure data.

New Blowouts

Eight new blowouts/well releases have been added to the database (ID612 – ID619). They

were observed for the following countries and years:

Table 0.1 New blowouts/well releases 2010 version

Blowout ID Country Main Category Phase Well depth Date

612 US/GOM OCS Well release Production Deep 07.10.2010

613 US/GOM OCS Blowout (surface flow) Workover Deep 16.01.2011

614 UK Well release Completion Deep 23.12.2009

615 US/GOM NOT OCS Blowout (surface flow) Production Deep 27.07.2010

616 US/GOM NOT OCS Well release Workover Deep 01.12.2010

617 AZERBAIJAN Blowout (surface flow) Production Deep 17.09.2008

618 NETHERLANDS Well release Workover Deep 01.04.2010

619 BRAZIL Blowout (surface flow) Expl.drlg Deep 08.12.2011

Edited Blowouts

Twelve blowouts/well releases have been significantly edited. Table 0.2 shows where and

when these blowouts/well releases occurred.

Page: 4 Blowout and Well Release Characteristics and Frequencies, 2011 version

Table 0.2 Edited blowouts and well releases

Blowout ID Country Main Category Phase Well depth Date

378 US GoM OCS Diverted Well Release Dev.drlg Shallow 10.05.1990

495 UK Blowout (surface flow) Expl.drlg Shallow 12.11.1992

497 UK Well release Workover Deep 11.05.1995


499 UK Well release Completion Deep 14.08.1997

500 UK Well release Unknown drlg Deep 28.10.1998

530 UK Blowout (surface flow) Wireline Deep 01.05.2000

595 UK Well release Dev.drlg Deep 17.11.2007

596 UK Well release Production Deep 04.06.2007



610 US GoM OCS Well release Other Deep 20.11.2007

Deleted Blowouts, 2011

No blowouts have been deleted in 2011


LIST OF CONTENTS

PREFACE ..................................................................................................................................................... 3

1. ABOUT THE DATABASE ................................................................................................................................ 7

1.1 PARTICIPANTS ................................................................................................................................................... 7 1.2 DATABASE STRUCTURE ....................................................................................................................................... 7 1.3 IMPORTANT DEFINITIONS .................................................................................................................................... 9 1.4 CATEGORY AND SUB-CATEGORY ......................................................................................................................... 10 1.5 PHASE OF OPERATION ....................................................................................................................................... 11 1.6 NORTH SEA STANDARDS ................................................................................................................................... 11

2. OVERVIEW OF BLOWOUTS/WELL RELEASES INCLUDED IN THE DATABASE ................................................ 13

2.1 INTRODUCTION ............................................................................................................................................... 13 2.2 DATA QUALITY ................................................................................................................................................ 13 2.3 OVERVIEW OF COUNTRIES REPRESENTED IN THE DATABASE ..................................................................................... 14 2.4 DURING WHAT OPERATIONAL PHASES DO BLOWOUTS/WELL RELEASES OCCUR? ......................................................... 16 2.5 NO. OF BLOWOUTS/WELL RELEASES PER YEAR ...................................................................................................... 17 2.6 WATER DEPTH VS. BLOWOUTS/WELL RELEASES..................................................................................................... 18 2.7 INSTALLATION TYPE VS. WATER DEPTH FOR DRILLING INCIDENTS ............................................................................... 18

3. BLOWOUTS VS. WELL RELEASES ................................................................................................................ 21

4. OVERALL BLOWOUT/WELL RELEASE EXPERIENCE ...................................................................................... 23

4.1 BLOWOUT/WELL RELEASE VS. FLOW MEDIUM ..................................................................................................... 23 4.2 BLOWOUT/WELL RELEASE VS. FLOW-RATES ......................................................................................................... 24 4.3 SEVERITY ....................................................................................................................................................... 24 4.4 IGNITION OF BLOWOUTS/WELL RELEASES ............................................................................................................ 24 4.5 BLOWOUT/WELL RELEASE DURATION ................................................................................................................. 26 4.6 BLOWOUT/WELL RELEASE FLOW-PATHS AND RELEASE POINTS ................................................................................ 27 4.7 BLOWOUT/WELL RELEASE CAUSES ..................................................................................................................... 31 4.8 OPERATIONS AND ACTIVITIES WHEN BLOWOUT/WELL RELEASE OCCURS .................................................................... 35 4.9 EXPLORATION WILDCATS VS. EXPLORATION APPRAISAL BLOWOUTS/WELL RELEASES .................................................... 39 4.10 BLOWOUTS FROM AUSTRALIA, CANADA EAST COAST, THE NETHERLANDS, AND US/CALIFORNIA OCS .......................... 39

5. “NORMAL” DRILLING AND PRODUCTION EXPOSURE DATA ....................................................................... 41

5.1 DRILLING EXPOSURE DATA ................................................................................................................................ 41 5.1.1 US GoM OCS ....................................................................................................................................... 41 5.1.2 United Kingdom .................................................................................................................................. 43 5.1.3 Norway ............................................................................................................................................... 43 5.1.4 The Netherlands ................................................................................................................................. 46 5.1.5 Canadian East Coast ........................................................................................................................... 47 5.1.6 US Pacific OCS ..................................................................................................................................... 49 5.1.7 Australia ............................................................................................................................................. 50 5.1.8 Denmark ............................................................................................................................................. 52 5.1.9 Compiled Drilling Exposure Data ........................................................................................................ 52

5.2 PRODUCTION EXPOSURE DATA ........................................................................................................................... 54 5.2.1 US GoM OCS ....................................................................................................................................... 54 5.2.2 United Kingdom .................................................................................................................................. 55 5.2.3 Norway ............................................................................................................................................... 56 5.2.4 US Pacific OCS ..................................................................................................................................... 57 5.2.5 Compiled Production Exposure Data .................................................................................................. 58

6. VARIOUS EXPOSURE DATA ........................................................................................................................ 61

6.1 WELL DEPTH RELATED EXPOSURE DATA .............................................................................................................. 61 6.1.1 US GoM OCS Wells .............................................................................................................................. 61 6.1.2 Norwegian Wells ................................................................................................................................ 62

6.2 WATER DEPTH RELATED DRILLING EXPOSURE DATA ............................................................................................... 64


6.3 DRILLING INSTALLATION TYPE VS. WELL TYPE AND WATER DEPTH ............................................................................. 68 6.4 SHUT-IN WELLHEAD PRESSURE RELATED EXPOSURE DATA ...................................................................................... 69

6.4.1 US GoM OCS Drilling Wells ................................................................................................................ 69 6.4.2 Norwegian Drilling Wells ................................................................................................................... 71 6.4.3 US GoM OCS Wells in Production ....................................................................................................... 72

6.5 PRODUCTION RATES AND GAS OIL RATIO DATA, US GOM OCS .............................................................................. 73 6.5.1 Production Rates ................................................................................................................................ 73 6.5.2 Gas Oil Ratio ...................................................................................................................................... 75

6.6 WORKOVER FREQUENCY EXPOSURE DATA ........................................................................................................... 76 6.7 WIRELINE FREQUENCY EXPOSURE DATA .............................................................................................................. 77 6.8 COILED TUBING AND SNUBBING EXPOSURE DATA ................................................................................................. 78

7. OVERALL BLOWOUT/WELL RELEASE FREQUENCIES ................................................................................... 81

REFERENCES .................................................................................................................................................. 85

APPENDIX 1 BLOWOUT DATABASE STRUCTURE AND CODING ........................................................................ I

A1. OVERALL DATABASE STRUCTURE .......................................................................................................................... II A2. DESCRIPTION OF DATABASE FIELDS AND ASSOCIATED CODES .................................................................................... IV FIELD 3 CATEGORY ......................................................................................................................................... IV FIELD 4 SUB CATEGORY ....................................................................................................................................V FIELD 5 COUNTRY .......................................................................................................................................... VI FIELD 10 INSTALLATION TYPE ............................................................................................................................. VI FIELD 12 WELL STATUS ..................................................................................................................................... VI FIELD 18 MTSIP (MAKS THEORETIC SHUTIN WH PRESSURE) ................................................................................. VI FIELD 24 ROCK TYPE ...................................................................................................................................... VIII FIELD 25 FORMATION AGE .............................................................................................................................. VIII FIELD 27 PHASE ............................................................................................................................................. VIII FIELD 28 OPERATION ....................................................................................................................................... IX FIELD 29 ACTIVITY ........................................................................................................................................... XI FIELD 30 EXTERNAL CAUSE ............................................................................................................................... XII FIELD 31 LOSS OF BARRIER 1 ............................................................................................................................ XII FIELD 32 LOSS OF BARRIER 2 ........................................................................................................................... XIV FIELD 34 NORTH SEA STANDARDS .................................................................................................................... XIV FIELD 35 FLOWPATH ....................................................................................................................................... XV FIELD 36 RELEASE POINT .................................................................................................................................. XV FIELD 37 FLOW MEDIUM ................................................................................................................................ XVI FIELD 41 IGNITION TYPE.................................................................................................................................. XVI FIELD 42 CONSEQUENCE CLASS ....................................................................................................................... XVII FIELD 44 POLLUTION ..................................................................................................................................... XVII FIELD 48 CONTROL METHOD .......................................................................................................................... XVII FIELD 50 DATA QUALITY ................................................................................................................................ XVII


1. About the Database

1.1 Participants

The SINTEF Offshore Blowout Database was initiated in 1984. There are two new

participants in 2011, URS Energy and Construction, Inc and Maersk Drilling. One

participant, Mide Technology Corporation, has left the project. By December 2 2011 the

following companies were sponsoring the database:

1. Statoil

2. BP Norge

3. Safetec Nordic A/S

4. Total E&P Norge AS

5. Scandpower AS

6. Shell Research Limited

7. DNV

8. Lilleaker Consulting a.s.

9. Eni Norge AS

10. ConocoPhillips Norge

11. BHP Billiton

12. Torus Insurance Marketing Limited

13. Husky Energy

14. AconaWellpro AS

15. Proactima

16. URS Energy and Construction, Inc

17. Maersk Drilling

1.2 Database Structure

The SINTEF Offshore Blowout Database includes blowout/well release descriptions, drilling

and production exposure data for certain areas in the world.

Blowout/ well release descriptions

The database contains 51 different fields describing each blowout/well release. The various

fields are grouped in six different groups. They are:

1. Category and location

2. Well description

3. Present operation

4. Blowout causes

5. Blowout Characteristics

6. Other


Category and location

Includes information related to the incident category (blowout vs. well leak), offshore

installation such as location, operator, installation name and type, and water depth.

Well description

Includes well and casing depths, last casing size, mud weight, bottom hole- and shut in

pressure, GOR, formation age and rock type.

Present operation

Includes the phase (exploration drilling, development drilling, workover etc.), the operation

presently carried out (for example casing running) and the present activity (for example

cementing)

Blowout causes

Include external cause (stating if an external cause contributed to the incident), loss of the

primary barrier, loss of the secondary barrier (describing how primary and secondary barrier

were lost) and human error. It should be noted that the field regarding human error in general

holds low quality information. Human errors are frequently masked. A field named North Sea

standards highlights if the development of the blowout could have been avoided if North Sea

type equipment had been used (for instance in other parts of the world a blind shear ram is

not required in surface BOP stacks)

Blowout characteristics

Twelve fields are included comprising flow-path, flow medium, flow-rate (low quality),

release point, ignition type, time to ignition, lost production (low quality), duration, fatalities,

consequence class, material loss and pollution

Other

In the Other screen five fields is included, they are: control method, remarks (includes a

description of the incident, data quality (includes an evaluation of the source data quality),

last revision date and references.

Exposure data

The various areas represented with exposure data area shown in Table 1.1.

Table 1.1 Overview of exposure data included in the database

Country Drilling exposure data Production exposure data

US GoM OCS Yes Yes

Norway Yes Yes

United Kingdom Yes Yes

The Netherlands Yes No

Canada East Coast Yes No

Australia Yes No

US Pacific Yes Yes

Denmark Yes No

Search possibilities and reporting facilities

Almost any type of search may be performed to select specific blowout /well release event

types. Search criteria may be established by selecting predefined codes, specific numeric

values, specific free text, or any combinations of these. The predefined codes are spelled out

to ease understanding.


The database program counts and presents the events satisfying the search criteria. The

selected data may be viewed, printed or copied to separate Excel files for further analyses.

The exposure data and the blowout data are not linked. Blowout frequencies can therefore not

directly be established.

1.3 Important Definitions

The following main definitions have been utilised when categorising the blowouts/well

releases in categories and sub-categories.

Blowout definition

NPD came up with a blowout definition in their proposal for the new regulations.

(“Aktivitetsforskriften, eksternt høringsutkast av 3.7.2000, høringsfrist 3.11.2000”).

Med utblåsing som nevnt i denne paragrafen første ledd, menes formasjonsfluid som

strømmer ut av brønnen eller mellom formasjonslagene etter at alle definerte tekniske

brønnbarrierer eller operasjon av disse har sviktet.

Translated to English the definition will be:

A blowout is an incident where formation fluid flows out of the well or between

formation layers after all the predefined technical well barriers or the activation of

the same have failed.

The definition has however not become a part of the Petroleum Safety Authority Norway

regulation, but remains the database blowout definition.

Well release definition: The reported incident is a well release if oil or gas flowed from the

well from some point were flow was not intended and the flow was stopped by use of the

barrier system that was available on the well at the time the incident started.

Shallow gas definition: Any gas zone penetrated before the BOP has been installed. Any

zone penetrated after the BOP is installed is not shallow gas (typical Norwegian definition of

shallow gas).

All shallow gas incidents in the database have at the extent possible been categorised

according to the typical Norwegian definition of shallow gas. This definition is not relevant

for all US GoM incidents because:

US GoM OCS reservoirs vary highly in depth. Some reservoirs were as shallow as

200 meters.

For some incidents they had sat a full BOP stack, but had no intention to use it

because it would likely cause a blowout outside the casing and a possible crater.

For some incidents they had drilled very deep without running an extra casing string

and the BOP.

And for some incident they had used a combination of a BOP and a diverter.


Further, for many of the incidents the description of the incident in the sources is insufficient,

and some assumptions have to be made. A general comment is that it is not easy to categorise

all the incidents in shallow and deep incidents because of the above.

It should further be noted that it is in many cases difficult to determine if a shallow gas

incident shall be regarded as a blowout or not. In February 2007 a report was published,

named “Shallow Gas Project, Shallow gas events 1984 – 2006 in the Norwegian Sector”, by

AGR – Triangle. The report was prepared for the Petroleum Safety Authority Norway. This

report describes 44 shallow gas events. These 44 events have been reviewed, and some

blowouts were added to the database, and many incidents were disregarded. Typically

incidents that were reported with a strong seafloor flow, or the diverter was used, were

regarded as blowouts. Incidents only referring to gas bubbles were disregarded. This report is

enclosed the West Vanguard Blowout (Blowout ID 278) in the database.

1.4 Category and Sub-category

The categories and subcategories utilised when classifying the incidents in the SINTEF

Offshore Blowout Database are shown in Table 1.2.

Table 1.2 Main categories and subcategories for the incidents in the SINTEF Offshore

Blowout database Main Category Sub category Comments/Example

Blowout and well release

Blowout (surface flow)

1. Totally uncontrolled flow, from a deep zone

Totally uncontrolled incidents with surface/subsea flow.

2. Totally uncontrolled flow, from a shallow zone

Typical the diverter system fails

3. Shallow gas “controlled” subsea release only

Typical incident is that riserless drilling is performed when the well starts to flow. The rig is pulled away

Blowout (underground flow)

4. Underground flow only 5. Underground flow mainly, limited

surface flow The limited surface flow will be incidents were a minor flow has appeared, but typical the BOP has been activated to shut the surface flow

Well release 6. Limited surface flow before the secondary barrier was activated

Typical incident will be that flow is through the drillpipe and the shear ram is activated

7. Tubing blown out of well, then the secondary barrier is activated

Typical incident occurring during completion or workover. Shear ram is used to close the well after the tubing has been blown out of the well.

Diverted well release

8. Shallow gas controlled flow (diverted)

All incidents were the diverter system functioned as intended.

Unknown Unknown Unknown may be selected for both the category and the subcategory

The list of sub-categories, shown in Table 1.2, may be extended if found appropriate. One

option will be to split the sub category for Well release further down to highlight incidents

with an ignition potential.


1.5 Phase of operation

Each of the blowout/well releases in the database is categorised in the phase of operation they

occurred. Table 1.3 shows the pre-set codes used for phase of operation.

Table 1.3 Phase of operation

Description Remarks

Completion Activities associated to well completion activities

Dev.drlg Development drilling

Expl.drlg Exploration drilling, includes wildcats and appraisal wells

Production Production, injection, closed in wells

Unknown drlg When it is not known whether it is dev.drlg or expl.drlg

Unknown Unknown

Wireline Wireline operations in connection with a production/injection well, not wireline operations carried out as a part of well drilling, well completion or well workover

Workover Workover activities, not including wireline operations. Snubbing and coiled tubing operations

1.6 North Sea Standards

The intention with the field North Sea Standards is to identify blowout/well release incidents

that likely would have been prevented in North Sea operations because the procedures or

equipment utilised when the incident occurred are different from North Sea equipment or

procedures.

Table 1.4 presents the coding used for this field.

Table 1.4 North Sea standards

Description

Yes

No, no shear ram

No, BOP not North Sea standard

No, two barrier principle not followed

Sometimes not relevant, BOP removed to install casing seal

Unknown

Not evaluated



2. Overview of Blowouts/Well releases Included in the Database

2.1 Introduction

The SINTEF Offshore Blowout Database does per December 2010 include information about

584 offshore blowouts/well releases that have occurred world-wide since 1955.

The number of blowouts/well releases related to the different periods is presented in Table

2.1

Table 2.1 Number of blowouts/well releases related to the different periods

Period No. of blowouts/well releases

1950-ties 9

1960-ties 54

1970-ties 114

1980-ties 177

1990-ties 119

2000 – 2009-12-31 112

2010 and 2011 7

Total 592

Blowouts/well releases that have occurred in the period 1980-01-01 - 2009-12-31 in US GoM

OCS, UK, and Norway are focused on. Blowouts/well releases that have occurred after 2009-

12-31 are not included in this report at all. Blowouts/well releases from before 1980 and the

rest of the world are only briefly included.

2.2 Data Quality

SINTEF's intention is to collect data from all occurring blowouts. However, it is a fact that

many blowouts/well releases occurring in this period have never been recorded in the

database. This because, public sources, which are the main source of information for

blowouts/well releases occurring outside US GoM OCS, and UK, and Norway, do frequently

not describe blowouts/well releases with small consequences. Therefore, several

blowouts/well releases are believed to be missing from the database.

It is SINTEF's belief that from 1980-01-01 most blowouts occurring in the US Gulf of

Mexico (GoM) Outer Continental Shelf (OCS), the UK, and Norway have been included in

the database.

The quality of data related to blowouts occurring after 1970-01-01 is significantly better than

the data from before 1970. However, for many blowouts the quality still is low because

proper descriptions of the incidents are lacking. Blowout information is frequently hidden

from the public.


For each of the blowout/well release records in the database the quality of the source material

is given. Table 2.2 shows an overview of the data quality for the blowouts/well releases that

have occurred in the period 1980-01-01 – 2009-12-31.

Table 2.2 Quality of blowout/well release data source material

Quality of blowout/well release data source material

All blowouts except US GoM OCS, UK, and Norwegian blowouts in the period

1980-01-01 – 2009-12-31

Only US GoM OCS, UK, and Norwegian blowouts in the period 1980-01-01 –

2009-12-31

Very good 9 65

Good 11 55

Fair 20 61

Low 36 54

Very low 79 18

Total 155 253

2.3 Overview of Countries Represented in the Database

In Table 2.3 shows an overview of the number of blowouts and well releases for the countries

represented in the database.

Blowout and Well Release Characteristics and Frequencies, 2011 version Page: 15 Table 2.3 Overview of countries represented in the database

COUNTRY 50-ties

60-ties

70-ties

80-ties

90-ties

1Jan 00 - 31 Dec 09

later than 31 Dec 09

Total

ANGOLA 1 1

AUSTRALIA 3 1 1 1 1 7

AZERBAIJAN 3 2 5

BRAZIL 3 2 1 6

BRUNEI 2 1 1 4

BURMA 1 1

CABINDA 1 1 2

CANADA EAST 2 2

CANADA NORTH 2 2

CHINA 1 2 1 4

CONGO 1 2 3

DENMARK 1 1

DUBAI 2 1 3

EGYPT 3 1 3 7

EQUATORIAL GUINEA 1 1

ETHIOPIA 1 1

GABON 1 1

GERMANY 1 1

INDIA 3 5 8

INDONESIA 4 11 2 5 22

IRAN 1 4 7 1 1 14

ITALY 1 1 1 3

LIBYA 1 1

MALAYSIA 1 2 3

MEXICO 2 6 2 2 12

NETHERLANDS 1 1 2

NIGERIA 3 3 2 1 1 10

NORWAY 3 13 15 4 35

PAPUA NEW GUINEA 1 1 2

PERU 2 2

PHILLIPPINES 1 1

QATAR 2 2

SAUDI ARABIA 1 3 1 5

SOUTH KOREA 1 1

SPAIN 1 1

TAIWAN 2 2

THAILAND 2 2

TRINIDAD 3 1 1 2 7

UK 4 1 8 11 15 39

UNKNOWN 1 1

US 1 1 2

US/ALASKA State 1 3 1 5

US/CALIFORNIA OCS 1 1 3 5

US/CALIFORNIA state 2 2

US/GOM NOT OCS 2 5 17 7 10 9 2 52

US/GOM OCS 6 30 58 77 52 58 3 284

USSR 2 6 8

VENEZUELA 1 3 1 5

VIETNAM 1 1

YUGOSLAV 1 1

Total 9 54 114 177 119 112 7 592


2.4 During what Operational Phases do Blowouts/Well Releases Occur?

In Table 2.4 and Table 2.5 no. of blowouts/well releases have been related to the operational

phases.

Table 2.4 No. of blowouts/well releases experienced during different operational phases

(including all blowouts/well releases until 2009-12-31)

PERIOD Dev. drlg

Expl. drlg

Unk. drlg

Compl-etion

Work-over

Produ-ction

Wireline Un-known/other

Total

Before 1980 43 75 1 12 18 20 3 5 177 24,3 % 42,4 % 0,6 % 6,8 % 10,2 % 11,3 % 1,7 % 2,8 %

1980 to 2009-12-31 95 141 9 26 64 45 9 19 408 23,3 % 34,6 % 2,2 % 6,4 % 15,7 % 11,0 % 2,2 % 4,7 %

Total 138 216 10 38 82 65 12 24 585 23,6 % 36,9 % 1,7 % 6,5 % 14,0 % 11,1 % 2,1 % 4,1 %

Table 2.5 Area specific overview of no. of blowouts/well releases experienced during

different operational phases (including all blowouts/well releases 01-01-1980 - 2009-12-31)

AREA Dev. drlg

Expl. drlg **

Unk. drlg

Comp-letion

Work-over

Production Wire-line

Un-known/other

Total Total excl. ext. cause*

External cause*

No ext. cause*

US GoM OCS 54 53 13 39 8 11 5 4 187 179 28,9 % 28,3 % 7,0 % 20,9 % 4,3 % 5,9 % 2,7 % 2,1 % 100,0 %

UK, and Norw-egian waters

9 33 1 7 9 1 2 4 66 65 13,6 % 50,0 % 1,5 % 10,6 % 13,6 % 1,5 % 3,0 % 6,1 % 0,0 % 100,0 %

Rest of the world

32 55 8 6 16 12 11 15 155 143 20,6 % 35,5 % 5,2 % 3,9 % 10,3 % 7,7 % 7,1 % 9,7 % 100,0 %

Total 95 141 9 26 64 21 24 9 19 408 387 23,3 % 34,6 % 2,2 % 6,4 % 15,7 % 5,1 % 5,9 % 2,2 % 4,7 % 100,0 %

* External causes are typical; storm, military activity, ship collision, fire and earthquake.

** One of the Expl. drilling blowouts in the "rest of the world” was caused by volcanic activities

When reading and Table 2.5, it is important to note that the most thorough data is from the

US GoM OCS, UK, and Norway.

In the US GoM OCS they have experienced a relatively high no. of blowouts/well releases

during development drilling compared to exploration drilling. This is explained by the fact

that in US GoM OCS they are drilling relatively more development wells than exploration

wells, compared to UK and Norway. Further, the relatively high no. of well workover

blowouts/well releases in US GoM OCS area does indicate that the number of workovers in

that area is high. It should, further, be noted that external causes were involved in

approximately 50% of the production blowouts. External causes are discussed in Section 4.7,

on page 31.


2.5 No. of Blowouts/Well releases per Year

Table 2.6 shows a year-to-year overview of no. of blowouts/well releases for US GoM OCS,

UK, and Norway in the period 1980-01-01 - 2009-12-31.

Table 2.6 Year to year overview of no. of blowouts/well releases for US GoM OCS, UK, and

Norway in the period 1980-01-01 – 2009-12-31

Year Dev. Drlg

Expl. Drlg Un-known drilling

Comp-letion

Work-over

Production Wire-line

Un-known/other

Total

App- raisal

Wild- cat

Un- known

No ext. cause*

External cause*

1980 2 1 2 1 2 1 9

1981 2 2 5 2 11

1982 5 1 4 1 11

1983 7 2 3 1 1 14

1984 1 6 1 8

1985 2 2 6 2 12

1986 1 1 2

1987 1 2 1 1 2 1 8

1988 1 3 1 1 6

1989 4 5 2 3 2 1 17

1990 3 3 2 3 1 12

1991 4 1 3 1 1 10

1992 2 2 1 1 3 9

1993 2 2 2 6

1994 1 1 1 1 4

1995 1 1 2 4

1996 1 2 2 1 6

1997 3 1 5 2 2 13

1998 3 1 1 1 2 1 9

1999 3 2 5

2000 3 2 3 1 1 1 11

2001 3 1 1 2 4 2 13

2002 2 1 1 1 1 1 7

2003 2 1 1 1 1 1 7

2004 2 1 3 6

2005 2 1 1 4

2006 3 1 4

2007 1 1 5 2 1 10

2008 1 2 3 1 1 8

2009 2 2 1 1 1 7

Total 63 33 51 2 1 20 48 13 9 9 4 253

* External causes are typical; storm, military activity, ship collision, fire and earthquake.


2.6 Water depth vs. Blowouts/Well releases

Table 2.7 shows the water depth vs. blowouts/well releases for US GoM OCS, UK, and

Norway in the period 1980-01-01 - 2009-12-31.

Table 2.7 Water depth vs. blowouts/well releases for US GoM OCS, UK, and Norway in the

period 1980-01-01 – 2009-12-31

Phase MainCategory Deep or Shallow

Water depth grouped (m)

<50 50 - 100

100 - 200

200 - 400

400 - 600

600 - 1000

1000 - 1500

1500-2500

Un-known/other

Total

Develop-ment drilling

Blowout (surface flow) Deep 2 4

1

1

8

Shallow 6 12 4 1

23


Deep 2 1 1

4

Shallow

1

1

Diverted well release Shallow 4 9 6

19

Well release Deep

3 2 1

6

Shallow

1 1

2

Total

14 30 15 3

1

63

Explor-ation drilling

Blowout (surface flow) Deep 13 6 2

1 1

23

Shallow 9 11 6 2 2 1

1 32


Deep 3 3

2

8


1

1

Shallow 2 7 2 1

12

Well release Deep

2 1 2

1

1 7

Shallow

1 1

2

Unknown Deep

1

1

Total

27 30 12 8 3 3 1

2 87

Unknown drilling

Well release

1 1

Total

1 1

Com-pletion


6 3 1

10


1

1

Well release

2 3 1 1 1

1 9

Total

8 6 2 1 1 1

1 20

Work-over


15 4 3 1

23

Well release

10 8 4

1

2 25

Total

25 12 7 1 1

2 48

Prod-uction *


6 2 1

9

Blowout (underground flow) 1 1

Well release

2 1

3

Total

9 3 1

13

Wire-line


2

1

1 4

Well release

3 1 1

5

Total

5 1 2

1 9

Un-known/ other


1

1

Blowout (underground flow) 1

1

Well release 1

1 2

Total

3

1 4

Total 91 82 39 13 5 5 1 1 7 244

* External causes not included.

2.7 Installation type vs. Water depth for drilling incidents

Table 2.8 shows the installation type vs. water depth for drilling incidents for US GoM OCS,

UK, and Norway in the period 1980-01-01 - 2009-12-31.

Blowout and Well Release Characteristics and Frequencies, 2011 version Page: 19 Table 2.8 Installation type vs. Water depth for drilling incidents for US GoM OCS, UK, and

Norway in the period 1980-01-01 - 2009-12-31

Installation Type

Phase II Main Category


<50 50 – 100

100 - 200

200 - 400

400 - 600

600 - 1000

1000 - 1500

Un-known

Total

Deep

Drillship Expl.drlg Diverted well release

1

1

Jacket Dev.drlg

Blowout (surface flow) 1 3

1

5


1

1

Well release

1 1 1

3

Jackup

Dev.drlg

Blowout (surface flow) 1 1

2


2

Well release

1

1

Expl.drlg Blowout (surface flow) 12 5

17

Unknown drlg

Blowout (underground flow) 2 1

3

Unknown

1

1

Well release

1 1

Semisub-mersible

Dev.drlg


1

1


1

1

Well release

1 1

2

Expl.drlg


1 2

1 1

5


2

2

4

Well release

2 1 2

1 1 7

Sub-mersible

Expl.drlg Blowout (surface flow) 1

1


1

Total 20 20 6 6 1 3 1 2 59

Shallow

Drillship Expl.drlg Blowout (surface flow) 1

1

Jacket Dev.drlg


4 2 1

7


1

1

Diverted well release 1 8 7

16

Well release

1 1

2

Expl.drlg Blowout (surface flow)

1

1

Jackup

Dev.drlg Blowout (surface flow) 5 7

12

Diverted well release 2 1

3

Expl.drlg Blowout (surface flow) 8 2

10

Diverted well release 2 7 1

10

Semisub-mersible

Dev.drlg Blowout (surface flow) 1 1 2

4

Expl.drlg


9 5 2 2 1

1 20


1 1

2

Well release

1 1

2

Total

20 40 22 5 2 1

1 91

Total all

40 60 28 11 3 4 1 3 150



3. Blowouts vs. Well Releases

As explained in Section 1.4 on page 10, the incidents in the database has been categorised in

blowouts and well releases.

When excluding the blowouts with external causes the database includes 244 blowouts/well

releases for the US GoM OCS, Norway and UK in the period January 1980 until December

2009.

Table 3.1 shows an overview of the no. of blowouts/well releases within the main phases of

operation, categories and sub categories.

Table 3.1 Overview of the no. of incidents within the main phases of operation, categories

and sub categories for US GoM OCS, Norway and UK blowouts/well releases in the period Jan. 1980 until Dec. 2009

Incident category

Sub category According to North Sea standard? (See

Table 1.4 page11)

Dev. drlg

Expl. drlg

Unk. drlg

Comp-letion

Work-over

Prod-uction

Wire-line

Other/Un-known

Total


Totally uncontrolled flow, from a deep zone

No, no acoustic backup BOP control system 1 1

No, no shear ram 1 3

5 7

16

No, two barrier principle not followed

1 1

2

Sometimes not relevant, BOP removed to install casing seal 2 1

1 4

Unknown

4

4

Yes 5 18

4 11 8 4

50

Totally uncontrolled flow, from a shallow zone

No, BOP not North Sea standard

1

1

Sometimes not relevant, BOP removed to install casing seal 1 1

2

Yes 22 18

1

41

Shallow gas "controlled" subsea release only

Yes

12

12

Total 31 55 10 23 9 4 1 133

Blowout (under-ground flow)

Underground flow only Yes 4 6 1 1 12

Underground flow mainly, limited surface flow

Yes 1 2

3

Total

5 8

1

1 15


Shallow gas controlled flow (diverted)

Yes 19 12

31

Other (Kick in riser above BOP)

Yes

1

1

2

Total 19 13

1

33

Well release

String blown out of well, then the secondary barrier

Yes 1

1 7

9

Limited surface flow before the secondary barrier was activated

Yes 6 8 1 8 17 3 5

48

No, no shear ram

1

1

Other Yes 1 1

2 3

Total 8 9 1 9 25 3 5 2 62

Unknown Unknown Yes

1

1

Total

1

1

Total all incidents 63 86 1 20 48 13 9 4 244



4. Overall Blowout/Well Release Experience

4.1 Blowout/Well Release vs. Flow Medium

Table 4.1 shows an overview of the blowout/well release flow medium for the different

incidents. Only US GoM OCS, UK, and Norwegian incidents in the period 1980-01-01 -

2009-12-31 are included.

Table 4.1 Blowout/well release flow medium for US GoM OCS, UK, and Norway in the period

1980-01-01 - 2009-12-31 Incident category

Flow medium Dev. drlg

Expl. Drlg

Unk. Drlg

Comp-letion

Work-over

Prod-uction*

Wire-line

Other/-unknown

Total


Condensate, Gas (deep) 2

4 1

7 Condensate, Gas (deep), water

1

1

Gas (deep) 2 15

9 13 4

43

Gas (deep), Mud, Water

1

1 Gas (deep), Water

1

1

Mud

1

1

Oil

1

1 Oil, Gas (deep) 2 1

1 4 3 2

13

Oil, Gas (deep), H2S

1

1

Oil, Gas (deep), Mud

1

1 Oil, Gas (deep), Water 1

1

2

Shallow water 19 26

45

Shallow gas 1 3

4 Shallow gas H2S 1 3

1

5

Shallow gas, Water 1

1

Shallow, unknown fluid 1

1 Unknown

1

1 1 3

Water 1 1

2

Total 31 55

10 23 9 4 1 133


Condensate, Gas (deep)

1

1

Gas (deep) 3 4

7 Oil, Gas (deep)

1

1

2

Shallow gas 1

1

Unknown

2

1 3 Water 1

1

Total 5 8

1

1 15


Gas (deep), Mud

1

1

2

Shallow gas 15 10

25 Shallow gas, Mud 3 1

4

Shallow gas, Water 1 1

2

Total 19 13

1

33

Well release

Condensate, Gas (deep)

1

1

Condensate, Gas (deep), water

1

1 Gas (deep) 1

3 6 1 2

13

Gas (deep), Methanol 1

1

Gas (deep), Mud 2 1

1

4 Gas (gas lift gas) 1

1

Gas (trapped gas)

1

1

Mud

1 1 2 4

8 Oil

1 2 3

Oil, Gas (deep)

1

1 8

1

11

Oil, Gas (deep), Mud

2

1

3 Oil, Gas (deep), Water

1

1

Oil, Water

1 1

2

Shallow gas 1 2

3 Shallow gas, Mud 1

1

Unknown 1 1

1 4

1

8

Total 8 9 1 9 25 3 5 2 62

Unknown Gas (deep)

1

1

Total

1

1

Total 63 86 1 20 48 13 9 4 244

* Blowouts caused by external loads are excluded (storm, military activity, ship collision, fire and earthquake). ** Stems from a blowout outside the casing from a shallow zone during production


4.2 Blowout/Well Release vs. Flow-rates

The blowout/well release flow-rates from the actual incidents described in the database are

poorly documented. For some blowouts flow-rate figures exist, but for most blowouts they do

not exist.

The database has, however, three fields that describe the flow-rates during well tests for the

actual well or close by wells. These fields are Gas volume, Oil volume and Water volume.

Flow-rates are important figures in risk and environment analyses. To establish a realistic

distribution of flow-rates to expect for specific fields, field specific productivity data should

be compared to blowout/well release experience with respect to remaining restrictions in the

wells during the blowout/well release situations. For several blowouts/well releases there are

significant flow restrictions that will reduce the flow.

4.3 Severity

The blowout/well release database contains a specific field describing blowout/well release

severity. The quality of the information in this field is relatively low. These data are therefore

not presented in this report. However, it should be noted that most of the blowouts/well

releases do cause relatively small damages.

4.4 Ignition of Blowouts/Well Releases

In Table 4.2 and Table 4.3 experienced data related to ignition of blowouts/well releases are

presented. Only incidents from the period 1980-01-01 - 2009-12-31 have been included. It

has been chosen to separate US GoM OCS, UK, and Norwegian blowouts/well releases from

the rest of the world. Blowouts caused by external loads (storm, fire etc. are not included)

Please note that it should not be differed between ignition probability for an oil blowout/well

release and a gas blowout, because for oil blowouts the volume of gas blowing is very high

compared to the volume of oil blowing.

Blowout and Well Release Characteristics and Frequencies, 2011 version Page: 25 Table 4.2 Experienced ignition for US GoM OCS, UK, and Norwegian blowouts/well releases

in the period 1980-01-01 - 2009-12-31. Blowouts caused by external loads (storm, fire etc.) are not included

Main category

Phase Deep or shallow

No ignition

Immediate ignition

(<5 mins)

Delayed Ignition Total 5 mins –

1 hour 1 hour –

6 hrs 6 hrs – 24 hrs

>24 hrs


Dev.drlg Deep 5 2

1

8

Shallow 17 2 2

1 1 23

Expl.drlg Deep 17 2

4

23

Shallow 31

1

32

Completion 7 2

1

10

Workover 18 1

1

3 23

Production 9

1

Wireline 4

4

Other/Unknown 1

1

Total 109 9 3 2 6 4 133

82,0 % 6,8 % 2,3 % 1,5 % 4,5 % 3,0 % 100,0 %


Dev.drlg Deep 4

4

Shallow 1

1

Expl.drlg Deep 8

8

Production 1

1

Other/Unknown 1

1

Total 15

15

100.0%

100.0%


Dev.drlg Shallow 19

19

Expl.drlg Deep 1

1

Shallow 11

1

12

Completion 1

1

Total 32

1

33

97,0 %

3,0 %

100,0 %

Well release

Dev.drlg Deep 6

6

Shallow 1 1

2

Expl.drlg Deep 7

7

Shallow 2

2

Unknown drlg Deep 1

1

Completion 9

9

Workover 23 2

25

Production 3

3

Wireline 5

5

Other/Unknown 2

2

Total 59 3

62

95,2 % 4,8 %

100,0 %

Unknown

Expl.drlg Deep 1

1

Total 1

1

100,0 %

100,0 %

Total 215 12 4 2 6 4 244

88,5 % 4,9 % 1,6 % 0,8 % 2,5 % 1,6 % 100,0 %

Table 4.3 Experienced ignition for rest of the world (US GoM OCS, UK, and Norway are not

included) blowouts/well releases in the period 1980-01-01 - 2009-12-31. Blowouts caused by external loads are not included.

PHASE No ign-ition

Ignited blowouts Total

Immediate ign-ition (<5mins)

Delayed ignition

Unknown

Development drilling 17 8 4 3 32

Exploration drilling 39 8 3 4 54

Unknown drlg 5 1 2 8

Completion 1 3 1 1 6

Workover 9 3 3 1 16

Production 7 1 1 2 11

Unknown 10 3 1 1 15

Total 88 27 15 12 142

62,0 % 19,0 % 10,6 % 8,5 % 100,0 %


If comparing Table 4.2 and Table 4.3, far more ignited blowouts/well releases in the material

for the "rest of the world". The main reason is probably that from "rest of the world"

blowouts with small consequences are more seldom reported.

4.5 Blowout/Well Release Duration

In Table 4.4 the experienced blowout/well release duration is presented. Only US GoM OCS,

UK, and Norwegian blowouts/well releases in the period 1980-01-01 - 2009-12-31 have been

included. Blowouts caused by external loads (storm, fire etc.) are not included.

It should be noted that bridged or depleted are listed as primary cause for regaining well

control for 31 out of the 55 exploration drilling Blowout (surface flow), and 14 of the 31

development drilling Blowout (surface flow).

For the diverted well releases (both exploration and development drilling) bridged or

depleted are listed as primary cause for regaining well control for 15 out of the 32 well

releases.

Blowout and Well Release Characteristics and Frequencies, 2011 version Page: 27 Table 4.4 Blowout/well release duration for US GoM OCS, UK, and Norwegian blowouts/well

releases in the period 1980-01-01 - 2009-12-31. Blowouts caused by external loads (storm, fire etc.) are not included

Phase Shallow or deep

T ≤10 mins

10min < T ≤

40min

40min < T ≤ 2

hrs

2 hrs < T ≤ 12 hrs

12 hrs < T ≤ 2 days

2 days < T ≤ 5 days

T > 5 days

Un-known

Total


Dev.drlg Deep 1 2 1 1 1 2 8

Shallow 3 2 4 4 4 6 23

Expl.drlg Deep 1 2 6 4 4 6 23

Shallow 1 2 4 2 7 8 8 32

Completion 1 3 1 4 1 10

Workover 1 4 9 2 4 3 23

Production 4 2 2 1 9

Wireline 1 2 1 4

Other/Unknown 1 1

Total 1 2 7 17 30 21 27 28 133

0,8 % 1,5 % 5,3 % 12,8 % 22,6 % 15,8 % 20,3 % 21,1 % 0,8 %


Dev.drlg Deep 1 1 2 4

Shallow 1 1

Expl.drlg Deep 1 1 4 2 8

Production 1 1

Other/Unknown 1 1

Total 1 1 1 7 5 15

6,7 % 6,7 % 6,7 % 46,7 % 33,3 % 100,0 %


Dev.drlg Shallow 2 5 4 3 2 1 2 19

Expl.drlg Deep 1 1

Shallow 1 1 1 5 2 1 1 12

Completion 1 1

Total 4 7 5 8 4 2 3 33

12,1 % 21,2 % 15,2 % 24,2 % 12,1 % 6,1 % 9,1 % 100,0 %

Well release

Dev.drlg Deep 4 2 6

Shallow 2 2

Expl.drlg Deep 5 1 1 7

Shallow 1 1 2

Unknown drlg Deep 1 1

Completion 9 9

Workover 21 1 1 2 25

Production 2 1 3

Wireline 5 5

Other/Unknown 2 2

Total 47 2 1 3 2 1 6 62

75,8 % 3,2 % 1,6 % 4,8 % 3,2 % 1,6 % 9,7 % 100,0 %

Unknown

Expl.drlg Deep 1 1

Total 1 1

100.0% 100.0%

All blowuts/well releases 52 11 13 29 37 24 35 43 244

21,3 % 4,5 % 5,3 % 11,9 % 15,2 % 9,8 % 14,3 % 17,6 % 100,0 %

4.6 Blowout/Well Release Flow-paths and Release Points

In Table 4.5 – Table 4.7 the experienced release point vs. the final blowout/well release flow

paths for the various phases of operation are presented. Only US GoM OCS, UK, and

Norwegian blowouts/well releases in the period 1980-01-01 – 2009-12-31 have been

included. Blowouts caused by external loads (storm, fire etc.) are not included.

Page: 28 Blowout and Well Release Characteristics and Frequencies, 2011 version Table 4.5 Release point vs. final flow-path for drilling shallow gas blowouts and well

releases

Incident main type

Final flow-path

Release point

Through drill

string

Through annulus

Through outer

annulus

Outside casing

Under-ground blowout

Un-known

Total

Development drilling shallow gas incidents


Diverted and BOP valve outlet

1

1

Diverter syst.leak - line eroded

1

1

Diverter syst.leak - line parted

2

2

Diverter syst.leak - main diverter

2 1

3

Drillfloor - through rotary

2

1 3

From wellhead

6

1

7

Subsea - outside casing

4

4

Subsea wellhead

1 1

2

Total

8 9 4 1 1 23

Blowout (underground flow) From wellhead

1

1

Total

1

1

Diverted well release Diverted

16 3

19

Total

16 3

19

Well release Drillfloor - through rotary

1

1

From wellhead

1

1

Total

1 1

2

Development drilling total

25 13 4 2 1 45

Exploration drilling shallow gas incidents

Blowout (surface flow) Diverter syst.leak- line eroded

3

3

Diverter syst.leak- line parted

1

1

Diverter syst.leak-main diverter

2

2


1

1

Drillfloor - top of drill string 1

1

From wellhead

3

3


4

4

Subsea crater

1

1

Subsea wellhead

15

15

Unknown

1 1

Total 1 21 4 5

1 32

Diverted well release Diverted

12

12

Total

12

12

Well release Subsea wellhead

1 1

2

Total

1 1

2

Exploration drilling total 1 34 5 5

1 46

TOTAL ALL SHALLOW GAS INCIDENTS 1 59 18 9 2 2 91

Most shallow gas blowouts/well releases have their final flow-path through the well bore

annulus. The flow is either diverted without any problems, the diverter system fails, or the

flow is released through the subsea wellhead.

Blowout and Well Release Characteristics and Frequencies, 2011 version Page: 29 Table 4.6 Release point vs. final flow-path for “deep” drilling blowouts and well releases

Incident main type

Final flow-path

Release point

Through drill

string

Through test

string

Through annulus

Through outer

annulus

Outside casing


Un-known

Total

Develop-ment drilling, deep



1

1

Drillfloor choke manifold

1

1

From wellhead

1 3

4


1

1

Unknown

1

1

Total

4 3 1

8


No surface flow

4

4

Total

4

4

Well release


1 3

4


1

1

Unknown

1 1

Total

1 3

1

1 6

Dev.drlg total 1 7 3 2 4 1 18

Explora-tion drilling, deep


Bop valve outlet

1

1

Diverter syst.leak- line parted

1

1


2

1

3


2

From wellhead

3 3

6

Shaker room

1

1


5

5

Subsea BOP

2

2

Subsea crater

1

1

Subsea wellhead

1

1

Total 2

10 4 7

23


No surface flow

6 6


1

1

Unknown

1 1

Total

1 6 1 8



1

1

Total

1

1

Well release

Diverted

1

1


3

3


2

Drillfloor - tubing valve 1

1

Total 2 1 5

7

Unknown

Unknown

1 1

Total

1 1

Expl.drlg total 4 1 15 4 8 6 2 40

Unknown drilling, deep

Well release


1

1

Total

1

1

Unknown drlg total 1 1

Total all deep 4 2 23 7 10 10 3 59

Through annulus is the most common final flow-path for both exploration and development

drilling “deep” blowouts/well releases. Forty percent of the deep drilling blowouts/well

releases was flowing through the annulus. Ten incidents came outside the casing, causing

subsea releases. One of them also ignited when the gas reached the surface (64 meter of

water). Also for one of the two subsea BOP releases (94 meter of water) the gas ignited. In

general subsea releases are more frequent for exploration well blowouts than for development

well blowouts. This was also observed for the shallow gas blowouts. Eleven incidents only

caused underground flow. Probably more of these incidents occur than reported in the

database.

Page: 30 Blowout and Well Release Characteristics and Frequencies, 2011 version Table 4.7 Release point vs. final flow-path for completion, workover, production and wireline

blowouts and well releases

Phase Final flow-path

Release point

Through Coiled tuning

Through drill

string

Through tubing

Through annulus

Through outer

annulus

Outside casing


Total

Comp-letion

Blowout (surface flow) Drillfloor - drillpipe valve

1

1


1

1

2 Drillfloor - top of drill string

3 1

4

Drillfloor - top of tubing

1

1 From x-mas tree

1

1

Mud room

1

1

Total

5 4 1

10


Diverted

1

1

Total

1

1

Well release Drillfloor - through rotary

1

4

5


1 2

3 Shaker room

1

1

Total

3 2 4

9

Completion total 8 6 6 20

Work- over

Blowout (surface flow) BOP valve outlet

4

4


2


4

4

Drillfloor - top of tubing 1

2

3 Drillfloor - tubing valve

1

1

From wellhead

1 1

2 From x-mas tree

1 1

2

Mud room

1

1


2

2

Subsea wllhead

1

1

Unknown

1

1 Total 1 5 5 9 1 2

23

Well release BOP valve outlet

3

3


1 13


1

1


3

3 From above x-mas tree

1 1

2

From x-mas tree

1 1

2 Total

7 18

25

Workover total 1 5 12 27 1 2

48

Prod-uction

Blowout (surface flow) From wellhead

1 1 1

3

From x-mas tree

2

2 Subsea - outside casing

2

2

Subsea crater

1

1 Subsea x-mas tree

1

1

Total

4 1 1 3

9

Blowout (underground flow) No surface flow

1 1

Total

1 1

Well release From x-mas tree

2

2

Subsea x-mas tree

1

1 Total

3

3

Production total 7 1 1 3 1 13

Wireline

Blowout (surface flow) Drillfloor

1

1

From above x-mas tree

2

2 From x-mas tree

1

1

Total

3

1

4

Well release Drillfloor -Wireline stuffing box/BOP

1

1

From above x-mas tree

2

2 From x-mas tree

1

1

Unknown

1

1 Total

1 4

5

Wireline total 1 7 1 9

Other/ Un-known

Blowout (surface flow) From wellhead

1

1

Total

1

1

Blowout (underground flow) No surface flow

1 1

Total

1 1

Well release

2

2

Subsea wellhead

2

2

Unknown total 2 1 1 4

Total 1 14 32 36 4 5 2 94


Most blowouts during completion result in flow through the tubing or the drill string/work

string. It is important to note that for several of these blowouts the BOP stack did not include

a blind-shear ram (Table 3.1 on page 21). With a blind-shear ram these blowouts could have

been stopped at an earlier stage, and they would in many cases not have been categorised as a

blowout. It is not mandatory to use blind-shear rams in US OCS surface BOPs.

The normal flow-paths for workover blowouts/well releases are either through the drill

string/tubing or through the annulus. It is important to note that also for several of these

blowouts the BOP stack did not include a blind-shear ram (Table 3.1 on page 21). Further,

the drill string/tubing blowouts are mostly released from the top of the drill string/tubing

hanging in the rotary table slips. Annulus blowouts do mostly come through the rotary.

Wireline blowouts typically flow through the tubing and the release point is above the X-mas

tree.

Eight of the twelve production blowouts came to the air in the wellhead/X-mas tree area.

4.7 Blowout/Well Release Causes

Normally to experience a blowout, at least one primary and one secondary barrier have to

fail. For drilling, workover and completion blowouts the primary barriers are usually the

hydrostatic pressure from the mud column and the secondary barrier is the mechanical

barriers, either subsea or on the installation. For production wells the primary and secondary

barriers are mechanical barriers.

It should be noted that when drilling in shallow zones there is normally only one blowout

barrier. The installations do, however, have means for forcing the gas away from the

installation. In this report those means are treated as a secondary barrier.

The blowout database does contain fields for describing the blowout/well release causes, i.e.

why were the primary and secondary barrier lost?

Further, the database contains one field that describes whether the blowout/well release was

"caused" by an external load. Out of the 253 blowouts/well releases from US GoM OCS, UK,

and Norway in the period 1980-01-01 - 2009-12-31, nine were "caused" by an external load

(Table 2.6, page 17). It is, however, important to note that an external load normally only

ruins the topside barrier. To experience a blowout, the downhole barrier also has to fail. So an

external load will not be the single blowout cause. Typically the external load ruins the

wellhead/X-mas tree barriers of an active well, and the downhole barrier fails to activate or is

leaking.


Table 4.8 shows an overview of blowouts caused by external loads.

Table 4.8 Overview of blowouts caused by external loads for US GoM OCS, UK, and Norway

in the period 1980-01-01 - 2009-12-31 Water

depth (m) Phase

Oper-ation

Activity External cause

Primary barrier Secondary barrier Flow-

medium

6 Prod-uction

Closed in gas well

Ship collision

C5.SCSSV/storm choke failure (Not enough surge to close valve)

A8.X-mas tree failed (leakage between tubing head flanges and master valve)

Oil, Gas (deep)

143 Prod-uction

Produc-ing oil

Gas lifting Fire/-explosion

C5.SCSSV/storm choke failure & C4.Tubing to annulus communication, equipment or nipple failure (5 to 6 wells failed)

A8.X-mas tree failed (all trees failed due to topside fire)

Oil, Gas (deep)

12 Prod-uction

Produc-ing gas

Regular production

Ship collision

C5.SCSSV/storm choke failure (not installed?)

A8.X-mas tree failed (due to collision)

Oil, Gas (deep)

10 Prod-uction

Produc-ing oil

Regular production

Storm C5.SCSSV/storm choke failure (Assumed, may also have been a tubing annulus communication)

A8.X-mas tree failed (damaged by storm)

Oil

13 Prod-uction

Produc-ing oil

Regular production



Oil

10 Prod-uction

Produc-ing oil

Regular production



Oil

15 Prod-uction

Produc-ing oil

Regular production

Storm C5.SCSSV/storm choke failure B4.Wellhead failed (hurricane damage)

Oil

40 Prod-uction

Closed in gas well

Surface mainten-ance

Storm C5.SCSSV/storm choke failure A8.X-mas tree failed (damaged by Hurricane Ike)

Gas (Deep)

52 Prod-uction

Closed in gas well

Wait on repair

Storm C5.SCSSV/storm choke failure (Trapped hydraulic in control line)

A8.X-mas tree failed (damaged by Hurricane Ike)

Gas (Deep)

Table 4.9 and Table 4.10 show the different causes for losing the primary and secondary

barriers, as reported in the database.

Blowout and Well Release Characteristics and Frequencies, 2011 version Page: 33 Table 4.9 Primary barrier failure causes listed in the database for the US GoM OCS, UK, and

Norwegian blowouts/well releases in the period Jan. 1980 - Dec. 2009

Category Primary barrier failure Dev.drlg Expl.drlg Unk drlg Comp-

letion Work-over

Prod-uction

Wire-line

Un-known

Total Deep Shal. Deep Shal. Deep


Too low hyd. head

Too low mud weight

2 3 3

2 4

14

Annular losses 1 1 4 1

1

8

While cement setting 3 9 4 3

1 20

Cmt preflush weight low

1

1

Trapped gas

1

1

Unknown why 1 4 2 6

1 1

15

Swabbing

6 2 3

2 4

17

Gas cut mud

2 2

4

Improper fill up

2

1

3

Disconnected riser

1 1

2

Unexp. high well pressure

1 2 10

1

14

Reservoir depth uncertainty 1

1

2

Poor cement

1 2

1 1

5

Formation breakdown

1

1

2

Packer leakage

1

1

Stripper BOP failure

1

1

Tubing plug failure 1

1

2

Snubbing equipment failure

4

4

X-mas tree failure

1

1

Packer plug failure

1

1

Tubing leakage/burst

2 2

3

Tubing equipm./nipple leak

1

1

2

SCSSV/storm choke failure

1 1 5

7

Well test string barrier failure 1

1

Wireline stuffing box failure

1

1

Wireline lubricator failure

2

2

Unknown

1

1

2

Total No. of primary barrier failures 8 24 26 32 10 23 9 4 1 136

Incidents with two prim. barrier failures 1 3 3

Blowout (surface flow) Total 8 23 23 32 10 23 9 4 1 133


Too low hyd. head

Too low mud weight 1

1

2

Annular losses

1

1

While cement setting

1

1

Unknown why 2

2

4

Unexp. high well pressure 1

2

3

Tubing leakage

1

1

Unknown

2

1 3

Blowout (underground flow) Total 4 1 8 1 1 15


Too low hyd. head

Too low mud weight

1

2

3

Annular losses

4

1

5

While cement setting

4

1

5

Trapped gas

1

1

Unknown why

1 1

2

Swabbing

9

9

Unexp. high well pressure

3

7

10

Total No. of primary barrier failures 21 1 12 1 35

Incidents with two prim. barrier failures 2 2

Diverted well release Total 19 1 12 1 33

Well release

Too low hyd. head

Too low mud weight 1

1

1 1

4

Annular losses

1 1

2

Drilling into neighbor well 1

1

Trapped gas

1

7

8

Unknown why

1

2 1

4

Swabbing

1 1 1 3 3

9

Gas cut mud

1

1

Unexp. high well pressure 3 1 1

1

6

Poor cement

1

1

2

Coiled tubing failure.

1

1

Tubing plug failure

1

1

Casing plug failure

2 2

Snubbing equipment failure

2

2

X-mas tree failure

1

1

Packer plug failure

1

1

Tubing to annulus leak - tubing burst

3

3

Tubing leakage

1

1

SCSSV/storm choke failure

2 2 2

6

Well test string barrier failure 1

1

2

Wireline stuffing box failure

1

1

Wireline lubricator failure

1

1

Other

2

1

3

Unknown

1

1

2

Total No. of primary barrier failures 6 2 7 2 1 9 27 3 5 2 64

Incidents with two prim. barrier failures 2 2

Well release Total 6 2 7 2 1 9 25 3 5 2 62

Unknown Unknown

1

1

Unknown Total

1

1

Total all 18 45 40 46 1 20 48 13 9 4 244

Page: 34 Blowout and Well Release Characteristics and Frequencies, 2011 version Table 4.10 Secondary barrier failure causes listed in the database for the US GoM OCS, UK,

and Norwegian blowouts/well releases in the period Jan. 1980 - Dec. 2009.

Category Secondary barrier failure Dev.drlg Expl.drlg Unk drlg Comp-

letion Work-over

Prod-uction

Wire-line

Un-known

Total Deep Shal. Deep Shal. Deep


String safety valve failed

1

1 2

4

String safety valve not available

1

1 2

4

Failed to stab kelly valve

1

3 3

7

SCSSV/storm choke failed

1

1

X-mas tree failed

1

5 2

8

Failed to close BOP 1

2 1

3 7

14

Diverted - no problem

1

1

Failed to operate diverter

3

3

Diverter failed after closure

7 1 8

16

Drilling without riser

2

11

13

Disconnected riser

1

1

Annulus valve failed

1

1

Not sufficient frictional backpressure

1

1

BOP failed after closure 2 1 5

1

9

BOP/diverter not in place 3 4 3 2

1 13

Wellhead failed

2

1

3

Casing head failed

1

1

2

Tubing to annulus communication

1 1

2

Poor cement

3 3

6

Casing valve failure

1

1

2

Wellhead seal failed

1

1

Outer casing failed

1

1

Inner casing failed 1

1

2

Fracture at csg shoe

2 4

1

7

Casing leakage

1 4 1

2 2

10

Formation breakdown 1 1

2

Not relevant

2

4

2

8

Unknown

1

1

1

3

Total no. of secondary barrier failures 8 25 27 34 10 26 10 4 1 145

Incidents with two sec. barrier failures

2 4 2

3 1

12

Blowout (surface flow) total 8 23 23 32 10 23 9 4 1 133


Failed to close BOP

1

1


1

1

Fracture at csg shoe 1 1 1

3

Casing leakage

2

1

3

Formation breakdown 2

2

4

Unknown 1

3

1 5

Total no. of secondary barrier failures 4 2 9 1 1 17


1 1

2

Blowout (underground flow) total 4 1 8 1 1 15


Failed to close BOP

1

1

2


19

12

31

Diverted well release total 19 1 12 1 33

Well release

String safety valve failed

1

1

2

String safety valve not available

1

1

Failed to stab kelly valve

2

1 1

4

Wireline BOP/lubricator not installed

1

1

Wireline BOP/lubricator failed

1

1

SCSSV/storm choke failed

1 1

2

X-mas tree failed

1 1 1

3

Coiled tubing stuffing box failed

1

1

Failed to close BOP 3

1

1 4 7 1

17


1

1

Drilling without riser

1

1

Not sufficient frictional backpressure

1 1

1 6

9

BOP failed after closure

2

2

Wellhead failed

1

1

Wellhead seal failed

1

1

2

Outer casing failed

1

1

Fracture at csg shoe 1

1

Not relevant 1

1 2

4

Other

1 2 3

Unknown 1

1

1

1 1

5

Well release total 6 2 7 2 1 9 25 3 5 2 62

Unknown Unknown

1

1

Unknown total 1 1

Total no. of secondary barrier failures 18 48 45 48 1 20 51 14 9 4 258


3 5 2

3 1

14

Total 18 45 40 46 1 20 48 13 9 4 244


4.8 Operations and Activities when Blowout/Well Release Occurs

In Table 4.11 to Table 4.16 an overview of the operations and activities in progress when the

blowouts/well releases occurred is presented for the various operational phases.

The data is from the US GoM OCS, UK, and Norwegian blowouts/well releases in the period

1980-01-01 - 2009-12-31.

Table 4.11 Operations and activities in progress when the shallow gas blowouts/well releases

occurred

Operation

Activity

Drilling activity Casing running Other/unknown

operations Total

Dev. Expl. Dev. Expl. Dev. Expl. Dev. Expl. Total

Blowout (surface flow) Actual drilling 3 15

3 15 18

Well suspended

1 1 1

Tripping out 6 2

6 2 8

Out of hole

1

1 1

Coring

1

1 1

Milling

1 1 1

Cementing casing

1 1 1 1 2

Wait on cement

9 3 9 3 12

Install BOP

1 1 1

Nipple down BOP 1 1 1

Changing equipment

1

1 1

Wait on weather

1 1 1 1 2

Unknown 1 4

1 1 2 5 7

Total no. of activities 10 24 11 4 3 4 24 32 56

No. of blowouts listed with two activities

1

1 No. of blowouts (surface flow) 10 24 10 4 3 4 23 32 55


Wait on cement 1 1 1

No. of blowouts (underground flow) 1 1 1


Actual drilling 4 9 4 9 13

Tripping out 8 1 8 1 9

Circulating 1 1 1

Casing running 2 2 2

Cementing casing 1 1 1

Wait on cement 4 4 4

Unknown 1 1 1

No. of diverted well releases 13 9 6 1 2 19 12 31

Well release

Actual drilling 1 1 1

Tripping out 1 1 1

Leak off test 1 1 1

Unknown 1 1 1

No. of diverted well releases 1 1 1 1 2 2 4


No. of incidents listed with two activities

1

1 1

Total no. of incidents 24 34 18 5 3 7 45 46 91

Page: 36 Blowout and Well Release Characteristics and Frequencies, 2011 version Table 4.12 Operations and activities in progress when the “deep” drilling blowouts/well

releases occurred

Operation

Activity

Drilling activity Casing running Other/unknown

operations Total

Dev. Expl. Dev. Expl. Dev. Expl. Unk. drlg

Dev. Expl. Unk. drlg

Total

Blowout (surface flow) Actual drilling 1 10 1 10 11

Tripping out 3 3 3

Out of hole 1 1 1

Circulating 1 1 1

Casing running 1 1 1

Cementing casing 1 1 1

Wait on cement 3 3 3 3 6

Cement squeeze 1 1 1

Install BOP 1 1 1

Nipple down BOP 2 2 2

Actual well test 1 1 1

Pull wireline 1 1 1 1 2 3

Unknown 1 1 1


No. of blowouts listed with two activities 2 2 2

No. of blowouts (surface flow) 2 15 4 7 2 1 8 23 31


Actual drilling 3 4 3 4 7

Logging 1 1 1

Unknown 1 3 4 4

No. of blowouts (underground flow) 4 5 3 4 8 12

Well release

Actual drilling 4 4 4

Tripping out 1 1 1

Circulating 1 1 1 1 2

Pulling casing 1 1 1

Pull/drill out well plugs 1 1 1 1 2

Actual well test 1 1 1 1 2

Gravel pack 1 1 1

Maintenance surface equipment 1 1 1

Well closed in 1 1 1

Unknown 1 1 1


No. of well release listed with two activities 1 1 1

No. of well releases 5 2 1 6 1 6 8 1 15

Unknown

Unknown 1 1 1

No. of unknown incidents 1 1 1

Total no. of incidents 11 22 4 7 3 11 1 18 40 1 59

Blowout and Well Release Characteristics and Frequencies, 2011 version Page: 37 Table 4.13 Operations and activities in progress when the completion blowouts/well releases

occurred Operation

Activity

Running/-installing well

equipment

Well testing incl.

preparations

Circu-lating

Perfo-rating

Coiled tubing

Other/-unknown

Total

Blowout (surface flow) Tripping out

2 2

Circulating

1

1

Killing

1

1

Perforating

1

1

Gravel pack 2

2

Cleaning well 1

1

Other , bleed off pressure above SCSSV 1

1

Unknown

1 1

No. of blowouts (surface flow) 4 2 1 3 10

Diverted well release Circulating

1 1

No. of diverted well releases

1 1

Well release Tripping out

1

1 2

Tripping in

1

1

Flow check 1

1

Pull tubing

1 1

Perforating

1

1

Gravel pack 1

1

Cleaning well

1

1

Maintenance well equipment 1

1

2

Total no. of activities 3 2 1 1 1 2 10

No. of well releases listed with two activities

1

1

No. of well releases 3 1 1 1 2 9

Total no. of incidents 7 1 3 2 1 6 20

Page: 38 Blowout and Well Release Characteristics and Frequencies, 2011 version Table 4.14 Operations and activities in progress when the workover blowouts/well releases

occurred

Operation

Activity

Pulling well

equip-ment

Run-ning well

equip-ment

Inst-alling equip-ment

Well testing

incl. prepare

Circ-ulat-ing

Per-for-

ating

Snubb-ing

Coiled tubing

Aban-don well

Temp plu-

gged

Wire-line

opera-tions

Total


Tripping out 2

2

Tripping in

1

1

Out of hole

1

1

Circulating 1

1

2

Pulling casing 1

1

Cement squeeze

1

1

Set well plug

1

1

Pull tubing 1

1

2

Perforating

1

1

Gravel pack

1

1

Cleaning well

1

1

2

Coiled tubing operation

1 1

2

Snubbing in

1 2 1

4

Other

2

2

Unknown

1

1


24

No. of blowouts with two activities

1

1

No. of blowouts (surface flow) 5 1 2 1 2 1 3 3 5

23

Well release

Circulating 1

1

2

Pulling casing 1

1

Install BOP

1

1

Pull/drill out well plugs 1

1

1 1 4

Nipple down x-mas tree

1

1

Snubbing out

2

2

Pull tubing 8

2

10

Acidizing

1

1

Run coiled tubing

1

1

Coiled tubing operations

1

1

Changing equipment

1

1

No. of well releases 11

2

2 2 2 4 1 1 25

Total no. of incidents 16 1 4 1 2 3 5 5 9 1 1 48

Table 4.15 Operations and activities in progress when the production blowouts/well releases

occurred Operation

Activity Producing

oil Producing

condensate Producing

gas Closed in gas/-

condensate well Unknown Total

BLOWOUT

Maintenance well equipment 1 1

Regular production 1 4 1 6

Failure diagnosing 2 2

No. of blowouts 1 4 3 1 9

BLOWOUT (UNDERGROUND FLOW)

Failure diagnosing 1 1

No. of blowouts (underground flow) 1 1

WELL RELEASE

Regular Production 2 1 3

No. of well releases 2 1 3

TOTAL NO. OF INCIDENTS 1 2 5 4 1 13

Blowout and Well Release Characteristics and Frequencies, 2011 version Page: 39 Table 4.16 Operations and activities in progress when the wireline blowouts/well releases

occurred Operation

Activity Rigging up wireline

equipment Running wireline

operations

Total

BLOWOUT (SURFACE FLOW)

Run wireline 2 2

Pull wireline 1 1

Logging 1 1

No. of blowouts 4 4

WELL RELEASE

Changing Equipment 1 1

Run wireline 2 2

Pull Wireline 1 1

Unknown 1 1

No. of well releases 1 4 5

Total no. of incidents 1 8 9

One of the blowout listed with “Unknown” as Phase was a Blowout (underground flow) with

no information related to operation and activity. The other blowout listed with “Unknown” as

Phase was a Blowout (surface flow) with installing equipment listed as operation and nipple

down BOP as activity.

4.9 Exploration Wildcats vs. Exploration Appraisal Blowouts/well releases

The incidents occurring during drilling in exploration wells for the US GoM OC, UK waters

and Norwegian waters are also categorized in exploration wildcats and exploration appraisal

incidents. Table 4.17 shows the number of exploration wildcats and exploration appraisal

blowouts/well releases.

Table 4.17 Exploration wildcats and Exploration appraisal blowouts/well releases for the US

GoM OCS, UK, and Norwegian in the period Jan. 1980 - Dec. 2009 Main category Shallow or deep Exploration well type No of incidents


Deep

Appraisal 10

Wildcat 13

Shallow

Appraisal 12

Wildcat 19

Unknown 1

Blowout (surface flow) total 55

Blowout (under-ground flow) Deep Appraisal 1

Wildcat 7

Blowout (underground flow) total 8


Deep Wildcat 1

Shallow Appraisal 5

Wildcat 7

Diverted well release total 13

Well release

Deep

Appraisal 3

Wildcat 3

Unknown 1

Shallow Appraisal 1

Wildcat 1

Well release total 9

Unknown Deep Appraisal 1

Unknown total 1

Total all exploration incidents 86

4.10 Blowouts from Australia, Canada East Coast, The Netherlands, and US/California OCS

Exposure data from Australia, Canada East Coast, The Netherlands and US/California OCS

has been included in this report (Section 5). The associated blowouts and well releases are,


however, not included in the previous chapters of the report. Table 4.18 and Table 4.19 list

key data for the observed blowouts in these areas in the period 1980-01-01 - 2009-12-31.

Table 4.18 Key data for blowouts observed blowouts/well releases for the Canadian East

Coast, and Australian waters Id_no 259 266 268 548 590

Country Canada East Coast Canada East Coast

Australia Australia Australia

Phase Expl.drlg Expl.drlg Production Expl.drlg Dev.Drlg

Category Blowout (surface flow) Blowout (underground flow)




Sub category Totally uncontrolled flow, from a deep zone

Underground flow only


Underground flow only


Date 22-Feb-84 20-Sep-84 17-Dec-84 07-Feb-1991 21-Aug-2009

Flow medium Condensate, Gas (deep) Gas (deep) Oil, Gas (deep) Gas (deep) Oil, Gas (deep)

Ignition type NO NO NO NO Yes

Duration days 10 270 10 Unknown 73

Loss of primary barrier

C14.Casing plug failure (HP zone isolating bridge plug broke at 5200 meters)

A8.Too low hyd. head - unexpected high well pressure

C4.Tubing to annulus com-munication - equipm./nip-ple failure (assumed)

A15.Too low hyd. head - unknown why

C14.casing plug failure

Loss of secondary barrier

B1.Failed to close BOP (First annular, obstruction in BOP,then S/R,- to little power to cut, then acoustic close failed)

D2.Casing leakage

D2.Casing leakage (assumed)

D3.Formation breakdown

Not relevant

Operation D4.Well testing (preparing to test shallow zone)

D1.Drilling activity P1.Producing oil Unknown A10.well suspended

Activity B1.Circulating A7.Fishing P1.Regular production

Unknown D7.temporary plugged

Data quality Very good Fair Very low Low Very good

Table 4.19 Key data for blowouts observed blowouts/well releases for the Dutch waters and

US California OCS Id_no 405 618 449 475 482 539

Country Netherlands Netherlands US/California OCS

US/California OCS

US/California OCS

US/California OCS

Phase Production Workover Workover Workover Dev.drlg Workover

Category Blowout (surface flow)

Well release Well release Well release Well release Blowout (surface flow)

Sub category Totally uncontrolled flow, from a deep zone




Shallow gas controlled flow (diverted)


Date 15-May-83 01-April 2010 7-Mar-98 19-Nov-00 24-Mar-01 18/11/2004

Flow medium Gas (deep) Gas (deep) Gas (deep), Water

Oil, Water Mud Gas (deep)

Ignition type NO NO NO NO NO NO

Duration days 10 10 minutes (assumed)

Unknown Unknown 0.0104 (15 mins)

0.1042 (2.5 hrs)

Loss of primary barrier

C3.Tubing to annulus communication - tubing leakage

C15. Snubbing equipment failure

A15.Too low hyd. head - unknown why

C13.Tubing plug failure

A10.Too low hyd. head - annular losses

A10.Too low hyd. head - annular losses. (Stop pumping for 30 minutes for removal of lock down pin)

Loss of secondary barrier

D2.Casing leakage B1.Failed to close BOP. Closed after string ejected from the well

Not relevant Not relevant B10.Diverted - no problem

B4.Wellhead failed (removed lock down pin)

Operation P2.Producing gas W8.snubbing W1.Pulling well equipment

W1.Pulling well equipment

D1.Drilling activity

W3.Installing equipment

Activity P1.Regular production

F9.snubbing in A2.Tripping out D6.Pull/drill out well plugs

Unknown G4.Maintenance surface equipment

Data quality Fair Low Fair Low Good Very good


5. “Normal” Drilling and Production Exposure Data

The exposure date in this section of the report includes yearly well drilling and no. of wells in

production for some specific areas. The offshore drilling wells are from Norway, UK, US

GoM OCS, East Coast of Canada and the Netherlands. The production data stems from

Norway, UK, and US GoM OCS.

The format of the exposure data varies for the different areas.

5.1 Drilling Exposure Data

5.1.1 US GoM OCS

The drilling exposure data for the US GoM OCS stems from a computerised list of all wells

drilled (/1/). A version from November 2011 was used for this report. The file includes

information on borehole activities such as drilling activity, counts on the number of boreholes

completed, and number of shut-in's. Additional information includes the lease number, well

name, and spud date, the well class, surface area/block number, well depths, and statistics on

well status summary. Per November 2011 the data-file includes information from more than

51 700 wells drilled all time in the US GoM OCS.

The number of wells drilled in the US GoM OCS area is presented in Table 5.1.

Page: 42 Blowout and Well Release Characteristics and Frequencies, 2011 version Table 5.1 Number of drilled wells in US GoM OCS area

Spud year

Exploration wells Development wells

Wildcat* Appraisal* Total All wells

inc. sidetracks

Side-tracked wells***

All wells inc.

sidetracks


All wells inc.

sidetracks


Completed wells**

All wells inc.

sidetracks


Completed wells**

1980 140 11 253 21 393 32 104 904 118 529

1981 162 10 218 22 380 32 99 965 125 571

1982 204 22 217 27 421 49 112 912 100 560

1983 187 16 230 29 417 45 112 828 142 511

1984 371 35 254 34 625 69 161 816 151 511

1985 312 28 238 48 550 76 147 745 157 439

1986 169 27 117 17 286 44 77 483 109 286

1987 213 30 220 36 433 66 116 496 104 301

1988 342 51 240 47 582 98 154 481 106 302

1989 228 26 254 43 482 69 132 558 115 348

1990 281 33 240 38 521 71 141 621 197 377

1991 168 21 179 20 347 41 98 475 142 285

1992 113 14 115 15 228 29 57 372 115 223

1993 179 20 182 45 361 65 98 624 218 385

1994 230 21 208 34 438 55 120 661 262 379

1995 201 36 194 52 395 88 110 765 337 431

1996 263 42 200 49 463 91 127 775 335 463

1997 291 58 254 69 545 127 153 905 453 565

1998 267 79 229 101 496 180 149 646 383 446

1999 201 55 169 69 370 124 121 669 370 462

2000 223 53 219 53 442 106 146 938 602 659

2001 229 56 182 56 411 112 123 851 542 531

2002 174 43 135 35 309 78 112 633 358 337

2003 200 62 154 57 354 119 114 539 306 309

2004 201 55 162 66 363 121 132 553 301 322

2005 191 66 164 64 355 130 109 457 273 251

2006 242 79 171 81 413 160 153 359 196 212

2007 178 59 122 52 300 111 102 316 174 186

2008 128 44 139 75 267 119 91 299 189 168

2009 91 30 56 30 147 60 46 173 103 99

Total 6379 1182 5715 1385 12094 2567 3516 18819 7083 11448

* To differ between Wildcats and Appraisal wells the following has been assumed; All exploration wells drilled in certain areas are numbered from 1 and further, where well number 1 is the first well drilled. For US GoM OCS all exploration wells numbered as 1 have been regarded as Wildcats, while all the other wells are regarded as Appraisal wells. This may be inaccurate, but this will likely lead to an underestimation of no. of Wildcats compared to no. of Appraisal wells for the US GoM OCS

** In the 2000 version and earlier versions of this report the number of completed wells as listed in the source file was used directly for this column. Closer investigation showed that when a production well is abandoned it would be re-categorized to abandoned. This will lead to an underestimation of number of completed wells. To adjust the figure to a more correct number 30 % of all exploration wells and 70% of all development wells are assumed to be completed each year for the whole period 1980 – 1999. These figures stems from the average in the period 1992 – 1997.

*** No. of sidetracks are from 2011 version based on the API numbering instead of a well Status code as used in earlier version. This has caused an approximately reduction in the number of side tracked wells for exploration wells and an increase for development wells

As seen from Table 5.1 many of the US GoM wells are side-tracked. The wells in the Gulf of

Mexico are primarily side-tracked for deflecting the direction of the borehole to encounter an

alternate target horizon or potential productive interval at a selected aerial location. Deviation

of a well bore to bypass junk in the hole is not classified as a side-track.

Quite a number of wells in the Gulf of Mexico are completed in producing intervals at subsea

depths between 1000 feet and 10 000 feet. In areas where the geology and formation

pressures have previously been established, such development wells are routinely drilled in

from 1 to 10 days, due to the unconsolidated nature of the formations at depths above 10 000

feet.

It should further, be noted that the drilling period for many of the US GoM wells is of very

short duration. If looking at all the wells (1980 – 2006);

Approximately 26 % of the development wells were drilled in less than 10 days.

Approximately 20 % of the exploration wells were drilled in less than 10 days.


5.1.2 United Kingdom

The drilling exposure data for UK is based on the Department of Trade and industry web

page (https://www.og.decc.gov.uk/information/bb_updates/appendices/Appendix4.htm). The

number of wells drilled in the UK area is presented in Table 5.2. It should be noted that a

change of data source have increased the number of wells drilled with approximately 3%,

compared to the number of wells reported the previous years.

Table 5.2 Number of drilled wells in UK offshore sector

Year

Exploration wells Development wells

Wild cat Appraisal Total All wells inc.

sidetracks Sidetrack-ed wells

All wells inc. sidetracks

Sidetrack-ed wells

All wells inc. sidetracks

Sidetrack-ed wells

1980 32 1 22 0 54 142 16

1981 47 0 26 1 73 146 10

1982 68 5 48 5 116 133 11

1983 79 7 56 8 135 102 12

1984 107 5 84 7 191 123 13

1985 91 4 63 1 154 149 16

1986 75 4 43 5 118 99 12

1987 74 5 69 12 143 140 18

1988 93 7 79 18 172 175 6

1989 94 7 83 13 177 154 12

1990 157 12 67 11 224 124 17

1991 103 3 78 21 181 150 25

1992 77 13 55 15 132 170 29

1993 51 2 60 12 111 169 37

1994 61 2 39 14 100 208 54

1995 60 10 34 8 94 266 62

1996 71 4 42 10 113 283 84

1997 59 2 36 12 95 255 80

1998 46 4 32 16 78 289 102

1999 18 2 17 3 35 237 91

2000 27 4 34 12 61 225 84

2001 24 3 35 19 59 286 118

2002 16 2 29 11 45 260 129

2003 26 2 19 9 45 207 83

2004 30 4 34 12 64 167 69

2005 41 8 37 15 78 228 98

2006 29 1 41 17 70 202 83

2007 34 2 77 35 111 165 82

2008 44 3 61 26 105 170 99

2009 23 2 41 22 64 131 53

Total 1757 130 1441 370 3198 5555 1605

5.1.3 Norway

The drilling exposure data for Norway is based on the NPD Borehole list as published on the

Internet (http://www.npd.no/engelsk/cwi/pbl/en/index.htm).

NPD has from 2001 changed the well naming. This is also reflected in their borehole lists

published on the Internet.

The tables presenting number of drilled wells in earlier versions of this report have been

based on the number of wellbores. A wellbore is now categorized as;

Initial well bore

Re-entry

Sidetrack

https://www.og.decc.gov.uk/information/bb_updates/appendices/Appendix4.htm

http://www.npd.no/engelsk/cwi/pbl/en/index.htm


Earlier another category named technical sidetrack also was included. This category is not

used anymore. The practical effect is that the number of wells drilled has been reduced. The

NPD wellbore categorizing can be downloaded from the NPD homepage.

The number and type of development wells are presented in Table 5.3. Table 5.4 presents the

exploration wells drilled in the Norwegian area alongside the total number of development

wells and the type of well bore. Table 5.5 shows the number of Norwegian wells drilled

within each main NCS area

Table 5.3 Norwegian development wells drilled

Spud year

Production Injection Obser-vation

All wells Oil Gas

Oil/-gas

Gas/-conden

sate

Other/-un-

known Total Water Gas

Water/-gas

Other/-un-

known Total

1980 20 6 26 2 2 28

1981 8 5 13 1 2 3 16

1982 12 6 18 3 2 5 23

1983 14 1 15 6 3 9 24

1984 16 10 26 7 1 8 34

1985 25 11 36 10 2 12 48

1986 37 4 41 7 2 9 50

1987 25 13 38 9 1 10 48

1988 38 4 42 12 1 13 55

1989 45 3 48 16 3 19 67

1990 35 4 39 19 2 21 60

1991 50 1 51 12 1 13 1 65

1992 55 7 62 15 1 16 8 86

1993 69 7 76 15 3 18 11 105

1994 71 6 1 78 25 4 29 13 120

1995 59 11 2 72 19 3 1 23 14 109

1996 84 20 3 107 9 5 3 17 20 144

1997 73 19 1 93 5 10 1 1 17 26 136

1998 87 10 97 14 8 1 23 19 139

1999 89 8 1 98 17 3 6 26 25 149

2000 110 16 2 3 131 14 10 2 26 29 186

2001 123 13 2 138 15 4 2 2 23 39 200

2002 106 9 2 117 15 6 2 2 25 26 168

2003 111 7 2 2 122 14 2 6 3 25 18 165

2004 96 4 1 6 1 108 10 4 14 16 138

2005 100 9 2 10 121 8 2 1 11 18 150

2006 92 8 3 2 105 9 5 3 2 19 25 149

2007 101 5 5 5 1 117 15 1 1 2 19 17 153

2008 81 7 4 5 3 100 15 4 6 2 27 11 138

2009 84 8 10 10 3 115 17 1 5 23 25 163

Total 1916 241 28 40 25 2250 353 92 37 23 505 361 3116

http://www.npd.no/Global/Norsk/5%20-%20Regelverk/Tematiske%20veiledninger/B_og_b_betegnelser_og_klassifiserin.pdf


Table 5.4 Number of drilled wells and type of well bore in Norwegian offshore sector

Drilled year

Exploration wells Development

Appraisal Wildcat Total explor-ation

Initial Multi-lateral

Side-track

Total develop-

ment Initial Re-

entry Side-track

Total Initial Re-entry

Side-track

Total

1980 10 1 11 26 5 31 42 27 0 1 28

1981 15 1 16 24 3 27 43 16 0 0 16

1982 13 1 1 15 35 2 37 52 21 0 2 23

1983 10 2 12 30 30 42 21 0 3 24

1984 13 3 16 33 3 1 37 53 31 0 3 34

1985 20 1 21 30 2 32 53 47 0 1 48

1986 12 2 1 15 22 5 1 28 43 35 0 15 50

1987 11 3 1 15 24 3 27 42 36 0 12 48

1988 8 2 3 13 18 18 31 46 0 9 55

1989 5 4 2 11 21 3 24 35 47 0 20 67

1990 9 4 2 15 25 6 31 46 43 0 17 60

1991 11 7 3 21 33 3 36 57 52 0 13 65

1992 10 5 15 27 2 1 30 45 65 0 21 86

1993 7 4 11 19 4 1 24 35 75 0 30 105

1994 2 3 1 6 17 3 1 21 27 78 1 41 120

1995 10 1 4 15 22 3 25 40 73 0 36 109

1996 8 1 2 11 20 1 21 32 92 1 51 144

1997 8 1 4 13 33 4 5 42 55 81 1 54 136

1998 6 2 2 10 15 3 18 28 90 3 46 139

1999 6 1 1 8 12 1 3 16 24 94 1 54 149

2000 4 2 6 18 3 21 27 108 10 68 186

2001 5 2 4 11 24 3 1 28 39 91 19 90 200

2002 2 2 3 7 11 1 3 15 22 74 18 76 168

2003 6 2 2 10 12 2 2 16 26 59 32 74 165

2004 4 4 8 10 10 18 60 29 49 138

2005 3 2 5 9 9 14 56 33 61 150

2006 8 1 9 14 1 4 19 28 57 37 55 149

2007 9 4 13 19 19 32 52 38 63 153

2008 6 9 15 37 4 41 56 43 37 58 138

2009 8 14 22 40 1 3 44 66 49 34 80 163

Total 249 53 74 376 680 64 33 777 1153 1719 294 1103 3116

Page: 46 Blowout and Well Release Characteristics and Frequencies, 2011 version Table 5.5 Norwegian drilled wells separated on main NCS area

Spud year

Development wells Exploration wells Total all

wells Barents

Sea North Sea

Norwegian Sea

Total Barents

Sea North Sea

Norwegian Sea

Total

1980 28 28 2 39 1 42 70

1981 16 16 3 38 2 43 59

1982 23 23 4 43 5 52 75

1983 24 24 6 29 7 42 66

1984 34 34 7 39 7 53 87

1985 48 48 8 29 16 53 101

1986 50 50 4 22 17 43 93

1987 48 48 5 23 14 42 90

1988 55 55 4 21 6 31 86

1989 67 67 4 28 3 35 102

1990 60 60 1 35 10 46 106

1991 65 65 3 46 8 57 122

1992 84 2 86 3 37 5 45 131

1993 94 11 105 2 25 8 35 140

1994 107 13 120 22 5 27 147

1995 104 5 109 32 8 40 149

1996 132 12 144 24 8 32 176

1997 119 17 136 36 19 55 191

1998 113 26 139 21 7 28 167

1999 117 32 149 13 11 24 173

2000 155 31 186 4 12 11 27 213

2001 167 33 200 4 21 14 39 239

2002 150 18 168 17 5 22 190

2003 145 20 165 20 6 26 191

2004 1 115 22 138 12 6 18 156

2005 8 115 27 150 3 6 5 14 164

2006 1 122 26 149 6 13 9 28 177

2007 134 19 153 3 20 9 32 185

2008 119 19 138 8 32 16 56 194

2009 135 28 163 48 18 66 229

Total 10 2745 361 3116 84 803 266 1153 4269

5.1.4 The Netherlands

The drilling exposure data for The Netherlands is based on information from the NL Oil and

Gas Portal (http://www.nlog.nl/nl/activity/activity.html). The number of wells drilled in the

Dutch Continental Shelf is presented in Table 5.6.

http://www.nlog.nl/nl/activity/activity.html

Blowout and Well Release Characteristics and Frequencies, 2011 version Page: 47 Table 5.6 Number of drilled wells on the Dutch Continental Shelf

YEAR Exploration wells Development wells

Total all wells Exploration Appraisal Total

1980 26 5 31 7 38

1981 15 17 32 5 37

1982 35 10 45 20 65

1983 31 12 43 15 58

1984 26 7 33 24 57

1985 36 7 43 35 78

1986 25 5 30 15 45

1987 22 5 27 13 40

1988 21 5 26 21 47

1989 23 5 28 17 45

1990 29 6 35 14 49

1991 43 2 45 18 63

1992 19 1 20 15 35

1993 13 1 14 17 31

1994 10 2 12 10 22

1995 5 3 8 16 24

1996 24 5 29 6 35

1997 21 10 31 13 44

1998 17 3 20 13 33

1999 12 2 14 6 20

2000 6 6 12 9 21

2001 15 4 19 12 31

2002 16 3 19 13 32

2003 7 4 11 13 24

2004 11 2 13 6 19

2005 4 1 5 8 13

2006 9 3 12 16 28

2007 5 2 7 12 19

2008 8 3 11 13 24

2009 7 3 10 11 21

Total 541 144 685 413 1098

5.1.5 Canadian East Coast

Table 5.7 shows the number of wells drilled on the Canadian East Coast. Before 1980

approximately 225 wells were drilled. (http://basin.gdr.nrcan.gc.ca/index_e.php). There has

in addition been drilled approximately 160 well in the Northern areas all time. No detailed

data has, however, been made available from this area. Some drilling activity is also carried

out on the West Coast of Canada.

http://basin.gdr.nrcan.gc.ca/index_e.php

Page: 48 Blowout and Well Release Characteristics and Frequencies, 2011 version Table 5.7 Number of drilled wells on the Canadian East Coast

Year

Exploration Development

Total Wild cat Delination

Total Original drilling

Re-entry Total Original drilling

Re-entry Original drilling

Re-entry

1980 8 4 5 1 18 18

1981 11 2 3 2 18 18

1982 15 5 1 1 22 22

1983 14 6 4 1 25 25

1984 21 4 5 30 1 1 31

1985 13 9 8 7 37 1 1 38

1986 9 3 4 1 17 17

1987 4 1 4 2 11 11

1988 6 2 2 4 14 14

1989 1 1 2 2

1990 1 1 1

1991 4 4 4 1 5 9

1992 4 3 7 7

1993 10 1 11 11

1994 2 4 6 6

1995 1 2 3 3

1996 1 1 2 1 3 4

1997 1 1 6 6 7

1998 1 1 2 21 7 28 30

1999 5 4 9 15 22 37 46

2000 6 1 5 12 15 23 38 50

2001 6 6 12 8 20 26

2002 7 1 8 25 8 33 41

2003 7 2 9 19 12 31 40

2004 2 2 22 11 33 35

2005 4 3 7 16 17 33 40

2006 4 8 1 13 12 13 25 38

2007 3 1 4 8 6 14 18

2008 1 2 3 8 5 13 16

2009 1 1 8 5 13 14

Total 153 38 65 21 277 212 149 361 638


5.1.6 US Pacific OCS

Table 5.8 shows the number of wells drilled on the in the US Pacific OCS area. The data

stems from MMS Pacific Division.

Table 5.8 Number of drilled wells in the US Pacific OCS area

Year Expl. wells spudded Dev. wells spudded Total

1980 10 40 50

1981 14 50 64

1982 27 58 85

1983 38 44 82

1984 19 45 64

1985 6 39 45

1986 5 34 39

1987 4 39 43

1988 3 29 32

1989 4 15 19

1990 17 17

1991 8 8

1992 5 5

1993 21 21

1994 25 25

1995 19 19

1996 31 31

1997 29 29

1998 19 19

1999 11 11

2000 13 13

2001 16 16

2002 21 21

2003 18 18

2004 20 20

2005 23 23

2006 17 17

2007 12 12

2008 5 5

2009 7* 7

Total 130 730 860

*estimated


5.1.7 Australia

Table 5.9 shows the number of wells drilled on the in Australian waters. The data from 1980

to 2005 stems from Geoscience Australia. Geoscience Australia is the national agency for

geoscience research and geospatial information. The data from 2006 stems from Australia

and APPEA (Australia Petroleum Production and Exploration Association Limited) Quarterly

Drilling Reports.

Table 5.9 Number of drilled wells in Australian waters

Year

Exploration Development

Total all wells

Wildcat Appraisal Total Original

hole Side track

Total Original

hole Side track

Total Original

hole Side track

Total

1980 15 3 18 2 2 20 6 1 7 27

1981 13 13 5 5 18 16 16 34

1982 42 5 47 4 4 51 12 12 63

1983 41 3 44 4 4 48 29 29 77

1984 29 3 32 12 12 44 42 1 43 87

1985 23 23 18 18 41 18 18 59

1986 20 20 7 7 27 19 19 46

1987 9 1 10 6 6 16 21 21 37

1988 27 5 32 9 1 10 42 13 13 55

1989 32 10 42 10 4 14 56 26 1 27 83

1990 46 8 54 19 6 25 79 18 6 24 103

1991 34 5 39 6 4 10 49 17 5 22 71

1992 28 3 31 13 2 15 46 14 1 15 61

1993 36 1 37 14 3 17 54 18 3 21 75

1994 28 6 34 20 1 21 55 28 6 34 89

1995 32 2 34 23 2 25 59 32 8 40 99

1996 34 9 43 15 15 58 34 4 38 96

1997 39 1 40 19 2 21 61 81 14 95 156

1998 61 5 66 10 1 11 77 41 8 49 126

1999 45 5 50 9 9 59 35 3 38 97

2000 60 10 70 4 4 74 22 3 25 99

2001 48 3 51 10 10 61 24 7 31 92

2002 31 4 35 16 3 19 54 26 8 34 88

2003 44 5 49 16 16 65 32 12 44 109

2004 36 36 14 4 18 54 41 7 48 102

2005 45 3 48 14 1 15 63 33 8 41 104

2006 32 3 35 10 1 11 46 27 2 29 75

2007 37 37 24 2 26 63 27 1 28 91

2008 49 5 54 16 16 70 45 8 53 123

2009 48 48 20 1 21 69 43 3 46 115

Total 1064 108 1172 369 38 407 1579 840 120 960 2539

Government of Western Australian, Department of Mines and Petroleum, reports number of

wells drilled in the Western Australia (https://wapims.doir.wa.gov.au/dp/index.jsp).

Approximately 50% of the Australian offshore wells drilled since 1980 have been drilled in

Western Australia. Table 5.10 shows the number of wells drilled on the in the Western

Australian waters.

https://wapims.doir.wa.gov.au/dp/index.jsp

Blowout and Well Release Characteristics and Frequencies, 2011 version Page: 51 Table 5.10 Number of drilled wells in Western Australian waters

Year Development

well Extension

well New Field

Wildcat

New Pool

Wildcat

Water Injector well

Total

1980 1 11 12

1981 3 3 6

1982 1 20 21

1983 3 1 21 25

1984 4 6 14 24

1985 4 9 9 22

1986 5 3 9 17

1987 4 3 3 10

1988 2 2 8 12

1989 6 4 10 20

1990 14 9 14 37

1991 7 4 20 31

1992 4 7 15 26

1993 12 6 20 38

1994 17 14 10 41

1995 10 9 19 38

1996 18 8 21 2 49

1997 13 14 24 51

1998 5 7 34 3 49

1999 10 5 37 2 54

2000 14 4 44 62

2001 16 5 33 54

2002 9 13 24 46

2003 8 17 39 64

2004 21 17 22 60

2005 15 16 28 6 65

2006 24 14 29 5 72

2007 19 14 40 4 77

2008 33 19 22 4 78

2009 21 22 34 4 81

Total 318 257 637 2 28 1242


5.1.8 Denmark

Table 5.11 shows the number of wells drilled on the offshore Denmark. The data stems from The

Danish Energy Authority

(http://www.ens.dk/EN-US/OILANDGAS/REPORTOILGAS/Sider/Forside.aspx)

Table 5.11 Number of drilled wells offshore Denmark

Year Exploration and

appraisal Development Sum

1980 1 7 8

1981 4 9 13

1982 5 18 23

1983 14 13 27

1984 8 15 23

1985 14 18 32

1986 7 3 10

1987 8 3 11

1988 3 13 16

1989 4 9 13

1990 2 15 17

1991 6 14 20

1992 11 15 26

1993 2 30 32

1994 2 15 17

1995 1 16 17

1996 4 13 17

1997 8 15 23

1998 6 23 29

1999 9 17 26

2000 12 17 29

2001 15 29 44

2002 9 27 36

2003 8 24 32

2004 10 23 33

2005 2 10 12

2006 6 20 26

2007 4 20 24

2008 7 15 22

2009 2 14 16

Total 194 480 674

5.1.9 Compiled Drilling Exposure Data

Table 5.12 below is based on Table 5.1 to Table 5.4, and shows compiled offshore drilled

wells in Norway, UK and US GoM OCS.

http://www.ens.dk/EN-US/OILANDGAS/REPORTOILGAS/Sider/Forside.aspx


Table 5.13 is based on Table 5.6 to Table 5.11 and shows compiled offshore drilled wells in

the Netherlands, Canada East Coast, Australia, US Pacific OCS, and Denmark.

Table 5.12 An overview of offshore drilled wells in Norway, UK, and US GoM OCS

Year US GoM OCS UK Norway Total

Expl. Dev. Expl. Dev. Expl. Dev. Expl. Dev.

1980 393 904 54 142 42 28 483 1074

1981 380 965 73 146 43 16 496 1127

1982 421 912 116 133 52 23 589 1068

1983 417 828 135 102 42 24 594 954

1984 625 816 191 123 53 34 869 973

1985 550 745 154 149 53 48 757 942

1986 286 483 118 99 43 50 447 632

1987 433 496 143 140 42 48 618 684

1988 582 481 172 175 31 55 785 711

1989 482 558 177 154 35 67 694 779

1990 521 621 224 124 46 60 791 805

1991 347 475 181 150 57 65 585 690

1992 228 372 132 170 45 86 405 628

1993 361 624 111 169 35 105 507 898

1994 438 661 100 208 27 120 565 989

1995 395 765 94 266 40 109 529 1140

1996 463 775 113 283 32 144 608 1202

1997 545 905 95 255 55 136 695 1296

1998 496 646 78 289 28 139 602 1074

1999 370 669 35 237 24 149 429 1055

2000 442 938 61 225 27 186 530 1349

2001 411 851 59 286 39 200 509 1337

2002 309 633 45 260 22 168 376 1061

2003 354 539 45 207 26 165 425 911

2004 363 553 64 167 18 138 445 858

2005 355 457 78 228 14 150 447 835

2006 413 359 70 202 28 149 511 710

2007 300 316 111 165 32 153 443 634

2008 267 299 105 170 56 138 428 607

2009 147 173 64 131 66 163 277 467

Total 12094 18819 3198 5555 1153 3116 16445 27490

Page: 54 Blowout and Well Release Characteristics and Frequencies, 2011 version Table 5.13 An overview of offshore drilled wells in Canada East Coast, the Netherlands,

Australia, US Pacific OCS, and Denmark

Year Dutch Canada E. Coast Australia US Pacific OCS Denmark Total

Expl. Dev. Expl. Dev. Expl. Dev. Expl. Dev. Expl. Dev. Expl. Dev.

1980 31 7 18 20 7 10 40 1 7 80 61

1981 32 5 18 18 16 14 50 4 9 86 80

1982 45 20 22 51 12 27 58 5 18 150 108

1983 43 15 25 48 29 38 44 14 13 168 101

1984 33 24 30 1 44 43 19 45 8 15 134 128

1985 43 35 37 1 41 18 6 39 14 18 141 111

1986 30 15 17 27 19 5 34 7 3 86 71

1987 27 13 11 16 21 4 39 8 3 66 76

1988 26 21 14 42 13 3 29 3 13 88 76

1989 28 17 2 56 27 4 15 4 9 94 68

1990 35 14 1 79 24 17 2 15 117 70

1991 45 18 4 5 49 22 8 6 14 104 67

1992 20 15 7 46 15 5 11 15 77 57

1993 14 17 11 54 21 21 2 30 70 100

1994 12 10 6 55 34 25 2 15 69 90

1995 8 16 3 59 40 19 1 16 68 94

1996 29 6 1 3 58 38 31 4 13 92 91

1997 31 13 1 6 61 95 29 8 15 101 158

1998 20 13 2 28 77 49 19 6 23 105 132

1999 14 6 9 37 59 38 11 9 17 91 109

2000 12 9 12 38 74 25 13 12 17 110 102

2001 19 12 6 20 61 31 16 15 29 101 108

2002 19 13 8 33 54 34 21 9 27 90 128

2003 11 13 9 31 65 44 18 8 24 93 130

2004 13 6 2 33 54 48 20 10 23 79 130

2005 5 8 7 33 63 41 23 2 10 77 115

2006 12 16 13 25 46 29 17 6 20 77 107

2007 7 12 4 14 63 28 12 4 20 78 86

2008 11 13 3 13 70 53 5 7 15 91 99

2009 10 11 1 13 69 46 7 2 14 82 91

Total 685 413 277 361 1579 960 130 730 194 480 2865 2944

5.2 Production Exposure Data

5.2.1 US GoM OCS

The production exposure data for US GoM OCS is shown in Table 5.14. The data is based on

MMS Ogor A files from 1986 – 2009 (/1/). These files list the well individual activity for

each month. It was selected to use the data from December each year. All the production

wells listed with production in December are counted as active wells.

Blowout and Well Release Characteristics and Frequencies, 2011 version Page: 55 Table 5.14 Producers in the US GoM OCS area.

Year Oil production Gas production

Total production

Water injection (active or inactive)

Gas injection (active or inactive)

Flowing Gas lift Total

1980 NA NA 3 165 3 023 6 188 107

1981 NA NA 3 260 3 106 6 366 121

1982 NA NA 3 412 3 223 6 635 143

1983 NA NA 3 539 3 243 6 782 187

1984 NA NA 3 688 3 355 7 043 219

1985 2 695 1 101 3 796 3 229 7 025 327 100

1986 2 523 1 206 3 729 3 239 6 968 327 88

1987 2 461 1 284 3 745 3 311 7 056 320 105

1988 2 382 1 361 3 743 3 364 7 107 327 100

1989 2 230 1 270 3 500 3 429 6 929 311 91

1990 2 283 1 246 3 529 3 682 7 211 320 89

1991 2 206 1 339 3 545 3 580 7 125 323 80

1992 2 195 1 311 3 506 3 346 6 852 325 80

1993 2 216 1 326 3 542 3 458 7 000 315 72

1994 2 228 1 286 3 514 3 483 6 997 307 72

1995 2 189 1 258 3 447 3 430 6 877 305 70

1996 2 016 1 424 3 440 3 444 6 884 294 61

1997 2 002 1 434 3 436 3 467 6 903 270 52

1998 1 936 1 364 3 300 3 315 6 615 261 51

1999 1 712 1 538 3 250 3 282 6 532 248 50

2000 1 723 1 590 3 313 3 308 6 621 246 45

2001 1 523 1 716 3 239 3 217 6 456 225 34

2002 1 327 1 782 3 109 2 993 6 102 207 27

2003 1 160 1 926 3 086 3 043 6 129 205 30

2004 1 060 1 539 2 599 2 804 5 403 199 35

2005 719 786 1 505 1 977 3 482 195 15

2006 990 1 333 2 323 2 457 4 780 195 21

2007 1 084 1 607 2 691 2 597 5 288 186 16

2008 744 1116 1 860 1560 3 420 185 13

2009 993 1436 2 429 2005 4 434 163 10

Total (44597) (34579) 96 240 92 970 189 210 7 363 1 407

5.2.2 United Kingdom

The production/injection exposure data for UK is shown in Table 5.15. The figures are valid

for the number of wells that have been in service for the listed year. The data from before

1991 is based on well data systematically collected in the SINTEF study "Reliability of Well

Completion Equipment" SINTEF report STF 75 F92019, "Development of the Oil and Gas

resources of the United Kingdom" 1980, 1992 and 1993 edition, North Sea Field

Development Guide, 4th edition, OPL and coarse assumptions where well data are missing.

The data is therefore not exactly correct. The data from 1991 to 1999 is based on statistics

from Health & Safety Executive (HSE). HSE has now stopped reporting this information on

an individual well basis. They now report the production data for each field.

Deal Data Registry for UK Offshore Oil & Gas (http://www.ukdeal.co.uk/) reports individual

well information, but the quality of information is variable. During the work with the 2011

release an updated version of the data was downloaded. The data was analysed with the

objective to update the production exposure data for the UK. The quality was however low

and the data cannot be used for our purpose. The main problems for 20% of the wells the

detailed data is not released, further that many wells seems to be active producers, but the

platform has been decommissioned, i.e. they should have been categorised as plugged and

abandoned. It is believed that many of the wells the database indicates as active are plugged

and abandoned.

http://www.ukdeal.co.uk/


The Department of Industry was contacted in October 2004 and in January 2007 but they are

referring to Deal that now has the responsibility of reporting on an individual well level. The

last year these data was collected by the Department was in 1999. All they could suggest was

that the oil companies that operate the field or well could be approached and requested for

data. This will be a too time-consuming task.

The exposure data for 2000 - 2009 has therefore been estimated based on the production rates

per year and the number of active wells in 1999. It is assumed that the coarse formula

estimates a too low number of wells in production, because it is likely that the average

production from each well declines every year.

Table 5.15 Producers and injectors in the UK waters

Year Production wells Injection wells Total wells Oil Gas/con Total Gas Water Total

1980 291 249 540 10 92 102 642

1981 318 252 570 11 104 115 685

1982 349 256 605 13 116 129 734

1983 399 258 657 17 140 157 814

1984 448 266 714 22 170 192 906

1985 456 298 754 21 194 215 969

1986 525 322 847 27 206 233 1080

1987 558 355 913 29 218 247 1160

1988 550 390 940 35 217 252 1192

1989 575 419 994 35 227 262 1256

1990 599 474 1073 37 249 286 1359

1991 844 344 1188 68 350 418 1606

1992 918 502 1420 68 363 431 1851

1993 968 549 1517 66 369 435 1952

1994 1041 598 1639 62 399 461 2100

1995 1131 703 1834 60 413 473 2307

1996 1215 695 1910 69 428 497 2407

1997 1252 725 1977 68 434 502 2479

1998 1160 713 1873 58 369 427 2300

1999 1118 678 1796 37 345 382 2178

2000* 1027 742 1769 37 345 382 2151

2001* 953 723 1676 37 345 382 2058

2002* 943 706 1649 37 345 382 2031

2003* 867 699 1566 37 345 382 1948

2004* 777 656 1432 37 345 382 1814

2005* 685 604 1289 37 345 382 1671

2006* 622 548 1170 37 345 382 1552

2007* 624 497 1122 37 345 382 1504

2008* 584 484 1068 37 345 382 1450

2009* 560 407 967 37 345 382 1349

Total 22357 15114 37471 1183 8853 10036 47507

* Data are no longer available from HSE. The number of wells in production has been assumed to be relative to the UK annual oil and gas production. Injection wells remain unchanged.

5.2.3 Norway

Table 5.16 shows the production/injection exposure data for the Norwegian waters. The

figures are valid for the number of wells in service per December 31 the listed year. The data

is from the NPD Annual reports 1980 – 1999, and for the year 1999 and later the data stems

from the NPD Borehole list as published on the Internet

(http://www.npd.no/engelsk/cwi/pbl/en/index.htm).

http://www.npd.no/engelsk/cwi/pbl/en/index.htm

Blowout and Well Release Characteristics and Frequencies, 2011 version Page: 57 Table 5.16 Production/injection exposure data for the Norwegian waters

Year Producers Injection/-observation

Suspended/-closed

in/plugged

Total Oil Cond Gas Other/-

unknown Total

1980 84 29 47 160 8 23 191

1981 89 34 48 171 11 26 208

1982 114 35 47 196 13 24 233

1983 113 32 53 198 17 37 252

1984 128 31 61 220 23 42 285

1985 145 29 61 235 32 60 327

1986 160 38 64 262 41 71 374

1987 176 41 60 277 41 102 420

1988 201 43 65 309 59 110 478

1989 235 38 48 321 74 151 546

1990 258 33 31 322 88 191 601

1991 285 31 33 349 109 207 665

1992 324 29 30 383 116 247 746

1993 371 31 32 434 136 280 850

1994 385 32 34 451 163 357 971

1995 434 35 24 493 180 409 1 082

1996 494 33 53 580 189 459 1 228

1997 519 31 62 612 194 544 1 350

1998 535 25 64 624 211 649 1 484

1999 746 25 83 854 259 549 1 662

2000 787 25 85 897 259 701 1 857

2001 813 21 95 929 266 833 2 028

2002 820 32 101 953 257 1 030 2 240

2003 849 30 97 976 261 1 111 2 348

2004 848 32 97 7 984 264 1 244 2 492

2005 831 3 120 7 961 269 1 411 2 641

2006 863 9 124 11 1 006 278 1 576 2 860

2007 886 12 129 10 1 038 282 1 644 2 964

2008 910 15 135 10 1 070 285 1 712 3 067

2009 1078 22 143 8 1251 317 1 639 3 207

Total 14 481 856 2 126 53 17 516 4 702 17 439 39 657

Note! NPD stopped listing the number of wells in production in the annual reports in 1999. From 1999 the no. of oil producers seems high, and the no. of closed in/suspended wells seems low, compared to the earlier years.

5.2.4 US Pacific OCS

The production exposure data for US Pacific OCS is shown in Table 5.17. The data is based

on MMS Ogor A files (/1/). These files list the well individual activity for each month. It was

selected to use the data from December each year. All the production wells listed with

production in December are counted as active wells.

Page: 58 Blowout and Well Release Characteristics and Frequencies, 2011 version Table 5.17 Producers in the US Pacific OCS area.

Year Oil production Gas production

Total production

Water injection (active or inactive)

Gas injection (active or inactive) Flowing Gas lift Total

1986 262 79 341 20 361 79 6

1987 280 81 361 20 381 84 6

1988 284 83 367 16 383 88 4

1989 293 79 372 13 385 83 4

1990 305 72 377 19 396 83 4

1991 321 65 386 20 406 84 5

1992 340 49 389 19 408 84 4

1993 337 54 391 20 411 88 4

1994 322 79 401 17 418 93 4

1995 300 104 404 17 421 94 6

1996 287 118 405 13 418 84 7

1997 289 107 396 17 413 87 9

1998 285 100 385 19 404 93 13

1999 264 100 364 18 382 93 14

2000 264 103 367 16 383 83 15

2001 255 105 360 17 377 74 11

2002 257 120 377 16 393 97 11

2003 256 122 378 15 393 98 12

2004 251 121 372 15 387 100 14

2005 239 127 366 16 382 104 13

2006 251 121 372 15 387 109 12

2007 241 141 382 8 390 109 14

2008 252 130 382 9 391 117 16

2009 256 125 381 10 391 127 15

Total 6691 2385 9076 385 9461 2235 223

5.2.5 Compiled Production Exposure Data

Table 5.18 is based on Table 5.14, Table 5.15 and Table 5.16, and shows overall production

data for the Norway, UK and US GoM OCS. The figures are valid for number of wells in

service per December the listed year. Note that it has been selected not to include data from

the US Pacific OCS.

Blowout and Well Release Characteristics and Frequencies, 2011 version Page: 59 Table 5.18 Overall production data for the US GoM OCS, UK, and Norway based on Table

5.14, Table 5.15 and Table 5.16. Year US GoM OCS United Kingdom Norway Total

Production wells Inject-ion

wells


wells

Production wells Inje-ction wells


wells Oil Gas/-

cond Total Oil Gas/-



cond Total

1980 3 165 3 023 6 188 107 291 249 540 102 84 76 160 8 3 540 3 348 6 888 217

1981 3 260 3 106 6 366 121 318 252 570 115 89 82 171 11 3 667 3 440 7 107 247

1982 3 412 3 223 6 635 143 349 256 605 129 114 82 196 13 3 875 3 561 7 436 285 1983 3 539 3 243 6 782 187 399 258 657 157 113 85 198 17 4 051 3 586 7 637 361

1984 3 688 3 355 7 043 219 448 266 714 192 128 92 220 23 4 264 3 713 7 977 434

1985 3 796 3 229 7 025 427 456 298 754 215 145 90 235 32 4 397 3 617 8 014 674

1986 3 729 3 239 6 968 415 525 322 847 233 160 102 262 41 4 414 3 663 8 077 689 1987 3 745 3 311 7 056 425 558 355 913 247 176 101 277 41 4 479 3 767 8 246 713

1988 3 743 3 364 7 107 427 550 390 940 252 201 108 309 59 4 494 3 862 8 356 738

1989 3 500 3 429 6 929 402 575 419 994 262 235 86 321 74 4 310 3 934 8 244 738

1990 3 529 3 682 7 211 409 599 474 1073 286 258 64 322 88 4 386 4 220 8 606 783 1991 3 545 3 580 7 125 403 844 344 1188 418 285 64 349 109 4 674 3 988 8 662 930

1992 3 506 3 346 6 852 405 918 502 1420 431 324 59 383 116 4 748 3 907 8 655 952

1993 3 542 3 458 7 000 387 968 549 1517 435 371 63 434 136 4 881 4 070 8 951 958

1994 3 514 3 483 6 997 379 1041 598 1639 461 385 66 451 163 4 940 4 147 9 087 1 003 1995 3 447 3 430 6 877 375 1131 703 1834 473 434 59 493 180 5 012 4 192 9 204 1 028

1996 3 440 3 444 6 884 355 1215 695 1910 497 494 86 580 189 5 149 4 225 9 374 1 041

1997 3 436 3 467 6 903 322 1252 725 1977 502 519 93 612 194 5 207 4 285 9 492 1 018

1998 3 300 3 315 6 615 312 1160 713 1873 427 535 89 624 211 4 995 4 117 9 112 950 1999 3 250 3 282 6 532 298 1118 678 1796 382 746 108 854 259 5 114 4 068 9 182 939

2000 3 313 3 308 6 621 291 1027 742 1769 382 787 110 897 259 5 127 4 160 9 287 932

2001 3 239 3 217 6 456 259 953 723 1676 382 813 116 929 266 5 005 4 056 9 061 907

2002 3 109 2 993 6 102 234 943 706 1649 382 820 133 953 257 4 872 3 832 8 704 873 2003 3 086 3 043 6 129 235 867 699 1566 382 849 127 976 261 4 802 3 869 8 671 878

2004 2 599 2 804 5 403 234 777 656 1432 382 848 129 977 264 4 224 3 589 7 812 880

2005 1 505 1 977 3 482 210 685 604 1289 382 831 123 954 269 3 021 2 704 5 725 861

2006 2 323 2 457 4 780 216 622 548 1170 382 863 133 996 278 3 808 3 138 6 946 876

2007 2 691 2 597 5 288 202 624 497 1122 382 886 141 1027 282 4 201 3 235 7 437 866

2008 1 860 1560 3 420 198 584 484 1068 382 910 150 1060 285 3 354 2 194 5 548 865

2009 2 429 2005 4 434 173 560 407 967 382 1078 165 1243 317 4 067 2 577 6 644 872

Total 96 240 92 970 189 210 8 770 22 357 15 114 37 471 10 036 14 481 2 982 17463 4 702 133 078 111 066 244 144 23 508



6. Various Exposure Data

This section includes various exposure data. Limitations related to the exposure data are

explained where the data is presented. The exposure data presented in this section covers the

following:

1. Well Depth Related Exposure Data

US GoM OCS Wells

Norwegian Wells

2. Water depth related drilling exposure data

US GoM OCS Wells

UK Wells

Norwegian Wells

3. Shut-in Wellhead Pressure Related exposure data

US GoM OCS Drilling Wells

Norwegian Drilling Wells

US Wells in Production

4. Gas Oil Ratio Related Exposure Data

5. Workover Frequency Exposure Data

6. Wireline Frequency Exposure Data

7. Coiled Tubing and Snubbing Exposure Data

Data from the US Mineral Management Service (MMS) and NPD has formed the main input

to this section.

6.1 Well Depth Related Exposure Data

6.1.1 US GoM OCS Wells

The information in this sub-section stems from the BOEM Borehole file (/1/). The drilling

vertical depths for the exploration and development wells in the US GoM OCS are presented

in Figure 6.1. Approximately 0.8 % of the exploration wells and 1.3% of the development

wells were not listed with a True Vertical Depth (TVD). These wells are not included in

Figure 6.1. The deepest exploration well has been drilled to a depth of 10411 m TVD, while

the deepest development well has been drilled to 9881 mTVD.


Figure 6.1 All exploration and development wells drilled in 1980 – 2004 listed with true

vertical depth

6.1.2 Norwegian Wells

For Norwegian wells True Vertical Depth (TVD) of wells is available for neither exploration

nor development wells drilled before 1995. Measured Depths (MD) is, however, available.

For most exploration wells the MD is a good approximation for the TVD. For development

wells the MD will not be a good approximation.

Figure 6.2 shows the true vertical depth for production wells drilled in the period 1995 – mid

1998. Figure 6.3 shows the measured depth for development wells drilled in the period 1980

– 2004. Figure 6.4 shows the measured depth for exploration wells drilled in the period 1980

- 2004. The data shown in Figure 6.2 stems from the NPD Daily Drilling Report system,

Figure 6.3 and Figure 6.4 stems from the NPD well files as published on the Internet.

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

0 % 10 % 20 % 30 % 40 % 50 % 60 % 70 % 80 % 90 % 100 %

Met

ers

(TV

D)

Percentage Distribution

Well depth, US GoM OCS (1980 - 2009)

TVD (m) development wells

TVD (m) exploration wells


Figure 6.2 True Vertical Depth, Norwegian production wells

Figure 6.3 Measured depth for development wells 1980 – 2004

True vertical depth, production wells,

(mainly drilled in 95 - mid 98)

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Percentage distribution (total 478 wells)

TV

D (

m R

KB

)

Development wells, Norwegian waters (1980 - 2004)

0

2000

4000

6000

8000

10000

12000

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Percentage distribution

Measu

red

dep

th (

m)


Figure 6.4 Measured depth, Norwegian exploration wells 1980 – 2004.

6.2 Water Depth Related Drilling Exposure Data

The past years some deepwater blowouts have occurred. This section presents the water related drilling exposure data. Table 6.1 and

Table 6.2 present the water depth specific no. of exploration and development wells drilled in

the US GoM OCS.

Exploration wells, Norwegian waters (1980 - 2004)

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Percentage distribution

Measu

red

dep

th

Blowout and Well Release Characteristics and Frequencies, 2011 version Page: 65 Table 6.1 Exploration wells drilled in the US GoM OCS vs. water depth (/1/) Spud year

Number of wells drilled within water depth range (m)

<50 50-100 100-200 200-400 400-600 600-1000 1000-1500 1500-2000 2000- 2500 2500- 3000 >3000 Total

1980 232 126 19 14 1 1 393

1981 220 113 29 9 9 380

1982 287 94 24 9 7 421

1983 277 85 29 17 8 1 417

1984 362 136 41 36 32 16 2 625

1985 275 118 61 47 27 22 550

1986 133 56 39 20 17 21 286

1987 230 96 51 18 12 16 6 2 2 433

1988 314 104 66 34 25 31 5 1 2 582

1989 253 107 48 20 22 26 5 1 482

1990 286 112 51 15 13 32 9 2 1 521

1991 182 91 25 19 5 18 6 1 347

1992 103 91 14 11 4 3 2 228

1993 194 97 39 12 11 6 2 361

1994 247 107 26 15 6 26 9 2 438

1995 194 99 34 22 14 22 8 2 395

1996 223 112 28 22 10 32 29 5 2 463

1997 239 127 43 27 20 27 53 5 4 545

1998 228 120 23 16 30 33 39 2 4 495

1999 147 97 19 7 14 27 26 26 7 370

2000 216 91 18 9 12 34 34 9 17 2 442

2001 165 58 26 18 7 39 55 24 16 3 411

2002 149 48 8 7 12 23 25 17 17 3 309

2003 176 62 17 9 8 19 29 21 6 6 1 354

2004 174 45 18 19 8 22 27 21 17 12 363

2005 179 47 15 9 7 27 38 17 10 6 355

2006 216 48 15 11 11 30 40 22 19 1 413

2007 123 56 6 3 8 41 28 21 13 1 300

2008 119 26 12 5 2 23 37 22 16 3 2 267

2009 52 7 3 2 1 18 25 20 19 147

Total 6195 2576 847 482 363 635 538 244 173 37 3 12093

Table 6.2 Development wells drilled in the US GoM OCS vs. water depth (/1/) Spud year

Number of wells drilled within water depth range (m) Total <50 50-100 100-200 200-400 400-600 600-1000 1000-1500 1500-2000 2000- 2500 >2500

1980 419 371 73 41 904

1981 535 315 81 34 965

1982 500 328 64 20 912

1983 487 259 61 21 828

1984 474 261 62 19 816

1985 349 294 63 37 2 745

1986 196 190 63 33 1 483

1987 278 127 47 40 4 496

1988 224 152 58 31 14 2 481

1989 264 165 64 45 18 2 558

1990 275 186 108 24 27 1 621

1991 208 148 94 14 7 4 475

1992 188 102 31 41 1 9 372

1993 327 212 43 36 5 1 624

1994 336 233 49 34 5 4 661

1995 364 277 67 30 19 6 1 1 765

1996 380 249 79 36 7 22 2 775

1997 442 310 68 25 27 24 6 1 2 905

1998 323 185 62 36 11 11 16 1 1 646

1999 307 219 45 29 11 27 25 5 1 669

2000 446 302 48 42 8 22 60 9 1 938

2001 417 225 69 35 17 23 36 23 6 851

2002 303 146 21 34 9 24 76 11 9 633

2003 307 90 33 20 8 18 48 12 1 2 539

2004 329 105 33 15 8 15 13 16 19 553

2005 244 135 21 12 14 19 10 1 1 457

2006 202 73 17 9 8 6 36 6 2 359

2007 153 71 28 3 6 13 10 7 25 316

2008 154 73 41 3 10 15 3 299

2009 67 32 19 3 12 22 6 11 1 173

Total 9498 5835 1612 796 242 274 376 101 78 7 18819


Table 6.3 and Table 6.4 present the water depth specific no. of exploration and development

wells drilled in Norwegian waters.

Table 6.3 Exploration wells drilled in UK waters vs. water depth (http://www.ukdeal.co.uk/)

Spud year Number of wells drilled within water depth range (m)*

Total < 50 50-100 100-200 200-400 400-600 600–1000 1000–1500 1500–2000 Unknown

1980 15 49 2 1 3 1 71

1981 2 28 58 2 2 92 1982 23 41 64 2 1 131

1983 34 39 74 2 149

1984 47 65 86 4 6 1 1 210

1985 41 43 81 4 7 176 1986 30 39 61 2 132

1987 43 39 68 2 152

1988 58 46 86 2 192

1989 58 44 95 2 199 1990 60 50 129 2 3 244

1991 48 57 104 1 3 213

1992 29 45 67 1 5 147

1993 31 35 51 6 123 1994 36 25 27 3 11 1 3 106

1995 25 32 33 5 9 4 5 113

1996 28 34 53 3 2 3 1 124

1997 23 23 50 5 1 102 1998 16 24 39 3 2 1 85

1999 6 12 25 1 1 1 46

2000 11 10 29 1 1 3 2 1 58

2001 10 20 46 2 1 79 2002 10 13 17 1 1 2 44

2003 12 14 14 3 1 44

2004 12 15 40 1 3 1 3 75

2005 17 19 51 87 2006 19 31 38 2 2 92

Total 729 858 1535 43 69 25 14 3 10 3286

* Note, the no. of wells is 13% higher than in Table 5.2, page 43 because different sources of information have been used.

Table 6.4 Development wells drilled in UK waters vs. water depth (http://www.ukdeal.co.uk/)

Spud year Number of wells drilled within water depth range (m)*

Total < 50 50-100 100-200 200-400 400-600 600–1000 1000–1500 1500–2000 Unknown

1980 9 11 130 150

1981 12 12 126 150

1982 14 19 105 138

1983 15 15 75 105 1984 26 20 81 2 129

1985 41 20 93 154

1986 35 3 61 99

1987 41 20 81 142 1988 57 33 87 177

1989 59 13 83 1 1 157

1990 41 14 69 2 1 127

1991 48 38 70 1 157 1992 58 32 79 4 173

1993 35 26 105 3 169

1994 40 39 114 1 2 16 212

1995 48 43 146 1 5 21 264 1996 30 68 168 5 12 283

1997 21 56 179 3 3 262

1998 33 67 167 10 7 284

1999 38 55 125 2 12 232 2000 33 37 148 6 4 228

2001 32 41 195 3 9 280

2002 35 51 171 7 6 270

2003 40 44 111 3 8 1 207 2004 13 44 105 2 3 167

2005 33 55 135 4 9 236 2006 17 59 124 7 207

Total 904 935 3133 57 90 3 37 5159

* Note, the no. of wells is 6% higher than in Table 5.2, page 43 because different sources of information have been used.




Table 6.5 and Table 6.6 present the water depth specific no. of exploration and development

wells drilled in Norwegian waters.

Table 6.5 Exploration wells drilled in Norwegian waters vs. water depth Spud year Number of wells drilled within water depth range (m) Total

<50 50–100 100-200 200-400 400-600 600-1000 1000-1500 1500-2000

1980 9 13 20 42 1981 8 22 13 43 1982 18 19 15 52 1983 6 14 22 42 1984 12 12 29 53 1985 3 16 34 53 1986 5 13 24 1 43 1987 4 16 19 3 42 1988 9 7 13 2 31 1989 11 14 9 1 35 1990 19 12 15 46 1991 21 13 22 1 57 1992 10 11 23 1 45 1993 10 11 14 35 1994 1 4 12 10 27 1995 7 24 9 40 1996 7 5 19 1 32 1997 13 19 19 1 1 2 55 1998 4 11 10 3 28 1999 3 5 15 1 24 2000 2 7 15 2 1 27 2001 1 16 19 2 1 39 2002 2 10 7 1 1 1 22 2003 6 11 7 2 26 2004 1 8 9 18 2005 1 2 9 1 1 14 2006 5 6 15 1 1 28 2007 8 10 11 2 1 32 2008 12 11 23 5 1 4 56 2009 5 30 26 2 1 2 66

Total 1 226 380 495 24 10 15 2 1153

Table 6.6 Development wells drilled in Norwegian waters vs. water depth

Spud year Number of wells drilled within water depth range (m) Total <50 50 - 100 100 - 200 200 - 400 400 - 600 600 - 1000 1000 - 1500

1980 21 7 28 1981 10 6 16 1982 5 18 23 1983 9 15 24 1984 13 21 34 1985 12 36 48 1986 25 25 50 1987 25 23 48 1988 35 20 55 1989 34 30 3 67 1990 27 25 8 60 1991 31 24 10 65 1992 25 50 11 86 1993 31 48 26 105 1994 38 40 42 120 1995 26 43 40 109 1996 27 61 56 144 1997 29 43 64 136 1998 28 47 64 139 1999 16 60 72 1 149 2000 19 79 88 186 2001 26 89 85 200 2002 27 73 67 1 168 2003 30 66 69 165 2004 1 30 51 56 138 2005 39 43 68 150 2006 39 55 48 6 1 149 2007 30 66 55 2 153 2008 33 51 50 4 138 2009 45 52 63 3 163

Total 1 785 1267 1045 2 15 1 3116


6.3 Drilling installation type vs. Well type and Water depth

Exposure data related to type of drilling installation type used have not been reported in the

previous years because it has not been practical to establish this data set. However in 2004

US MMS/Boemre/Boeem started to publish APDs (Application for Permit to Drill) as a part

of their public E-well reporting. In these applications the drilling installation types are listed.

This information has been combined with the BOEM Borehole file (/1/) to establish an

overview of the drilling vessel types used vs. the water depth and main well type.

Table 6.7 shows the drilling installation type vs. well type and water depth (US GoM OCS,

2005 – 2009).

Table 6.7 Drilling installation type vs. Well type and Water depth (US GoM OCS, 2005 – 2009)

Well type and drilling installation type


<50 50 - 100

100 - 200

200 - 400

400 - 600

600 - 1000

1000 - 1500

1500 -2000

2000 - 2500

2500 - 3000

>3000 Total

Development wells

Barge 2

2

Dp semisubmersible

2 5 3 6

16

Drillship

5 21 9

1

36

Jackup 679 269 16

964

Platform 7 62 101 14 15 21 28 2

250

Semisubmersible

1 4 10 14 22 3 29 3

86

Submersible 25

25

Total development 713 331 118 18 25 42 76 17 35 4

1379

Exploration wells

Barge 24

24

Dp semisubmersible

3 37 44 24 1 2 111

Drillship

5 28 23 22 8

86

Jackup 512 155 15

682

Platform 1 14 7

2 7 10 1

42

Semisubmersible

14 21 24 109 76 29 29 2

304

Submersible 70

70

Total exploration 607 169 36 21 26 124 151 97 75 11 2 1319

Total all 1320 500 154 39 51 166 227 114 110 15 2 2698

It should be noted that for the years 2007 - 2009, nearly all wells drilled are included. For

2005 and 2006 some wells are missing.

NPD are presently (autumn 2011) in the progress of launching new fact pages. The well files

in the fact pages includes a column specifying the drilling installation type.

Table 6.8shows the drilling installation type vs. well type and water depth (Norway NCS,

1980 – 2009).

http://www.gomr.boemre.gov/homepg/data_center/well.html

http://factpages.npd.no/factpages/

Blowout and Well Release Characteristics and Frequencies, 2011 version Page: 69 Table 6.8 Drilling installation type vs. Well type and Water depth (Norway NCS, 1980 – 2009)

Well type and drilling installation type


<50 50 - 100

100 - 200

200 - 400

400 - 600

600 - 1000

1000 - 1500

> 1500 Total

Development wells

Condeep

34 458 120

612

Drillship

24 1

25

Jacket 1 490 512

1003

Jack-up

245 43

288

Semisubmersible

45 299 852 2 1

1199

TLP

123

123

Total development 1 814 1312 1095 2 25 1

3250

Exploration wells

Condeep

1 7 2

10

Drillship

1 7 1

2

11

Jacket

5 14

19

Jack-up 1 60 9

70

Semisubmersible

165 353 487 24 10 13 2 1054

Total exploration 1 231 384 496 25 10 15 2 1164

Total all 2 1045 1696 1591 27 35 16 2 4414

6.4 Shut-in Wellhead Pressure Related Exposure Data

All data for the US GoM OCS wells stems from (/1/). Only data for wells that are completed

as producers are included.

For the Norwegian wells the main source of information has been a list of HPHT wells from

NPD combined with the NPD Borehole list.

For the UK wells no pressure related data is presented.

6.4.1 US GoM OCS Drilling Wells

The shut-in wellhead pressure exposure data for drilling wells (both development and

exploration wells) are all based on the first production well test carried out on the well.

In US GoM OCS many exploration wells are completed as producers (see Table 5.1). It

should also be noted that many development wells are not completed as producers, because

they are dry.

Since the shut-in wellhead pressures have been recorded more frequent the last 5 to 10 years

than the previous years it was selected to only include data from wells that have been

spudded after January 1988

Development drilling

There were in total 1417 development wells listed with a shut-in wellhead pressure on the

first well test after completion.


In Figure 6.5 the development wells shut-in wellhead pressures have been plotted against the

well depth.

Figure 6.5 Development wells shut-in wellhead pressures plotted against well-depth

Exploration drilling

There were in total 508 exploration wells listed with a shut-in wellhead pressure on the first

well test after completion.

In Figure 6.6 the exploration wells shut-in wellhead pressures have been plotted against the

well depth.

Development wells

Shut-in pressure v.s. well depth, sorted

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

22000

24000

0 10 20 30 40 50 60 70 80 90

Cumulative percent

We

ll d

ep

th (

fee

t)/S

hu

t-in

pre

ss

ure

(p

si)

Shut-in test pressure (psi) True vertical depth (ft) Expon. (True vertical depth (ft))


Figure 6.6 Exploration wells shut-in wellhead pressures plotted against well depth

When looking at Figure 6.6 it is important to note that the number of wells drilled is based on

only the exploration wells that have been completed as producers and listed with a well test

with a positive pressure. If looking at the Mobile area, 33 exploration wells have been drilled

to more than 20000 feet (6100 meters) in the period 1980 - 1996. These wells are likely all

HPHT (more than 10000 psi) wells. In the Destin Dome Blocks six wells have been drilled in

the same formation as the Mobile wells. In the Pensacola one well has been drilled.

In addition 401 exploratory wells have a well depth between 16000 – 20000 feet. By

reviewing the test pressures for development wells drilled in the same block and evaluating

shut-in test pressure and the well spud dates, at least 57 of these were likely to be HPHT

wells (close to 10000 psi or above). Further, some of the wells drilled to less than 16000 feet

have been HPHT wells. It is then likely that it has been drilled in the range of 100 to 200

exploration HPHT wells in the US GoM OCS in the period 1980 - 1998.

6.4.2 Norwegian Drilling Wells

The number of HPHT wells drilled in Norway is shown in Table 6.9. The data from before

1996 stems from the NPD daily drilling report system (DDRS). The data from 1996 and later

stem from the report ”Utvikling i risikonivå norsk sokkel”, hovedrapport, Fase 6 – 2005,

www.ptil.no .

Exploration wells

Shut-in pressure v.s. well depth, sorted

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

22000

24000

0 20 40 60 80 100

Cumulative percent

We

ll d

ep

th (

fee

t)/S

hu

t-in

pre

ss

ure

(p

si)

Shut-in test pressure (psi) True vertical depth (ft) Expon. (True vertical depth (ft))

http://www.ptil.no/

Page: 72 Blowout and Well Release Characteristics and Frequencies, 2011 version Table 6.9 Number of HP/HT wells drilled in the Norwegian waters sorted on years

Year No. of HPHT wells (>690 bar and/or > 150

oC)

Exploration Production

1984 3

1985 2

1986 2

1987 0

1988 3

1989 3

1990 8

1991 7

1992 9

1993 5

1994 3

1995 2

1996 3 4

1997 5 1

1998 2 1

1999 4 2

2000 2

2001 3

2002 3 2

2003 2 1

2004 2 10

2005 3 20

Total 76 41

6.4.3 US GoM OCS Wells in Production

The pressure exposure data for production wells are based on all the well tests with a listed

shut-in wellhead pressure in the period 1980 – 1996 (/1/).

Totally 48264 tests were listed with a positive wellhead shut-in pressure. Many well tests

were not listed with well test pressures. The distribution of well tests in four different

pressure ranges is presented in Table 6.10.

Table 6.10 Pressure ranges in production wells in US GoM OCS wells

Pressure range No. of well tests

Relative distribution

below 6000 psi (414 bar) 46928 97,23 %

6000 – 8000 psi pressure 926 1,92 %

8000 – 10000 psi 336 0,70 %

more than 10000 psi (690 bar) 74 0,15 %

Total 48264 100,00 %

In Figure 6.7 the development wells shut-in wellhead pressures have been plotted against the

well depth.


Figure 6.7 All well tests performed 1980-1996 and listed with a shut-in wellhead pressure

6.5 Production Rates and Gas Oil Ratio Data, US GoM OCS

This section is based on MMS Ogor A files from 1980 – 1999 (/1/). These files list the well

individual production amount (gas, oil and water) for each month. Only the December data

each year has been used to reduce the amount of information to handle

6.5.1 Production Rates

Figure 6.8 and Figure 6.9 show the production rate for the US GoM OCS oil and gas wells

respectively. The production rate data has been grouped in two different groups, the 80-ties

and the 90-ties.


Figure 6.8 Oil well production rates, US GoM OCS wells, 1980 - 1999

The number of wells in production in the December month was slightly higher in the 90's

than in the 80's. The average produced amount of oil was 41 m3/day in the 90's and 36 m

3/day

in the 80's per oil well that produced in the December month. In the end of the 90's some

wells have experienced flow-rates of more than 3000 m3/day. The highest flow-rate seen was

5600 m3/day (or approximately 35 000 bbls). The wells are only those wells categorized as

oil wells in the MMS files (some of them were only producing gas, and no oil). Nearly 99%

of these wells have also produced gas, in average 13013 Sm3/day. Water production was also

listed for 88% of these wells. On average for all wells the water production was 49.5 m3/day,

i.e. more water was produced than oil.

0

20

40

60

80

100

120

140

160

180

2000%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Perecentage of oil wells

Oil

pro

duction

(m

3/d

ay)

Daily Oil Volume in the 80's

Average 80's

Daily Oil Volume in the 90's

Average 90's


Figure 6.9 Gas well production rates, US GoM OCS wells, 1980 - 1999

The number of wells in production in the December month was slightly higher in the 90's

than in the 80's. The average produced amount of gas was 108 000 Sm3/day in the 90's and

124 000 Sm3/day in the 80's per gas well that produced in the December month. The best

producers produced nearly one million Sm3/day. The wells are only those wells categorized

as gas wells in the MMS files (some few of them were only producing oil, and no gas).

Approximately 66% of these gas wells also produced oil, in average 7.3 m3/day for all the

wells. Water production was also listed for 67% of these wells. In average for all wells the

water production was 18.2 m3/day.

6.5.2 Gas Oil Ratio

The gas oil ratio data has been grouped in two different groups, the 80-ties and the 90-ties.

0

50000

100000

150000

200000

250000

300000

350000

400000

450000

500000

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Perecentage of gas wells

Ga

s p

rod

uction

(S

m3

/da

y)

Daily Gas Volume 80's

Daily Gas Volume 90's

Average 80's

Average 90's


Figure 6.10 Well test GOR data sorted on period

Figure 6.11 Well test GOR data sorted on period

6.6 Workover Frequency Exposure Data

Very little statistical material related to number of workovers carried out exists. From the

SINTEF study "Reliability of Surface Controlled Subsurface Safety Valves, Phase III",

SINTEF report STF 75 F89030, it was observed 498 workovers on a total of 7790 well years.

The data was mainly collected in the period 1985 - 1989 for North Sea wells. This gives in

average:

0

500

1000

1500

2000

2500

3000

3500

40000%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Perecentage of oil wells

Sm

3/S

m3

GOR 80's (Sm3/Sm3)

GOR 90's (Sm3/Sm3)

0

20000

40000

60000

80000

100000

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Perecentage of gas wells

(Sm

3/S

m3) GOR 90's (Sm3/Sm3)

GOR 80's (Sm3/Sm3)


15.6 well years per workover

The NPD Annual reports from 1980 to 83 lists the number of workovers carried out the

actual year alongside the number of production wells. A total of 88 workovers were listed and

a total of 731 production well years. This gives in average:

8.3 well years per workovers

In the autumn 2001 a search in the NPD Daily Drilling Report System (DDRS) was carried

out. The search criteria specified:

Traditional type of equipment was used (i.e. the permanently installed drilling rig and not

a coiled tubing or snubbing unit).

The main operation was Workover

Sub operation was completion string (i.e. involved pulling of the completion string).

Each well that had at least on occurrence with the above combinations within one year was

counted as a workover. This means that if two workovers were carried out the same year it

will be counted as one workover only. On the other hand if the workover starts in December

one year and is completed in January the next year it will be counted as two workovers.

This count of workovers has been possible for the period after 1995 when NPD introduced

some new codes in the DDRS. Seventy-six workovers were carried out in the year 2000. The

result from this count for the years 1996 to 1999 is shown in Table 6.11.

Table 6.11 Workover frequencies in Norwegian waters

Year No. of workovers

No. of prod-uction wells

No. of inject-ion wells

Sum no. of wells

No of well years per workover

1996 56 580 189 769 13.7

1997 72 612 194 806 11.2

1998 86 624 211 835 9.7

1999 59 854 259 1113 18.9

Total 273 2670 853 3523 12.9

It seems that the workover frequencies related to conventional workovers has decreased since

the beginning of the 1980-ties when comparing with the above results.

It is recommended that 10.6 well years per workover is used for the estimates related to

blowout/well release frequencies per workover operation. This value will represent the

average for the period 1980 - 2000.

6.7 Wireline Frequency Exposure Data

Very little statistical material related to number of wireline runs exists. To establish an

estimate for wireline exposure data, experience from the Ekofisk field in 1992 has been used.

In 1992, 135 wells were in service (production and injection). A total of 220 wireline jobs

were carried out. If in average each wireline job includes 2.5 wireline runs a total of 550

wireline runs were carried out for the 135 wells. This gives in average:

4.2 wireline runs per well year or

1.7 wireline jobs per well year


It is important to note that the Ekofisk field mainly has wireline retrievable SCSSVs, and not

tubing retrievable SCSSVs that most operators prefer when completing new wells today.

It should further, be noted that most likely several minor incidents (small gas releases) during

wireline jobs have never been recorded as blowouts.

6.8 Coiled Tubing and Snubbing Exposure Data

Table 6.12 lists the number of coiled tubing and snubbing workovers that have been carried

out in the Norwegian waters in the period 1984 - 1995.

The NPD Daily Drilling Report System (DDRS) was used to extract the data. The data may

not be exact because the DDRS did not include a specific code for these operations before

1995. The results are based on a search in the activity description for all production wells

stored in the database. Coiled tubing and snubbing activities during regular drilling and

completion are not included in Table 6.12. Coiled tubing and snubbing operations carried out,

as a part of a conventional workover, is included. These operations should not have been

included because they were only a sub-operation during a conventional workover. Therefore

the activity level as listed in Table 6.12 probably is 10 – 20% higher than the real figures.

Table 6.12 Coiled tubing and snubbing workover exposure data for the Norwegian sector of

the North Sea, 1984 - 1995

Year Snubbing workovers Coiled tubing workovers

1984 1 0

1985 5 1

1986 5 3

1987 7 5

1988 8 3

1989 12 13

1990 4 16

1991 15 13

1992 28 19

1993 21 32

1994 33 38

1995 49 48

Total 188 191

In the autumn 2007 a search in the NPD Daily Drilling Report System (DDRS) was carried

out. The search criteria specified that either a snubbing or a coiled tubing unit was used. The

main operation was Workover and Drilling and the sub operation was not specified. Each

well that had at least on occurrence with the above combinations within one year was counted

as a snubbing workover , a coiled tubing workover, or coiled tubing drilling. This means that

if two operations of one kind were carried out the same year it will be counted as one

operation only. On the other hand if the operation starts in December one year and is

completed in January the next year it will be counted as two operations. If dedicated

snubbing or coiled tubing units are used in association with a conventional workover they

will be regarded as separate operations, i.e. the total number of operations indicated in Table

6.13 may be some higher than the real figures.

The result from this count for the years 1996 to 2006 is shown in Table 6.13.

Blowout and Well Release Characteristics and Frequencies, 2011 version Page: 79 Table 6.13 Coiled tubing and snubbing workover exposure data for the Norwegian sector of

the North Sea, 1996 - 2000

Year Snubbing workovers

Coiled tubing workovers

Coiled tubing drilling

1996 42 83 5

1997 39 81 7

1998 32 83 31

1999 30 49 21

2000 24 50 23

2001 15 50 21

2002 8 57 17

2003 6 74 19

2004 8 37 11

2005 3 37 11

2006 1 44 10

Total 167 346 176



7. Overall Blowout/Well Release Frequencies

Only overall blowout/well release frequencies for the different operational phases have been

calculated. If required, analyses that are more detailed can be carried out by using the

information presented in the various tables in the previous sections and/or the SINTEF

Offshore Blowout Database. The listed frequencies in this section are based on the experience

from US GoM OCS, UK and Norway in the period 1980-01-01 - 2009-12-31 only.

The blowout frequencies during the different operational phases are presented in Table 7.1 to

Table 7.6. The four blowouts listed with the phases “Unknown” and Unknown drilling” are

not included. Please also note that blowouts caused by external loads are disregarded when

calculating the blowout/well release frequencies.

Table 7.1 Blowout/well release frequencies during completion (based on Table 4.4, Table 5.1,

Table 5.2, and Table 5.4)

Category No. of completions* No. of incidents No. of completions

per incident No. of incidents per completion

Blowout (surface flow) 23 635 10 2364 0,00042

Blowout (underground flow) 23 635 0 - 0

Diverted well release 23 635 1 23 635 0,00004

Well release 23 635 9 2626 0,00038

Total 23 635 20 1182 0,00085

* Based on total number of wells completed in Table 5.1, number of developments wells drilled in Table 5.2, and

Table 5.4.

Table 7.2 Blowout/well release frequencies during development drilling (based on Table 4.4

and Table 5.12)

Category Type of incident

No. of dev. wells drilled

No. of incidents

No. of drilled wells per incident

No. of incidents per drilled well


Deep 27490 8 3436 0,00029

Shallow 27490 23 1195 0,00084


Deep 27490 4 6873 0,00015

Shallow 27490 1 27490 0,00004


Deep 27490 0 - 0,00000

Shallow 27490 19 1447 0,00069

Well release Deep 27490 6 4582 0,00022

Shallow 27490 2 13745 0,00007

Total 27490 63 436 0,00229

Page: 82 Blowout and Well Release Characteristics and Frequencies, 2011 version Table 7.3 Blowout/well release frequencies during exploration drilling (based on Table 4.17,

Table 5.1, Table 5.2, and Table 5.4)

Category Type of incident

Exploration well type

No. of. wells drilled

No. of incidents

No. of drilled wells per incident

No. of incidents per drilled well


Deep Appraisal 7 532 10 753 0,00133

Wildcat 8 913 13 686 0,00146

Shallow Appraisal 7 532 12 628 0,00159

Wildcat 8 913 19 469 0,00213

Unknown - 1 -

Total 16 445 55 299 0,00334


Deep Appraisal 7 532 1 7 532 0,00013

Wildcat 8 913 7 1 273 0,00079

Total 16 445 8 2 056 0,00049


Deep Appraisal 7 532 0 - 0

Wildcat 8 913 1 8 913 0,00011

Shallow Appraisal 7 532 5 1 506 0,00066

Wildcat 8 913 7 1 273 0,00079

Total 16 445 13 1 265 0,00079

Well release

Deep Appraisal 7 532 3 2 511 0,00040

Wildcat 8 913 3 2 971 0,00034

Unknown - 1 -

Shallow Appraisal 7 532 1 7 532 0,00013

Wildcat 8 913 1 8 913 0,00011

Total 16 445 9 1 827 0,00055

Unknown

Deep Appraisal 7 532 1 7 532 0,00013

Wildcat 8 913 0 - 0

Total 16 445 1 16 445 0,00006

All

Deep Appraisal 7 532 15 502 0,00199

Wildcat 8 913 24 371 0,00269

Unknown - 1 -

Shallow Appraisal 7 532 18 418 0,00239

Wildcat 8 913 27 330 0,00303

Unknown - 1 -

Total exploration drilling 16 445 86 191 0,00523

Table 7.4 Blowout/well release frequencies during production (based on Table 4.4 and Table

5.18). Blowouts caused by external loads (storm, fire etc.) are disregarded

Category No. of well years in

service No. of

incidents No. of well years per

incident No. of incidents per

well year

Blowout (surface flow) 244 144 9 27 127 0,000037

Blowout (underground flow) 244 144 1 244 144 0,000004

Diverted well release 244 144 0 -

Well release 244 144 3 81 381 0,000012

Total 244 144 13 18 780 0,000053

Table 7.5 Blowout/well release frequencies during well workover (based on Table 4.4, Table

5.18 and Section 6.6)

Category No. of workovers* No. of

incidents No. of workover per

incident No. of incidents per

workover



Diverted well release 21 882 0 - 0

Well release 23 032 25 921 0,00109

Total 23 032 48 480 0,00208

* Based on in average one workover per 10.6 production well years (Section 6.6)

Blowout and Well Release Characteristics and Frequencies, 2011 version Page: 83 Table 7.6 Blowout/well release frequencies during wireline (based on Table 4.4, Table 5.18

and Section 6.7)

Category No. of wireline

jobs* No. of

incidents No. of wireline jobs

per incident No. of incidents per

wireline job



Diverted well release 403 818 0 - 0

Well release 415 045 5 83 009 0,000012

Total 415 045 9 46 116 0,000022

* Based on in average 1.7 wireline jobs per production well years (Section 6.7)



REFERENCES

1 Files retrieved from/bought from BOEM in the US (former MMS (Mineral Management

Service) and Boemre):

http://www.gomr.mms.gov/homepg/pubinfo/freeasci/freedesc.html (used for

downloading files related to well drilling and well production data)

File: 5137 Historical Well Test by Area and Block ASCII (bought from MMS)

Ogor A, Well production files bought from MMS (1980 –1996)

Ogor A, Well production files downloaded from MMS (1996 –2009) US GoM region

Ogor A, Well production files downloaded from MMS (1986 –2009) US Pacific region

http://www.gomr.mms.gov/homepg/pubinfo/freeasci/freedesc.html

Blowout and Well Release Characteristics and Frequencies, 2011 version, Appendix 1 Page: i

Appendix 1 Blowout Database Structure and Coding

LIST OF CONTENTS

A1. OVERALL DATABASE STRUCTURE .............................................................................................................. II

A2. DESCRIPTION OF DATABASE FIELDS AND ASSOCIATED CODES ................................................................. IV

FIELD 3 CATEGORY ................................................................................................................................... IV

FIELD 4 SUB CATEGORY ............................................................................................................................. V

FIELD 5 COUNTRY ..................................................................................................................................... VI

FIELD 10 INSTALLATION TYPE ..................................................................................................................... VI

FIELD 12 WELL STATUS ............................................................................................................................... VI

FIELD 18 MTSIP (MAKS THEORETIC SHUTIN WH PRESSURE)....................................................................... VI

FIELD 24 ROCK TYPE ................................................................................................................................. VIII

FIELD 25 FORMATION AGE ....................................................................................................................... VIII

FIELD 27 PHASE ........................................................................................................................................ VIII

FIELD 28 OPERATION ................................................................................................................................. IX

FIELD 29 ACTIVITY ...................................................................................................................................... XI

FIELD 30 EXTERNAL CAUSE ........................................................................................................................ XII

FIELD 31 LOSS OF BARRIER 1 ..................................................................................................................... XII

FIELD 32 LOSS OF BARRIER 2 .................................................................................................................... XIV

FIELD 34 NORTH SEA STANDARDS............................................................................................................ XIV

FIELD 35 FLOWPATH ................................................................................................................................. XV

FIELD 36 RELEASE POINT ........................................................................................................................... XV

FIELD 37 FLOW MEDIUM.......................................................................................................................... XVI

FIELD 41 IGNITION TYPE ........................................................................................................................... XVI

FIELD 42 CONSEQUENCE CLASS ...............................................................................................................XVII

FIELD 44 POLLUTION ...............................................................................................................................XVII

FIELD 48 CONTROL METHOD ...................................................................................................................XVII

FIELD 50 DATA QUALITY..........................................................................................................................XVII

Page: ii Blowout and Well Release Characteristics and Frequencies, 2011 version, Appendix 1

A1. Overall database structure

The database contains 51 different fields describing each blowout/well release. The various

fields are grouped in six different groups. They are:

1. Category and location

2. Well description

3. Present operation

4. Blowout causes

5. Blowout Characteristics

6. Other

Category and location

Includes information related to the incident category (blowout vs. well leak), offshore

installation such as location, operator, installation name and type, and water depth.

Well description

Includes well and casing depths, last casing size, mud weight, bottom hole- and shut in

pressure, GOR, formation age and rock type.

Present operation

Includes the phase (exploration drilling, development drilling, workover etc.), the operation

presently carried out (for example casing running) and the present activity (for example

cementing)

Blowout causes

Include external cause (stating if an external cause contributed to the incident), loss of the

primary barrier, loss of the secondary barrier (describing how primary and secondary barrier

were lost) and human error. It should be noted that the field regarding human error in general

holds low quality information. Human errors are frequently masked. A field named North Sea

standards highlights if the development of the blowout could have been avoided if North Sea

type equipment had been used (for instance in other parts of the world a blind shear ram is

not required in surface BOP stacks)

Blowout characteristics

Twelve fields are included comprising flow-path, flow medium, flow-rate (low quality),

release point, ignition type, time to ignition, lost production (low quality), duration, fatalities,

consequence class, material loss and pollution

Other

In the Other screen five fields are included, they are: control method, remarks (includes a

description of the incident, data quality (includes an evaluation of the source data quality),

last revision date and references.

Each field and a brief description of the field content are shown in Table A 1.

Blowout and Well Release Characteristics and Frequencies, 2011 version, Appendix 1 Page: iii

Table A 1 Blowout database fields Field no.

Drop down list?

Field Name Brief description

1 No Id_no Chronological input no. (ID no.) 2 No Date Date of incident (dd-mm-yy) 3 Yes Category Classification of incident in Blowout, underground blowout, or well leak 4 Yes Sub_category Related to the main category 5 Yes Country Country in which incident occurred 6 No Field Specification of offshore field 7 No Water depth Water depth (meter) (0=unknown) 8 No Operator Name of responsible for the operations 9 No Installation_name Rig name or installation name

10 Yes Installation_type Type of installation No Slots Not included in database program

11 No Well depth Well depth (meter)(0=unknown) 12 Yes Well status Killed or alive 13 No Casing size Size of deepest casing (inches)(0=unknown) 14 No Casing depth Position of deepest casing shoe (meter)(0=unknown) 15 No Mud weight Mud weight (kg/m3)(0=unknown) 16 No B.h. pressure Bottom hole pressure (bar)(0=unknown) 17 No MMSIP Max Measure ShutIn Pressure (bar)(0=unknown) 18 No MTSIP Maks Theoretic ShutIn WH Pressure, Based on coarse

estimates if not given in the source 19 No Gas volume Gas Volume pr 24 hours (measured by a well test) 20 No Oil volume Oil Volume pr 24 hours (measured by a well test) 21 No Water_volume Water Volume pr 24 hours (measured by a well test) 22 No Gas/oil_ratio Based on the above gas and oil volume fields Sm3/Sm3 23 No API_grade Related to the blowout medium 24 Yes Rock_type Sandstone or limestone 25 Yes Formation_age Age of formation (Jurassic etc.) 26 No Formation_name Local name of formation 27 Yes Phase Drilling, production, workover etc. 28 Yes Operation Main operation when incident occurred 29 Yes Activity Present activity 30 Yes External cause External cause if any, else NO 31 Yes Loss of barrier 1 Loss of primary barrier 32 Yes Loss of barrier 2 Loss of secondary barriers 33 No Human error Human errors 34 Yes North_Sea_standards States if blowout barriers were not according to North Sea standards 35 Yes Flowpath Main flow path

No Finflowpat Not included in database program 36 Yes Release point Release point 37 Yes Flow medium Type of blowout flow medium 38 No Flow rate Blowout flowrate (m3/day) (0=unknown) 39 No Ignit time Time to ignition from start of blowout (hours) 40 Yes Ignit type Type of ignition (No, fire, explosion, not relevant) 41 Yes Consequence class Consequence classification 42 No Material loss Material losses (Million US$)(0=unknown) 43 Yes Pollution Spill to sea 44 No Lost production Lost production (production facilities only) 45 No Fatalities Number of lives lost because of the blowout 46 No Duration Duration of blowout (days)(0=unknown) 47 Yes Control method The method used to stop the blowout 48 No Revision date Date for last update of database record 49 Yes Data quality Quality of reference data 50 No References Refers to the sources of information 51 No Remarks Verbally description of incident

Page: iv Blowout and Well Release Characteristics and Frequencies, 2011 version, Appendix 1

A2. Description of database fields and associated codes

Field 3 Category

For the field Category the Table A 2 shows the pre-defined fields.

Table A 2 Category fields

ID Description

1 Blowout (surface flow) 2 Blowout (underground flow) 3 Well release 4 Diverted well release 5 Unknown

20 Not evaluated

The following main definitions have been utilised when categorising the blowouts/well

releases in main categories and sub-categories.

Blowout definition

NPD came up with a blowout definition in their proposal for the new regulations.

(“Aktivitetsforskriften, eksternt høringsutkast av 3.7.2000, høringsfrist 3.11.2000”).

Med utblåsing som nevnt i denne paragrafen første ledd, menes formasjonsfluid som

strømmer ut av brønnen eller mellom formasjonslagene etter at alle definerte tekniske

brønnbarrierer eller operasjon av disse har sviktet.

Translated to English the definition will be:

A blowout is an incident where formation fluid flows out of the well or between

formation layers after all the predefined technical well barriers or the activation of

the same have failed.

The definition does however not seem to have become a part of the final new NPD

regulation, but remains the database blowout definition.

Well release definition: The reported incident is a well release if oil or gas flowed from the

well from some point were flow was not intended and the flow was stopped by use of the

barrier system that was available on the well at the time the incident started.

Shallow gas definition: Any gas zone penetrated before the BOP has been installed. Any

zone penetrated after the BOP is installed is not shallow gas (typical Norwegian definition of

shallow gas).

All shallow gas incidents in the database have at the extent possible been categorised

according to the typical Norwegian definition of shallow gas. This definition is not relevant

for all US GoM incidents because:

US GoM OCS reservoirs vary highly in depth. Some reservoirs were as shallow as

200 meters.

Blowout and Well Release Characteristics and Frequencies, 2011 version, Appendix 1 Page: v

For some incidents they had sat a full BOP stack, but had now intention to use it

because it would likely cause a blowout outside the casing and a possible crater.

For some incidents they had drilled very deep without running an extra casing string

and the BOP.

And for some incident they had used a combination of a BOP and a diverter.

Further, for many of the incidents the description of the incident in the sources is insufficient,

and some assumptions have to be made. A general comment is that it is not easy to categorise

all the incidents in shallow and deep incidents because of the above.

Field 4 Sub Category

For the field Sub category the Table A 3 shows the pre-defined fields.

Table A 3 Sub category

ID Description

1 Totally uncontrolled flow, from a deep zone

2 Totally uncontrolled flow, from a shallow zone

3 Shallow gas “controlled” subsea release only

4 Underground flow only

5 Underground flow mainly, limited surface flow

6 Limited surface flow before the secondary barrier was activated

7 String blown out of well, then the secondary barrier is activated

8 Shallow gas controlled flow (diverted)

9 Unknown

10 Other

20 Not evaluated

Table A 4 shows the link between the category and sub category.

Table A 4 Categories and subcategories for the incidents in the SINTEF Offshore Blowout

database Main Category Sub category Comments/Example

Blowout and well release


1. Totally uncontrolled flow, from a deep zone

Totally uncontrolled incidents with surface/subsea flow.

2. Totally uncontrolled flow, from a shallow zone

Typical the diverter system fails

3. Shallow gas “controlled” subsea release only

Typical incident is that riserless drilling is performed when the well starts to flow. The rig is pulled away


4. Underground flow only 5. Underground flow mainly, limited

surface flow The limited surface flow will be incidents were a minor flow has appeared, but typical the BOP has been activated to shut the surface flow

Well release 6. Limited surface flow before the secondary barrier was activated

Typical incident will be that flow is through the drillpipe and the shear ram is activated

7. Tubing blown out of well, then the secondary barrier is activated

Typical incident occurring during completion or workover. Shear ram is used to close the well after the tubing has been blown out of the well.


8. Shallow gas controlled flow (diverted)

All incidents were the diverter system functioned as intended.

Unknown Unknown Unknown may be selected for both the category and the subcategory

The list of sub-categories shown in Table A 3 may be extended if found appropriate. One

option will be to split the sub category for Well leakage further down to highlight incidents

with an ignition potential.

Page: vi Blowout and Well Release Characteristics and Frequencies, 2011 version, Appendix 1

Field 5 Country

All countries that have experienced an offshore blowout are included in the dropdown list. It

should be noted that for US several options for Country exist, depending on the area.

Field 10 Installation Type

This is a pre-coded field. Table A 5 shows the existing installation types.

Table A 5 Installation types

Description Comments

BARGE

DRILLSHIP

JACKET Includes Condeep

JACKUP

SATELLITE One well structure

SEMISUBMERSIBLE

SUBMERSIBLE

SUBSEA PROD

TENSION LEG

Other

UNKNOWN

Field 12 Well Status

Table A 6 shows the Well status classification used.

Table A 6 Well status

ID Description Remarks

0 ALIVE Mainly production and wireline, may also in some cases apply for

workover

1 KILLED Drilling, workover, completion) applies when the wellhead normally

should only be exposed to hydrostatic pressure.

2 UNKNOWN

Field 18 MTSIP (Maks Theoretic Shutin WH Pressure)

This field was developed when working with a project focusing HP HT blowout risk. The

information included stems from various sources and estimates.

NOTE:

High shut-in wellhead pressure wells have been focused:

Blowouts/well leaks listed with 345 bar shut-in pressures are wells were the shut-in

pressure is unknown, but less than 345 bars

Blowouts/well leaks listed with 1 bar shut-in pressures are wells were the shut-in pressure

is Not relevant

Blowouts/well leaks listed with 0 bar shut-in pressures are wells were the shut-in pressure

is Unknown

The most used pressure definition for a HPHT well in Norway is that wells with a shut-in

well head pressure above 690 bar (10000 psi) are to be regarded as a HPHT wells. The

maximum Shut-in wellhead pressures are normally not listed in the sources of information

used for the blowout input data, so these pressures had to be deducted from other sources or

Blowout and Well Release Characteristics and Frequencies, 2011 version, Appendix 1 Page: vii

parameters for the given blowout/well leak. The following three main approaches were:

1. Review the blowout description in the database records and in the files to see if any

specific wellhead shut-in pressures were given.

2. Find the actual shut-in wellhead pressures in the US GoM OCS well test database (/1/), or

for close by wells at approximately the same depth. This was for US blowouts/well leaks

only.

3. Estimate the shut-in wellhead pressure based on information about the mud weight and

the true vertical depth, or the down hole well pressure, and assuming the well was filled

with methane gas

The shut-in well head pressures have been divided in the following four main groups

For the blowouts/well leaks that obviously did have a shut-in wellhead pressure below 345

bar (5000 psi) it has not been made any attempts to find the approximate maximum shut-in

wellhead pressure. The blowout was just categorised in that group.

For the other blowouts/well leaks more efforts were used. When reviewing the well tests data

file including shut-in wellhead pressures for approximately 48 000 well tests, some pressures

could directly be found, while for other an approximate pressure was found.

For the blowouts/well leaks were the down hole pressure were given in the source this was

used for estimating the shut-in wellhead pressure. For the blowouts/well leaks where a mud

weight was given the shut-in pressures were estimated based on the mud weight and the true

vertical well depth. Either the mud weight when the blowout occurred or the mud weight

after the well control was re-established were used. It was then estimated that the complete

well bore was filled with methane with a density of 0,71 kg/m3 at atmospheric pressure

The formula used was as follows (only metric units were used):

PSI = Pbottom - methane * g * DTVD * (Pbottom + PSI)/ (2 * PATM)

the solution for PSI will then be:

PSI = Pbottom (1- methane * g * DTVD/ 2 * PATM)/(1 + methane * g * DTVD/ 2 * PATM)

Where;

DTVD = True vertical depth

Pbottom = Bottom hole pressure = listed or = mud * g * DTVD

methane = density of methane at atmospheric pressure = 0,71 kg/m3

mud = density of mud

g = gravity force

PSI = Shut-in wellhead pressure

PATM = Atmospheric pressure

Page: viii Blowout and Well Release Characteristics and Frequencies, 2011 version, Appendix 1

Field 24 Rock Type

Rock type describes the type to rock the blowout flows from. The Rock type codes used are

shown in Table A 7.

Table A 7 Rock type

ID Description

0 A.SANDSTONE

1 B.LIMESTONE

2 NOT RELEVANT

3 UNKNOWN

Field 25 Formation Age

Formation age gives the geological name of the formation. Table A 8 shows the codes used

for formation age.

Table A 8 Formation age

ID Description 0 A.PLIOCENE 1 B.MIOCENE 2 C.OLIGOCENE 3 D.ECOCENE 4 E.UPPER CRETACEOUS 5 F.CRETACEOUS 6 G.LOWER CRETACEOUS 7 H.UPPER JURASSIC 8 I.MIDDLE JURASSIC 9 J.LOWER JURASSIC 10 K.TRIAS 11 L.PERMIAN 12 M.CARBONIFEROUS 13 N.DEVONIAN 14 NOT RELEVANT 15 O.SILURIAN 16 P.CAMBRIAN 17 Q.PRECAMBRIAN 18 R.ARCHEAN 19 UNKNOWN 20 AA.PLEISTOCENE

Field 27 Phase

PHASE refers to the main type of activity. The following preset codes used are shown in

Table A 9.

Blowout and Well Release Characteristics and Frequencies, 2011 version, Appendix 1 Page: ix

Table A 9 Phase

Description COMPLETION Activities associated to well completion DEV.DRLG Development drilling

EXPL.DRLG Exploration drilling, includes wildcats and appraisal wells (for incidents where appraisal or wiuldcat well has not or can not be determined.

EXPL.DRLG WILDCAT* Exploration drilling, wildcat wells EXPL.DRLG APPRAISAL* Exploration drilling, appraisal wells PRODUCTION Production, injection, closed in wells UNKNOWN DRLG When it is not known whether it is DEV.DRLG or EXPL.DRLG

WIRELINE Wireline operations in connection with a production/injection well, not wireline operations carried out as a part of well drilling, well completion or well workover

WORKOVER Workover activities, not including wireline operations. Snubbing and coiled tubing operations

Other UNKNOWN

To differ between Wildcats and Appraisal wells the following has been assumed;

- For Norwegian waters the NPD classification has been used as it is.

- For the UK waters all wells classified as Exploration wells are regarded as Wildcats,

while the wells classified as Appraisal wells are of regarded as Appraisals.

- For the US GoM OCS a different approach has been used. All exploration wells drilled in

certain areas are numbered from 1 and further, where well number 1 is the first well

drilled. For US GoM OCS all exploration wells numbered as 1 have been regarded as

Wildcats, while all the other wells are regarded as Appraisal wells. This may be

inaccurate, but this will likely lead to an underestimation of no. of Wildcats compared to

no. of Appraisal wells for the US GoM OCS.

Field 28 Operation

This field includes preset codes that describe the main operation carried when starting to

loose well control. Table A 10 shows the available selections.

Page: x Blowout and Well Release Characteristics and Frequencies, 2011 version, Appendix 1 Table A 10 Operation

ID Description Remarks 0 C1.RUNNING WELL EQUIPMENT These main operation alternatives

exist for the completion phase

(PHASE = COMPLETION):

1 C2.INSTALLING EQUIPMENT 2 C3.PRESSURE TESTING 3 C4.WELL TESTING INCL.PREPARATIONS 4 C5.CIRCULATING 5 C6.HANDLING TECHNICAL PROBLEMS 6 C7.PERFORATING 7 D1.DRILLING ACTIVITY These main operation alternatives

exist for the drilling phase

(PHASE = EXPL.DRLG,

DEV.DRLG or UNKNOWN

DRLG):

8 D2.CASING RUNNING 9 D3.INSTALLING EQUIPMENT 10 D4.WELL TESTING 11 D5.PRESSURE TESTING 12 D6.ABANDON WELL 13 D7.TEMPORARY PLUGGED 14 D8.HANDLING TECHNICAL PROBLEMS 15 D9.CIRCULATING 16 OTHER General 17 UNKNOWN 18 W1.PULLING WELL EQUIPMENT These main operation alternatives

exist for the workover phase

(PHASE = WORKOVER):

19 W10.TEMPORARY PLUGGED 20 W11.HANDLING TECHNICAL PROBLEMS 21 W12.PERFORATING 22 W13.FISHING 23 W14.KILLING 24 W15.COILED TUBING 25 W2.RUNNING WELL EQUIPMENT 26 W3.INSTALLING EQUIPMENT 27 W4.PRESSURE TESTING 28 W5.WELL TESTING INCL.PREPARATIONS 29 W6.CIRCULATING 30 W7.DRILLING ACTIVITY 31 W8.SNUBBING 32 W9.ABANDON WELL 33 WL1.RIGGING UP WIRELINE EQUIPMENT These main operation alternatives

exist for the workover phase

(PHASE = WIRELINE)

34 WL2.RUNNING WIRELINE OPERATIONS 35 WL3.HANDLING TECHNICAL PROBLEMS

36 P1.PRODUCING OIL These main operation alternatives

exist for the production phase

(PHASE = PRODUCTION):

37 P2.PRODUCING GAS 38 P3.PRODUCING CONDENSATE 39 P4.INJECTING GAS 40 P5.INJECTING WATER 41 P6.CLOSED IN OIL WELL 42 P7.CLOSED IN GAS WELL 43 P8.CLOSED IN CONDENSATE WELL

Blowout and Well Release Characteristics and Frequencies, 2011 version, Appendix 1 Page: xi

Field 29 Activity

The field "Activity" is intended to give a more complete coded description of the present

operation carried out.

Table A 11 shows the codes used for the activity field.

Table A 11 Activities

ID Description Remark

0 A1.ACTUAL DRILLING When the bit is on bottom

1 A10.WELL SUSPENDED

2 A2.TRIPPING OUT

3 A3.TRIPPING IN

4 A4.OUT OF HOLE

5 A5.CORING

6 A6.MILLING.

7 A7.FISHING

8 A8.STUCK PIPE

9 A9.PLUGGED PIPE

10 B1.CIRCULATING

11 B2.WEIGHT UP MUD

12 C1.CASING RUNNING Actual running the casing in the hole

13 C2.CEMENTING CASING

14 C3.WAIT ON CEMENT

15 C4.PRESSURE TEST CASING

16 C5.DRILLING OUT CASING

17 C6.PULLING CASING

18 C7.CEMENT SQUEEZE

19 C8.LEAK OFF TEST

20 D1.INSTALL BOP

21 D2.NIPPLE DOWN BOP

22 D3.TEST BOP

23 D4.MAINTENANCE BOP

24 D5.SET WELL PLUGS

25 D6.PULL/DRILL OUT WELL PLUGS

26 D7.NIPPLE DOWN X-MAS TREE

27 E1.SURVEYING

28 E2.LOGGING

29 E3.ACTUAL WELL TEST

30 F1.RUN TUBING

31 F10.SNUBBING OUT

32 F11.KILLING

33 F2 PULL TUBING

34 F3.PERFORATING

35 F4.STIMULATING

36 F5.GRAVEL PACK

37 F6.ACIDIZING

38 F7.CLEANING WELL

39 F8.PULL COILED TUBING

40 F9.SNUBBING IN

41 G1.CHANGING EQUIPMENT

42 G2.PRESSURE TEST SURF. EQUIPMENT

43 G3.PRESSURE TEST WELL EQUIPMENT

44 G4.MAINTENANCE SURFACE EQUIPMENT

45 G5.MAINTENANCE WELL EQUIPMENT

46 G6.MAINTENANCE OTHER

47 O1.WAIT ON REPAIR

48 O2.WAIT ON WEATHER

Page: xii Blowout and Well Release Characteristics and Frequencies, 2011 version, Appendix 1

ID Description Remark

49 O3.WAIT ON ORDER

50 O4.DISCONNECT RISER

51 OTHER

52 P1.REGULAR PRODUCTION

53 P2.REGULAR INJECTION

54 P3.PRODUCTION TESTING

55 P4.SURFACE MAINTENANCE

56 P5.TESTING SAFETY VALVES

57 P6.GAS LIFTING

58 P7.FAILURE DIAGNOSING

59 P8.GAS LIFTING

60 UNKNOWN

61 W1.RUN WIRELINE

62 W2.PULL WIRELINE

63 W3.FISH FOR WIRELINE

64 F8b.RUN COILED TUBING

65 F8c.COILED TUBING OPERATIONS

66 E4. FLOW CHECK

Field 30 External Cause

The field External cause indicates if the incident was caused by an External cause, and if so

what type of, external cause.

Table A 12 shows the used external causes.

Table A 12 External cause


0 NO No external cause

1 A1.STORM

2 A2.SHIP COLLISION

3 A3.TRAWL/ANCHOR

4 A4.FIRE/EXPLOSION

5 A5.EARTHQUAKE

6 A6.SABOTAGE/MILITARY ATTACK

7 UNKNOWN

Field 31 Loss of Barrier 1

The field Loss of barrier 1 describes the primary barrier lost.

Table A 13 shows the codes used for loss of barrier 1.

Blowout and Well Release Characteristics and Frequencies, 2011 version, Appendix 1 Page: xiii

Table A 13 Loss of barrier 1

ID Description Remarks/criteria

0 A1.TOO LOW HYD. HEAD - TOO LOW MUD

WEIGHT

When too low mudweight is stated in the

source, many of these incidents may actually be

caused by an unexpected high well pressure

1 A10.TOO LOW HYD. HEAD - ANNULAR LOSSES

2 A11.TOO LOW HYD. HEAD - WHILE CEMENT

SETTING

When the kick occur in the first period after the

cementing operation is completed

3 A12.TOO LOW HYD. HEAD - CEMENT PREFLUSH

WEIGHT TOO LOW

When stated in the source

4 A13.TOO LOW HYD. HEAD - DRILLING INTO

NEIGHBOUR WELL

5 A14.TOO LOW HYD. HEAD - TRAPPED GAS When stated in the source

6 A15.TOO LOW HYD. HEAD - UNKNOWN WHY

7 A16.TOO LOW HYD. HEAD - SQUEEZED PERF.

BROKE DOWN

8 A2.TOO LOW HYD. HEAD - SWABBING When swabbing is stated in the source, or the

blowout occur when pulling out of the hole

9 A3.TOO LOW HYD. HEAD - GAS CUT MUD When gas cut mud is stated in the source

10 A4.TOO LOW HYD. HEAD - WATER CUT MUD When water cut mud is stated in the source

11 A5.TOO LOW HYD. HEAD - IMPROPER FILL UP When improper fill-up is stated in the source

12 A6.TOO LOW HYD. HEAD - DISCONNECTED RISER When stated in the source

13 A7.TOO LOW HYD. HEAD - RISER LEAK

14 A8.TOO LOW HYD. HEAD - UNEXPECTED HIGH

WELL PRESSURE

When stated in the source, or if the kick occur

when actual drilling

15 A9.TOO LOW HYD. HEAD - RESERVOIR DEPTH

UNCERTAINTY

When stated in the source, some unexpected

high well pressure incident is likely caused by

reservoir depth uncertainty

16 B1.POOR CEMENT Typical when gas starts to flow/bubble outside

or in between casing, not in connection with

cementing operations

17 B2.FORMATION BREAKDOWN

18 C1.PACKER LEAKAGE

19 C10.SHEAR VALVE FAILURE

20 C11.COIL TUBING FAILURE

21 C12.ANNULUS SAFETY VALVE FAILURE

22 C13.TUBING PLUG FAILURE

23 C14.CASING PLUG FAILURE

24 C15.SNUBBING EQUIPMENT FAILURE

25 C16.X-MAS TREE FAILURE

26 C17.PACKER PLUG FAILURE

27 C18.WELLHEAD FAILURE

28 C2.TUBING TO ANNULUS COMMUNICATION -

TUBING BURST


TUBING LEAKAGE


EQUIPM./NIPPLE FAILURE

31 C5.SCSSV/STORM CHOKE FAILURE

32 C6.WELL TEST STRING BARRIER FAILURE

33 C7.WIRELINE STUFFING BOX FAILURE

34 C8.WIRELINE LUBRICATOR FAILURE

35 C9.WIRELINE BOP FAILURE

36 OTHER

37 UNKNOWN

38 C11a. STRIPPER BOP FAILURE

Page: xiv Blowout and Well Release Characteristics and Frequencies, 2011 version, Appendix 1

Field 32 Loss of Barrier 2

The field Loss of barrier 2 describes the secondary barrier lost.

Table A 14 shows the alternatives for loss of barrier 2.

Table A 14 Loss of barrier 2


0 A1.STRING SAFETY VALVE FAILED When stated in the source

1 A2.STRING SAFETY VALVE NOT AVAIL When stated in the source

2 A3.FAILED TO STAB KELLY VALVE When stated in the source, or when the

flow comes through the drillstring an no

attempts to stab the valve is mentioned

3 A5.WIRELINE BOP/LUBRICATOR NOT INST

4 A6.WIRELINE BOP/LUBRICATOR FAILED

5 A7.SCCSV/STORM CHOKE FAILED

6 A8.X-MAS TREE FAILED

7 B1.FAILED TO CLOSE BOP

8 B10.DIVERTED - NO PROBLEM

9 B11.FAILED TO OPERATE DIVERTER

10 B12.DIVERTER FAILED AFTER CLOSURE

11 B13.DRILLING WITHOUT RISER

12 B14.DISCONNECTED RISER

13 B15.ANNULUS VALVE FAILED

14 B16.NOT SUFFICIENT FRICTIONAL BACKPRESSURE

15 B17.NO PUMPING

16 B2.BOP FAILED AFTER CLOSURE

17 B3.BOP NOT IN PLACE

18 B4.WELLHEAD FAILED

19 B5.CASING HEAD FAILED

20 B6.TUBING TO ANNULUS COMMUNICATION

21 C1.BAD CEMENT

22 C2.CASING VALVE FAILED

23 C3.WELLHEAD SEAL FAILED

24 C4.OUTER CASING FAILED

25 C5.INNER CASING FAILED

26 D1.FRACTURE AT CSG SHOE

27 D2.CASING LEAKAGE

28 D3.FORMATION BREAKDOWN

29 NOT RELEVANT - ONLY ONE BARRIER PRESENT

30 NOT RELEVANT

31 OTHER

32 UNKNOWN

33 A9.COILED TUBING STUFFING BOX FAILED

Field 34 North Sea Standards

The field North Sea Standards is intended for highlighting crucial differences between the

well control equipment involved in the incident and what is required equipment in North Sea

operations.

This is a pre-coded field and the alternatives are listed in Table A 15.

Blowout and Well Release Characteristics and Frequencies, 2011 version, Appendix 1 Page: xv

Table A 15 North Sea standards

ID Description

1 Yes

2 No, no shear ram

3 No, BOP not North Sea standard

4 No, two barrier principle not followed

5 Sometimes not relevant, BOP removed to install casing seal

6 Unknown

20 Not evaluated

Field 35 Flowpath

Flowpath gives information related to the blowout flowpath. This is a pre-coded field and the

alternatives are listed in Table A 16.

Table A 16 Flowpath

ID Description

0 A.THROUGH DRILL STRING/TUBING

1 B.THROUGH ANNULUS

2 C.THROUGH OUTER ANNULUS

3 D.OUTSIDE CASING

4 E.UNDERGROUND BLOWOUT

5 UNKNOWN

Field 36 Release Point

Release point gives information related to the release point. This is a pre-coded field. The

pre-coded alternatives are shown in Table A 17.

Table A 17 Release point

ID Description

0 BOP VALVE OUTLET

1 DIVERTED

2 DIVERTER SYST.LEAK

3 DRILLFLOOR - CHOKE MANIFOLD

4 DRILLFLOOR - DRILL PIPE VALVE

5 DRILLFLOOR - THROUGH ROTARY

6 DRILLFLOOR - TOP OF DRILL STRING

7 DRILLFLOOR - TOP OF TUBING

8 DRILLFLOOR - TUBING VALVE

9 FROM ABOVE X-MAS TREE

10 FROM WELLHEAD

11 FROM X-MAS TREE

12 NO SURFACE FLOW

13 NOT EVALUATED

14 SHAKER ROOM

15 SUBSEA - OUTSIDE CASING

16 SUBSEA CRATER

17 SUBSEA WELLHEAD

18 SUBSEA X-MAS TREE

19 TEST SEPARATOR

20 UNKNOWN

21 MUD ROOM 22 SUBSEA BOP

Page: xvi Blowout and Well Release Characteristics and Frequencies, 2011 version, Appendix 1

Field 37 Flow Medium

Flow medium gives information related to the blowout flow medium. This is a pre-coded

field and the alternatives are listed in Table A 18.

Table A 18 Flow medium


10 Shallow gas Definition of shallow gas:

- Any gas zone penetrated before the BOP has been

installed. Any zone penetrated after the BOP is

installed is not shallow gas.

*See page iv, shallow gas definition

20 Shallow gas H2S

30 Shallow gas, Oil

40 Shallow gas H2S, Oil

50 Shallow gas, Water

60 Shallow gas H2S, Water

70 Shallow gas, Mud

80 Shallow water

90 Shallow water, other

100 Gas (deep)

105 Gas (deep), H2S

110 Gas (gas lift gas)

120 Gas (trapped gas)

130 Gas (deep), Water

135 Gas (deep), Water, H2S

140 Gas (deep), Mud

143 Gas (deep), Methanol

145 Gas (deep), Mud, Water

150 Condensate, Gas (deep)

155 Condensate, Gas (deep), water

160 Oil

165 Oil, Shallow gas, H2S

170 Oil, Gas (deep)

175 Oil, Gas (deep), H2S

177 Oil, Gas (deep), Mud

180 Oil, Gas (deep), Water

185 Oil, Gas (deep), Condensate

190 Oil, Water

200 Mud

205 Water

210 Unknown

Field 41 Ignition Type

Ignition type describes whether the blowout was ignited or not. Table A 19 shows the

possible ignition type selections.

Table A 19 Ignition type

ID Description

0 NO

1 EXPLOSION

2 FIRE

3 UNKNOWN

Blowout and Well Release Characteristics and Frequencies, 2011 version, Appendix 1 Page: xvii

Field 42 Consequence Class

Consequence Class gives a consequence classification of the various incidents. The

consequence types are listed in Table A 20.

Table A 20 Consequence type


0 NO

1 DAMAGE Material loss > $ 0.5 M

2 SEVERE Material loss > $ 3 M

3 SMALL

4 TOTAL LOSS

5 UNKNOWN

Field 44 Pollution

Table A 21 shows the classification for oil/condensate pollution to the sea.

Table A 21 Pollution

ID Description

0 NO

1 LARGE

2 MEDIUM

3 SMALL

4 UNKNOWN

In case the amount of oil/condensate pollution has been determined it is commented under

remarks

Field 48 Control Method

Control method includes information related to the method used to stop the blowout. Table A

22 shows the possible key words.

Table A 22 Control method


0 BOP

1 BRIDGED

2 CAPPED

3 CEMENTED

4 DEPLETED

5 INSTALLED Equipment, e.g. VALVE

6 MUD Killed with mud

7 RELIEF WELL

8 UNKNOWN

9 CEASED

Field 50 Data Quality

The Data quality field gives an indication of the reference data quality. Table A 23 shows the

alternatives.

Page: xviii Blowout and Well Release Characteristics and Frequencies, 2011 version, Appendix 1 Table A 23 Data Quality


3 VERY GOOD is used if the data record is based on the authorities or the companies investigation

report

1 GOOD Is used if the incident is well documented through technical articles or other sources

0 FAIR If the source list an overall description of the incident

2 LOW If the quality of the source information is low, but some crucial facts are described

4 VERY LOW When the source material is very scarce

Documents

Annual report 2011 SINTEF Offshore Blowout Database Final_tcm109-486730.pdf