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Master in Petroleum Engineering 2007-2008 Kick Tolerance Definition, calculation and analysis of results for the application in well design, drilling and well control operations. Choke and Kill friction losses influence in Deep Water Wells. San Donato Milanese October the 23 rd -24 th 2008 Author Gabriele Zaccaria Division Exploration & Production Dept. WEDE/PERF Company Tutors Giuseppe Lanzi Luca Carazza University Tutor Francesca Verga

Kick Tolerance

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Page 1: Kick Tolerance

Master in Petroleum Engineering 2007-2008

Kick ToleranceDefinition, calculation and analysis of results

for the application in well design, drilling and well control operations.Choke and Kill friction losses influence in Deep Water Wells.

San Donato Milanese – October the 23rd-24th 2008

Author

Gabriele Zaccaria

Division Exploration & Production

Dept. WEDE/PERF

Company Tutors

Giuseppe Lanzi

Luca Carazza

University Tutor

Francesca Verga

Page 2: Kick Tolerance

Master in Petroleum Engineering 2007-2008

Introduction

Scope of the work

Kick Tolerance Definition

Kick Tolerance Calculation

Kick Tolerance in Planning Phase

Kick Tolerance in Drilling Phase

Kick Tolerance Parameters

Deep Water Environment

Innovative Drilling Technologies

Conclusions

Page 3: Kick Tolerance

3 Introduction

The importance of kick tolerance in well operations has recently increased

due to its implications in well design, in drilling and well control.

These implications are still

more evident in wells

currently drilled by oil

industry, for which more

complex planning and

execution are required in

comparison with the past.

Deep HPHT Well

Page 4: Kick Tolerance

4 Scope of the work

To study a simple method for the application of kick tolerance concept

in an effective way both in well design and drilling phase.

The proposed method allows to know, to evaluate and to analyze the kick

tolerance problem in order to make the drilling execution safer and more

economical by reducing the probability to have an incident.

This document purpose is to improve knowledge about Kick Tolerance

and represents a technical basis for the discussion on revision of

STAP/PERF standard/procedure.

Page 5: Kick Tolerance

5 Kick Tolerance Definition

Kick Tolerance is defined as the maximum kick volume that can be

taken into the wellbore and circulated out without fracturing the

formation at weak point (shoe), given a difference between pore

pressure and mud weight in use.

It is very important to recognise a

kick and quick shut-in the well in

order to limit Kick Volume and to

carry out a successful control.

Page 6: Kick Tolerance

6 KICK TOLERANCE CALCULATOR (Beta Version)

CLOSE

CALCULATEDP OD (in) 5

Shoe Depth (m) 3200

Hole Size (in) 8.5

DC OD (in) 6.75

TD (m) 5000

Shoe Fracture Gradient (sg) 2.15

Safety Factor (kgf/cm2) 15.0

Mud Weight (sg) 1.90

DC length (m) 200

Pore Gradient at TD (sg) 2.00

Gas Gradient (sg) 0.3

MAASP (kgf/cm2) 75 KICK TOLERANCE VOLUME (bbl) 60

Kick Tolerance Calculation

The maximum kick volume which can be circulated to surface without fracturing

is function of:

well phase geometrical configuration;

drill string dimension;

formation, fracture, mud & influx gradients.

A spreadsheet has been implemented in

order to obtain the kick tolerance volume.

Page 7: Kick Tolerance

7 Kick Tolerance Calculation

The amount of influx volume that entering in well depends on:

underbalance between mud weight and pore pressure

reservoir porosity and permeability

influx type

sensibility and reliability of detection equipment

reaction time of well control crew

type well shut in procedure

time of BOP closure

The same kick tolerance between two wells may not mean that they share

the same level of risk because it is important to consider how quickly an

influx will grow!

Page 8: Kick Tolerance

8

It has been assumed:

vertical well

single monophase gas bubble

two drill string diameters (BHA & DP)

one open hole size

constant ECD profile

It has been neglected:

gas velocity and its real distribution in the annulus

P & T influence on mud weight and influx gradient

gas composition, dispersion and solubility

Driller’s method has been used for the calculation.

These assumptions assures a conservative (safer) kick tolerance.

Calculation Assumptions

Page 9: Kick Tolerance

9 Kick Tolerance Formula

Two mirror approaches have been performed in order to obtain a

correlation linking kick tolerance volume to the corresponding pore gradient

or kick intensity.

(KI = PG – MW)

The correlation is biunique:

by fixing bottom hole volume it is possible to obtain the

corresponding increase of pore gradient.

by fixing pore gradient it is possible to calculate the

corresponding bottom hole kick tolerance volume.

Page 10: Kick Tolerance

10

First Approach

TDV

C

V

CHFGIG)(MW

MWTDSF10MW)(FGHHFG

PGi_BH

DPHS

i_BH

DPHSshoe

shoeshoe

Second Approach

TDPG

HFG

IG)(MW

MW)(PGTDSF10MW)(FGHCV shoeshoe

DPHSi_bh

Page 11: Kick Tolerance

11 Kick Tolerance Plot

This correlation is very incisive, especially in its graphical form.

TD = 4000 m

Hshoe = 3000 m

HS = 12” ¼

DP OD = 5”

BHA OD = 8”

BHAlength = 190 m

DPlength = 810 m

MW = 1.6 kg/l

IG = 0.3 kg/l

FG = 1,75 kg/l

TD

MAASPMWPG

10

Zero Kick Tolerance Volume

“zero influx”

0,00

0,01

0,02

0,03

0,04

0,05

0,06

0,07

0,08

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75

Kick Tolerance Volume (bbl)

Kic

k In

ten

sit

y (

kg

/l)

Kick Tolerance Plot

0KIMWPG

Max Kick Tolerance Volume

Zero underbalance → swab case

Page 12: Kick Tolerance

12 KT in Planning Phase

During the casing seat design, MAASP and Differential Pressure criteria

are used to select casing setting points.

10

)( shoeHMWFGMAASP

10

HPGMWeal PressurDifferenti

Fracture

Gradient

Pore

Gradient

D

E

P

T

H

PRESSURE GRADIENT

kg/cm2/10m

m

M.A.A.S.P. =Maximum Allowable Annular Shut in Casing Pressure

Page 13: Kick Tolerance

13KT in Planning Phase

Kick Tolerance limits are fixed basing on diameter of the drilled open hole.

Hole Size Kick Tolerance Volume

(inch) (bbl)

≥ 12.25 > 50

8.5 – 12.25 > 35

≤ 8.5 > 25

These values help the drilling engineer to verify the casing shoe depth.

The maximum pit gain used in the calculation is critical and must be

selected as appropriate given existing field operating practices, rig

equipment, and the skills of the rig personnel.

The lower value (25 bbl) is usually composed by :

The minimum noticeable pit gain (15 bbl)

The estimated pit gain that will occur to when

the well is finally shut in (10 bbl)

Page 14: Kick Tolerance

14 KT in Planning Phase

The requested kick tolerance volume limits have to satisfy the planned

casing shoe depths.

Page 15: Kick Tolerance

15KT in Planning Phase

0,00

0,01

0,02

0,03

0,04

0 2 4 6 8

Kick Tolerance Volume (bbl)

Kic

k In

ten

sit

y (

kg

/l)

Hshoe = 3200 m

DC 6 ¾”

MW = 2.10 kg/l

DP 5”

8 ½” Hole Size

PG = 2.05 kg/l

TD = 5000 m

FG = 2.15 kg/l

9 5/8” CSG

200 m

KICK TOLERANCE APPLICATION EXAMPLE

Page 16: Kick Tolerance

16KT in Planning Phase

Mud Weight Kick Intensity SIDPP PG* PG*-PG ΔBHP

kg/l kg/l kg/cm2 kg/l kg/l kg/cm2

1.90 0.100 40.0 2.000 0.150 60.0

1.95 0.056 22.4 2.006 0.156 62.4

2.00 0.012 4.80 2.012 0.162 64.8

DC 6 ¾”

DP 5”

8 ½” Hole Size

PG = 1.85 kg/l

TD = 4000 m

Hshoe= 3200 m

FG = 2.15 kg/l

200 m

0,00

0,05

0,10

0,15

0,20

0,25

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70

Kick Tolerance Volume (bbl)

Kic

k In

ten

sit

y (

kg

/l)

MW=1.90 kg/l

MW=1.95 kg/l

MW=2.00 kg/l

MW=2.05 kg/l

MW=2.10 kg/l

1,90

1,95

2,00

2,05

2,10

2,15

2,20

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70

Kick Tolerance Volume (bbl)

Po

re G

rad

ien

t (k

g/l)

MW=1.90 kg/l

MW=1.95 kg/l

MW=2.00 kg/l

MW=2.05 kg/l

MW=2.10 kg/l

Page 17: Kick Tolerance

17 KT in Drilling Phase

Following the example of many drilling’s contractors procedures, if kick tolerance

assume a value lower than the following limits, it is necessary to inform a

competent authority that will decide how to carry on the operations.

Well Type DevelopmentExploration

& AppraisalDevelopment

Exploration

& Appraisal

> 50 bbls

25 - 50 bbls

< 25 bbls

Bottom SupportedFloater

Division Manager Approval or

Business Unit Director of Operations

Performance Approval

OIM and Rig Manager

Performance Informed

Operations Managers

Performance Informed

Page 18: Kick Tolerance

18

Kick Identification Chart

0

20

40

60

80

100

120

0 10 20 30 40 50 60 70 80 90 100 110

Pit Gain (bbl)

(SIC

P-S

IDP

P)

(kg

/cm

2)

Gas Kick

Oil Kick

Water Kick

MAASP

Gas Kick

Water Kick

Oil Kick

Kick Identification Chart

During the drilling phase it is possible to identify the influx type

In case of HPHT wells, gas could be in a liquid state until it reaches the

bubble point, therefore the gas detection is more difficult.

iH

SIDPPSICPMWIG

10)(

Page 19: Kick Tolerance

19 KT in Drilling Phase

Knowing pit gain and SIDPP, the same diagram used in the planning phase,

allows to estimate if or kick volume can be circulated out or bullheaded back

immediately into formation avoiding potential underground blowout phenomena.

Kick Tolerance

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80

Kick Volume (bbl)

SID

PP

(k

g/c

m2 )

UNDERGROUND

BLOWOUT

WITHIN

KICK TOLERANCE

FRACTURING LINE

KICK CIRCULATION

WITH DRILLER’S OR

WAIT AND WEIGHT

METHOD BULLHEADING

Page 20: Kick Tolerance

20 Kick Tolerance Parameters

p

fracshoei

BHiP

PVV

_

_

DPHSshoe

DPHSishoei CIGMW

MWPGTDSFMWFGHCHV

)(

)()10)((max__

Increase FG:

- Formation Strengtheners

- Cement Squeeze

- Repeat LOT

- Improve IG estimation

knowing SICP and SIDPP

- Knowledge of reservoir

characteristics

- Increase MW

- Use ECD Minimize SF by reducing

choke operator error thank

to drill crew training

Improve FG

estimation

Use W&W method to limit

casing pressure and to

reduce the force generated

by pore pressure

Early kick detection and hard

well shut-in to minimize

influx volume

Reduce open hole total

depth by adding a casing

Page 21: Kick Tolerance

21 Deep Water Environment

The continuous research of new

hydrocarbons reservoir into increasing

water depths means new challenges due

to the environment in which to work and

to the equipment used for deep water.

Off lineDual Activity

Scarabeo 7

Page 22: Kick Tolerance

22 Choke and Kill lines effect

In deepwater, Choke and Kill line friction is an important factor, particularly

when the threshold between mud density and fracture gradient is really narrow.

Pressure losses in these lines are

relatively high even at low circulation

rates because of the considerable

length and small diameter.

They reduce the MAASP and in

some instances the margin to circulate

out the kick becomes is very low.

Page 23: Kick Tolerance

23Choke and Kill lines effect

Weight PV YP Mud SCR Range

(sg) (cP) (lbf/100sqft) (bbl/min)

Original Mud: 1,5 30 20 Minimum: 1

Kill Weight Mud: 2,0 30 20 Maximum: 5

CHOKE LINE DIMENSION:

Length ID

(m) (inch)

Section 1: 2000 3

Section 2: 0 0

Choke Line Pressure Loss:

Mud SCR Pressure Loss (psi)

(bbl/min)

Original

Mud Kill Mud

1 222 222

2 250 250

3 304 378

4 503 625

5 744 923

ANNULUS DIMENSION:

Length Casing ID String OD

(m) (inch) (inch)

3200 9,625 5

4000 8,500 5

Annulus Pressure Loss:

Mud SCR Pressure Loss (psi)

(bbl/min)

Original

Mud Kill Mud

1 617 617

2 633 633

3 648 648

4 664 664

5 679 679

TD = 4000 m

Hshoe = 3000 m

HS = 12” ¼

DP OD = 5”

BHA OD = 8”

BHAlength = 190 m

DPlength = 810 m

MW = 1.5 kg/l

PG = 1.55 kg/cm2/10m

IG = 0.3 kg/l

FG = 1.75 kg/cm2/10m

On-shore (without choke effect)

MAASP = 75 kg/cm2

Kick Tolerance Volume = 155 bbl

Off-shore (including choke effect)

MAASP = 40 kg/cm2

Kick Tolerance Volume = 46 bbl

Page 24: Kick Tolerance

24 Innovative drilling technologies

In challenging Deep HPHT wells, where kick tolerance is very narrow or

doesn’t exist at all, it is necessary to use innovative technologies in order

to be able to drill on.

Managed Pressure Drilling (MPD)

ENI Near Balance Drilling (ENBD)

They allow to manage the bottom hole pressure properly.

Page 25: Kick Tolerance

25 Managed Pressure Drilling (MPD)

MPD technology is the use of a closed,

pressurizable mud returns system that provides

the ability to drill ahead and make jointed-pipe

connections while maintaining the appropriate

annular pressure profile.

RBOP

Page 26: Kick Tolerance

26 ENI Near Balance Drilling (ENBD)

ENBD allows “walking the line” between pore pressure and fracture gradient,

through precise and safe control of the annular pressure profile, during drilling.

ENBD integrates the advantages both of Continuous Circulation and

Managed Pressure Drilling. Application of a continuous circulation device

may give great benefit, especially in combination with annular back-pressure.

Page 27: Kick Tolerance

27 Conclusions

Kick Tolerance is an important concept that can be applied both in drilling

operations and in casing program design.

Application of kick tolerance concept is especially helpful in wells

currently drilled by oil industry, for which more complex planning and

execution are required.

Considering Kick Tolerance made drilling execution safer and more

economical by reducing the probability to have an incident.

Page 28: Kick Tolerance

28 Conclusions

A correlation linking kick tolerance volume to the corresponding

kick intensity has been drawn.

During the planning phase, a diagram can be used in order to verify if

planned casing setting depth and mud weight are suitable to assure the minimum

kick tolerance requirements.

During the drilling phase, knowing pit gain and SIDPP, the same diagram

allows to estimate if or kick volume can be circulated out or bullheaded back

immediately into formation avoiding potential underground blowout phenomena.

Page 29: Kick Tolerance

29

It is important monitoring the kick tolerance in real time, by updating the

calculation every time there is a variation of the parameters which influence its

value.

An analysis has also been carried out on the parameters that influence

kick tolerance. Based on it, some indications have been suggested in order to

optimize the parameters.

In deepwater, Choke and Kill line friction is an important factor,

particularly when the threshold between mud density and casing shoe fracture

gradient is really narrow.

Conclusions

Page 30: Kick Tolerance

30 Acknowledgements

I would thank Eni E&P Division Management for

permission to present this work and related results

and WEDE/PERF colleagues for the technical support

and needed assistance.