Risk Assessment and Oil Spill Modellingenvironmentclearance.nic.in/writereaddata/online/RiskAssessment/... · Risk Assessment and Oil Spill Modelling ... Figure 1-4 provide the typical

Risk Assessment and Oil Spill Modelling

EIA for Drilling of Exploratory/ Appraisal Wells in KG-OSN-2009/3 Block in Offshore KG Basin, Guntur and Prakasam Districts, Andhra

Pradesh

August 2015

Submitted by: Cairn India Limited

Contents

1. RISK ASSESSMENT AND OIL SPILL MODELLING ..................................................................................... 1

1.1 QUANTITATIVE RISK ASSESSMENT ............................................................................................. 1

1.1.1 Introduction ............................................................................................................... 1

1.1.2 Objective and Scope .................................................................................................. 2

1.1.3 Methodology ............................................................................................................. 2

1.1.4 HAZID (Hazard Identification) .................................................................................... 7

1.1.5 Selection of Failure Scenarios .................................................................................. 10

1.1.6 Consequence Analysis .............................................................................................. 11

1.1.7 Consequence Calculations ....................................................................................... 14

1.1.8 Failure Frequency Analysis ...................................................................................... 17

1.1.9 Calculation of Individual and Societal Risk .............................................................. 19

1.1.10 Comparison to Risk Acceptance Criteria .................................................................. 19

1.1.11 Risk Reduction Recommendations .......................................................................... 23

1.1.12 Analysis of Results.................................................................................................... 23

1.1.13 Recommendations ................................................................................................... 24

1.2 OIL SPILL MODELLING ........................................................................................................... 31

1.2.1 Key Activities Undertaken ........................................................................................ 31

1.2.2 Data Sources ............................................................................................................ 31

1.2.3 Hydrodynamic Modelling......................................................................................... 33

1.2.4 Oil Spill Modelling .................................................................................................... 39

1.2.5 Conclusions and Recommendations ........................................................................ 47

List of Figures

Figure 1-1: Risk Assessment Process ................................................................................................. 2

Figure 1-2: Risk Assessment Methodology ........................................................................................ 4

Figure 1-3: Typical Layout of Jackup Rig ............................................................................................ 5

Figure 1-4: Typical Layout for Drill Ship ............................................................................................. 6

Figure 1-5: UK HSE- Individual Risk Criteria ..................................................................................... 21

Figure 1-6: UK HSE-Offsite Group Risk Criteria ................................................................................ 22

Figure 1-7: FN Curve for Jackup rig (Day Time) ............................................................................... 25

Figure 1-8: FN Curve for Jackup rig (NightTime) .............................................................................. 26

Figure 1-9: FN Curve for Semi-Sub/Drill ship (DayTime) ................................................................. 27

Figure 1-10: FN Curve for Semi-Sub/Drill ship (Night Time) ............................................................ 27

Figure 1-11: Overall Risk contours on Jackup Rig Typical Layout .................................................... 29

Figure 1-12: Overall Risk contours on Drillship Typical Layout ........................................................ 30

Figure 1-13: Bathymetry of the area of Interest .............................................................................. 32

Figure 1-14: Annual Wind Rose off Chirala ...................................................................................... 32

Figure 1-15: Wind rose off Chirala – SW Monsoon ......................................................................... 33

Figure 1-16: Wind rose off Chirala – NE Monsoon .......................................................................... 33

Figure 1-17: Computational hydrodynamic model grid .................................................................. 34

Figure 1-18: Model Bathymetry ....................................................................................................... 35

Figure 1-19: Comparison of tide extracted from TIPS with simulated tide at location TIPS-C1 ...... 36






Figure 1-25: Maximum flow field during SW monsoon (July) ......................................................... 38

Figure 1-26: Maximum flow field during NE monsoon (November) ............................................... 39

Figure 1-27: Oil Spill Locations ......................................................................................................... 41

Figure 1-32: Dispersion of spilled oil at near shore location S1- NE Monsoon ............................... 42

Figure 1-33: Dispersion of spilled oil at offshore location S1- SW Monsoon .................................. 43

Figure 1-28: Dispersion of spilled oil at far shore location S6- NE Monsoon .................................. 44

Figure 1-29: Dispersion of spilled oil at far shore location S6- SW Monsoon ................................. 45

Figure 1-30: Dispersion of spilled oil at far shore location S7- NE Monsoon .................................. 46

Figure 1-31: Dispersion of spilled oil at far shore location S7- SW Monsoon ................................. 47

List of Tables

Table 1-1: Input Parameter Summary – HSD on Jackup rig ............................................................. 13

Table 1-2: Input Parameter Summary – HSD on Drillship ............................................................... 13

Table 1-3: Input Parameter Summary for- Well Fluid Blow Out-2000m ......................................... 14

Table 1-4: Input Parameter Summary – Well Fluid Blow Out-5000m ............................................. 14

Table 1-5: Definition of Pasquill Stability Class ................................................................................ 15

Table 1-6: Representative Weather Class ........................................................................................ 15

Table 1-7: Effects Due To Incident Radiation .................................................................................. 16

Table 1-8: Failure Frequency Data ................................................................................................... 17

Table 1-9: Generic failure data ........................................................................................................ 17

Table 1-10: Consequence Analysis-Damage distance in m ............................................................. 23

Table 1-11: Accident Events at Jackup Rig/ Semi-sub Drill ship ...................................................... 25

Table 1-12: Details of Aspects Considered for Modelling ............................................................... 40

Table 1-13: Co-ordinates of the oil spill locations ........................................................................... 40

Table 1-14: Recommended Precautionary and Mitigation Measures ............................................. 48

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1. RISK ASSESSMENT AND OIL SPILL MODELLING

This section presents the Quantitative Risk Assessment (QRA) study and Oil Spill Modelling

carried out for the exploratory and appraisal drilling project in KG-OSN-2009/3 Block. The key

activities undertaken as part of both studies, results gathered in due course and

recommendations thereof have been provided in sub sections below.

1.1 QUANTITATIVE RISK ASSESSMENT

1.1.1 Introduction

QRA study is undertaken in order to develop and understand numerical estimates of the risk (i.e.,

combinations of the expected frequency and consequences of potential accidents) associated

with a facility or operation. It uses a set of highly sophisticated, but approximate tools for

acquiring risk understanding.

“Risk” is defined as the combination of the expected frequency and consequence of accidents

that could occur as a result of an activity. Risk assessment is a formal process of increasing the

understanding of the risk associated with an activity. The process of risk assessment includes

answering three questions:

1. What can go wrong?

2. How likely is it?

3. What are the impacts?

Qualitative answers to one or more of these questions are often sufficient for making good

decisions about the allocation of resources for safety improvements. But, as managers seek

quantitative cost/benefit information upon which to base their decisions, they increasingly turn

their attention to the use of QRA.

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Figure 1-1: Risk Assessment Process

1.1.2 Objective and Scope

The objective of the QRA study is to identify major risk contributing events, demarcate,

vulnerable zones and evaluate the nature of risk due to proposed project expansion activity, in

addition to ensure compliance to statutory rules and regulations.

The scope of work for the study is described below:

Identify potential risk scenarios that may arise from Exploratory / Appraisal Drilling in

KG-OSN-2009/3 Block in Offshore KG Basin.

Analyze the possible likelihood and frequency of such risk scenarios by reviewing

historical accident related data.

Predict the consequences of such potential risk scenarios and if consequences are high,

establish the same by through application of quantitative simulations.

Recommend feasible preventive and risk mitigation measures as well as provide inputs

for drawing up of Emergency Response Plan (ERP) for the project.

1.1.3 Methodology

The risk assessment process is primarily based on likelihood of occurrence of the risks identified

and their possible hazard consequences particularly being evaluated through hypothetical

accident scenarios. With respect to the proposed project, major risks viz. blow outs, process leaks

and fires, non-process fires etc. have been assessed.

The QRA has been carried out as per the following broad steps.

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Data collection for the project - involves capture of data relating to the process to be

followed, meteorology, demographic profile of the area, distribution of personnel within the

plot boundary, ignition source and other relevant information. This data was obtained from

CIL’s project department.

System definition - where the potential hazards associated with the project activities are

organized and the overall QRA working strategy is evolved

Hazard identification – which consists of a qualitative review of possible incidents that may

occur, based on previous experience or judgment where necessary.

Consequence Analysis - which is carried out in order to evaluate the resulting consequential

effects of the incidents, with specific emphasis on the impact on personnel.

“Failure Frequency (FF)” analysis - estimation of the “Probability” of the incident, or related

incident outcome case. Failure frequencies so derived shall be combined with the

consequence models predictions to derive composite risk values/results in the fourth stage of

QRA.

Calculation of Individual and Societal Risk - which are yardsticks to indicate whether the risks

are acceptable, ALARP principle adopted from UK HSE shall be used for the purpose.

Comparison to Risk acceptance criteria - essentially to understand whether the risks posed

by the project are “Acceptable”, “As Low as Reasonably Practical (ALARP)” or

“Unacceptable”.

Provide recommendations for Risk Reduction

The flowchart representing risk assessment methodology has been provided in Figure 1-2.

Figure 1-3 and Figure 1-4 provide the typical layout of a jack up rig and drill ship that would be

used for drilling activities.

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Figure 1-2: Risk Assessment Methodology

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Figure 1-3: Typical Layout of Jackup Rig

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Figure 1-4: Typical Layout for Drill Ship

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1.1.4 HAZID (Hazard Identification)

This section looks into potential incidents, which could result in injuries or fatalities. For the

activities envisaged for this project, these incidents typically include the following:

Hydrocarbon Well-fluid releases - small, medium and large well fluid releases from

exploratory/appraisal drilling wells. Possibilities include blowouts (due to either downhole

or surface abnormality or possible cratering (a basin like opening in the Earth surface

surrounding a well caused by erupted action of gas, oil or water flowing uncontrolled

Loss of containment of fuels (HSD) and consequent pool fire on encountering an ignition

source.

Apart from the above categories, there are also “occupational” risks involved with working

on a Drilling Rig. These risks are not specifically dealt with in a “Quantitative” manner in the

QRA- however, their presence must be acknowledged qualitatively. These risks include:

Possibility of dropped objects on the drilling platform due to lifting of heavy

equipment including components like draw works, drilling pipe, tubing, drill bits,

Kelly, mud equipment, shale shakers, BOP components, power generating

equipment and others.

Single fatality occupational incidents such as trips and falls. These are more likely in

drilling rigs due to the hazardous nature of operations and general high congestion

and large extent of the manual operation involved.

Structural failure of the drilling rig due to excessive static or rotating loads,

earthquake, Cyclone, design defect, construction defect etc. It may be noted that

rotating loads are induced due to the specific rotating actions of the rotary drilling

mechanism (Drill string rotated by means of rotary table etc.)

Loss of Buoyancy of the installation.

Helicopter collision.

Risk due to collision of another ship.

The HAZID is the front ends of the QRA process failure scenarios for modeling are selected. These

two categories are discussed in more detail in the following sections.

1.1.4.1 Hydrocarbon Releases- Important Issues

The events of blowouts during drilling are divided in the databases according to the

consequences and well control success. Such blow outs can be ignited or un-ignited. Blow outs

are uncontrolled sudden expulsions of oil, gas, water or drilling fluids from wells to the surface

which result in loss of control of the well.

Sources of hydrocarbon release during the drilling phase include the following:

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Dissolved gas which comes out of solution under reduced pressure often while drilling at

near balance or under balance hydrostatically or as trip gas during a round trip to pull the

drill string around from the hole. Such sources could include releases at bell nipple and

around mud return flow line outlet, shale shakers and active mud pits.

As a “kick”, this occurs as the downhole formation pressure unexpectedly exceeds the

hydrostatic head of the circulating mud column. Significant releases can occur from the

vent lines of the mud /gas separator and other locations.

From residual mud on the surface of the drill pipe being racked in the derrick during the

round trip, or on production of coil tubing being withdrawn from the hole, or from core

samples laid out for inspection. Usually any liquid hydrocarbon system entering the down

hole under normal circumstances are very much diluted by the mud system. However,

under conditions of under balanced drilling, the proportion of hydrocarbons in mud

returns may be significant with a potential for continuous release.

Small hydrocarbon release from rotating equipment, pipes and pump work occurring

during normal operations/ maintenance during drilling. These are not likely to be

significant in open derrick or mast structures.

Possible shallow gas blowout – these may occur at sumps or drainage tanks and be

conveyed by vents or drains to areas of potential ignition sources resulting in fire/

explosion.

Vapour present in oily drainage systems, vents, and ducting.

Flammable materials used in drilling operations (oil based drilling fluids)- release points

could include high pressure mud points, mud degassing equipment, shale shaker, mud

pits and active tanks etc.

Protection against Blowouts

The primary protections against blow outs during drilling are the BOP’s or Blow out Preventers.

These are used to shut in and control the well in the event of gas or oil being encountered at

pressures higher than those exerted by the column of mud in the hole.

BOPs typically consists of 2-3 ram preventers designed at high pressures- (ram preventer is

basically a double operated valve with one ram or gate on each side of the bore hole). The BOPS

are hydraulically operated with a second remote control panel situated someway away from the

rig for use in emergencies when the rig is unapproachable. Connected to the side of the ram type

preventers (usually below the blind rams) are the kill and choke lines which are used to control

the well in the event of any imbalance between the drilling fluid column pressure and the

formation pressure. Both lines are high pressure 2-3 inch hydraulic pipes, the kill line being

connected to the mud circulation system and the high pressure cement pumps and the choke line

leading to a back pressure control Manifold and the mud degasser unit.

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In the event of the high pressure kick with the drill string in the hole, the BOP is closed around

the drill pipe and the mud is circulated down the drill string and back to the mud tanks through

the choke line and back pressure manifold. The manifold consists of a series of valves and chokes

- the choke can be adjusted to give the orifice opening required such as to give a back pressure

on the well in order to control it. There should be two chokes in order to allow maintenance on

one.

If a kick or blow out occurs with the drill string out of the hole, the blind rams are closed and

heavy mud is pumped into the well through the kill line. Any gas can be bled off through the

choke line and fluids are usually squeezed back into the formation.

The correct installation of the drilling equipment and the operational reliability of the BOPs are

essential for the safety of well drilling operation. In addition, initial and periodic testing of the

BOPs, choke and kill manifolds, high pressure/ heavy mud system etc before installation and

periodically is absolutely essential. Most important is the presence of highly trained skilled

personnel on the rig. In addition, the use of the correct drilling fluid in the circulatory system is

extremely vital.

The drilling fluid basically does the following:

To cool and lubricate the drilling bit and the drill string

To remove drill solids and allowing the release at their surface.

To form a gel to suspend the drill cuttings and any fluid material when the column is static

To control sub surface pressures

To prevent squeezing and caving if formations

To plaster the sides of the borehole

To minimize the damage to any potential production zone.

Pressures associated with the sub surface oil, gas or water can be controlled by increasing the

specific gravity of the fluid and thereby by reducing the hydrostatic head of the drilling fluid

column.

The squeezing of formations in the drilled hole can be checked by increasing the hydrostatic head

of the drilling fluid.

Special additives for the drilling fluid for controlling viscosity, lubricating properties, gelling

properties etc. play an important role in the drilling fluid integrity. Sealing agents such as

cellulose, mica can also be added to make up the drilling fluid loss into the porous and fractured

formations.

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1.1.4.2 Release of Other Flammable Material

HSD is used in the mobile generators at the drill sites to cater to the power requirement of the

drill equipment, area lighting, etc. Storage of fuels would primarily pose fire hazard. The credible

accident scenarios include:

Catastrophic tank rupture (Large Leak)

Leak from a 3” pipeline (Medium Leak)

1” leak from the tank/pipe/flange (Small Leak)

The catastrophic Rupture (CR) of the tank would involve a large leak/big hole in the tank or

disengagement of a joint/large leak from a flange sufficient enough to discharge tank inventory in

a short time. The spilled material shall get filled into the dyke area. In presence of an ignition

source, it may catch fire and result in Pool fire of the dyke area.

A 6” leak from a pipeline or a flange shall have similar consequences as to CR, only the time for

loss of containment may be more. Fire being a surface phenomenon, the pool fire in the dyke

area would pose similar heat radiation to the surrounding area.

A 1” leak from the tank or the pipeline would result in the loss of inventory at a much reduced

rate. Counter-measures shall be available to arrest the leak within reasonable time. With a

limited loss of inventory, the damage distances in such case would be less in comparison to the

above case.

The tank design and construction takes into account the possible stress loads imposed due to

exploration and appraisal activities at the drill site. This would be in-built into the design for safe

operation. Dyke with adequate capacity (110%) is being provided to contain the spill, if any.

Standard well area inspection and maintenance procedures of CIL shall be implemented at the

exploratory and appraisal wells to identify any abnormalities.

1.1.5 Selection of Failure Scenarios

Potential release rates for a material from containment depend significantly on the initial

operating conditions. Factors affecting the “release rate” include the initial pressure,

temperature, hole size, hole roughness, hole orientation, gas properties, atmospheric conditions

and many other parameters.

Both, the complexity of study and the number of incident outcome cases are affected by the

range of initiating events and incidents covered. This not only reflects the inclusion of accidents

and / or non-accident-initiated events, but also the size of those events.

Loss of Containment- leak sizes

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It must be understood that there are an infinite range of possible releases of flammable material

on the facilities For example, a hole could appear at any point in a well, at any time of the year

and the hole could have any size (right from pinhole to catastrophic line guillotine rupture) and

also possibly any shape! In order to allow management of the study, it is per force necessary to

divide the infinite range into a number of smaller ranges through representation as a single event

or a failure case. In the study, only small, medium and large well fluid blowouts were considered.

Hydrocarbon Leaks due to Loss of Containment (Leak during Well Testing) were not taken into

consideration since they are likely to be controlled about 95% of the time. The category includes

releases that may be isolated from the reservoir fluids, typically release from the well testing

equipment and mud line.

The following four scenarios have been quantitatively evaluated in the study:

Small and medium size holes - these typically represent failures such as gasket leaks, flange

leaks etc. This scenario has been considered as 1” leak for HSD

Medium leaks – these typically represent disengagement of flanges, full bore failure of

pipelines, large leaks from flanged joints, etc. This scenario has been considered as a 3” leak

of HSD.

Large holes 6” leak– these typically represent “catastrophic” or “guillotine” rupture scenarios.

This scenario has been considered as a Catastrophic Failure of HSD Tank.

Well Blow out case. This has been considered as Well Blow out scenario involving crude oil.

The selection of initiating events and incidents should take into account the goals or objectives of

the study. The main reasons for including release sizes other than the catastrophic are to reduce

the conservatism in an analysis and to better understand the relative contributions to risk of

small versus large releases. Only leakage events leading to possibility of serious injury are

considered in the study.

1.1.6 Consequence Analysis

Consequence analysis involves the calculation of the initial “release rate” and then predicting the

consequence of the release through computer modeling- it forms an important ingredient in the

QRA approach. Consequence analysis is a complex procedure involving numerous calculations. It

must also be noted that a single starting incident could have numerous outcomes depending

upon factors such as escalation, ignition and others. The various factors of importance in this

study with respect to consequence analysis are described below.

1.1.6.1 Consequence Analysis for Blowouts

A blowout on the topsides may take one of several forms and release locations. Any release not

immediately ignited would give a flammable vapour cloud, which could cause a vapour cloud

explosion in the drill floor or the mud pit areas.

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A pressurized jet release could lead to a very large jet fire, producing high levels of thermal

radiation. The flame could impinge on structural members in the derrick. These could then fail as

they lose their mechanical properties at high temperature. This may lead to objects falling from

the derrick and causing more damage below, especially if the derrick has already been weakened

by the blast from a vapour cloud explosion. If the fire continues for a long period (say one to two

hours) then the derrick may collapse causing serious damage to surrounding areas. However,

evacuation is expected to have occurred by any available means before this time.

Unburnt oil from a potential blowout will typically form running or evaporating pools, which

could create a hazard from heat and smoke in all areas that the pools reach. If the blow out

originates on the drill floor then the burning oil will run over the side of the drill floor.

Blowout release rate is taken as 13.25 kg/s. It is expected that the uncontrolled release of fluids

on the drill floor will ignite almost immediately and that the resulting fire will engulf the drill

floor. Higher ignition probabilities are expected for large releases compared to smaller releases.

The flames are likely to impinge on structural members on the drill floor. These may fail as they

lose their mechanical properties at high temperature. This may lead to objects falling from the

derrick and causing more damage below. If the fire continues for a long period (blowouts have

been reported to last for several days) then the entire rig will be lost. This is an issue for asset

damage rather than fatality predictions since persons in the rig would have left the fire location

by then!

1.1.6.2 Consequence Analysis for HSD Pool Fires

HSD stored in steel tanks will have steel low height dyke wall as secondary containment of

adequate capacity to impound any accidental leaks.

As mentioned, liquid releases may result in pool fires within the drilling area. Pool fires have been

assumed to be confined, since there are steel low height dykes provided to arrest the liquid

movement. Unlike a jet fire, the pool flame has negligible momentum and is treated as an upright

cylinder, with some wind tilt.

1.1.6.3 Inventory

Inventory can get discharged to Environment due to Loss of Containment. Inventory Analysis is

commonly used in understanding the relative hazards and short listing of release scenarios and

plays an important role in regard to the potential hazard. The larger the inventory of a vessel or a

“system”, the larger the quantity of potential release. The potential release depends upon the

quantity of release, the properties of the materials and the operating conditions (pressure,

temperature etc. described later). Table 1-1 to Table 1-4 provides a summary of input parameters

for consequence modeling for HSD and Blowout scenarios.

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Table 1-1: Input Parameter Summary – HSD on Jackup rig

Material Identifier HSD

Type of Vessel Unpressurised (At Atmospheric

Pressure) Pressure Specification Pressure Not Used

Discharge Temperature 31 0C

Phase Liquid

Tank Head 8.5 m

Total Mass Inventory of Material Discharge 544512 Kg

Volume inventory of Material 640 KL

No of tanks (assume) 4

Mass inventory of Material per tank 136128 Kg

Volume inventory of Material per tank 160 KL

Bund

Area of Dike 36 m2

Bund Height 1.2 m

HSD leakage 1 inch leak from storage tank on Jackup rig (10% mass released assumption)

13612.8 Kg

HSD leakage 3 inch leak from storage tank on Jackup rig (30% mass released assumption)

40838.4 Kg

HSD line leakage 6 inch leak from storage tank on Jackup rig (60% mass released assumption)

81676.8 Kg

Table 1-2: Input Parameter Summary – HSD on Drillship

Material Identifier HSD

Type of Vessel Unpressurised (At Atmospheric

Pressure)

Pressure Specification Pressure Not Used

Discharge Temperature 31 0C

Phase Liquid

Tank Head 18 m

Total Mass Inventory of Material Discharge 6806400 Kg

No of storage tanks (assume) 4

Mass inventory per tank 1701600 kg

Volume inventory of Material 8000 KL

Volume inventory of Material per tank 2000 KL

Bund

Area of Dike 225 m2

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Bund Height 1.2 m

HSD leakage 1 inch leak from storage tank on Drill ship (10% mass released assumption)

170160 Kg


510480 Kg


1020960 Kg

Table 1-3: Input Parameter Summary for- Well Fluid Blow Out-2000m

Material Identifier Crude Oil

Vessel/Tank

Release Type Continuous

Release Rate (taken as 5 times the

maximum well flow rate)

13.25 Kg/s

Discharge velocity of the Well fluid 14.42 m/s

Expected formation pressure @

500-2000m

700-4000 psi

Temperature @ 2000m 60-100 deg c

Table 1-4: Input Parameter Summary – Well Fluid Blow Out-5000m

Material Identifier Crude Oil

Vessel/Tank

Release Type Continuous

Release Rate (taken as 5 times the

maximum well flow rate)

13.25 Kg/s

Discharge velocity of the Well fluid 36 m/s

Expected formation pressure@

2001-5000m

2900-10000 psi

Temperature @ 5000m 150-200 deg c

1.1.7 Consequence Calculations

Using the failure case data developed, the consequence program of the software package,

undertakes consequence calculations for each identified failure.

For flammable materials, the software then proceeds to determine the effect zones for the

various possible outcomes of such a release. A release can ignite as the result of the event, which

causes it, or can ignite close to the source before the flammable cloud has travelled away from

the release source. If a release does not ignite in this way, and it is still flammable, it can be

ignited at a number of points.

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The particular outcome(s) modeled depends on the behavior of the release and the dilution

regimes, which exist. This can be quite complex. The program undertakes these calculations for

the selected representative meteorological conditions, which are derived from the annual

meteorological conditions in the study area.

Consequence models are used to predict the physical behavior of hazardous incidents. Some

models only calculate the effect of a limited number of physical processes, like discharge or

radiation effects. More complex models interlink the various steps in consequence modeling into

one package.

Important inputs to the Consequence analysis calculations include the weather conditions and

the damage criteria, both of which are discussed in the following pages.

1.1.7.1 Weather Conditions

The weather stability class is normally Class D on sunny days. The average wind speed most of

the time is 5 m/s. Combining this with stability class D, consequence modeling is done in this

study for weather 5D.

The ambient condition considered in this study is as under:

Average Ambient Temperature: 31˚C

Average Humidity: 78 (%)

Table 1-5: Definition of Pasquill Stability Class

SURFACE WIND SPEED (M/S)

INSOLATION DAY TIME NIGHT SKY

Strong Moderate Thinly Overcast <3/8 Cloud

<2 A A/B - -

2-3 A/B B E F

3-5 B B/C D E

5-6 C C/D D D

>6 C D D D

The six representative weather classes on which the analysis is based are detailed in Table 1-6.

Table 1-6: Representative Weather Class

WEATHER CLASS WIND SPEED (m/s) PASQUILL STABILITY

I 3 B

II 1.5 D

III 5 D

IV 9 D

V 5 E

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WEATHER CLASS WIND SPEED (m/s) PASQUILL STABILITY

VI 1.5 F

Source:-Handbook of Chemical Hazard Analysis Procedures volume-I

1.1.7.2 Damage Criteria

Heat Radiation

The consequence caused by exposure to heat radiation is a function of:

The radiation energy onto the human body [kW/m2];

The exposure duration [sec];

The protection of the skin tissue (clothed or naked body).

It can be assumed that people would be able to find a cover or a shield against thermal radiation

in 30 seconds time. Furthermore, 100% lethality may be assumed for all people suffering from

direct contact with flames, such as the pool fire, a flash fire or a jet flame. The effects due to

relatively lesser incident radiation intensity are given below.

In the study, the following criteria were used for estimation of heat radiation due to fire fatalities:

37.5 kw/m2- represents 99% fatalities based on 30 s exposure.

9.46 kw/m2- represents 50% fatalities based on 30 s exposure time.

6.31 kw/m2 represents 10% fatality based on 30 s exposure time.

4.73 Kw/m2 represents 1% fatality based on 30 s exposure time

These values may be compared to commonly encountered heat radiation values:

Table 1-7: Effects Due To Incident Radiation

Incident Radiation

– kw/m2

Type of Damage

0.7 Equivalent to Solar Radiation

1.6 No discomfort for long exposure

4.0 Sufficient to cause pain within 20 sec. Blistering of skin (first

degree burns are likely)

9.5 Pain threshold reached after 8 sec. second degree burns after 20

sec.

12.5 Minimum energy required for piloted ignition of wood, melting

plastic tubing’s etc.

Pool fires are more difficult to predict as the shape and size depends a lot on the terrain, the

mode of 2 phase release, the aerosol formation and other factors. The damage distances are

relatively less. Pools have been assumed to be “unconfined” since there are as such NO specific

barriers to restrict the fluid flow. Heat radiation distances are based on 30 seconds exposure. It is

highly probable on the installation that personnel on the rig would be able to find a safe shelter

within the period.

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1.1.8 Failure Frequency Analysis

Frequency analysis involves estimating the likelihood of each of the failure cases identified during

the hazard identification stage. The analysis of frequencies of occurrences for the key hazards

that has been listed out is important to assess the likelihood of such hazards to actually unfold

during the lifecycle of the project. The frequency analysis approach for the proposed project is

based primarily on historical accident frequency data and judgmental evaluation. Major oil and

gas industry information sources viz. statistical data, historical records and global industry

experience were considered during the frequency analysis of the major identified risks.

For QRA for the proposed project, various accident statistics and published oil industry databases

have been consulted for arriving at probable frequencies of identified hazards. Data base

published by the International Association of Oil & Gas Producers (OGP) has been referred to.

Table 1-8: Failure Frequency Data

ITEM FAILURE FREQUENCY

HSD Storage Tank Leak

For 1” leak 1.12E-04/year

For 3” leak 9.30E-05/year

For Catastrophic Rupture 6 inch 9.30E-05/year

Blowout 1.6E-4/year

Helicopter 5.6E-06 (OGP Data base report no. 434- 2010)

Table 1-9: Generic failure data

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1.1.9 Calculation of Individual and Societal Risk

Individual Risk or IR represents the geographical distribution of risk to any individual.

Societal Risk is represents the risk the project poses to society as a whole. The Societal Risk or

Group risk (F-N) curves indicate the cumulative frequency (F) of (N) or more fatalities. Society is

typically not willing to accept industrial installations that result in many fatalities, even with a

low frequency rate.

The estimation of risks in the software is done through estimation of “risks” attributed to each

failure case by determining the impact in terms of fatalities. In this step, the hazard or effect zone

information, ignition source, population distribution, meteorological data and other relevant

details are combined to determine risks.

In order to estimate risks (IR or SR), the number of fatalities for each incident outcome case is

calculated and the frequencies of outcomes with equal fatalities summed up.

1.1.10 Comparison to Risk Acceptance Criteria

This penultimate step compares the estimated risk with respect to the Company’s internal risk

acceptability criteria or specific legislative or regulatory (as applicable in the country of operation)

risk acceptability criteria. In this step, the risk “band” is determined- typically, the project risk

band is determined to be either negligible, acceptable, not acceptable. The risk assessment stage

determines whether the risks are “Broadly Acceptable”, “Intolerable” or “Tolerable if ALARP”.

1.1.10.1 CIL Risk Acceptability Criteria

CIL risk acceptability criteria is derived from interpretation of the risk acceptability criteria

published by UK HSE-92 and is applied when assessing the tolerability of risk to persons for CIL

facilities, sites, combined operations or activities. It broadly indicates as follows:

(a) Individual risk to any worker above 10-3 per annum shall be considered intolerable and

fundamental risk reduction improvements are required.

(b) Individual risk below 10-3 for but above 10-6 per annum for any worker shall be considered

tolerable if it can be demonstrated that the risks are As Low As Reasonably Practicable

P a g e | 20

(ALARP).

(c) Individual risk below 10-6 per annum for any worker shall be considered as broadly

acceptable and no further improvements are considered necessary provided documented

control measures are in place and maintained.

(d) Individual risk to any member of the general public as a result of CIL Businesses activities shall

be considered as intolerable if greater than10-4 per annum, broadly acceptable if less than

10-6 per annum and shall be reduced to As Low As Reasonably Practicable (ALARP) between

these limits.

For new facilities, CIL shall strive to achieve lower risks compared with that typical for existing

facilities, down at least to an individual risk to any worker of 10-4 per annum, by the appropriate

use of best practice including technology and management techniques. For existing facilities,

higher risk levels may be tolerated provided that they are As Low As Reasonably Practicable

(ALARP) and meet the minimum standards given herein.

As facilities under the proposed project may be considered as “new” facilities; it is proposed that

individual risk to any worker above 10-4 per annum shall be considered intolerable. The risk

acceptability criteria are indicated in the following pages.

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Figure 1-5: UK HSE- Individual Risk Criteria

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The UK-HSE Off-site Group Risk criteria is shown at Figure 1-6.

Figure 1-6: UK HSE-Offsite Group Risk Criteria

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1.1.11 Risk Reduction Recommendations

This step analyses the risks estimated, their tolerability with respect to the risk acceptability

criteria.

In case risks are found to fall in the “Unacceptable” region, risk reduction recommendations

aimed at bringing risks to within the “Tolerable region if ALARP” are proposed. In such

conditions, the Cost Benefit Analysis (CBA) is also carried out for specific risk reduction measures

in order to “quantify” them.

In case risks have been found to be the ALARP or Broadly Acceptable region, recommendations

may still be suggested for generic risk reduction based on industry best practice. Such risk

reduction recommendations are not “quantified” or mandatory, but are nevertheless proposed

for safer operation of the facilities.

1.1.12 Analysis of Results

The results of consequence analysis carried out for the identified four accident scenarios are

given below:

Table 1-10: Consequence Analysis-Damage distance in m

S.No. Isolatable section Leak Size Pool fire-Intensity Radii Damage Distance (m)

4.73 KW/m2

6.31 KW/m2

9.46 KW/m2

37.5 KW/m2

1 Well blowout- 5000m Full Bore 177 162 132 ----

2 Well blowout- 2000m Full Bore 135 120 85 ----

3 HSD leakage on Jackup rig 1 inch 32.1 30.1 27.1 12.2

4 HSD leakage on Jackup rig 3 inch 41 38 33 15.2

5 HSD leakage on Jackup rig 6 inch (CR) 40.6 37.6 32.6 14.7

6 HSD leakage on Drill Ship 1inch 46.5 45.2 43.5 37.9

7 HSD leakage on Drill Ship 3inch 74 70 63.2 ----

8 HSD leakage on Drill Ship 6 inch (CR) 90 79 63 ----

9 Helicopter Crash CR 21.5 19.2 16.7 5.7

10 HSD Line leakage 1 inch 29 26.3 24 11.2

11 HSD Line leakage 3 inch 45 41 35 ----

12 HSD Line leakage 6 inch (CR) 45.8 42.2 35.7 ----

The main conclusions for the Jackup rig and Semi submersible Drill Ship option are as follows:

1. From the F-N Curve, it is seen that the risks are within the “ALARP” band for both Jackup

Rig and Semi-sub drill ship- this indicates that no further “specific” risk reduction options

need to be implemented. Only large incidents are likely to affect persons in the Living

Quarters (LQ). Otherwise, the smaller incidents are likely to only affect rig personnel on

the Rig Floor and NOT personnel in the LQ. The LQ will be 2 hour fire rated and have

P a g e | 24

appropriate safety arrangements for rescue, escape paths and also be equipped with Fast

Rescue Craft (FCR) and lifeboats/life rafts etc. In line with NFPA 101 Life SAFETY Code and

SOLAS (Safety of Life at Sea). Helicopter and FCR evacuation is available in the LQ.

2. Overall risk to personnel at the site for the Jackup Rig is in the region of 1E-05 to 1E-09

which is well within the acceptable risk region.

3. Overall risk to personnel at the site for the semi-sub drill ship is in the region of 1E-04 to

1E-0 9 which is within the acceptable risk region.

4. The maximum damage distance for 4.73 kW/M2 which corresponds to 1% lethality level

for a 30 s exposure is for well blow out @ 5000 m depth catastrophic rupture, for which

the damage distance is approximately 177 m.

5. The maximum damage distance for 37.5 kW/M2 which corresponds to 100% lethality

level for a 30 s exposure is for well blow out @ 5000m depth catastrophic rupture, for

which the damage distance will be 62 m approx.

6. Diesel tank /piping leak incidents are typically expected to have local damage only and

not spread through the facility

1.1.13 Recommendations

From the F-N Curve and Iso Risk Contours, risks are found to be within the ALARP region, hence

cost benefit analysis is not necessary to bring about further risk reduction. However, the

following actions must be ensured to ensure that the risks remain reasonable and do not

escalate:

As Living Quarters are likely to be affected due to large incidents on the Rig Floor, it is

essential to ensure the upkeep of the safety devices (Smoke Detection, Fast Rescue Craft

(FRC), escape routes, ensure Mock evacuation drills etc are carried out periodically.

Escape routes for personnel on the Drill Floor towards the LQ must be properly protected

and kept free of any debris/obstructions etc. to ensure minimum loss of life.

The correct installation of the safety critical equipment and their operational reliability

are essential for the safety of the facility. In addition, initial and periodic testing of the

safety critical equipment before installation and periodically is absolutely essential and

the same must be ensured.

Storage tank dykes must be drained periodically during the rainy season in particular.

Key non routine activities must be preceded by a Job Safety Analysis and Job or Task Risk

Assessment involving key personnel that would be working on the facility.

Work Permit System must be implemented during the construction and operational

phases of the project to safeguard against any accidents.

Trips and falls hazard, electrical hazards etc. must be minimized through periodic safety

audits and site inspections using third party and CIL Internal audit teams. Actions arising

out of the audits must be implemented in a time bound manner and followed up for

closure.

CIL must ensure suitable training to all personnel (Company as well as Contractor

personnel) to help prevent incidents/ accidents- such training must be refreshed

P a g e | 25

periodically and a list of trained personnel must be maintained by CIL.

Proper periodic maintenance for all critical components of the rigs and connected

equipment/ systems must be ensured to minimize failure potential.

As hydrocarbon related risks exist at the facility, ignition source control must be ensured

during routine and non routine operations.

Table 1-11: Accident Events at Jackup Rig/ Semi-sub Drill ship

Type of Hazardous Event Specific Accident Events included in QRA

Hydrocarbon Releases Uncontrolled Blow out

Release from Diesel tanks – Catastrophic failure,

medium and small leaks

Occupational accidents Single fatality accidents such as slips, trips, falls,

dropped objects etc.

Structural Failure Structural collapse of drilling rig/drilling ship due to

static or rotating load, fatigue, construction defect,

design defect, earthquakes, etc.

The FN Curve drawn for this project is given at Figure 1-7 to Figure 1-10 below. The FN Curve

represents combined risk covering all the identified scenarios.

Figure 1-7: FN Curve for Jackup rig (Day Time)

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Figure 1-8: FN Curve for Jackup rig (NightTime)

From the above figure it can be seen that the combined risk from the identified accident

scenarios is in the AS LOW AS REASONABLY POSSIBLE or in the “ALARP”-band. The project does

not pose any intolerable risk to the population of the area.

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Figure 1-9: FN Curve for Semi-Sub/Drill ship (DayTime)

Figure 1-10: FN Curve for Semi-Sub/Drill ship (Night Time)

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From the above figure it can be seen that the combined risk from the identified accident

scenarios is in the AS LOW AS REASONABLY POSSIBLE or in the “ALARP”-band . The project does

not pose any intolerable risk to the population of the area.

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Figure 1-11: Overall Risk contours on Jackup Rig Typical Layout

Figure 4.4 ISO-Risk contours on Semi-Sub/ Drill Ship Typical Layout

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Figure 1-12: Overall Risk contours on Drillship Typical Layout

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1.2 OIL SPILL MODELLING

A hydrodynamic and oil spill modelling study was undertaken for the proposed project.

Hydrodynamic modelling was required to evaluate the flow conditions in and around the exploration

sites. Further, these hydrodynamic conditions were used to assess the dispersion of oil spills from

the exploration sites. The proposed mathematical modelling study was carried for typical periods of

South West and North East monsoon seasons. The output of the hydrodynamic modelling and oil

spill study is summarised in the following sections, which documents the estimation of

hydrodynamic conditions and assessment of the dispersion of oil spill of the proposed one far-shore

and two near-shore exploration locations.

1.2.1 Key Activities Undertaken

The key activities undertaken for the modelling exercise include:

Extraction of winds from the open source database and analysis of these wind conditions for

annual and seasonal.

Evaluation of hydrodynamic conditions within and around the proposed exploration sites.

Assessment of the oil spill dispersion for the selected exploration locations based on

hydrodynamic modelling results and wind conditions.

Estimation of oil spill dispersion during SW and NE monsoon seasons.

1.2.2 Data Sources

The following datasets were used in this study:

Bathymetric survey data (Figure 1-13) around the area of interest

Open source wind climate data for NE and SW monsoon period downloaded from the

National Center of Environmental Prediction (NCEP) GFS Numerical Weather Prediction

Model, shown in Figure 1-14, Figure 1-15 and Figure 1-16.

Digitized admiralty charts of the area of interest,

TPXO1 tidal constituents for hydrodynamic modelling boundary conditions,

Tides extracted at 6 locations from TIPs global model for calibration.

1 is a current version of a global model of ocean tides

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Figure 1-13: Bathymetry of the area of Interest

Figure 1-14: Annual Wind Rose off Chirala

N

NE

E

SE

S

SW

W

NW

Calm0.2%

5

10

15%

0-2

2-4

4-6

6-8

8-10

10+

U (m/s)

Offshore Wind Rose at 15N, 81E

NCEP Offshore Wind Data from Jan.2013 to Jan.2014

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Figure 1-15: Wind rose off Chirala – SW Monsoon

Figure 1-16: Wind rose off Chirala – NE Monsoon

1.2.3 Hydrodynamic Modelling

In order to compute the flow conditions and assessment of dispersion of oil spill from the

exploration sites a local hydrodynamic model developed and calibrated against the observed data.

As currents are main driving force of the oil spills therefore the accurate estimation of flow

conditions was of utmost important. The output from the hydrodynamic model was then used as

forcing in a tracking model (GNOME) to simulate oil dispersion.

The hydrodynamic module within the Delft3D package has been used to simulate and evaluate the

flow pattern in the area of interest. The Delft3D-Flow model solves the 2D or 3D shallow water

N

NE

E

SE

S

SW

W

NW

Calm0.2%

10

20

30

40%

0-2

2-4

4-6

6-8

8-10

10-12

12+

U (m/s)

Offshore Wind Rose at 15N, 81E-SW Monsoon


N

NE

E

SE

S

SW

W

NW

Calm0.2%

5

10

15

20

25%

0-2

2-4

4-6

6-8

8-10

10-12

12+

U (m/s)

Offshore Wind Rose at 15N, 81E-NE Monsoon


P a g e | 34

equations on a rectangular or curvilinear grid (Refer to Annexure IV of EIA Report). For the modelling

study, Delft3D has been simulated in a 2D depth-averaged configuration. The 2D depth averaged

hydrodynamic model provides sufficient detail of flow circulation to simulate further the oil spill

model (GNOME). Details of the hydrodynamic model are presented in the subsequent sections of

this report.

1.2.3.1 Computational Grid and Bathymetry

The site-specific local curvilinear hydrodynamic model grid was built as shown in Figure 1-17. The

model grid is presented in the UTM-44N co-ordinate system and WGS84 datum. The grid covers an

area of approximately 150km x 80 km.

Figure 1-17: Computational hydrodynamic model grid

The bathymetry for the model was interpolated on to the computational grid using Delft3DQuickin

module. For the present study, depth information has been compiled from bathymetry surveys

(provided by client) and digitised Admiralty/Indian naval hydrographic charts. Mean Sea Level (MSL)

is taken as reference level. The bottom depths were therefore corrected to MSL with the relation:

MSL = CD + 0.9m, which is based on the information provided in the Indian Tide Table (ITT) and

Admiralty charts. Figure 1-18 shows model bathymetry.

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Figure 1-18: Model Bathymetry

1.2.3.2 Boundary Conditions

Tide

The boundary conditions for the model were based on tidal components, derived from TPXO-7.2

database. In total 11 tidal constituents (M2, S2, N2, K2, K1, O1, P1, Q1, MF, M4 and MN4) were used.

The phases of the components are with respect to UTC (or GMT), so the results should be shifted in

time to convert them to a local time zone.

Krishna River Discharge

The run-offs information of the Krishna River was extracted from the Integrated Hydrological Data

Book, 2012 published by Hydrological Data Directorate Information Systems organisation of water

planning & projects wing Central Water Commission, New Delhi.

The river discharge published at Prakasam Barrage Vijayawada and shows a large seasonal variation.

However, the average river discharge (14,080 m3/s) from the maximum (28,140 m3/s) and minimum

(18.95 m3/s) reported was used in the study.

Winds

The wind conditions at offshore location 15° N and 81°E off the project site were obtained from the

National Center of Environmental Prediction (NCEP). NCEP provides long-term offshore wind

conditions for the world oceans on a grid with 0.5° x 0.5° resolution. The offshore wind climate

derived from the NCEP database is presented in the form of wind roses. Figure 1-14 above shows the

annual offshore wind rose off Chirala. Seasonal wind roses are presented in Figure 1-15 and Figure

1-16.

Winds in this region are moderate with the hourly mean wind speed exceeds 12 m/s approximately

2.5% of the time. Wind speeds above 10 m/s mostly originates from directions between west and

P a g e | 36

south. Although, small percentage of winds (less than 1% of the time) with speeds above 10 m/s was

observed from NE direction.

1.2.3.3 Model Calibration

Hydrodynamic model were calibrated against the observed tide extracted from TIPS global model at

six coastal stations within the model domain and location of these coastal stations were presented in

Figure 1-17 and Figure 1-18. The local (detailed) model was simulated with tidal boundary conditions

derived from the TPXO database, NCEP wind and Krishna river discharge applied at upstream

boundary. Figure 1-19 to Figure 1-24 shows the comparison of model simulated tide and tide

extracted from TIPS global model at 6 coastal stations. It could be clearly seen the comparison with

observed TIPS tides are in good agreement with model simulated tide.

Figure 1-19: Comparison of tide extracted from TIPS with simulated tide at location TIPS-C1


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Current measurements for this region were not available to calibrate the model results. Literature

review indicated that the current speeds in this region are in the order of 0.15 to 0.30 m/s. Model

simulated currents with combination of astronomical tide, wind and Krishna river discharge

predicted the current speeds in the similar order of magnitude as reported in the literature.

These hydrodynamic conditions are sufficient for preliminary assessment of fate of the oil spills.

Therefore, we proceeded with oil spill dispersion study using the results from hydrodynamic

modelling.

1.2.3.4 Results

After model calibration, the detailed model was set up and run with proposed exploration sites.

Figure 1-25 shows the maximum flow field during the heavy winds in this region in the SW monsoon

period. Flow field during NE monsoon period during the heavy winds is presented in Figure 1-26. It

was observed that the current speeds are in the order of 0.15 to 0.35 m/s in the area of interest and

relatively higher during the SW monsoon due to stronger winds compared to NE monsoon.

Negligible current speeds less than 0.05 m/s were observed in the deeper waters during both the

seasons.

Figure 1-25: Maximum flow field during SW monsoon (July)

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Figure 1-26: Maximum flow field during NE monsoon (November)

1.2.4 Oil Spill Modelling

In order to assess the fate of the spilled oil from the exploration sites, GNOME model is used.

GNOME (General NOAA Oil Modelling Environment) is a two-dimensional Eulerian/Lagrangian oil

spill trajectory model that simulates the movement of oil due to winds, currents and spreading.

GNOME is freely available and may be run in “standard mode”, an automated mode used for spill

planning, and “diagnostic mode”, designed to accurately model real spills.

Currents are the main driving force for the movement the spilled oils in marine environment and for

the present study, output from the hydrodynamic modelling (Section 8.1.3) along with NCEP wind

data were used.

1.2.4.1 Model Setup

GNOME model was set up for real time scenarios in “diagnostic mode” using flow conditions

simulated by the hydrodynamic modelling and time varying NCEP wind speed/direction as movers.

1.2.4.2 Base map

Base map files represent the coastline/shoreline of the area of interest. Map file for the present

study was downloaded from the GOODS’ (GNOME Online Oceanographic Data Server) map

generator tool (http://gnome.orr.noaa.gov/goods). This tool produces shoreline data in a boundary

file atlas (BNA) format. BNA maps use vector shorelines which are rasterized by GNOME into a land

and water bitmap in order to track the oil beaching.

1.2.4.3 Movers – Currents and Winds

GNOME accepts currents and wind as movers. The movement of the oil is calculated from the u

(east-west) and v (north-south) velocity components. Hydrodynamic model output of u-currents and

v-currents were extracted and written in NetCDF format for the entire simulation period.

Time varying NCEP wind speed and direction applied spatially uniformly over the entire domain was

defined as another mover for the present GNOME model.

http://gnome.orr.noaa.gov/goods

P a g e | 40

1.2.4.4 Oil Type and Quantity

Oil spills in GNOME can be modelled as up to 10,000 lagrangian elements (LEs), each of which have

parameters assigned including location, release time, age, pollutant type, and status. The status of

each LE may be floating, beached, evaporated or off the map, and a mass balance summary provided

in GNOME shows the proportion of the total spill in each category throughout the simulation.

In this present study, the oil type considered is ‘non-weathering’ type2 which is typically used for all

the oil spill trajectory prediction studies. The spilled size considered is 10,000 barrels, which

represents a worst case scenario. The spilled 10,000 barrels of oil has been modelled as 10,000

splots, such that each splot represents one barrel of spilled oil. Table 1-12 presents the details of oil

parameters.

Table 1-12: Details of Aspects Considered for Modelling

Sl. No. Parameters Value/Type

1. Oil Type Non-Weathering oil

2. Quantity of oil Spilled 10,000 barrels

3. Spill Type Instant Release

4. Total no of Spill Locations 3

5. Seasons North East monsoon (Oct - Dec) and South West monsoon (Jun – Aug)

6. Total no of simulations 8

7. Modelling period 84 hours

8. Model Time step 1 hour

1.2.4.5 Oil Spill locations

As per the drilling plan, one near shore and two far shore exploration sites were considered in the

GNOME model for oil spill modelling study. Table 1-13 presents the co-ordinate of the oil spill

locations and shown in Figure 1-27.

Table 1-13: Co-ordinates of the oil spill locations

Code Latitude Longitude Type of Location

S1 15°41'52.74"N 80°23'38.79"E Nearshore

S6 15°34'3.31"N 80°45'47.29"E Far shore

S7 15°31'23.78"N 80°32'35.77"E Far shore

2 Non weathering oil is an oil type that does not change chemically or physically over time in the marine

environment. Weathering Processes like evaporation, emulsification etc., affect spills and no-weathering oils doesn’t considered these processes hence the trajectory oil spill analysis for non-weathering type represents worst case scenario.

P a g e | 41

Figure 1-27: Oil Spill Locations

1.2.4.6 GNOME Results

The amount of oil beached was output from the model 12, 24, 48 and 72 hours. Error! Reference

source not found. shows the GNOME model predicted dispersion of spilled oil from the nearshore

location (S1) during NE monsoon after 12, 24, 48 and 72 hours duration.

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Figure 1-28: Dispersion of spilled oil at near shore location S1- NE Monsoon

Dispersion of spilled oil at near shore location S1 after 12 hrs – NE Monsoon




The GNOME model predicted dispersion of spilled oil from the nearshore location (S1) during SW

monsoon after 12, 24, 48 and 72 hours duration are presented in Error! Reference source not

found..

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Figure 1-29: Dispersion of spilled oil at offshore location S1- SW Monsoon

Dispersion of spilled oil at offshore location S1 after 12 hrs – SW Monsoon




Figure 1-30 shows the GNOME model predicted dispersion of spilled oil from the far shore location

(S6) during NE monsoon after 12, 24, 48 and 72 hours duration.

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Figure 1-30: Dispersion of spilled oil at far shore location S6- NE Monsoon

Dispersion of spilled oil at far shore location S6 after 12 hrs – NE Monsoon




Similarly, the GNOME model predicted dispersion of spilled oil from the far shore location (S6)

during SW monsoon after 12, 24, 48 and 72 hours duration are presented in Figure 1-31. The change

in direction of wind takes the spill in the opposite direction away from the shores.

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Figure 1-31: Dispersion of spilled oil at far shore location S6- SW Monsoon

Dispersion of spilled oil at far shore location S6 after 12 hrs – SW Monsoon




It can be inferred from the above figures that the spilled oil at far shore exploration site (S6) is

floating on the seawater surface even after 72 hours. The spilled oil leaves the model domain

between 48 and 72 hrs of simulation.

Figure 1-32 shows the GNOME model predicted dispersion of spilled oil from the far shore location

(S7) during NE monsoon after 12, 24, 48 and 72 hours duration.

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Figure 1-32: Dispersion of spilled oil at far shore location S7- NE Monsoon





Similarly, the GNOME model predicted dispersion of spilled oil from the far shore location (S7)

during SW monsoon after 12, 24, 48 and 72 hours duration are presented in Figure 1-33.

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Figure 1-33: Dispersion of spilled oil at far shore location S7- SW Monsoon





Dispersion results at far shore exploration site (S7) indicate that the spilled oil was floating on the

seawater surface even after 72 hours during the SW monsoon. Whereas, the spilled oil is likely to be

beached in 72 hours of the release time during NE monsoon.

1.2.5 Conclusions and Recommendations

Overall the model predicts the dispersion of spilled oil at all three locations satisfactory. However,

the hydrodynamic model should be calibrated against the site measured current magnitude/

direction and re-assess the impact of dispersion of oil spill on the marine environment in this region

in the next stage of the project execution.

The following inferences are drawn from the present study:

P a g e | 48

Hydrodynamic model simulated and calibrated against the observed tide from TIPs.

Simulated tide was in good agreement against the observed tide.

Simulated currents are in the order of 0.15 to 0.35 m/s during both the seasons, as verified

with literature.

During the NE monsoon, the oil spill from the near-shore location is potentially threatening

for Ongole coastal regions.

During the SW monsoon, the spilled oil from near-shore location is potentially threatening

for Krishna Estuary region. Potentially, spilled oil can enter inside the Krishna river basin

from the near-shore location.

The oil spilled from far-shore locations has less impact on nearby coastal regions; however

during NE monsoon, the spill from far-shore locations nearer to Ongole coastal regions will

have potentially threatening impacts.

Spilled oil from nearshore locations requires immediate attention and containment activities

should start within 24 hours of spill to avoid major impacts on the marine environment.

The precautionary and mitigation measures are recommended below for each spill location.

Table 1-14: Recommended Precautionary and Mitigation Measures

Spill Location Precautionary Measure Mitigation Measure

Near Shore locations around S-1

No drilling activities to be undertaken during NE Monsoons.

Adequate arrangement for mobilization of containment boom within 12 hours and installation within 24 hours shall be ensured prior to any drilling activities during South West Monsoons

Arrangements shall be made at Nizamapatnam port or any other adjacent area to enable quick mobilization of response team (within 6 hours).

Far-shore locations around S-6

Potential for spill will reach Ongole coast after 72 hours in NE monsoons. No activity shall commence without adequate mitigation measures.

Adequate arrangement for mobilization of containment boom within 24 hours and installation within 48 hours shall be ensured prior to any drilling activities during North East Monsoons

Arrangements shall be made in any adjacent area to enable quick mobilization of response team (within 24 hours).

Far-shore locations around S7

Potential for spill to reach Ongole coast after 48 hours in NE monsoons. No activity shall commence without adequate mitigation measures.

Adequate arrangement for mobilization of containment boom within 12 hours and installation within 24 hours shall be ensured prior to any drilling activities during North East Monsoons

Arrangements shall be made in any adjacent area to enable quick

P a g e | 49

Spill Location Precautionary Measure Mitigation Measure

mobilization of response team (within 12 hours).

Although the spill will be away from Krishna Sanctuary during SW monsoon, however adequate preparation shall be there for mobilization within 24hours.

Documents

Risk Assessment and Oil Spill Modellingenvironmentclearance.nic.in/writereaddata/online/RiskAssessment/... · Risk Assessment and Oil Spill Modelling ... Figure 1-4 provide the typical