prefeasibility report for tapti offshore part b...

Enclosure -1

Prefeasibility Report for Tapti Offshore Part B

Decommissioning

By

Panna Mukta Tapti Joint venture (PMT JV)

April 2017

CONTENTS

1 EXECUTIVE SUMMARY 1

2 INTRODUCTION OF THE PROJECT / BACKGROUND INFORMATION 3

2.1 REGULATORY GUIDELINES AND STANDARDS 4

2.1.1 Applicable National Regulations 4

2.1.2 Applicable International Regulations 4

3 PROJECT DESCRIPTION 6

3.1 DECOMMISSIONING WORK FLOW 7

3.2 PLATFORM DETAILS 7

3.3 PLATFORM STATUS 8

4 SITE ANALYSIS 10

4.1 CONNECTIVITY 10

4.2 LAND OWNERSHIP 10

4.3 WEATHER CONDITIONS 10

4.4 SEABED AND SOIL CHARACTERISTICS 13

5 PLANNING BRIEF ERROR! BOOKMARK NOT DEFINED.

5.1 CONCEPT SELECTION 14

5.1.1 Select and Define Stage 14

5.2 COMPARATIVE ASSESSMENT 15

5.3 WASTE MANAGEMENT 18

6 PROPOSED INFRASTRUCTURE 20

7 REHABILITATION AND RESETTLEMENT (R&R) PLAN 21

8 PROJECT SCHEDULE & COST ESTIMATES 22

9 ANALYSIS OF PROPOSAL (FINAL RECOMMENDATIONS) 23

PMT JV PREFEASIBILITY REPORT – TAPTI OFFSHORE DECOMMISSIONING

ENCLOSURE 1 APRIL 2017

1

1 EXECUTIVE SUMMARY

Panna, Mukta and Tapti Joint Venture (PMT JV) comprising of Oil & Natural

Gas Corporation Limited (‘ONGC’), Reliance Industries Limited (‘RIL’) and

BG Exploration and Production India Limited (‘BGEPIL’) operates the Mid

and South Tapti Contract Areas (‘Tapti Fields’). The Tapti Fields (admeasuring

1,471 km2) is located offshore and are located 35 km from Saurashtra Coast, 75

km from Hazira and 160 km north-west of the city of Mumbai. The Tapti block

contains two fields - Mid Tapti and South Tapti and is governed by the Mid

and South Tapti Production Sharing Contract (the ‘Tapti PSC’). The Tapti

Fields lie in approximately 21 m of water depth, on the northeast flank of the

Surat Depression.

The Tapti Fields went into a phase of decline after 2008 and cessation of

production was finally declared in March 2016.

Certain Facilities at the Mid and South Tapti Fields known as the Tapti Part A

Facilities (comprising of platforms TCPP, TPP and TFP and the 18” and 20”

export pipelines) were handed over to ONGC pursuant to the directions

arising out of a meeting dated 5th January 2015, at the Ministry of Petroleum

and Natural Gas (MoPNG) under the chairmanship of Joint Secretary (E).

ONGC will be using the Tapti Part A Facilities for processing gas from its

nearby Daman and C-Series fields.

Post cessation of production, the remaining facilities in the Tapti Fields

(comprising of 38 wells and 5 wellhead platforms (STA, STB, STC, STD and

MTA and associated intra-field pipelines)) known as the Tapti Part B Facilities

are to be abandoned by the PMT JV as required under the Oilfields Act, 1948,

the Petroleum and Natural Gas Rules, 1959 and the Tapti PSC.

This pre-feasibility report is submitted in connection with procuring an

amendment to the existing Environment Clearances for the

abandonment/decommissioning of the Tapti Part B Facilities.

Regulatory Guidelines and Standards

Applicable National Regulations

Environmental (Protection) Act 1986, Ministry of Environment & Forests (India),

May 1986 and corresponding Rules as applicable;

Site Restoration and Abandonment Guidelines for Petroleum Operations,

Annexure 1 - Recommendations of the Committee, Ministry of Petroleum and

Natural Gas, March 2016.

Petroleum and Natural Gas (Safety in Offshore Operations) Rules (India), June

2008;

Guidelines and Standards for the Removal of Offshore Installations and Structures

on the Continental Shelf and in the Exclusive Economic Zone, International

Maritime Organisation (IMO), Resolution A.672 (16), October 1989

Hazardous and Other Wastes (Management and Transboundary Movement)

Rules, Ministry of Environment, Forest and Climate Change (India), April 2016



2

Guiding International Regulations

International Convention for the Prevention of Pollution from Ships (MARPOL

73/78);

United Nations Convention on the Prevention of Marine Pollution by Dumping of

Wastes and Other Matter, 1977;

London Convention: Convention on the Prevention of Marine Pollution by

Dumping of Wastes and Other Matter, 1972 with 2006 Amendments.

Project Description

The Tapti Decommissioning Project comprises of safe plugging and

abandonment of 38 wells, and safe and environment-friendly

decommissioning and disposal of 5 wellhead platforms (STA, STB,

STC, STD & MTA) and associated intra-field pipelines in Tapti Field

(i.e., the Tapti Part B Facilities).

Decommissioning Work Flow

Platform status transitions from Operating to Warm Stack once platform has

permanently ceased production and has live wells and/or live process.

Platform status transitions in to Cold Stack status when all wells have been

permanently plugged and abandoned, conductors cut below seabed and process

and pipeline systems are permanently decommissioned ready for removal.

Removal status commences once contractor heavy lift vessel removal work

commences.

Dismantle / Disposal status commences once platforms are transported to

onshore disposal site.

Platform Status

The platforms within Tapti Field have a nominal water depth of 21m. All facilities to

be removed (i.e., the Tapti Part B Facilities) have been flushed and cleaned, and will

be disconnected prior to removal. In general, the platforms will be available for

removal in the following condition:

Platform topside vessels and pipeline are cleaned and flushed. All hydrocarbons

are removed. Equipment are cleaned and purged for topside removal.

Intra-field pipelines are cleaned, flushed and pigged.

It was confirmed that Naturally Occurring Radioactive Material (NORM) and

heavy metal and wax are below allowable threshold levels.

Wells are currently being plugged and abandoned.

All process systems are isolated and disconnected at each platform end adjacent to

bridge link (STB).

Pipelines are cleaned to a defined standard with removal of all mobile

hydrocarbons.

Platform will be in Cold Stack status with all wells permanently plugged &

abandoned. Conductors will be secured to the jacket structure and cut below 5m

from seabed and removed with the topside and jacket lifts.

Platforms will be cold stacked with solar powered navigation aids and foghorn in

place.

Site Analysis

The Tapti Block (admeasuring 1,471 km2) is located offshore. The nearest shore

location is Hazira which is 75 km from mid Tapti Field and 60 km from the block

boundary.



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There are no issues of land ownership as the entire locality is defined as Government

controlled, with the ONGC, RIL and BGEPIL Joint Venture leasing the site from

Government.

Concept Selection

The concept selection was made through comparative assessment (CA) process. Final

options are evolved after rigorous screening process which considered various criteria

such as safety, environment, societal, technical and cost.

A number of studies were carried out for the jackets and pipelines to inform the

following comparative assessment criteria; As part of the development of this

Qualitative Comparative Assessment, high level HAZID and SENVID sessions were

held, together with the development of AACE Level 5 cost estimates. The criteria

adopted for selection of appropriate options is as below:

Safety risk for all personnel involved in, or affected by, the various

decommissioning options both onshore and offshore, including the residual risks

to fishermen and marine personnel.

Environmental impact of all activities at the offshore location, potential offshore

disposal sites and onshore disposal site.

Technical feasibility of implementing the decommissioning operation.

Societal impact on other users of the sea and business communities with the

potential to be impacted by the decommissioning activities.

Topside

It was decided that Topsides are not required to be considered in the CA process as all

topside facilities will be removed from the field and disposed off in a 3rd party

onshore yard.

Jacket

From the Tier 1 Comparative Assessment 1/screening workshop 1, External

stakeholders (DGH, OISD & MoEF) and PMT JV agreed that the only Option 1 –

Jacket removal and Onshore Disposal considered for Jacket structures.

Pipelines

From the Tier 2 Comparative Assessment 2/screening workshop 2, External

stakeholders (DGH, OISD & MoEF) and PMT JV agreed that Option 1 - Leave

pipeline in-situ, plug & protect pipeline end (concrete mattress) considered for

intra-field pipeline

Waste Management

The key underlying principle of waste management is the

application of the Waste Hierarchy. PMT JV has developed

inventory of material that will be recovered from the

decommissioning activities from the Tapti Part B facilities and will

be disposed of suitably at a 3rd party onshore yard. PMT JV will

ensure that the selected 3rd party has adequate capacity to carry out

dismantling and disposal of all offshore structures using safe and

environment-friendly practices. For storage of dismantled

structures/material in the onshore yard, the selected 3rd party will

obtain approval from Maharashtra State Pollution Control Board.



4

Proposed Infrastructure

The project involves decommissioning of Tapti Field (South and Mid

Tapti) comprising of five wellheads in the offshore area which is ~60

km from the Hazira, 20 km from Saurashtra Coast while the mid

Tapti Field is located 75 km from Hazira Coast and 35 km from

Saurashtra Coast near Gulf of Khambhat, West coast of India.

No construction work is envisaged as proposed activity is

decommissioning work. The activity will be mainly mechanical

dismantling and no demolition is envisaged as part of

decommissioning at offshore.

Rehabilitation and Resettlement

The offshore area is not inhabited. No local populations requiring rehabilitation or

resettlement.

Project Schedule and Cost Estimate

Facility removal and onshore disposal for the proposed decommissioning project is

expected to start by Q1 2019. The expected cost of the project is USD 80 million.



3

2 INTRODUCTION OF THE PROJECT / BACKGROUND INFORMATION

Panna, Mukta and Tapti Joint Venture (PMT JV) comprising of Oil &

Natural Gas Corporation Limited (‘ONGC’), Reliance Industries

Limited (‘RIL’) and BG Exploration and Production India Limited

(‘BGEPIL’) operates the Mid and South Tapti Contract Areas (‘Tapti

Fields’). The Tapti Fields (admeasuring 1,471 km2) is located offshore

and are located 35 km from Saurashtra Coast, 75 km from Hazira

and 160 km north-west of the city of Mumbai. The Tapti block

contains two fields - Mid Tapti and South Tapti and is governed by

the Mid and South Tapti Production Sharing Contract (the ‘Tapti

PSC’). The Tapti Fields lie in approximately 21 m of water depth, on

the northeast flank of the Surat Depression.

The Tapti Field is shown below in Figure 2.1

The South Tapti and Mid Tapti Fields have five (05) wellhead platforms which

are connected to the central processing complex TPP-TCPP via subsea

pipelines. The South Tapti field comprises of STA, STB, STC and STD well

head platforms, and the Mid Tapti Field comprises of MTA well head

platform. The processing platforms (TPP-TCPP) are connected to ONGC’s 36”

and 42” inch pipelines through 18” and 20” pipelines.

Figure 2.1 Tapti Field

Source: PMT JV



4

The Tapti Fields went into a phase of decline after 2008 and cessation of

production was finally declared in March 2016.

Certain Facilities at the Mid and South Tapti Fields known as the Tapti Part A

Facilities (comprising of platforms TCPP, TPP and TFP and the 18” and 20”

export pipelines) were handed over to ONGC pursuant to the directions

arising out of a meeting dated 5th January 2015, at the Ministry of Petroleum

and Natural Gas (MoPNG) under the chairmanship of Joint Secretary (E).

ONGC will be using the Tapti Part A Facilities for processing gas from its

nearby Daman and C-Series fields.

Post cessation of production, the remaining facilities in the Tapti Fields

(comprising of 38 wells and 5 wellhead platforms (STA, STB, STC, STD and

MTA and associated intra-field pipelines)) known as the Tapti Part B Facilities

are to be abandoned by the PMT JV as required under the Oilfields Act, 1948,

the Petroleum and Natural Gas Rules, 1959 and the Tapti PSC.

2.1 REGULATORY GUIDELINES AND STANDARDS

2.1.1 Applicable National Regulations

The decommissioning strategy for Tapti B Facilities shall

comply and be congnizant of the laws of India and in specific

with the following regulations:

Environmental (Protection) Act 1986, Ministry of Environment & Forests

(India), May 1986 and corresponding Rules as applicable;

Site Restoration and Abandonment Guidelines for Petroleum Operations,

Annexure 1 - Recommendations of the Committee, Ministry of Petroleum

and Natural Gas, March 2016.

Petroleum and Natural Gas (Safety in Offshore Operations) Rules (India),

June 2008;

Hazardous and Other Wastes (Management and Transboundary

Movement) Rules, Ministry of Environment, Forest and Climate Change

(India), April 2016

The following regulations may also be referred to as a source of guidance

throughout the project lifecycle as required:

OISD Guidance Note April 2012 on Rule 12 - Decommissioning Plan

OISD Guidance Note April 2012 on Rule 22 – Barriers

2.1.2 Guiding International Regulations

The decommissioning strategy for Tapti facilities as shall also be guided by

the following international standards and guidelines.



5

Guidelines and Standards for the Removal of Offshore Installations and

Structures on the Continental Shelf and in the Exclusive Economic Zone,

International Maritime Organisation (IMO), Resolution A.672 (16), October

1989

International Convention for the Prevention of Pollution from Ships

(MARPOL 73/78);

United Nations Convention on the Prevention of Marine Pollution by

Dumping of Wastes and Other Matter, 1977;

London Convention: Convention on the Prevention of Marine Pollution by

Dumping of Wastes and Other Matter, 1972 with 2006 Amendments.



6

3 PROJECT DESCRIPTION

The Tapti Decommissioning Project comprises of safe plugging and

abandonment of 38 wells, and safe and environment-friendly

decommissioning and disposal of 5 wellhead platforms (STA, STB, STC, STD

& MTA) and associated intra-field pipelines in Tapti Field (i.e., Tapti Part B

Facilities). Further details are provided in Appendix A.

Box 3.1 Platform Photographs

Source: PMT JV

A Tapti Abandonment Working Group had been set up under the DGH order

DG/DGH/Tapti/02/2013 of 12 December 2013, and has carried out a review

STA Wellhead Platform STB Wellhead Platform

STC Wellhead Platform STD Wellhead Platform

MTA Wellhead Platform



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of the available Indian and international regulations on offshore facilities

decommissioning, and accordingly defined the broad regulatory and technical

framework for abandonment of the Tapti Fields (the ‘Tapti Abandonment

Working Group’). The members of this Working Group included Directorate

General of Hydrocarbons (DGH), Oil Industry Safety Directorate (OISD),

Institute of Engineering and Ocean Technology (IEOT), ONGC, RIL, and

BGEPIL.

The Tapti Working Group report was submitted to DGH in March 2014 and a

‘Management Committee’ (MC) meeting with the GOI has given approval of

the Tapti High Level Abandonment Plan and the scope of the abandonment

obligations of the PMT JV for the Tapti Part B Facilities. The Working Group

report contains several options for abandonment of jackets, topsides,

pipelines, and wells (Rig based and Rig-less Abandonment), for the Tapti

wellhead platforms (STA, STB, STC, STD and MTA).

3.1 DECOMMISSIONING WORK FLOW

The workflow adopted for decommissioning of the Tapti Field is shown below

in Figure 3.1. The platforms are in warm stack at present but will be in cold

stack at the time of facility decommissioning, with the wells plugged and

abandoned.

Figure 3.1 Decommissioning Work Flow

Source: PMT JV

Platform status transitions from Operating to Warm Stack once platform

has permanently ceased production and has live wells and/or live process.

Platform status transitions in to Cold Stack status when all wells have been

permanently plugged and abandoned, conductors cut below seabed and

process and pipeline systems are permanently decommissioned ready for

removal.

Removal status commences once contractor heavy lift vessel removal work

commences.

Dismantle / Disposal status commences once platforms are transported to

onshore disposal site.

3.2 PLATFORM DETAILS

The summary of the Tapti Part B Facilities is provided in Table 3.1. Complete

details of these facilities are detailed in Appendix A.



8

Table 3.1 Platform Details

Facility Year of

Installation

Appurtenances No. of

wells

UTM-

Coordinates

Topsides Jacket

Dimensions

STA 1996 8x Conductors

2x Risers 8

2,284,117.25 N

819,725.51 E

Main Deck

Cellar Deck

18.6m x 18.6m

Plan

STB 1996 8x Conductors 8 2,280,930.46 N

816,491.79 E

Main Deck

Cellar Deck

18.6m x 18.6m

Plan

STC 1996 8x Conductors

2x Risers 8

2,278,152.61 N

813,003.76 E

Main Deck

Cellar Deck

18.6m x 18.6m

Plan

STD 2006 5x Conductors

2x Risers 5

2,274,759.53 N

810,175.30 E

Main Deck

Cellar Deck

18.77m x 22m

Plan

MTA 2007 9x Conductors

2x Risers 9

2,296,810.96 N

804,726.84 E

Main Deck

Cellar Deck

Helideck

16m x 18.3m

Plan

The weight details of various facilities of the platform are given below in

Table 3.2

Table 3.2 Weight Information

Facility MTA STA STB STC STD

Topsides Weight (tonnes) 845 502 575 505 770

Jacket Weight (tonnes) 817 763 759 794 1096

Conductors Dry Weight (tonnes) 517 312 312 312 266

Total Weight (tonnes) 2179 1577 1579 1611 2132

3.3 PLATFORM STATUS

The platforms within Tapti Field have a nominal water depth of 21m. All

facilities to be removed have been flushed and cleaned, and will be

disconnected prior to removal.

In general, the platforms will be available for removal in the following

condition:

Platform topside vessels and pipeline are cleaned and flushed. All

hydrocarbons are removed. Equipment are cleaned and purged for topside

removal.

Intra-field pipelines are cleaned, flushed and pigged.

It was confirmed that Naturally Occurring Radioactive Material (NORM)

and heavy metal and wax are below allowable threshold levels.

Wells are currently being plugged and abandoned.

All process systems are isolated and disconnected at each platform end

adjacent to bridge link (STB).

Pipelines are cleaned to a defined standard with removal of all mobile

hydrocarbons.

Platform will be in Cold Stack status with all wells permanently plugged

& abandoned. Conductors will be secured to the jacket structure and cut

below 5m from seabed and removed with the topside and jacket lifts.



9

Platforms will be cold stacked with solar powered navigation aids and

foghorn in place.



10

4 SITE ANALYSIS

4.1 CONNECTIVITY

The Tapti Block (admeasuring 1,471 km2) is located offshore, 160 km north-

west of the city of Mumbai. It lies in approximately 21 m of water depth, on

the northeast flank of the Surat Depression. The nearest shore location is

Hazira which is 75 km from mid Tapti Field and 60 km from the block

boundary.

4.2 LAND OWNERSHIP

There are no issues of land ownership as the entire locality is defined as

Government controlled, with the ONGC, RIL and BGEPIL Joint Venture

leasing the site from Government.

4.3 WEATHER CONDITIONS

The following sections cover general meteorological data – wind, current,

wave design criteria, water levels, etc.

General Meteorological Data

Parameter Details

Location South Tapti

Environment Marine

Air Temperature (Max. /Min.) 17.78 °C (64 °F) / 40 °C (104 °F) (Min / Max)

Seawater Temperature

(Max./Min.) 23 °C (73.4 / 27 °C / 80.6 °F (Min / Max)

Design Ambient Air

Temperature 17.78 °C (64 °F) / 40 °C (104 °F) (Min / Max)

Humidity 60 - 90%

Design Wet Bulb 100 % RH

Design Solar Radiation 288.468 Btu/ft2.h

Rainfall 1500mm per year (Average) 100mm in 2 hours

(Maximum)

Barometric Pressure

(Min/Max) 14.3587 / 14.6923 psi (Min / Max)

Water Depth

The minimum and maximum water depth values for a given soil type and

pipeline bearing angle are summarised below:

20” MTA-TCPP Pipeline with 4” TCPP-MTA Piggybacked

Parameter Pipeline Heading Water Depth [m]

Water Depth in Silty Sand 180° - -

135° 18.0 21.6

Water Depth in Silty Clay 180° 16.4 21.9



11

135° 19.2 21.2

All other pipelines are reported to be totally exposed as in the 2015 survey

data and as such, the minimum water depth along the pipeline route was

selected for analysis, as summarised below:

18” STD-TPP Pipeline


Water Depth in Silty Clay 239°

21.2 212°

12” STC-TPP Pipeline with 2” TPP-STC Piggybacked


Water Depth in Silty Clay 51° 21.2

10” STC-TPP Pipeline with 2” TPP-STA Piggybacked


Water Depth in Silty Clay 223° 21.2

Tidal and Strom Surge Data

The tide and storm surge data are listed as below:

Parameter Unit Return Period

1-Year 10-Year 100-Year

HAT m 4.36 4.33 4.36

Storm tide m 0.85 0.85 1.62

Total Tide (HAT + Storm) m 5.21 5.18 5.97

Tidal activity was observed at the TCPP platform in the Tapti field for the

month of May (2015). The maximum range of tide observed was 5.72 m during

the new moon phase and minimum range was observed to be 0.74 m during

neaps.

Wind, Current and Wave Design Criteria

Environmental data are in accordance with the A. H. Glenn & Associates

Metocean & Environmental data for the Tapti fields available unless noted

otherwise. Operating (One year) and extreme condition (100 year)

environmental parameters are given for reference. These data shall be

interpreted and utilised to suit during the SELECT stage as per recommended

code of practice and HSSE guidelines.

Waves

The environmental criteria shall be interpreted, computed and used based on

data provided in the report by A.H. Glenn & Associates for the Omni-

directional waves and currents for different analyses.

Return

Period

Design

Parameter N NE E SE S SW W NW

1-Year

Operating

Significant Wave

height (m) 2.62 2.68 2.68 2.71 4.60 5.58 5.58 2.47

Associated Wave

Period (S) 6.0 6.1 6.1 6.1 8.3 9.4 9.4 5.8



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100-Year

Storm

Significant Wave

height (m) 4.75 6.07 6.07 6.07 9.33 9.17 9.02 4.60

Associated Wave

Period (S) 8.5 9.7 9.8 9.9 12.5 12.4 12.3 8.3

Current

The current profile shall be stretched non-linearly above LAT in accordance

with API RP2A Latest Edition.

Return Period

% Water Depth

N NE E SE S SW W NW

1-Year Operating

0 1.3 1.5 1.2 0.8 1.3 1.5 1.3 0.9

50 1.0 1.2 1.0 0.6 1.0 1.2 1.1 0.7

90 0.7 0.9 0.7 0.5 0.7 0.9 0.8 0.5

100 0.6 0.7 0.6 0.4 0.6 0.7 0.6 0.4

100-Year Storm

0 1.6 1.8 1.6 1.2 1.6 1.8 1.1 1.3

50 1.2 1.4 1.2 0.8 1.2 1.3 0.8 1.0

90 0.8 0.9 0.8 0.5 0.8 0.9 0.5 0.8

100 0.6 0.7 0.6 0.4 0.6 0.7 0.4 0.6

Wind

The directionality data for wind speeds at 10.0m above mean sea level are

provided below:

Return

Period

Design

Parameter N NE E SE S SW W NW

1-Year

Operating

1-Hour

Wind 17.9 17.9 16.5 16.5 17.9 21.5 21.5 17.4

100-Year

Storm

1-Hour

Wind 37.5 38.4 38.4 38.4 38.4 36.7 35.3 35.8

Nominal wind, wave and current data for Tapti field are provided in A.H.

Glenn & Associates Environmental and Metocean data, which will be

prevailing during non-monsoon months (working weather window).

Following table presents the indicative values for ready reference

Tapti Field (Wind, Wave & Current)

Design Parameter Nominal (Working weather Window)

Wind (1 Hour) 15 m/sec

Wave (Hs) 2.4 m

Current 1.5 m/sec at surface 1 m/sec at mud-line

Operating Weather Windows

Below detail the weather windows that affect the decommissioning operations

in the Mid and South Tapti fields and defines the risk associated with each

weather window

Risk Rating Date Range

High Risk May - September

Medium Risk 2nd Half April & 1st Half October

Low Risk 2nd Half October – 1st Half April



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Tropical Storm Data

It is noted that the Arabian Sea is subject to cyclonic disturbances, the average

is between 2-3 per year between 1891 and 1970. About half of these

disturbances are classed as storms. Depressions with winds between beaufort

force 8 and 9 are termed tropical storms, wind forces 10-11 are classed with

severe tropical storms and wind force 12 and over are classed as cyclones. A

feature of these storms is a “storm surge”; the piling up of water which when

it reaches the coast causes widespread flooding.

There are two times of the year when tropical storms are frequent; one at the

onset of the southwest Monsoon extending from late May to early June, and

the second period at the onset of the northeast Monsson, from late October to

the end of November. About three quarters of all storms occur during these

periods. While the average frequency of tropical storms in the Arabian Sea is

once a year, there have been years when three have occurred. Gales (wind

force greater than 7) are most frequent at the height of the southwest

monsoon.

In June, storms form in the Arabian Sea and initially move north or northwest.

Some curve towards the west in their later stages while others curve north and

northeast towards the coast. Most tropical storms in October to November

originate in the Bay of Bengal and move west or northwest across India into

the Arabian Sea. Some continues to move west while others recurve towards

the northeast.

In winter and spring the northern part of the Arabian Sea may be affected by

western depressions moving east or northeast towards Pakistan. From

November to April, there may be four such depressions each month.

4.4 SEABED AND SOIL CHARACTERISTICS

Following table presents the Tapti soil characteristics of top 12 meters as

below:

Penetration Soil type Description

0 – 5 ft Very soft clay

5 – 14 ft Soft clay

14 – 45 ft Firm to stiff clay



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5 CONCEPT SELECTION

The concept selection was made through comparative assessment (CA)

process. Final options are evolved after rigorous screening process which

considered various criteria such as safety, environment, societal, technical and

cost.

5.1.1 Select and Define Stage

Various options as depicted below in Figure 5.1 were considered for

decommissioning of facilities, denoting ‘What to do’ such as leave in-situ or

remove, and also ‘How to do’ such as partial removal or complete removal or

reefing or deep water disposal.

The alternate use (in-situ) option is being exercised for TPP-TCPP-TFP

platforms and export pipelines only. Rest of the options shown in the options

tree above pertain to wellhead platforms, infield pipelines (to TPP/TCPP

processing platforms).

Figure 5.1 Select and Define Stage

Source: PMT JV

The Select and Define stage activities shall include the following:

Select (Concept Selection) stage – This involves eliminating the non-

starters (infeasible options) followed by evaluating the multiple options

for Facilities and Wells using agreed screening parameters and studies,

and narrowing it down to the final selected executable strategy (ies) to

decommission the Facilities and Wells in a safe, environmentally friendly

manner with optimized cost and schedule.



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The final selected executable strategy (ies) will be a combination and

sequencing of selected option(s) for jackets, topsides, pipelines and wells

into a full execution programme. More than one executable strategy may

be selected at the end of the Select stage, if they score equally on all

screening parameters, and these multiple executable strategies will be

taken to the execute stage for final selection by the execute stage

contractor.

The options screening will be carried out using a comparative assessment

process in 2 phases broadly – qualitative, followed by quantitative, finally

leading to selection of final strategy (ies) as below,

Within each stage (qualitative/ quantitative), comparative assessment will be

done by scoring each option on parameters such as safety, technical feasibility,

environmental impact, social impact, economics etc., and arriving at the final

score for each option using pre-agreed weightages for each parameter.

Technical and safety studies will be pre-agreed and carried out to score the

options as required as shown below in Figure 5.2

Figure 5.2 Workflow for Select and Define for Part B Facilities

Source: PMT JV

5.2 COMPARATIVE ASSESSMENT

A comparative assessment (CA) was carried out to compare and score options

for the decommissioning of Tapti pipelines and jackets and ultimately

development of decommissioning programmes. CA was conducted following

industry best practise. The CA workshops, held on the 17th January 2017 with

a follow up session on the 23rd January, used qualitative data to draw a



16

balanced assessment across the main criteria of safety, environmental impacts,

technical feasibility, societal impacts and project costs.

The summary findings from the comparative assessment workshop were

reported at Screening Workshop 1 attended by BGEPIL along with partners

and PDI project teams and regulatory stakeholders (DGH, OISD) in Noida on

the 7th February 2017. The summary finding was shared with MoEF&CC on 8th

February 2017.

A number of studies were carried out for the jackets and pipelines to inform

the following comparative assessment criteria; As part of the development of

this Qualitative Comparative Assessment, high level HAZID and SENVID

sessions were held, together with the development of AACE Level 5 cost

estimates. The criteria adopted for selection of appropriate options is as below:

Safety risk for all personnel involved in, or affected by, the various

decommissioning options both onshore and offshore, including the

residual risks to fishermen and marine personnel.

Environmental impact of all activities at the offshore location, potential

offshore disposal sites and onshore disposal site.

Technical feasibility of implementing the decommissioning operation.

Societal impact on other users of the sea and business communities with

the potential to be impacted by the decommissioning activities.

Topside

It was decided that Topsides are not required to be considered in the CA

process as all topside facilities will be removed from the field and disposed off

in a 3rd party onshore decommissioning yard.

Jackets

For the purposes of the Tier 1 CA, the jackets were considered collectively and

the most onerous impact was considered for the scoring. A ‘by-difference’

review was carried out for the jackets during the workshop, however no

additional issues were identified based on individual consideration.

The options considered from for jacket decommissioning from TAWG are

summarized below:

Option 1 - Removal and Disposal Onshore

Option 2 - Removal and Disposal in Deep Water

Option 3 - Removal and Disposal in an Artificial Reef

Option 4 – Partial Removal (Note 1)

Note 1: Partial removal was discounted based on insufficient water depth at the field

location.

The results of the Comparative Assessment for the jackets revealed the main

differentiators between the jacket decommissioning options to be Safety,

Technical, Societal and Cost. The Comparative Assessment concluded that

Option 1: Complete Removal and Onshore Disposal is the preferred option for



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decommissioning the Tapti jackets. The 3rd party onshore yard is not selected

yet.

From the Tier 1 Comparative Assessment, External stakeholders (DGH, OISD

& MoEF) and PMT JV agreed that the only Option 1 – Jacket removal and

Onshore Disposal considered for Jacket structures.

Pipeline

For the purposes of the Tier 1 CA, the pipelines were considered collectively

and the most onerous impact was considered for the scoring. A ‘by-difference’

review was carried out for the pipelines during the workshop, however no

additional issues were identified based on individual consideration.

The options considered for pipelines decommissioning are summarized

below:

Option 1 - Leave in-situ with no remediation if stable (Note 1)

Option 2 - Leave in-situ and stabilize

Option 3 - Partial removal of exposed sections and stabilize (Note 2)

Option 4 - Completely remove all pipelines

From the Tier 1 Comparative Assessment, External stakeholders (DGH, OISD

& MoEF) and PMT JV agreed that all option in pipeline (Leave in-situ with no

remediation, Leave In-situ and Stabilize, Partial removal for 20” MTA line

and Completely Remove all Pipelines) will be progressed to the next stage.

Recent study of on bottom pipeline stability analysis confirmed that all

pipelines are stable at seabed. Hence, Tier 2 comparative assessment will

consider only both options of option 1 – Leave In-Situ with no intervention

and Option 4 - Complete removal of pipeline.

Pipeline stability analysis has been performed to check the stability of intra-

field pipelines. Stability analysis confirms that all pipelines are found to be

stable. Based on stability analysis study outcomes, it was decided that only

leave-in situ and complete removal will be considered for comparative

assessment (CA) 2. Option 2 and 3 were discounted from CA 2.

Comparative assessment 2 was carried out on 24th April 2017 with PMT JV

and PDI Project team. The study results were presented to external

stakeholders on 8th February 2017 (DGH, OISD, MoS and MoEF).

From the Screening Workshop 2, External stakeholders (DGH, OISD & MoEF)

and PMT JV agreed that the only Option 1 – Leave pipeline in-situ, plug &

protect pipeline end (concrete mattress) considered for intra-field pipelines.

Infrastructure

STA and STD platform wells have been plugged and abandoned. In other

platform, Wells are being currently plugged and abandoned and expected to

be completed in Q1 2018. All the wells will be plugged and abandoned before

the commencement of the offshore facility removal. Topside and jacket will be



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cut and removed. Jacket will be cut at 5 m below seabed as dictated in Tapti

Abandonment Working Group committee report and transported in

designated navigational channel to onshore yard. Pipeline ends will be cut &

plugged and concrete mattress will be placed at ends. The dismantling and

disposal of the offshore structures will be performed in a 3rd party onshore

yard. PMT JV is in discussion in various yards regarding onshore dismantling

and disposal. PMT JV will ensure that the selected 3rd party has adequate capacity to

carry out dismantling and disposal of all offshore structures using safe and

environment-friendly practices. For storage of dismantled structures/material in the

onshore yard, the selected 3rd party will obtain approval from Maharashtra State

Pollution Control Board.

5.3 WASTE MANAGEMENT

The key underlying principle of waste management is the application of the

Waste Hierarchy as shown below in Figure 5.3. If a waste stream is not

managed within the hierarchy, it is probably “stranded” waste, i.e. not

managed. This may well carry significant financial, environmental,

reputational risk and, perhaps, risk to human health. To mitigate to As Low

As Reasonably Practicable (ALARP), mitigation measures may affect design

and/or require new or changes to local working procedures and practices, e.g.

local work instructions. In some cases, cost effectiveness will be a major

consideration in the mitigation process.

Figure 5.3 Waste Hierarchy

PMT JV has developed inventory of material that will be recovered from the

decommissioning activities from the Tapti Part B facilities. The detailed

inventory is listed below in Table 5.1:

Table 5.1 Waste Inventory

Category Material Location Weight (MT)



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Category Material Location Weight (MT)

Non-hazardous

Aluminium and

alloys

Anodes, Power socket, Junction box, Flood

Light, Bolts

194.7

Acrylic Optic Aviation Light, Beacon Light, Lantern 0.5

Bronze Cable Glands 2

Carbon Steel Structural, equipment’s, conductors and

casings, pipes, electrical and

instrumentations equipment’s

7802

Cement Boat landing front members, Conductors & Casing

892

Copper Cable, Cable Conductor 10.9

Glass Reinforced Plastic (GRP)

Cable trays, Firefighting equipment’s, piping

45.3

Poly Vinyl Chloride (PVC)

Water Tank, Cable, Cable sheath 16.2

Rubber Boat landing rub strips, barge bumper energy cell and neoprene on riser & clamps

43.6

Stainless Steel

pumps and tanks, Junction Box, F & G detectors, transmitters, Well head control panel, Tubes and fittings, RTU panel enclosure

129

Marine Growth Jackets 290

Nickel Fire water pumps, Valves 2.7

Miscellaneous Equipment’s, architectural items, woods, wires, ropes, Etc.

160

Hazardous

Paint (Lead) Top sides structural, Jackets, equipment’s, pipe supports

40.2

Asbestos Gaskets 3x10-3

Lead Acid Batteries 4.3

Nickel Cadmium

Batteries 0.6

Mercury Florescent light fittings 1.3x10-5

Radioactive Isotope

MTA wet gas flow meter Trace

Total 9679.3

Source: PMT JV



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6 PROPOSED INFRASTRUCTURE

The project involves decommissioning of Tapti Part B Facilities comprising of

five wellheads in the offshore area which is ~60 km from the Hazira, 20 km

from Saurashtra Coast while the mid Tapti Field is located 75 km from Hazira

Coast and 35 km from Saurashtra Coast near Gulf of Khambhat, West coast of

India.

No construction work is envisaged as proposed activity is decommissioning

work. The activity will be mainly mechanical dismantling and no demolition

is envisaged as part of decommissioning at offshore.



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7 REHABILITATION AND RESETTLEMENT (R&R) PLAN

The offshore area is not inhabited. No local populations requiring

rehabilitation or resettlement.



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8 PROJECT SCHEDULE & COST ESTIMATES

Facility removal and onshore disposal for the proposed decommissioning

project is expected to start by Q1 2019. Concept selection is being currently

exercised to select the concept for topside & jacket and pipeline. Invitation to

tender for Tapti decommissioning will be sent out in early next year. All

structure will be brought to onshore for disposal subsequent to removal.

The expected cost of the project is USD 80 million.



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9 ANALYSIS OF PROPOSAL (FINAL RECOMMENDATIONS)

Tapti Decommissioning project is wholly offshore and will be carried out in a

safe and environment friendly manner in accordance with the prescribed

local, national and international regulations. The decommissioning will also

help in creating indirect livelihood and employment by creation of 3rd party

yard.

prefeasibility report for tapti offshore part b...

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