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Environmental Impact Assessment Report
For
Exploratory Drilling Activities In NELP Block
CY-OSN-2009/2, Gulf Of Mannar, India
Prepared
For
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QCI Accreditation Certificate SENES Consultants India Pvt. Ltd.
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CONTENTS
EXECUTIVESUMMARY ......................................................................................................................... E-1
1
INTRODUCTION .................................................................................................................................. 1
1.1
PURPOSE .............................................................................................................................................. 1
1.2
IDENTIFICATION OF PROJECT PROPONENT &PROJECT ................................................................. 2
1.3
SCOPE OF STUDY ................................................................................................................................ 2
1.4 POINT WISE COMPLIANCE OF TOR ................................................................................................. 3
2
PROJECTDESCRIPTION .................................................................................................................... 9
2.1
TYPE OF PROJECT ................................................................................................................................ 9
2.2 LOCATION OF PROJECT ...................................................................................................................... 9
2.3
DRILLING WELL LOCATIONS ........................................................................................................... 14
2.3.1
CZR Regulation ................................................................................................................ 14
2.3.2 Proposed Sethusamudram Ship Channel Project ............................................. 17
2.3.3
Proposed Project Schedule ......................................................................................... 20
2.4 TECHNOLOGY AND PROCESS DESCRIPTION ................................................................................. 20
2.5
SOURCE OF WATER &PERMISSION FOR DRAWL OF WATER ..................................................... 28
2.6
WATER BALANCE ............................................................................................................................. 28
2.7
WASTEWATER GENERATION &DISCHARGE ................................................................................. 28
2 7 1 Bilge Fluids 29
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3.1
INTRODUCTION ................................................................................................................................ 33
3.2
STUDY AREA AND STUDY PERIOD ................................................................................................. 33
3.3 STUDY COMPONENTS ..................................................................................................................... 34
3.4
STUDY METHODOLOGY .................................................................................................................. 35
3.5
BASELINE ENVIRONMENT FOR ENVIRONMENTAL COMPONENTS............................................... 36
3.5.1
Bathymetry and Seabed Morphology .................................................................... 36
3.6
GEOLOGY AND SEDIMENTOLOGY .................................................................................................. 38
3.6.1
Climate and Hydrology of Gulf of Mannar........................................................... 38
3.6.2
Wind Patterns ................................................................................................................... 39
3.6.3
Circulation and Currents .............................................................................................. 40
3.6.4
Waves .................................................................................................................................. 42
3.7
CLIMATOLOGY &METEOROLOGY ................................................................................................. 43
3.8 MARINE WATER &SEDIMENT QUALITY ....................................................................................... 48
3.8.1
Physico-Chemical Aspects Sea Water & Sediment ....................................... 51
3.8.2 Ecological Aspects Sea Water & Sediment ...................................................... 54
3.9
MARINE ECOLOGY ........................................................................................................................... 58
3.9.1 Gulf of Mannar ................................................................................................................. 58
3.9.2
Marine & Coastal Ecosystems of GOM .................................................................. 61
3.9.3
Biodiversity in GOM ....................................................................................................... 66
3.10 SOCIOECONOMIC CONDITIONS .......................................................................................... 78
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4.1.3
Marine Ecological Impacts .......................................................................................... 95
4.1.4
Socio-Economic Impacts ............................................................................................. 97
4.2 MITIGATION MEASURES FOR SIGNIFICANT ENVIRONMENTAL IMPACTS................................... 98
4.2.1
Mud make-up and Mud & Cuttings disposal ..................................................... 98
4.2.2
Restoration Plans and Rig Decommissioning Measures ................................ 99
4.2.3
Restoration of On-Shore Support Facilities On-Land ...................................... 99
4.2.4
Membership of Common Disposal Facilities ....................................................... 99
4.2.5
Measures to Handle Oily Waste Discharges ........................................................ 99
4.2.6
Sewage Treatment and Disposal ............................................................................ 100
4.2.7
Solid Waste Handling ................................................................................................. 101
4.2.8
Spent Oil Handling ....................................................................................................... 101
4.2.9
Oil Handling from Well Test Operations ............................................................. 101
4.2.10 Noise Abatement Measures ..................................................................................... 102
4.2.11
Measures to Minimize Disturbance Due to Light and Visual Intrusions 102
5
ENVIRONMENTALMONITORINGPROGRAM .................................................................... 104
6
ADDITIONAL STUDIES ......................................................................................................................... 108
6.1
RISK ASSESSMENT ......................................................................................................................... 108
6.1.1
Different Stages during Which Risk Assessments Are Undertaken.......... 108
6.1.2 Objective of the QRA .................................................................................................. 109
6 1 3 Risk Assessment Methodology 110
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6.1.18
H2S Emission Control Plans ...................................................................................... 136
6.2
OIL SPILL RISK ASSESSMENT ......................................................................................................... 138
6.2.1 Oil spill scenarios ..........................................................................................................138
7
ENVIRONMENTMANAGEMENTPLAN ................................................................................. 144
7.1
SELECTION OF DRILLING LOCATION AND NAVIGATIONAL PATH WAYS .................................. 144
7.2
ATMOSPHERIC EMISSIONS ............................................................................................................ 145
7.3
STORAGE AND HANDLING OF CHEMICALS AND SUPPLIES ........................................................ 146
7.4
MANAGEMENT OF DRILL CUTTINGS &DRILLING MUD ............................................................ 147
7.5
OILY WATER DISCHARGES AND OTHER WASTES ...................................................................... 148
7.6 MANAGEMENT OF TRANSPORT OPERATION TO DRILLING RIG ................................................ 150
7.7
OILS MANAGEMENT SYSTEM ..................................................................................................... 151
7.7.1 Policy.................................................................................................................................. 152
7.7.2
Management Manual .................................................................................................. 153
7.7.3
Management System Procedures and Documentation ................................ 154
7.7.4 Implementation, Operation, Infrastructure and Work Environment........ 154
7.7.5
Management of Occupational Health & Safety Aspects .............................. 155
7.8 ORGANIZATIONAL STRUCTURE AND IMPLEMENTATION FRAMEWORK .................................... 156
7.9 CAPITAL AND RECURRING COST FOR ENVIRONMENTAL POLLUTION CONTROL MEASURES. 157
8 DISCLOSUREOFCONSULTANTSENGAGED ....................................................................... 159
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LIST OF TABLES
TABLE 1-1:COMPLIANCE WITH TORPROVIDED BY EXPERT APPRAISAL COMMITTEE OF MOEF ............ 3
TABLE 2-1:GEOGRAPHICAL COORDINATES OF BLOCK CY-OSN-2009/2 ........................................... 12
TABLE 2-2:PROSPECT AREAS &TENTATIVE WELL LOCATIONS IN BLOCK CY-OSN-2009/2 ........... 12
TABLE 2-3:BLOCK CY-OSN-2009/2&DISTANCE FROM COASTLINE................................................ 14
TABLE 2-4:PROSPECT DISTANCE FROM COAST &CRZLINE ................................................................. 15
TABLE 2-5:WATER BALANCE ...................................................................................................................... 28
TABLE 2-6:COMMON CHEMICALS LIKELY TO BE USED FOR PREPARATION OF DRILLING FLUIDS........ 31
TABLE 3-1:DETAILS OF STUDY COMPONENTS,STUDY AREA AND STUDY PARAMETER....................... 34
TABLE 3-2:SEA WATER &SEDIMENT SAMPLING LOCATIONS DETAILS ................................................. 49
TABLE 3-3:SEA WATER ANALYSIS DATA ................................................................................................... 51
TABLE 3-4:SEDIMENT ANALYSIS RESULT ................................................................................................... 53
TABLE 3-5:PLANKTON PROFILE OF MARINE SURFACE WATER ............................................................... 54
TABLE 3-6:BENTHIC PROFILE OF SEDIMENT SAMPLE .............................................................................. 56
TABLE 3-7:BIODIVERSITY INDEX FOR PHYTOPLANKTON &ZOOPLANKTON.......................................... 57
TABLE 3-8:PEOPLE INVOLVED IN FISHING AND RELATED ACTIVITIES ..................................................... 81
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TABLE
6-5:O
ILS
PILLS
CENARIOS............................................................................................................. 138
ANNEXURE I:TORISSUED BY MOEFFOR BLOCK CY-OSN-2009/2 ................................................. 160
ANNEXURE II:PROPOSED SETHUSAMUDRAM SHIP CHANNEL ALIGNMENT ......................................... 163
ANNEXURE III:DEMOGRAPHY DETAILS OF COASTAL VILLAGES AS PER CENSUS OF INDIA,2011 ..... 164
ANNEXURE IV:DISTRICTS WISE FISHERMEN AND KEY DETAILS ............................................................ 168
ANNEXURE V:DETAILS OF FISHERMEN POPULATION FOR COASTAL VILLAGES AS PER ..................... 170
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LIST OF FIGURES
FIGURE E-1:LOCATION MAP OF THE BLOCK CY-OSN-2009/2 .............................................................. 1
FIGURE 2-1:LOCATION MAP OF THE BLOCK CY-OSN-2009/2 ........................................................... 11
FIGURE
2-2:M
APINDICATING
PROSPECT
AREAS
&T
ENTATIVEW
ELLL
OCATIONS INB
LOCKCY-OSN-2009/2ALONG WITH NEARBY COASTAL AREAS................................................................. 13
FIGURE 2-3:BLOCK BOUNDARY WITH RESPECT TO COASTAL ZONE MANAGEMENT PLAN MAP...... 16
FIGURE 2-4: BLOCK BOUNDARY WITH RESPECT TO PROPOSED SETHUSAMUDRAM SHIP CHANNEL
PROJECT ................................................................................................................................................. 19
FIGURE 2-5:IMAGES OF DRILL SHIPS &SEMI-SUBMERSIBLE DRILLING RIG.......................................... 22
FIGURE 2-6:TYPICAL SCHEMATIC OF SUBSEA BLOWOUT PREVENTERS (BOP)SYSTEM....................... 24
FIGURE 2-7:TYPICAL DRILLING FLUID CIRCULATION SYSTEM ................................................................. 26
FIGURE 2-8:TYPICAL DRILLING RIG MODULE ........................................................................................... 27
FIGURE 3-1:BATHYMETRIC VARIATIONS IN THE BLOCK AREA ................................................................ 37
FIGURE 3-2:WIND PATTERN OF INDIAN OCEAN ...................................................................................... 39
FIGURE 3-3: SCHEMATIC REPRESENTATION OF CURRENTS OBSERVED DURING JANUARY-FEBRUARYAND JULY-AUGUST ............................................................................................................................... 40
FIGURE 3-4:COASTAL CURRENTS FOR TAMIL NADU COAST DURING SOUTHWEST AND NORTHEAST
MONSOON 42
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FIGURE 3-10:MEAN AIR TEMPERATURE (C)............................................................................................ 47
FIGURE 3-11:MEAN SEA SURFACE TEMPERATURE (C) .......................................................................... 48
FIGURE 3-12:SEA WATER &SEDIMENT SAMPLING LOCATIONS............................................................ 50
FIGURE 3-13:GOMBR&GOMNPAND PROJECT BLOCK .................................................................... 60
FIGURE 3-14:LOCATION OF LIVE CORALS AROUND GULF OF MANNAR.............................................. 63
FIGURE 3-15:SHORELINE CHANGE DUE TO EROSION/ACCRETION/STABLE COAST IN COASTAL AREAS
NEAR BLOCK CY-OSN-2009/2 ........................................................................................................ 85
FIGURE 6-1:RISK ASSESSMENT METHODOLOGY .................................................................................... 111
FIGURE 6-2:RISK MATRIX &ACCEPTABILITY CRITERIA .......................................................................... 115
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EEXXEECCUUTTIIVVEESSUUMMMMAARRYY
1 Introduction
Oil India limited (OIL) is a premier national Oil Company engaged in the business of
Exploration, Production and transportation of Crude Oil and Natural gas. OIL was awarded
the Cauvery offshore block CY-OSN-2009/2 (area: 1621 km) under NELP VIII bidding round
in the Gulf of Mannar. As Operator with 50% participating interest (PI) with OIL (50%PI), OIL
has a program of drilling six (6) exploratory drilling wells in the above block.
As per the EIA notification 2006 and its amendments, all projects of offshore oil and gas
exploration, development & production are included in Schedule 1(b) in Category A and they
require environmental clearance from Ministry of Environment and Forest (MoEF). OIL had
applied for the Terms of Reference to MoEF in August 2013. The project was discussed in
12thExpert Reconstituted Appraisal Committee (Industry) held during 30thSeptember to 1st
October, 2013. Terms of Reference (ToR) for the preparation of Environmental Impact
Assessment were issued by MoEF to OIL vide letter dated 29th Nov 2013. ToR copy is
attached as Annexure I.
OIL have appointed SENES Consultants India Pvt. Ltd. (SENES India) as environmental
consultant to obtain Environmental Clearance from the Ministry of Environment and Forests
(MoEF) for the proposed activities as per the EIA Notification, 2006. SENES has received QCI-
NABET accreditation (NABET/EIA/RA016/040) for carrying out EIA studies for Category A
projects of Off shore and on shore oil and gas exploration, development & production,
valid up to October 08 2013
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2 Project Details
2.1 Project Locations and Access
The offshore exploratory block lies in the Gulf of Mannar of Cauvery basin in the east coast
of India, Tamil Nadu. The offshore exploratory block lies near Ramanathapuram & Tuticorin
District.
The northeast (Point B) and northwest (Point A) points of the block are located closer to
coast with approximate aerial distance of around 13 km from Dhanushkodi coast and 18 km
from Ervadi coast, respectively. The southeast corner (Point C) is located at approximate
aerial distance of around 43 km from Dhanushkodi coast. The southwest corner (Point F) is
located at approximate aerial distance of around 51 km from Thanichiyam coast.
Nearest Railway stations are Mandapam and Rameshwaram located at approximate aerial
distance of 25 km from block boundary towards north. Tuticorin Port is located at
approximate aerial distance of 72 km from block boundary towards west. The nearest airport
is Madurai which is located at approximate aerial distance of 100 km from nearest coast to
block boundary towards northwest. The Shree Ramanathaswamy Temple in Rameshwaram
and Kothandaramaswamy Temple in Dhanushkodi are located towards north side of coastal
areas of block but these not located on Gulf of Mannar side but are located on Palk Bay side
at approximate aerial distance of 34 km and 30 km respectively from the nearest prospect
area - Prospect Area 3. The Adam's Bridge, also known as Rama's Bridge or Rama Setu is
located at approximate aerial distance of 25 km towards northeast from the nearest prospect
area - Prospect Area 3. Location map of the block is given in figure below.
2.2 Well Locations
Based on the 3D seismic survey, OIL has come up with 6 prospect areas where hydrocarbon
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Maps of Tamil Nadu for Ramanathapuram on the Google Earth image, it is evident that
prospect areas within which wells are proposed to be drilled, are located much beyond 12
Nm from LTL i.e. CRZ IV area. CRZ clearance is therefore not applicable for this project.
2.3 Onshore Support Services for Project
Being an offshore block, exploratory activity will require logistic support from Tuticorin
and/or Kakinada supply base. The logistic support would involve supply of Fuel Oil and freshwater, storage and transport of drilling related equipment (chemicals, etc), Shipping waste
disposal facilities, Oil spill response facilities and equipment (for contingency management).
2.4 Operational Details
Phases covered by exploratory drilling are 1) MODU mobilization 2) Drilling and well Testing
3) Decommissioning. Drilling activity under normal conditions would be completed in about
90-100 days for each well in the block from the day of spudding in. Drilling will be performed
using a self contained Mobile Offshore Drilling Unit (MODU), Semi-Submersible or drill
ship, capable of performing drilling at water depth in block areas [20m (approx.) to 985m].
Based on discovery of hydrocarbon bearing formations, well testing will be conducted
at such formation to establish hydrocarbon potential in terms of flow rates and reservoir
pressure. Following drilling and well testing activities, wells will be plugged and sealed as per
laid down guidelines of OISD P&NG Rules 2008. Once well has been secured and all
necessary equipment has been retrieved, MODU will be mobilized to the next drill location.
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P a g e |E-1
SSeepptteemmbbeerr22001144|OIL
FIGURE E-1:LOCATION MAP OF THE BLOCK CY-OSN-2009/2
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3 Baseline Environment
To assess the baseline environmental status of the block, primary monitoring has been
conducted at 6 locations in prospect areas which included 6 marine surface water & 6
sediment samples in the block. Secondary information on meteorology, ecology of Gulf of
Mannar, socio-economic profile of coastal villagers, etc. have been collected from literature
reviews and information available in public domain by various government departments andagencies.
Average rainfall:Average rainfall of the project area from January 2013 to December 2013,
for the proposed exploratory block is in the range of 4.12 mm to 4.75 mm /day
Mean Wind Speed:mean wind speed measured in m/sec for the period area of January 2013
to December 2013 for the study area lies in the range of 6.25 to 6.75 m/se
Mean Air Temperature: Maximum and minimum value of mean air temperature in the
Arabian Sea is of the order of 30.2 C and 24.4 C, respectively. Mean air temperature of the
area of exploratory block lies in the range of 26.5 C to 27.5 C
Mean Sea Surface Temperature:Mean air temperature of the area of exploratory block lies inthe range of 27.75 C to 28.05 C.
3.1 Marine Water & Sediment Quality
Based on the physico-chemical analysis of marine surface water samples, pH values were in
the range of 7.45 to 8.05. Turbidity of the water samples ranges from 0.9 to 1.5 NTU. Salinity
of sea water sample collected range from 35% to 38 %. Total Suspended Solids (TSS)
ranged from 13 to 20 mg/L. Oil & Grease was found to be within range of 12 to 17 mg/L.
Polycyclic aromatic Hydrocarbons (PAH) were found to be 0.009 to 0.05 mg/L and Total
Petroleum Hydrocarbons (TPH) ranged as 2 to 2 9 ppm The higher Petroleum Hydrocarbon
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concentration of Barium in collected sediment found in range of as 0.2 ppm to 0.35 ppm
whereas the concentration of mercury in collected sample found in below detection limit
(BDL). The petroleum hydrocarbon concentrations in sediments may be mainly from the land
based sources such as municipal waste waters, industrial discharge, urban runoff, river
discharges, ocean dumping and fishing vessels operating in the localized area.
3.2 Biological Environment Phytoplankton & Zooplankton
Marine surface water samples were analyzed for planktons. Around 26 families of
phytoplanktons were observed with species like Zygnemataceae, Volvocaceae, Naviculaceae,
Pyrocystaceae, Stephanopyxidaceae, Volvocaceae, Naviculaceae, Rhizosoleniacea and
Stephanopvxidaceae. Zooplankton families observed were Bosminidae, Pontellidae,
Lumbriculida, Calanoida, Collothecidae and Asterigerinacea. Phytoplankton and zooplanktoncount ranged between 19,000 to 21,000 cells/ml and 1800 to 2000 cells/m3.
Sediment samples were analyzed for presence of benthic species. Prominent macro bethos
species observed were Nephtyidae, Stylasteridae, Ampharetidae, Stylasteridae, Sabellidae.
Carterinidae, Centropagidae, Ammodiscacea, Carterinidae, Acartiidae, Chaetonotidae and
Misophriidae are the prominently observed in Meio bethos. Micro benthos showed presenceof Bacillariaceae, Cercomonadidae and Euglenaceae families.
3.3 Marine Ecology Gulf of Mannar
Project block is located in Gulf of Mannar (GoM) which has diverse ecology, mainly reported
from the areas closer to Gulf of Mannar Islands. GoM has a chain of 21 islands stretching
from Mandapam to Tuticorin to a distance of 140 km along the coast with total area of 623
hectares which form Gulf of Mannar Marine National Park (GoMNP) and Gulf of Mannar
Biosphere Reserve (GoMBR). GoM shows presence of variety of marine organisms because of
its varied ecosystems of coral reefs rocky shores sandy beaches mud flats estuaries
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Montipora, Favia, Favites, Goniopora, Goniastrea, Platygyra, echinopora, Galaxea, Turbinaria,
Leptoria, Pavona and Pachyseries. Seagrass species like Hydrocharitaceae and
Potamogetonaceae are reported which provide food sources and nursing ground for many
epiphytic fauna and feeding grounds for the Sea Cow - Dugong dugong. Marine algae or
seaweeds species observed in GoM are Gelidiella acerosa, Gracilaria edulis, G. follifera, crassa,
Gracilaria spp.; Hvpnea spp., Acanthophora spp..Mangroves are observed in coastal area with
dominant genera as Avicennia, Rhizophora, Bruguiera. Around 126 species of plankton and
360 species of zooplanktons are reported. 51 species of foraminiferans, 257 species of
sponges, 14 species of gorgonids, 75 species Polychaeta, 9 species Nematoda, 731 species of
mollusks are reported from GoM. Though pearl yielding species like Pinctada fucata, P.
chemnitzii, P. anomioides, P. atropurpura and Chank varieties likeXancus pyrum are reported
from GoM, their existence has reduced due to trawler operations. Various varieties of crabs,lobster, prawns, and shrimps are present. There are about 450 species of fishes belonging to
107 families inhabiting the coasts of Gulf of Mannar and Palk Bay. Though dolphins like
Dolphinus delphis, Stenella longirostris, Sousa chinensisand Tursiopstruncatesare reported in
GoM, no mass landing is reported. A total of 187 species of shore birds including wadors,
terns and gulls were recorded in the Gulf of Mannar, of which 84 were of aquatic species and
the remaining terrestrial. Five species of marine turtles - Chelonia mydas (green turtle),
Hepidochelys olivacea (olive ridley), Caretta caretta (loggerheads turtle), Eretmochelys
imbricata (Hawk bill turtle), Dermochelys coriacea (leather bask turtle) are reported in the
Gulf of Mannar. All are endangered species as per Wildlife (Protection) Act, 1972. Various
studies/reports mentioned in this section indicate turtle occurrence in Gulf of Mannar marine
waters and nearby coastal areas but no specific study/report could be traced indicating turtle
occurrence specific to block area.
Marine capture fishery is the major economic activity of coastal villages located near Gulf of
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The major towns/villages in nearby coastal areas are Ramanathapuram, Rameshwaram,
Peripattinam, Devipattinam, Sayalgudi, Mandapam, Keelakarai, Muttayyapuram and
Srivaikutram, etc. Fishing, chank and seaweed collection are prominent source of livelihood
in coastal villages with farming practiced in other areas. Salt farming is done majorly in
villages from Tuticorin district compared to Ramanathapuram district villages. The primary
schools are located in every village with higher secondary school within 5 km distance.
Colleges are located at Ramanathapuram, Tuticorin and Mandapam. Though electrify is
supplied to all villages, power cut are very frequent. Public transport is provided to all coastal
villages with frequency of bus at 1 hour. Primary health centers are located in each village
with big hospitals in Ramanathapuram, Tuticorin and Mandapam.
4 Impact Assessment
4.1 Potential Impacts on Noise Quality
Potential impacts on noise quality may arise from air borne noise generated during drilling
operations of rotary drilling equipment as part of rig, diesel engines for power generation
and mud pumps, helicopter movements, leading to perceptible increase in noise levels in
immediate vicinities.
4.2 Potential Impact on Marine Water Quality and Ecology
Activities related to various phases of the proposed drilling like physical presence of MODU,
disposal of drill cuttings and WBM, operational discharges like sanitary waste water, food
waste and residuals, washing fluids (deck drainage, rig floor washing etc), cooling water,
non-routine discharges that may be caused by ballast water, chemical spills has the potential
to impact marine water quality and consequently marine ecology adjacent to the drilling
locations. Some marine water quality impacts will also occur along corridors that are
proposed to be used for providing logistic support to MODU The non routine discharges
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The prominent commercial activities in the coastal villages near Block CY-OSN-2009/2 are
fishing and salt production. During exploratory drilling of wells, sea traffic will get marginally
increased due to supply vessels. Probably 1 or 2 vessels/week (as per the requirements) will
voyage from Tuticorin or Kakinada or both supply base to exploration area. But this being a
short term activity, effect on fishing activity in the region will be minimal. Impact on fishing
or salt framing may occur in the event of any accidental oil spill, depending upon severity of
spill.
5 Environmental Management Plan
5.1 OIL Management System
OIL is committed to protect the environment through improving the effectiveness of
management and reporting systems and ensuring the reduction of local environmental
impact from operations by improving environmental performance and implementing
initiatives for the conservation of biodiversity and the resource recovery and reuse. This is
achieved through the implementation of OIL HSE Policy and management system.
5.2 Organization Structure and Responsibility
In addition to regular operational roles & responsibilities defined for the drilling
organization, all personnel directly or indirectly have a role to play towards effective
environment management in the project, by implementing the HSE policy and the
environment management plan. The entire drilling organization will co-operate with
government agencies, regulatory authorities and other stakeholders who may haveenvironmental concerns associated with the project.
5.3 Management Plans for Environment
S l ti f D il li L ti d N i ti l P th W
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At present Gulf of Mannar Biosphere Reserve area is expected to overlap with project block
on north side but no exploratory drilling well is proposed in this region.
Occurrence of sensitive species in close proximity or within the block will also govern the
selection of drilling locations. If sensitive species viz. sea turtles or marine mammals are
observed/anticipated in the block area, their presence will be monitored in accordance with
the international sighting guidelines for marine mammals. Such monitoring will be
conducted before the onset of drilling activities, and will be maintained throughout the
offshore exploratory operations. In areas where significant impacts to sensitive species are
anticipated, experienced observers will be used for the monitoring exercise.
Selection of Navigational Pathway for MODU & Supply Vessels
Appropriate measures will be adopted by the project proponent to avoid migratory routes of
turtles and ecologically and culturally sensitive coastal areas during vessel movement. In
addition, consultations with relevant stakeholders (Directorate of Fisheries, Coast Guard,
government agencies related to Gulf of Mannar, Port Management Board, etc) will be carried
out to aid in the routing of supply vessels from the logistic base. The support vessels will also
have the relevant permits and certifications to comply with the requirements of theInternational Maritime Organization for operation in Gulf of Mannar.
Drill Cutting Management
The Hazardous Waste Rules require OIL to analyze the drill cuttings and establish whether
toxicity of constituents is high enough for the waste to be considered as hazardous. The
disposal of the drill cuttings shall also be conforming to the guidelines pertaining to the
Disposal of Drill Cuttings and Drilling Fluids for Offshore Installations provided by the
Ministry of Environment & Forests (MoEF) G.S.R. 546(E) August 2005.
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Bilge waters from machinery spaces in offshore facilities and support vessels will be routed
to the facility closed drainage system, or contained and treated before discharge to meet the
MARPOL 73/78 requirements.
Management of Transport Operation to MODU
Helicopter Operations Management Plan which will delineate operation procedures for
helicopter operations to the MODU helideck would be drawn up and a competent person
would be made responsible for the same. On the land side, necessary coordination would be
established with respective airport authorities from where the helicopters would fly.
Vessel Management Planwill be formulated and implemented to reduce collision risk, both
vesselvessel and MODUvessel and a person made responsible for all vessel operations. The
plan would establish a 500 m safety zone around platform, define operational procedures for
approach, movements during bad weather, no go areas, etc.
Management of Occupational Health & Safety Aspects
OIL places high emphasis on health and safety aspects of workers and staff on MODU and
will ensure that all activities will be conducted in a safe and skill full manner with staffappropriately trained and equipment maintained in safe condition. Safety cases will be
developed for appropriate facilities. Potential health, safety or fire hazards will be removed or
managed, based on risk assessments, safe systems of work, HSE management system
requirements, competency and skills of staff and workers, etc. and would be in line with
requirements specified in the OISD Rules (Chapter VII : Health and Welfare Measures). In
addition OIL would ensure that a trained Medical Officer or Paramedic is available on the
MODU during the drilling activity.
Monitoring Frame Work
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OIL will record daily discharge of drill cuttings & drilling fluids in Sea and also to monitor the
effluent quality. Compliance reports will be submitted to Regulatory Agencies. Monitoring
results would be to be documented, analyzed and reported internally to Offshore Drilling
Supervisor, Wells Operations Manager and HSE Coordinator.
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11 IINNTTRROODDUUCCTTIIOONN
11..11 PPUURRPPOOSSEE
Oil India limited (OIL) is a premier national Oil Company engaged in the business of
Exploration, Production and transportation of Crude Oil and Natural gas. OIL was awarded
the Cauvery offshore block CY-OSN-2009/2 (area: 1621 km) under NELP VIII bidding round
in the Gulf of Mannar. As Operator with 50% participating interest (PI) with OIL (50%PI), OIL
has a program of drilling six (6) exploratory drilling wells in the above block.
As per the EIA notification 2006 and its amendments, all projects of offshore oil and gas
exploration, development & production are included in Schedule 1(b) in Category A and they
require environmental clearance from Ministry of Environment and Forest (MoEF). OIL had
applied for the Terms of Reference to MoEF in August 2013. The project was discussed in
12thExpert Reconstituted Appraisal Committee (Industry) held during 30thSeptember to 1st
October, 2013. Terms of Reference (ToR) for the preparation of Environmental Impact
Assessment were issued by MoEF to OIL vide letter dated 29th Nov 2013. ToR copy is
attached as Annexure I.
OIL has appointed SENES Consultants India Pvt. Ltd. (SENES India) as environmental
consultant to obtain Environmental Clearance from the Ministry of Environment and Forests
(MoEF) for the proposed activities as per the EIA Notification, 2006. SENES has received QCI-
NABET accreditation (NABET/EIA/RA016/040) for carrying out EIA studies for Category A
projects of Off shore and on shore oil and gas exploration, development & production.
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11..22 IIDDEENNTTIIFFIICCAATTIIOONNOOFFPPRROOJJEECCTTPPRROOPPOONNEENNTT&& PPRROOJJEECCTT
Oil India Limited (OIL) is a National Oil Company engaged in Exploration & Production of
hydrocarbons. The story of Oil India Limited (OIL) traces and symbolizes the development
and growth of the Indian petroleum industry. From the discovery of crude oil in the far east
of India at Digboi, Assam in 1889 to its present status as a fully integrated upstream
petroleum company, OIL has come far, crossing many milestones. In 1981, OIL became awholly-owned Government of India enterprise. In a recent CRISIL-India Today survey, OIL was
adjudged as one of the five best major PSUs and one of three best energy sector PSUs in the
country.
Now, OIL intends to carry out drilling of six (6) exploratory drilling wells in the Block CY-OSN-
2009/2 which is located in the Offshore off the coast of Thoothukudi (Tuticorin) in the Gulf of
Mannar. The Block area is around 1621 sq. km. The block has been awarded on by
Government of India under Production Sharing Contract (PSC) in NELP-VIII bidding ground
to Oil India Limited (OIL) with 50% participating interest as operator along with 50%
participating interest of Oil & Natural Gas Corporation Limited (ONGC).
Based on the 3D seismic survey, OIL has come up with 6 prospect areas where hydrocarbon
discovery potential is high and exploratory drilling will be undertaken. Based on further
detailed study, the exact drilling well locations will be finalized in these prospect areas.
Offshore rigs will be deployed for the proposed drilling. One temporary shore base set up
with ware house and office facilities will be installed either at Tuticorin or Kakinada or at
both, to facilitate supply chain for rig operations. The personnel will be transported to the rig
by helicopters and supply boats.
11..33 SSCCOOPPEEOOFFSSTTUUDDYY
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Assess potential environmental impacts that may arise as a result of the project and
evaluate them.
11..44 PPOOIINNTTWWIISSEECCOOMMPPLLIIAANNCCEEOOFFTTOORR
OIL had applied for ToR to MoEF in August 2013. Terms of Reference (ToR) for the
preparation of Environmental Impact Assessment were issued by MoEF to OIL during the 12
th
Reconstituted Expert Appraisal Committee (Industry) held during 30th September to 1st
October, 2013. The salient points of ToR given by MoEF on 29thNovember, 2013, have been
duly addressed in EIA Report. Summary of the same is given below:
Table 1-1: Compliance with ToR provided by Expert Appraisal Committee of MoEF
S.No.
Points Of TOR Issues Addressed In EIA-EMP and RAReport
1 Executive summary of the project Executive summary included in EIA report
2 No. of exploratory wells for which
environmental clearance is accorded
and No. of new wells proposed during
expansion. Status and No. of the wellswhich are completed and closed.
No environmental clearance has been
accorded so far in this block.
OIL plans to drill 6 offshore exploratory
wells in the NELP Block CY-OSN-2009/2.Refer Chapter 2 - Project Description
3 Project Description and Project Benefits; The offshore exploratory block CY-OSN-
2009/2 covering an area of 1621 sq. km.
lies in the Offshore off the coast of
Tuticorin in the Gulf of Mannar. OIL plans
to drill 6 exploratory wells, which in case ofhydrocarbon discovery will help in
meeting the energy requirements of the
country.
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S.
No.
Points Of TOR Issues Addressed In EIA-EMP and RA
Report
5 Commitment for no drilling will be
carried within 1.0 Km
The nearest prospect area is located at an
approximate aerial distance of 31 km from
nearest coast. Thus no drilling will be
carried within 1.0 Km from coast.
Refer Chapter 2, Section 2.3 Drilling Well
Locations
6 Details of sensitive areas such as coral
reef, marine water park, sanctuary and
any other eco-sensitive area.
Gulf of Mannar National Park (GoMNP) is
located away from block boundary and
none of the block area overlaps with
GoMNP area. Gulf of Mannar Biosphere
Reserve (GoMBR) boundary passes
through block area on north side. The
nearest prospect area located to GoMBR
and GoMNP boundary is Prospect Area 3
with approximate aerial distance of 8 km
and 21 km respectively.
Refer Chapter 3, section 3.7 Ecologically
Sensitive Marine Areas
7 Approval for the forest land from the
State/Central Govt. under Forest
(Conservation) Act, 1980, if applicable
Being an offshore exploratory drilling
project, forest clearance is not applicable.
8 CRZ Clearance as per CRZ notification
dated 6thJanuary 2011.
As the project will not involve any
construction / operation activities in any
CRZ areas and hence CRZ clearance is not
applicable.
Refer Chapter 2, section 2.11 CRZ
Regulation
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S.
No.
Points Of TOR Issues Addressed In EIA-EMP and RA
Report
for the drawl of water from the
Competent Authority. Detailed water
balance, waste water generation and
discharge.
be 20-30 m3/day for drilling; will be
supplied from temporary onshore supply
base of OIL. Wastewater generation from
the drilling well is expected to be 9
m3/day. Sewage will be treated in a
sewage treatment plant (STP). The dirty
oil from bilge fluid will be periodically
sent to shore in drums or special
containers by supply vessels deployed for
the purpose.
Refer Chapter 2, Section 2.5 - Source of
Water & Permission for Drawl of Water,
Section 2.6 - Water Balance, Section 2.7 -
Wastewater Generation & Discharge
12 Noise abatement measures and
measures to minimize disturbance due
to light and visual intrusions in case
coastally located.
Chapter 4, section 4.2.10 - Noise
Abatement Measures and Section 4.2.11 -
Measures to minimize disturbance due to
light and visual intrusions
13 Procedure for handling oily water
discharges from deck washing, drainage
systems, bilges etc.
Chapter 7, Section 7.5 - Oily Water
Discharges and Other Wastes
14 Procedure for preventing spills and spill
contingency plans
Refer Chapter 6, Section 6.1.1.3 - Oil Spill
Contingency Plan
15 Procedure for treatment and disposal of
produced water
Produced Water from well testing, if
carried out, will be stored in storage tanks,
gas will be flared, and water will be
discharged to sea after treatment Oil will
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S.
No.
Points Of TOR Issues Addressed In EIA-EMP and RA
Report
18 Storage of chemicals on site Chapter 2, Section 2.9- Chemical Storage
at Rig and In On-Shore Facility
19 Commitment for the use of WBM and
synthetic oil based mud in special case
OIL is committed towards using of only
Water Based Mud (WBM) for the offshore
exploratory drilling operations. However,
Low Toxic synthetic oil based mud
(LTSOBM) will be used to combat specific
hole problems.
Refer Chapter 2, Section 2.4 -Technology
and Process Description
20 Risk assessment and mitigation
measures including whether any
independent reviews of well design,
construction and proper cementing and
casing practices have been followed
Refer Chapter 6, Section 6.1 and Section
6.1.9 - Risk Mitigation Measures
21 Handling of spent oils Chapter 4, Section 4.2.8 - Spent oil
Handling
22 Handling of oil from well test
operations
Chapter 4, Section 4.2.9 - Oil Handling
From Well Test Operations
23 Mud make up and mud and cuttings
disposal procedures
The disposal of the drill cuttings will be
conforming to the guidelines pertaining to
the Disposal of Drill Cuttings and Drilling
Fluids for Offshore Installations providedby the Ministry of Environment & Forests
(MoEF) G.S.R. 546(E) August 2005.
Refer Chapter 7, Section 7.4 -
Management of Drill Cuttings & Drilling
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S.
No.
Points Of TOR Issues Addressed In EIA-EMP and RA
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including Occupational Health
Surveillance Programme etc.
26 Restoration plans and measures to be
taken for decommissioning of the rig
and restoration of on-shore support
facilities on land
After drilling and initial testing, if the well
does not contain commercial quantities of
hydrocarbon, the well is plugged and
abandoned as per OISD guidelines of
P&NG rules 2008. Open rock formations
are sealed with cement plugs to prevent
upward migration of wellbore fluids. The
hazardous waste from onshore support
facility - Temporary supply base will be
sent to authorized hazardous waste
disposal facility.
Refer Chapter 4, Section 4.2.2 -Restoration
Plans and Rig Decommissioning Measures
and Section 4.2.3 - Restoration of on-
shore support facilities on-land.
27 Documentary proof for membership of
common disposal facilities, if required.
The solid waste generated on the rig will
be segregated and stored in colour coded
bags. The solid waste will be transported
back using support vessels or with the rig,
to the temporary supply base of OIL. At
Temporary supply base the segregated
waste will be treated separately.
Hazardous waste, if any, will be sent to
authorized hazardous waste recyclers and
disposal facility
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S.
No.
Points Of TOR Issues Addressed In EIA-EMP and RA
Report
measures. control measures
30 A tabular chart with index for point wise
compliance of above TOR.
Chapter 1, Table 1-1
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22 PPRROOJJEECCTTDDEESSCCRRIIPPTTIIOONN
22..11 TTYYPPEEOOFFPPRROOJJEECCTT
The offshore exploration blocks CY-OSN-2009/2 lies in the Gulf of Mannar of Cauvery basin
in the east coast of India. The block has been awarded by Government of India under
Production Sharing Contract (PSC) in NELP-VIII bidding round to Oil India Limited (OIL) with
50% participating interest as operator along with 50% participating interest of Oil & Natural
Gas Corporation Limited (ONGC). The proposed project is offshore exploratory drilling in the
block CY-OSN-2009/2 in the Gulf of Mannar of Cauvery basin in the east coast of India, TamilNadu state. OIL plans to drill 6 offshore exploratory wells in the block CY-OSN-2009/2. Wells
will be located within prospect areas identified based on the interpretation of 3D seismic
data collected.
22..22 LLOOCCAATTIIOONNOOFFPPRROOJJEECCTT
The offshore exploratory block covering an area of 1621 km2 lies in the Gulf of Mannar of
Cauvery basin in the east coast of India, Tamil Nadu. The offshore exploratory block lies near
Ramanathapuram & Tuticorin District.
The northeast (Point B) and northwest (Point A) points of the block are located closer to
coast with approximate aerial distance of around 13 km from Dhanushkodi coast and 18 km
from Ervadi coast, respectively. The southeast corner (Point C) is located at approximate
aerial distance of around 43 km from Dhanushkodi coast. The southwest corner (Point F) is
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pp pp yy gg
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The Shree Ramanathaswamy Temple in Rameshwaram and Kothandaramaswamy Temple in
Dhanushkodi are located towards north side of coastal areas of block but these not located
on Gulf of Mannar side but are located on Palk Bay side at approximate aerial distance of 34
km and 30 km respectively from the nearest prospect area - Prospect Area 3. The Adam's
Bridge, also known as Rama's Bridge or Rama Setu is located at approximate aerial distance
of 25 km towards northeast from the nearest prospect area - Prospect Area 3.
Location map of the block and the nearby coastal area are given in figure below.
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P a g e |11
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FIGURE 2-1:LOCATION MAP OF THE BLOCK CY-OSN-2009/2
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The geographical coordinates of the CY-OSN-2009/2 exploratory block are provided in the
table below.
Table 2-1: Geographical Coordinates of Block CY-OSN-2009/2
Location Longitude Latitude
Deg Min Sec Deg Min Sec
A 78 50 00 09 04 19.51B 79 22 11.05 09 04 19.51
C 79 14 09 08 49 21
D 79 03 45 08 47 56
E 78 52 07 08 44 02
F 78 50 00 08 44 5.77
A 78 50 00 09 04 19.51
Based on the 3D seismic survey, OIL has come up with 6 prospect areas where hydrocarbon
discovery potential is high for exploratory drilling. In each prospect area, tentative well
locations are represented in the table below. Based on the further detailed study, the specific
well locations for exploratory drilling will be established within each of these prospect areas.The geographical range of Prospect Areas is also are represented below.
Table 2-2: Prospect Areas & Tentative Well Locations in B lock CY-OSN-2009/2
Prospect
Area
Geographical
Coordinates of
Tentative Well Locations
Geographical Range of
Prospect AreasApprox. Water Depth
for Prospect Area(m)Latitude
Range
Longitude
RangeLatitude Longitude Minimum Maximum
P-1 8515.644" 785415.31"852'28.39"N848'24.62"N
7851'47.17"E7857'51.34"E
373.16 568.27
P-2 8554" 785833"856'55.24"N853'29 35"N
7855'6.05"E790'9 76"E
254.68 531.01
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P a g e |13
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FIGURE 2-2: MAP INDICATING PROSPECTAREAS &TENTATIVE WELL LOCATIONS IN BLOCK CY-OSN-2009/2ALONG WITH NEARBY COASTALAREAS
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22..33 DDRRIILLLLIINNGGWWEELLLLLLOOCCAATTIIOONNSS
MoEF, through its ToR issued for EIA studies, has sought from OIL a commitment on not
undertaking drilling within 1.0 km from coastline. Though the nearest land area for block
boundary is Dhanushkodi, which is at approximate aerial distance of 13 km from block
boundary (Point B) towards northeast, the nearest prospect area - Prospect Area 3 to
Dhanushkodi town land area is located at approximately at an aerial distance of 28 km. Thus
OIL will not have any drilling activity within 1.0 km distance from coast line. The location of
identified prospect areas and their approximate distance from the nearby coastare given in
table below.
Table 2-3: Block CY-OSN-2009/2 & Distance from Coastl ine
Prospect Area Approximate Distance From
Nearby Coast (Km)
P-1 40
P-2 34
P-3 28
P-4 34P-5 47
P-6 44
As per provisions of Forest (Conservation) Act, 1980 and its subsequent amendments,
clearance/approval from state/central government is required for diversion of forest land for
non-forestry purposes. Since this project is for offshore exploratory drilling, there is nodiversion of forest and hence forest clearance/approval for the forest land from the
State/Central Govt. under Forest (Conservation) Act, 1980 is not applicable.
There is no litigation pending against the project or any directions/order passed by any
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l d
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district are prepared by Department of Environment GIS Cell, Government of Tamil Nadu
which gives the CRZ demarcation with Low Tide Line (LTL).
Based on the superimposition of above mentioned Coastal Zone Management Plan Maps on
the Google Earth image, line delineating distance of 12 Nm from the low tide line (indicating
CRZ IV limit) is projected to assess the CRZ applicability. It is evident that only northwest and
northeast corners of block fall within 12 Nm zone and all 6 prospect areas are located well
beyond 12 Nm from LTL. The nearest prospect area to land i.e. Prospect Area - 3 is located 9
km further away toward sea from the 12 Nm distance line from the coast i.e. CRZ IV area.
Thus the prospect areas within which wells are proposed to be drilled, are located much
beyond 12 Nm from LTL i.e. CRZ IV area. CRZ clearance is therefore not applicable for this
project.
Table 2-4: Prospect Distance From Coast & CRZ line
Prospect
Location
Approximate Distance From
Nearby Coast 12 Nm Line
Km Nm Km
P-1 40 21.6 19
P-2 34 18.4 13
P-3 28 14.6 9
P-4 34 18.4 14
P-5 47 25.4 26
P-6 44 23.7 23
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P a g e |16
SSeepptteemmbbeerr22001144|OIL
FIGURE 2-3:BLOCK BOUNDARY WITH RESPECT TO COASTAL ZONE MANAGEMENT PLAN MAP
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TTaammiill NNaadduu
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22..33..22 PPrrooppoosseeddSSeetthhuussaammuuddrraammSShhiippCChhaannnneell PPrroojjeecctt
A navigation channel connecting the Gulf of Mannar and Palk Bay through north of Adam's
Bridge has been proposed by Government of India, called as Sethusamudram Ship Channel
Project. This proposed project is envisaged to reduce the steaming distances between the
East and West Coast of India and to improve the navigation within territorial waters of India.
The project was conceptualized with first route proposed in 1961. There were severalchanges in alignment of channel due to eco-sensitivity, cost, feasibility, presence of religious
structure Ram Sethu or Adams bridge, etc.
The proposed alignment which has received environmental clearance in 2005 by MoEF
passes through Adams bridge. The first phase proposes channel width as 300 m which
eventually can be expanded upto 500 m in third phase.
With proposed involvement of dredging and alignment route passing through Ram Sethu or
Adams bridge, various litigations started on the project, which resulted in temporary
suspension of the work. In July 2008, Prime Minister constituted panel headed by TERI
Director General which submitted report in July 2008 saying the project is ecologically and
economically not viable. In Feb 2013 Center rejected the report and decided to go ahead
with the alignment which passes through Adams bridge or Ram Sethu. In April 2013, Tamil
Nadu government urged Supreme Court to direct Center government on scrapping the
project. As per the latest proceedings on this, Central Government has taken the stand that
the 'Ram Sethu' or Adams bridge will not be broken as there are different geological and
religious theories behind the origin of the bridge. The Central government has certain"alternatives" in mind and will inform the Supreme Court an option 1. Thus there might be
revision in alignment of shipping channel.
B d th i f ti t li t f S th d Shi Ch l il bl i
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TTaammiill NNaadduu
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TTaammiillNNaadduu
figure below. The reference map used for the proposed Sethusamudram Ship Channel
alignment is attached as Annexure II.
It indicates that the proposed Sethusamudram Ship Channel alignment is likely to pass
through the southern part of the project block area. OIL will therefore ensure that any
development with regard to this alignment is monitored and co-ordination with
Sethusamudram Corporation Ltd is also ensured specifically prior to planning any permanent
offshore installations, although no such installations are anticipated during this exploratory
drilling stage of the project.
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P a g e |19
SSeepptteemmbbeerr22001144|OIL
FIGURE 2-4:BLOCK BOUNDARY WITH RESPECT TO PROPOSED SETHUSAMUDRAMSHIP CHANNEL PROJECT
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22..33..33
PPrrooppoosseeddPPrroojjeecctt SScchheedduullee
The project activities lifecycle for the proposed offshore drilling project has been divided into
three phases- Mobilization of drilling rig, Drilling and finally Decommissioning. Drilling
activity under normal conditions would be completed in about 90-100 days for each well in
the block from the day of spudding in.
The wells drilled will be tested by perforation in the production casing if sufficient indications
of the hydrocarbons presence are noticed. The well will be sealed off for further
development upon discovering it as a successful hydrocarbon bearing structure.
22..44 TTEECCHHNNOOLLOOGGYYAANNDDPPRROOCCEESSSSDDEESSCCRRIIPPTTIIOONN
The different phases covered for the exploratory drilling are
Mobilization of the drilling rigs
Drilling and testing
Decommissioning
These phases are explained in the subsequent sections
Drilling and Testing Phase
Exploitation of hydrocarbons requires the construction of a conduit between offshore
platform and reservoir. This is achieved by the drilling process. Offshore exploration wells will
be drilled using a rig and equipped with a Top Drive System for rotating the drilling string
including the drilling bit.
There are two basic categories of offshore drilling rigs those that can be moved from place
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FIGURE 2-5:IMAGES OF DRILL SHIPS &SEMI-SUBMERSIBLE DRILLING RIG
An opening called moon pool is equipped in the centre of the drill ship from the main deckto the water. Drilling assembly, riser joints, Blowout Preventer (BOP), wellhead equipment,
etc. are lowered through the moon pool to the sea floor to facilitate the drilling
process. The marine riser system consists of riser joints, riser tensioners and ancillary
equipment. The riser joints are connected to the top of sub- sea BOP and are pulled up by
the riser tensioning system onboard to keep a vertical configuration. The riser joints serve as
a conduit for returning drilling mud to surface from borehole and as guide for running drill
string and casing from the rig to the hole below seafloor.
Initial Well Construction
Offshore wells are drilled in sections, with the diameter of each section decreasing with
increasing depth. Lengths and diameters of each section are determined prior to drilling and
depend on geological conditions through which the well is to be drilled. The conduit or pipe
section will be set in place by jetting operations. Drilling starts with spudding a hole of
di t 26" th b d f ll d b li i it ith t l i f 20" Th b
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iilllliinnggAAccttiivviittiieessIInnNNEELL
TTaammiillNNaadd
BBlloocckkCCYY--
SSNN--22000099//2,,GGuullffOOff aannnnaarr,,
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As drill
and th
cuttin
and ou
riser a
surface
FIGURE 2
pipe is lo
n further d
s that are
t through t
d back to
in order t
6:TYPICAL
ered down
own into t
being chi
he drill bit.
the surfac
be dispo
CHEMATIC O
through t
e well, dril
ped away
The mud
of the oi
ed of. Pro
SUBSEA BL
e marine r
l fluid or
when drill
eventually
l rig. The
erly dispo
OWOUT PREV
iser, throu
ud (fluid t
d) is pum
circulates a
arine rise
sing of the
ENTERS (BO
h the BOP
at helps cl
ed back u
round up t
brings th
cuttings i
)SYSTEM
, into the
ear the roc
through
hrough th
se cutting
important
ellhead,
bits or
he pipe
marine
to the
so that
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circulation system after separation of drill cuttings /solids through solids control equipment.
Drilling fluid is essential to drilling operations in order to:
Control down-hole pressure
Lift soil/rock cuttings from the bottom of the borehole and carry them to settling pit
Allow cuttings to drop in the mud pit so that they are not re-circulated (influenced by
mud thickness, flow rate in settling pits and shape/size of pits)
Prevent cuttings to settle rapidly.
Particles on the borehole wall to prevent caving and to ensure that the upward flowing
stream of drilling fluid does not erode the adjacent formation.
Seal the borehole wall to reduce fluid loss. (Formation of filter cake)
Cool and clean the drill bit and lubricate drill bit, bearings, mud pumps and drill pipes
OIL is committed towards using only Water Based Mud (WBM) for the offshore exploratory
drilling operations. However, Low Toxic synthetic oil based mud (LTSOBM) will be used to
combat specific hole problems. Water-based mud is made up of clay (bentonite) and water;
it may include barite, a heavy mineral used as to add weight. Chemical additives are mixed into stabilize the drilling fluid during use, and to reduce corrosion and bacterial activity. Some
chemicals, called coagulants thicken and others, known as anticoagulants, thin the mud.
Water-based mud is increasingly used for most offshore wells and in the shallower parts of
deep wells. Chemical additives viz. glycols and salts may be used in conjunction to mitigate
potential problems related to hydrate formation.
The mud to be used will be continuously tested for its density, viscosity, yield point, water
loss, pH value etc. to ensure that drilling operations are successful and continued without
any down-hole complication The mud will be prepared onsite (drill location) using
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Cuttings will be then separated from drilling mud using solids- control equipment. This will
comprise of a stepped system of processes consisting of linear motion vibrating screens
called shale shakers, hydro-cyclones (including de- sanders and de-silters), and centrifuges
to mechanically separate cuttings from the mud. Thoroughly washed drill cuttings, separated
from mud will be discharged off- shore into sea intermittently. An estimated average volume
of 300 m3 of drill cuttings per well and 5-10 KL/day of drilling fluid waste is likely to be
generated. Once cuttings have been separated, drilling fluid used for the drilling operationswill be processed or reused after further treatment for the maximum possible extent.
The whole process by which drilling fluid will be reused during drilling operations is
commonly known as a closed loop mud circulating system. This system is ideal for drilling
operations in sensitive environments as it reduces the total water consumption for
formulation of drilling mud and it saves on consumption of chemicals. The unusable portionof mud will be discharged off shore into sea intermittently so as to have proper dilution and
dispersion without any adverse impact on marine environment.
FIGURE 2-7:TYPICAL DRILLING FLUID CIRCULATION SYSTEM
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FIGURE 2-8: TYPICAL DRILLING RIG MODULE
The time taken to drill a bore hole depends on the depth of the hydrocarbon bearing
formation and the geological conditions, but it is commonly of the order of one or two
months. Where hydrocarbon formations is found, initial well tests, possibly lasting another
month, are conducted to establish flow rates and formation pressure. These tests may
generate oil, gas and formation water, each of which needs to be disposed of.
After drilling and initial testing, the rig is usually moved to the next site after ensuring thatthe well has been plugged and sealed as per laid down guidelines of OISD P&NG Rules 2008.
If the exploratory drilling has discovered commercial quantities of hydrocarbons, a wellhead
valve assembly may be installed. If the well does not contain commercial quantities of
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22..55 SSOOUURRCCEEOOFFWWAATTEERR&& PPEERRMMIISSSSIIOONNFFOORRDDRRAAWWLLOOFFWWAATTEERR
Water requirement in a drilling rig is mainly meant for preparation of drilling mud apart from
washings and domestic use. While the former consumes the majority of water requirement,
the water requirement for domestic and wash use is very less. The average daily water
consumption will be 20-30 m3/day for drilling. The potable and drill water shall be supplied
from shore base by supply vessels. The shore base will be set up apart from this; the offshore
drilling unit shall have its own water maker which can be source of water for drill fluid. For
this, the onshore base will be setup in Tuticorin or Kakinada area. Thus the water required for
project will be taken from Tuticorin or Kakinada.
22..66 WWAATTEERRBBAALLAANNCCEE
The average daily water consumption will be 20-30 m3 /day for drilling including water
requirement for mud preparation, washing and domestic activities. Wastewater generation
from the proposed drilling activity will be from domestic activity @ 80 percent of the
domestic water requirement and from washing @100 percent of the washing water
requirement. Thus, wastewater generation from the drilling well is expected to be 9 m3
/day.
Table 2-5: Water Balance
Sr. No Particulars Water Requirement (m3/day)
Water Requirement
1 Mud preparation 20
2 Washing activities 5
3 Domestic purpose 5
Total water requirement 30
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The International Convention for the Prevention of Pollution from Ships (MARPOL) is the
main international convention covering prevention of pollution of the marine environmentby ships. The Convention includes regulations aimed at preventing and minimizing pollution
from ships - both accidental pollution and that from routine operations MARPOL has been
updated by amendments through the years and the rig to be used will always have certified
and annually endorsed by Classification society for compliance.
Procedure for disposal of Drill cutting wash-water has been furnished subsequently in the
paragraph 7.4 of Section-7 (EMP).
22..77..11 BBii llggeeFFlluu iiddss
Bilge fluids are a mix of sea water, petroleum products and other brackish material that
settles to the bottom of a ship. The collection and disposal system for this fluid will be done
in compliance with the International Convention for Prevention of Pollution from Ships,
1973 as modified by the protocol of 1978 (MARPOL 73/78). Bilge fluids mainly constituting
of water, diesel and oil. The rig will be having provision to collect bilge fluids into a sludge
tank and then to a water/oil separator. Separated oil will then be diverted into "dirty oil"
tank, where also exhaust oil coming from engine lubricant change is collected.
The dirty oil will be periodically sent to shore in drums or special containers by supply vessels
deployed for the purpose. Separated water can be directly discharged overboard, provided
that oil content does not exceed 15 ppm as per MARPOL standards.
22..77..22
DDeecckkDDrraaiinnaaggee
Drainage water generated from precipitation or routine operations, such as deck, rig floor
and equipment cleaning will be routed to separate drainage systems on the rig. This includes
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22..77..33 GGrreeyyaannddBBllaacckkWWaatteerr
Grey and Black Water will be generated from showers, toilets, laundry and kitchen facilities
on the rig and will primarily contain waste material, paper, soap etc. Rig operations will
typically result in the generation of sewage and wastes. Once collected through headers,
they will be passed through a sewage treatment plant (STP). The wastes will then be passed
through a screen of less than 25 mm diameter and an extended aeration system prior to
their discharge into the marine environment. In this case also, sewerage treatment on-site
will be done in compliance with MARPOL 73/78 requirements.
22..88 NNOOIISSEEGGEENNEERRAATTIIOONN
Major noise generating sources during offshore drilling and testing activities will:
Rotary drilling equipment as part of rig;
Diesel engines for power generation;
Mud pumps;
Cranes and material handling equipment;
Supply vessels and helicopter movement
As drilling activity is continuous, part of noise associated with the functioning of rig and
ancillaries will be generated only during drilling hours.
Sound pressure levels associated with drilling are the highest with maximum broadband (10
Hz to 10 kHz) energy of about 190 dB re 1Pa @ 1 m2.
22..99 CCHHEEMMIICCAALLSSTTOORRAAGGEEAATTRRIIGGAANNDDIINNOONN--SSHHOORREEFFAACCIILLIITTYY
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chemicals likely to be used during the drilling phase includes cement, surfactants, de-
foamers, lignin, inorganic salts, bentonite and barite.
Table 2-6: Common Chemicals Likely to be used for Preparation of Drilling Fluids
S. No. Name of Chemical S. No. Name of Chemical
1 Barytes 20 Mod. Guar Gum
2 Bentonite 21 PAC-LV
3 Biocide 22 PAC-RG4 Cal. Carb, Coarse 23 PGS
5 Lime Stone Powder (Marble) 24 PHPA
6 Cal. Carb, micronised 25 Pot. Chloride
7 Cal.Chloride 26 Resinated Lignite
8 Caustic Soda 27 Saw Dust
9 Citric Acid 28 Sodium Bicarbonate
10 CMC 29 Soda Ash
11 Common Salt 30 Sp. Fluid (N.W.)
12 Defoamer 31 Sp. Fluid (W)
13 Drilling Detergent 32 Sul. Asphalt
14 E.P. Lube 33 Thermogel
15 HEC 34 Walnut Shell
16 Hydrated Lime 35 XC-Polymer17 Ironite Sponge 36 Zin