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EIA for Exploratory Drilling in Onshore L-II PEL Block of Cauvery Basin,
Tamil Nadu by M/s ONGC
Prepared by M/s. RAMKY Enviro Engineers Ltd., Hyderabad
Page ES.1
Executive Summary
1 Introduction
Oil and Natural Gas Corporation Limited (ONGC) is a public sector petroleum company in India.
It is a company contributing 77% of India's crude oil and 81 % natural gas production. It is the
highest profit-making corporation in India. Oil and Natural Gas Corporation Ltd. (ONGC) has
been playing an important role to meet the energy requirements of the country to meet the
rapidly growing demand for petroleum products in the country. To meet growing energy
requirements a New Exploration Licensing Policy (NELP) has been formulated by The
Government of India. The Government of India gives emphasis for the exploration activity. Oil
and Natural Gas Corporation Ltd. is engaged in exploration and production activities.
Oil & Natural Gas Corporation Ltd. (ONGC) has been awarded an exploration of L-II PEL block in
Cauvery Basin of Tamil Nadu State.
Hydrocarbons have been established in central part of Cauvery Basin. This part of the basin
constitutes parts of Nagapattinam, Tanjore and southern part of Tranquebar sub basins. To
evaluate the hydrocarbon potential of this block, it is essential to take up the drilling of more
number of wells.
The effective date of exploration of this block commenced from dt. 01.04.2004 and consists of
4+1+2 years of exploration cycle of which 2 times extension was issued in year 2008 and 2009
accordingly. Total 7 years PEL cycle ends on 31st March 2011. PEL extension for another 2 years
has been agreed to; hence the environment clearance for the block is sought for upto 31st March
2013.
2 Necessity of the Proposed Project
India is heavily dependent on imports to meet the rapidly growing demand for petroleum
products. Substantial efforts are therefore, necessary to boost the level of exploration activity in
the country, so that new finds can be made and the level of crude oil and gas production
significantly increase in the years to come.
Secondary study about the Cauvery basin region and its surrounding area has the potential of
having oil and gas. On the basis of this assumption, the 3D seismic survey of the acquired block
has already been carried out to substantiate the presence of hydrocarbon in that region. On the
basis of the interpretation of the seismic study in L-II PEL Block, 25 additional exploratory wells
are to be drilled at Nagapattinam, Thiruvarur and Pudhukottai district. Among 25 wells in L-II
PEL block 18 are falling under Thiruvarur district. The wells will be drilled in the range 2100 –
6500 m of depth.
The Location of L-II PEL Block showing wells are shown in Figure 2.1 & lat long of the wells are
given in Table 2.1.Site Environs of the study area is given in Table 2.2(A). Site details of the
proposed 18 wells with 1km radius are given in Table 2.2(B) .
EIA for Exploratory Drilling in Onshore L-II PEL Block of Cauvery Basin,
Tamil Nadu by M/s ONGC
Prepared by M/s. RAMKY Enviro Engineers Ltd., Hyderabad
Page ES.2
Table 2.1
Location of Wells
Well
No.
Name of
location Latitude Longitude Name of the Village Block
Name of the Taluk District
1 KPBC(ML) 10°46’33.67”N 79°35’54.28”E Thandalai,Vilamal Thiruvarur Thiruvarur
Thiruvarur
2 VNAB 10°44’05.68”N 79°41’13.85”E Thappalampuliyur Thiruvarur Thiruvarur
3 PM5A(ML) 10°45’53.82”N 79°40’45.82”E Adiyakkamangalam Thiruvarur Thiruvarur
4 TAAE 10°24’44.92”N 79°37’49.72”E Idumbavanam Muthupet Thiruthuraipoondi
5 MTAM 10°52’05.4”N 79°26’08.4”E Keelavidayal Valangaiman Valangaiman
6 B-CY-NKK-1 10°36’21.77”N 79°31’41.09”E Renganathapuram Kottur Mannargudi
7 B-CY-NKK-2 10°35’38.67”N 79°32’15.61”E Panaiyur Kottur Mannargudi
8 B-CY-NKK-4 10°37’06.58”N 79°30’42.17”E Renganathapuram Kottur Mannargudi
9 B-CY-AB-1 10°52’33.83”N 79°36’25.69”E Nannilam Nannilam Nannilam
10 B-CY-VN-3 10°43’19.23”N 79°38’52.30”E Kalyanasundrapuram Thiruvarur Thiruvarur
11 B-CY-PM-4 10°45’35.16”N 79°38’43.03”E Palavanakkudi Thiruvarur Thiruvarur
12 B-CY-PD-3 10°41’22.23”N 79°32’50.65”E Sathanur Mannargudi Needamangalam
13 B-CY-PD-4 10°39’16.64”N 79°35’25.27”E Mavattagudi Kottur Needamangalam
14 B-CY-PD-5 10°41’30.05”N 79°37’38.29”E Chithraiyur Mannargudi Needamangalam
15 B-CY-KK-3 10°34’50.15”N 79°31’20.38”E Paingattur Kottur Mannargudi
16 B-CY-NKK-5 10°34’43.73”N 79°31’59.50”E Vattar Kottur Mannargudi
17 PMAF 10°48’24.56”N 79°40’41.28”E Pazhayavalam Thiruvarur Thiruvarur
18 AYAC 10°56’49.58”N 79°34’06.67”E Thiruvizhimizhalai Kodavasal Kodavasal
EIA for Exploratory Drilling in Onshore L-II PEL Block of Cauvery Basin,
Tamil Nadu by M/s ONGC
Prepared by M/s. RAMKY Enviro Engineers Ltd., Hyderabad
Page ES.3
Figure 2.1
Location of L-II PEL Block showing wells 18 exploratory drilling wells
EIA for Exploratory Drilling in Onshore L-II PEL Block of Cauvery Basin,
Tamil Nadu by M/s ONGC
Prepared by M/s. RAMKY Enviro Engineers Ltd., Hyderabad
Page ES.4
Table 2.2(A)
Site Environs of the L-II PEL Block covering 18 Exploratory Drilling wells in Thiruvarur District
Well No.
Well Name Name of the Village Nature of soil
Nature
of
Terrain
Nearest town/City
Nearest Highway
Nearest Major/
Minor Railway
station
Nearest Airport
Nearest Sea Port
Distance
to Bay of
Bengal
1 KPBC(ML) Thandalai,Vilamal Alluvial Plain Thiruvarur
(~3km-E) NH83
Thiruvarur
(~4km-ESE)
Tiruchirapalli
(~97Km, W)
Marg Port
Karaikal
(~28 Km, ENE)
~29Km
2 VNAB Thappalampuliyur Alluvial
Plain Thiruvarur
(~5km-NW) NH83
Adiyakkamangalam
(~2.5km-NNW)
Tiruchirapalli
(~176Km,WN
W)
Marg Port
Karaikal
(~21 Km, NE)
~25Km
3 PM5A(ML) Adiyakkamangalam Alluvial
Plain Thiruvarur
(~3.5km-W) NH83
Adiyakkamangalam
(~1km-S)
Tiruchirapalli
(~106Km, W)
Marg Port
Karaikal
(~20 Km, NE)
~20Km
4 TAAE Idumbavanam Sandy
Clay
Plain Muthupet
(~14km-WSW) NH83
Muthupet
(~14km-WSW)
Tiruchirapalli
(~108Km, NW)
Marg Port
Karaikal
(~52 Km,NNE)
~10Km
5 MTAM Keelavidayal Sandy
Clay
Plain Kumbakonam
(~11 - NNW) NH 36
Needamangalam
(~11km-NNE)
Tiruchirapalli
(~78Km,
WSW)
Marg Port
Karaikal
(~45 Km, E)
~49Km
6 B-CY-NKK-1 Renganathapuram Alluvial
Plain Mannargudi
(~10km - NW) NH 36
Mannargudi
(~10.5km - NW)
Tiruchirapalli
(~91Km,
WNW)
Marg Port
Karaikal
(~43 Km, NE)
~38Km
7 B-CY-NKK-2 Panaiyur Alluvial
Plain Mannargudi
(~11km - NW) NH 36
Mannargudi
(~11km - NW)
Tiruchirapalli
(~92 Km,
WNW)
Marg Port
Karaikal
(~43 Km, NE)
~36Km
8 B-CY-NKK-4 Renganathapuram Alluvial
Plain Mannargudi
(~9km - NW) NH 36
Mannargudi
(~9.5km - NW)
Tiruchirapalli
(~86Km,
WNW)
Marg Port
Karaikal
(~42 Km, NE)
~42Km
9 B-CY-AB-1 Nannilam Alluvial
Plain Thiruvarur
(~10km - SSE) NH88
Mannargudi
(~29km - SW)
Tiruchirapalli
(~99Km,
WSW)
Marg Port
Karaikal
(~27 Km, ESE)
~33Km
10 B-CY-VN-3 Kalyanasundrapuram Alluvial
Plain Thiruvarur
(~4km - NNW) NH15A
Thiruvarur
(~4.5km - NNW)
Tiruchirapalli
(~106Km, W)
Marg Port
Karaikal
(~25 Km, NE)
~22Km
11 B-CY-PM-4 Palavanakkudi Alluvial Plain Thiruvarur
(~0.3km, NW) NH36
Thiruvarur
(~0.6km, NW)
Tiruchirapalli
(~102Km, W)
Marg Port
Karaikal
(~24 Km, NE)
~22Km
EIA for Exploratory Drilling in Onshore L-II PEL Block of Cauvery Basin,
Tamil Nadu by M/s ONGC
Prepared by M/s. RAMKY Enviro Engineers Ltd., Hyderabad
Page ES.5
Well
No. Well Name Name of the Village
Nature
of soil
Nature
of
Terrain
Nearest
town/City
Nearest
Highway
Nearest Major/
Minor Railway
station
Nearest
Airport
Nearest Sea
Port
Distance
to Bay of
Bengal
12 B-CY-PD-3 Sathanur Alluvial Plain Koothanallur
(~4km - NW) NH15A
Thiruvarur
(~12.6km - NW)
Tiruchirapalli
(~90Km,
WNW)
Marg Port
Karaikal
(~37 Km, NE)
~59Km
13 B-CY-PD-4 Mavattagudi Alluvial Plain Thiruvarur
(~13km - NNE) NH15A
Adiyakkamangalam
(~15km - NE)
Tiruchirapalli
(~97Km,
WNW)
Marg Port
Karaikal
(~34 Km,NNE)
~32Km
14 B-CY-PD-5 Chithraiyur Alluvial Plain Thiruvarur
(~7km - N) NH – 15A
Thiruvarur
(~7km - N)
Tiruchirapalli
(~101Km,WN
W)
Marg Port
Karaikal
(~29 Km,NNE)
~26Km
15 B-CY-KK-3 Paingattur Alluvial Plain Mannargudi
(~12.6km - NW) NH – 15A
Mannargudi
(~13km - NW)
Tiruchirapalli
(~91km - ESE)
Marg Port
Karaikal
(~45 Km,NNE)
~20Km
16 B-CY-NKK-5 Vattar Alluvial Plain Thiruthuraipoondi
(~12km- ESE) NH – 15A
Thiruthuraipoondi
(~12km - ESE)
Tiruchirapalli
(~92Km, NW)
Marg Port
Karaikal
(~45 Km, NE)
~20Km
17 PMAF Pazhayavalam
Alluvial Plain Thiruvarur
(~5km - SW) NH 36
Thiruvarur
(~6.5km - SW)
Tiruchirapalli
(~106Km, W)
Marg Port
Karaikal
(~18 Km,
ENE)
~ 18Km
18 AYAC Thiruvizhimizhalai Alluvial Plain Poonthottam NH36 PeralamJn
(~10km - E)
Tiruchirapalli
(~96Km, SW)
Marg Port
Karaikal
(~33 Km, SE)
~38Km
EIA for Exploratory Drilling in Onshore L-II PEL Block of Cauvery Basin,
Tamil Nadu by M/s ONGC
Prepared by M/s. RAMKY Enviro Engineers Ltd., Hyderabad
Page ES.6
Table 2.2(B)
Site Details of the Proposed 18 Exploratory Drilling wells in Thiruvarur District (1km radius)
Well No.
Well Name Name of the Village
Elevation
above MSL
(m)
Any other
Installations/
activity
Flora & Fauna Approachability to the
site Activities around
1 KPBC(ML) Thandalai,Vilamal 12
None
No designated wild
life habitat was
reported during the
site survey in 1km
radius area except
for few small
mammals and
common birds
recorded during
faunal study.
~ 3.5 Km SH 33
None 2 VNAB Thappalampuliyur 9 ~ 0.2 Km SH 33
3 PM5A(ML) Adiyakkamangalam 11 ~ 0.3 Km SH 33
4 TAAE Idumbavanam
4 ~ 3.5 Km SH – 65 Agriculture is the major
activity within 1km radius
5 MTAM Keelavidayal 22 ~ 0.7 Km SH 99
None
6 B-CY-NKK-1 Renganathapuram 9 ~ 3.2 Km SH 83
7 B-CY-NKK-2 Panaiyur 9 ~ 4.5 Km SH 83
8 B-CY-NKK-4 Renganathapuram 12 ~ 7.8 Km SH 83
9 B-CY-AB-1 Nannilam 12 ~ 2.5 Km SH 83
10 B-CY-VN-3 Kalyanasundrapuram 12 ~ 5.7 Km SH 83
11 B-CY-PM-4 Palavanakkudi 10 ~ 1.0 Km SH 83
12 B-CY-PD-3 Sathanur 11 ~ 5 Km SH 83
13 B-CY-PD-4 Mavattagudi 8 ~ 2 Km SH 83
14 B-CY-PD-5 Chithraiyur 9 ~ 5.7 Km SH 83
15 B-CY-KK-3 Paingattur 8 ~ 8 Km SH 83
16 B-CY-NKK-5 Vattar 9 ~ 4.5 Km SH 83
17 PMAF Palayavalam 10 ~ 1.1 km SH 148 Agriculture is the major
activity within 1km radius 18 AYAC Thiruvizhimizhalai 19 ~ 9 km SH 23
SH – State Highway; NH – National Highway
EIA for Exploratory Drilling in Onshore L-II PEL Block of Cauvery Basin,
Tamil Nadu by M/s ONGC
Prepared by M/s. RAMKY Enviro Engineers Ltd., Hyderabad
Page ES.7
2.1 Technology and Process Description
Drilling Operations
Only water based drilling mud will be used. The rig will be provided with solids handling system
comprising Shale shakers (1200 GPM), Desander (1200 GPM) and degasser with vacuum pump.
Drilling operations will be carried out using an electrical type drilling unit for drilling of oil and
gas wells consists of a derrick and the top of which is mounted a crown block and a hoisting
block with a hook. From the swivel is suspended a Kelly stem passes through a square or
hexagonal Kelly bush which fits into the rotary table. The rotary table receives the power to
drive it from an electric motor. The electric motor rotates the rotary table which passes through
the Kelly bush and the rotations are transmitted to the bit as the drilling progresses, the drill
pipe in singles are added to continue the drilling process. At the end of the bit life, the drill pipes
are pulled out in stands and stacked on the derrick platform. A stand normally has 3 single drill
pipes. After changing the bit, the drill string is run back into the hole and further drilling is
continued. This process continues till the target depth is reached.
During the course of drilling, cuttings are generated due to crushing action of the bit. These
cuttings are removed by flushing the well with duplex/ triplex mud pumps. The mud from the
pump discharge through the rotary hose connected to stationery part of the swivel, the drill
string and bit nozzles. The mud coming out of the bit nozzles pushes the cuttings up hole and
transports them to the surface through the annular space between the drill string and the hole.
The mud not only carries away crushed rock from the bottom of the hole but it also cools the bit
as it gets heated due to friction with formation while rotating. The mud also helps in balancing
subsurface formation pressures and by forming a cake on the walls of the well diminishes the
possibility of crumbling or caving of the well bore.
At the surface, the mud coming out from well along with the cuttings falls in a trough passes
through the solids control equipments i.e. Shale shaker, de-sander and de-silter. These
equipments remove the solids of different sizes which get mixed with the mud during the
course of drilling. The cleaned mud flows back to the suction tanks to be again pumped into the
well. The drilling mud/ fluid circulation is thus a continuous cyclic operation. The most suitable
clay for mud preparation is bentonite which is capable of forming highly dispersed colloidal
solutions. Various other chemicals are also used in mud preparation as per requirements
dictated by the temperature/pressure conditions of the wells. The mud is continuously tested
for its density, viscosity, yield point, water loss, PH value etc. to ensure that the drilling
operations can be sustained without any down hole complications.
Technical Details of the proposed 18 wells coming under Thiruvarur district are given in Table
2.3. The general Drill site plan used for drilling activity is shown in Figure 2.2.
EIA for Exploratory Drilling in Onshore L-II PEL Block of Cauvery Basin,
Tamil Nadu by M/s ONGC
Prepared by M/s. RAMKY Enviro Engineers Ltd., Hyderabad
Page ES.8
Figure 2.2
Drill Site Plan
Diesel Tank
Diesel Tank
Power Pack
Power Pack
Power Pack
Power Pack
Oil
Store
Mech
Store
Utility House
Compressor Water Tank
Water Tank
D.C
Conv
erter
A.C
Conv
erter
Mud
Tank
Lined
Pit
Mud
Tank
MAIN
FOUN
DATI
ON Soak
Pit
4X2x1m
Elect
Store
Mud Pump
Mud Pump
Mud
Tank
Cellar pit
MAIN
FOUN
DATI
ON
Air Tank
Canteen Radio
Room
Rig I/C SCADA
Security
EIA for Exploratory Drilling in Onshore L-II PEL Block of Cauvery Basin,
Tamil Nadu by M/s ONGC
Prepared by M/s. RAMKY Enviro Engineers Ltd., Hyderabad
Page ES.9
Table 2.3
Technical Details of the Proposed Drilling Activities
S.No Well Name Depth
(m)
Duration of drilling (Days)
Qty. of cuttings
(m³)
Qty. Drilling Wastewater
(m³) 1 KPBC(ML) 4500 165 777 1320
2 VNAB 3500 125 589 1000
3 PM5A(ML) 3550 130 612 1040
4 TAAE 3600 140 659 1120
5 MTAM 2100 40 188 320
6 B-CY-NKK-1 2550 70 330 560
7 B-CY-NKK-2 2550 70 330 560
8 B-CY-NKK-4 2450 132 622 1056
9 B-CY-AB-1 5500 180 848 1440
10 B-CY-VN-3 4500 165 777 1320
11 B-CY-PM-4 4000 135 636 1080
12 B-CY-PD-3 6000 210 989 1680
13 B-CY-PD-4 6500 235 1107 1880
14 B-CY-PD-5 6000 210 989 1680
15 B-CY-KK-3 2250 68 320 544
16 B-CY-NKK-5 2250 68 320 544
17 PMAF 4200 150 706 1200
18 AYAC 4500 165 777 1320
EIA for Exploratory Drilling in Onshore L-II PEL Block of Cauvery Basin,
Tamil Nadu by M/s ONGC
Prepared by M/s. RAMKY Enviro Engineers Ltd., Hyderabad
Page ES.10
3 Baseline Environmental Status
Meteorology (Climate)
The baseline data generation for the Rapid EIA has been carried out during the winter season
(December 2011 to March 2012) in the Study Area, which is considered as L-II PEL Block,
covering the area of all the proposed drilling wells for various/environmental attributes so as to
compute the impacts that are likely to arise due to Exploratory Drilling at L-II PEL Block of
Cauvery Basin, Tamil Nadu. The predominant wind direction during the study period was
blowing from NE to SW followed by NW to SE.
The average maximum temperature is 33.9°C and minimum is 25.8°C. Maximum Humidity is
73% and Minimum Humidity is 55%.
Ambient Air Quality
The study area represents mostly rural environment. Ambient Air Quality Monitoring (AAQM)
stations were set up at 10 locations. Different air pollutants namely Respirable Particulate
Matter (PM<2.5µ, PM<10µ), Sulphur Dioxide (SO2), Oxides Of Nitrogen (NOx), and VOCs, HC
(Methane) and HC (Non-Methane) were sampled on 24 hourly as per MoEF guidelines and
results are compared with the standards stipulated by CPCB. The observed air pollutants were
within the standard limits.
Water Quality Status
Ground water (9 no) and surface water samples (2 no) were collected from different sources
within the study area and some important physical and chemical parameters including heavy
metals were considered for depicting the baseline status of the study area. The samples
collected from the study area were found to be fit for human consumption; however the
hardness, dissolved solids and most of ground water samples seem to be above desirable limit
but well within the permissible limits. Most of the heavy metals in all samples are below
detectable limits.
Noise Quality
Noise levels are monitored in the study area within 10Km and 1 Km. The main sources of noise
in the study area are domestic activities, and vehicular traffic. The main occupation of the
villagers in the study area is agricultural. The noise levels observed in some of the rural areas
are primarily owing to vehicular traffic and other anthropogenic activities. In rural areas, wind
blowing and chirping of birds would contribute to noise levels especially during the nights. The
day equivalents during the study period are ranging between 51.8 to 63.2 dB (A), whereas the
night equivalents were in the range of 40.6 to 43.0 dB (A). From the results, it can be seen that
the Day equivalents and the Night equivalents were within the Ambient Noise standards of
residential area standards.
Soil Quality
The soil of the PEL Block area is mainly characterized by alluvium composed of sand (course to
fine) and sandy clay in varying proportions. The soil characteristics in the study area, especially
the physical quality and fertility of the soil have been characterized by analyzing the soil
EIA for Exploratory Drilling in Onshore L-II PEL Block of Cauvery Basin,
Tamil Nadu by M/s ONGC
Prepared by M/s. RAMKY Enviro Engineers Ltd., Hyderabad
Page ES.11
samples collected from 10 locations within the exploratory block. The texture of soil samples
collected from the monitoring locations was characterized as sandy loam.
Flora & Fauna
There are no endangered or endemic species of flora and fauna within 1km radius of the
proposed drilling well sites. However, few small mammals and common birds recorded during
faunal study.
4. Anticipated Environmental Impacts and Mitigation Measures
Environmental impact statement focuses on the study area within block boundary of the
proposed drilling sites. The five basic environmental components of concern are: Air
Environment, Noise Environment, Water Environment, Land Environment, Socio-economic
Environment.
Impact on air Quality
A number of sources are there to cause potential impacts on air quality, which are as Follows:
� Emissions from DG sets used as part of the drilling rig;
� Fugitive emissions during site preparation and closure phases;
The Major Air pollutants generated:
� The primary pollutants emitted by a DG set consist of particulate matter, Oxides of
Sulphur and Nitrogen. To assess the quantitative impact of generation of gases, air
quality modeling has been carried out using USEPA (United State Environmental
Protection Agency) and MoEF approved model version AERMOD, assuming an operation
time of 24 hours, in relation to on-site observed meteorological parameters.
� For GLC prediction in air modeling Bharath Stage III (BS III) fuel is considered. The
emissions from DGs will be passed through the stacks and below are the emission rates
of the pollutants.
� Some fugitive emissions are also anticipated from storages of volatile chemicals and fuel
at the site, if not capped properly or are not handled with due care. However, such
emissions will not disperse widely and can only affect workers health at site.
For each exploratory drilling activity, 3 no.s DG sets are required. For modelling of the DG set
emissions from each well, 20km X 20km area is considered. The predicted GLCs for PM, SO2, and
NOx from DG set emissions by drilling activity with baseline environmental results calculated
the Post project scenario and compared with NAAQ standards, which are found to be within the
limits.
The mitigation measures for air quality impacts are briefly described below:
� The exhaust of the DG set will be at sufficient height to allow dispersion of the pollutants
and DG sets will be properly maintained so that emissions will be under statutory limits;
� Improvement of combustion efficiency by ensuring maintenance and replacement of air,
fuel filters for DG sets;
� The storage and handling of spoil, sub-soils, top-soils and materials will be carefully
managed to minimize the risk of windblown material and dust;
EIA for Exploratory Drilling in Onshore L-II PEL Block of Cauvery Basin,
Tamil Nadu by M/s ONGC
Prepared by M/s. RAMKY Enviro Engineers Ltd., Hyderabad
Page ES.12
� Water spraying will be done on the access roads to control re-entrained dust during dry
season;
� Most of the equipment, machinery and vehicles have inbuilt pollution control devices.
Thus selection of equipment and machinery will be considered as a measure for source
prevention of air pollution;
� The engines and exhaust systems of all vehicles and equipment used in this project will
be maintained as such, that exhaust emissions are low and do not breach statutory limits
set for the concerned vehicle/equipment type;
Water Requirement & utilization
The daily water consumption per well will be approximately 25 KLD of which 13 KLD will be
used for mud preparation, 6KLD will be used for de-sander and de-silter, 2KLD for Derrick floor
washing. The water used for de-sander and de-silter and Derrick floor washing will be reused
for cutting washing. Engine cooling / mud pump liner requirement is 2KL in loop. Domestic
water requirement per each drill site will be 4KLD.
Impact on water quality
The proposed drilling operation would include construction site preparation, drilling of wells
which involves use of surface water for domestic purpose and for mud preparation and would
cause generation of wastewater.
Following mitigation measures will be implemented for water pollution control at each drilling
site:
� Efforts will be made to reduce water requirement and recycling will be practiced
wherever possible;
� Wastewater from drilling activity will be sent to cement lined waste pit Wastewater
characteristics would be of varied nature and likely to contain soil particulate matter
along with organics. The treatment scheme comprises of Sedimentation cum Coagulation
Tank and clarification by settling and the treated wastewater will be sent to waste lined
pit for solar evaporation.
� The domestic wastewater will be discharged into the septic tanks followed by soak pits;
� The storm water system will be efficiently designed and maintained;
� At the initial stage, drilling is likely to be avoided during monsoon season;
� Drill cutting waste to be disposed on-site in waste lined pit.
All chemical and fuel storage areas will have proper bunds so that contaminated run-off
cannot meet the storm-water drainage system;
Impact on Noise Levels
The potential impacts on noise level may arise out of the following:
� Noise from the Drilling Rig:
� Noise Emanated by Machineries & Equipments:
� Noise from Vehicular Traffic
EIA for Exploratory Drilling in Onshore L-II PEL Block of Cauvery Basin,
Tamil Nadu by M/s ONGC
Prepared by M/s. RAMKY Enviro Engineers Ltd., Hyderabad
Page ES.13
Typical mitigation measures for noise at each drilling site will include the following:
� Sufficient engineering control during installation of equipments and machineries (like
mufflers in DG sets) is to be ensured to reduce noise and vibration emission levels at
source;
� Proper and timely maintenance of machineries is to be adopted;
� Effective noise barrier at the fence-line of the site needs to be setup.
� All noise generating operations, except drilling is to be restricted to daytime only to the
extent possible;
� Personnel Protective Equipments (PPE) like ear plugs/muffs is to be given to workers at
site.
� Undertake preventive maintenance of vehicles and machinery to reduce noise levels.
Impact on Land Environment
The existing land and land use pattern of the site area will slightly get affected from the
construction of drilling site and associated activities, like elevation of land, installation of rig &
machineries, temporary storage of domestic waste and other kind of waste material etc.
Mitigation Measures
� Necessary efforts will be made during selection of drill site to minimize disruption of
current land use to the extent possible and this should be a criteria as part of initial
project planning;
� Temporary camp site will be provided with complete amenities and sanitation facilities
for the labourers to be deployed in the site during construction of the site as well as
during drilling phase;
� Necessary restoration efforts will be made during decommissioning and site closure to
restore the site back to its original condition to the extent possible;
� On completion of works (in phases), all temporary structures, surplus materials and
wastes will be completely removed;
� Optimization of land requirement through proper site lay out design will be a basic
criteria at the design phase;
� Temporary new approach roads can be constructed and existing roads can be improved,
if required, for smooth and hassle free movement of personnel as well as materials and
machineries;
� Proper restoration of site will be carried out to bring the physical terrain, soils and
vegetation, as closely possible, to their original condition;
Following is a brief description of the soil quality impacts:
� Alteration of Topsoil Environment & Fertility
� Runoff and soil erosion
� Compaction of Soil
� Soil Contamination if certain operations like storage of chemicals and fuels, cement and
mud preparation, spent oil and lubricants are managed inefficiently.
EIA for Exploratory Drilling in Onshore L-II PEL Block of Cauvery Basin,
Tamil Nadu by M/s ONGC
Prepared by M/s. RAMKY Enviro Engineers Ltd., Hyderabad
Page ES.14
Mitigative Measures
� Store, preserve and protect topsoil separately to use it during restoration period;
� Carry out adequate restoration of soil in the project site, to the extent possible;
� Restrict movement of vehicles only to designated areas within the site to the extent
possible
� Domestic waste will be segregated at the source itself like recyclable and non-recyclable
wastes. Recyclable waste will be sent to recyclers and non-recyclable waste will be
disposed to nearby domestic bins.
� Install properly designed garland drains along the site to channelize the storm water
properly.
� Management of spilling of contaminants on the soil
� The drill cuttings will be separated and conveyed to a specially designed lined pit at site;
� The cuttings will be treated and disposed in accordance with GSR 546 (E) regulation
under Environmental (Protection) Act, 1986 specified for onshore oil & gas industry;
� Provisions for mobile toilets can be kept for labourers, which can be finally transported
to the designated disposal site;
� Proper arrangement of septic tanks and soak pits can be provided at site
Impact on Biological Environment
The land use data presented earlier in the baseline shows that most of the area of study area
come under man made ecosystem, viz agricultural land, village woodlot, etc. No designated wild
life habitat was reported during the site survey in 1km radius from each well site except for few
small mammals and common birds recorded during faunal study. However, the drilling activity,
being a temporary work, will not hamper the ecological balance of the area and will not cause
permanent shifting of any birds or any faunal habitats.
Impact on Socio-Economic Environment
The population living in the surrounding villages will be exposed to noise, dust and frequent
movement of trucks at the time of site preparation at the initial stage of drilling activity.
Adequate onsite precautions will be adopted to minimize those effects.
The proposed drilling activity requires limited manpower. Hence, there will not be any influx of
population due to proposed drilling activity.
5 Risk Assessment
Risk Assessment considered the systematic analysis and evaluation of risks related to the
exploratory drilling in the acquired block. The Risk Assessment involved the identification and
evaluation of major risks, prioritizing the risks identified based on their hazard consequences
and formulating suitable risk reduction/mitigation measures.
The associated risk have been determined semi-quantitatively as the product of
likelihood/probability and severity/consequence by using order of magnitude data (risk
ranking = severity/consequence factor X likelihood/probability factor). Significance of such
project related risks was then established through their classification as high, medium, low, very
low depending upon risk ranking. The major risks viz. blow out/loss of well control, process
EIA for Exploratory Drilling in Onshore L-II PEL Block of Cauvery Basin,
Tamil Nadu by M/s ONGC
Prepared by M/s. RAMKY Enviro Engineers Ltd., Hyderabad
Page ES.15
leaks/fire, non-process fire and explosion and their resultant consequences viz jet fire, pool fire,
heat radiation effects have been assessed and evaluated.
6 Environmental Monitoring Program
Environmental Monitoring Program has been designed for assessing the efficiency of
implementation of Environment Management Plan and to take corrective measures in case of
any degradation in the surrounding environment.
Different activities involved in the proposed project and their impact on various environmental
attributes have been taken into account while designing a detailed environmental monitoring
program.
Implementation of EMP and periodic monitoring is proposed to be carried out at study area.
Environmental protection measures like dust suppression, treatment and recycling of
wastewater, noise control in the premises, housekeeping, implementation of EMP and
Environmental Clearance conditions will be monitored by the project site authorities.
7 Project Benefits
The proposed exploratory drilling of oil and gas will impose the following benefits to the society
as well as the economy at a large scale. Following benefits are envisaged from the proposed
drilling operation:
Improvements in the physical infrastructure:
The site development may lead to additional improvement in the access road connectivity in the
area, if required.
Employment potential:
A small scale temporary job generation will be there for unskilled workers towards road and
site preparations and as guards.
During site construction, approximately 35 to 40 workmen are likely to be involved per one
exploratory drilling well. People from adjoining areas would be given preference according to
the skill sets possessed.
Improvement in the future economy:
The proposed exploratory drilling activity may have the potential for future benefits, if proved
to be economically viable for future production of oil.
8 Environmental Management Plan
The EMP comprises a series of components covering direct mitigation and environmental
monitoring, an outline waste management plan and a drilling site restoration plan. The
exploratory drilling programme has been designed to avoid or minimise impacts to the
environment and local communities wherever practicable.
Based on the impacts identified, a conceptual Environmental Management Plan (EMP) is
recommended as below:
EIA for Exploratory Drilling in Onshore L-II PEL Block of Cauvery Basin,
Tamil Nadu by M/s ONGC
Prepared by M/s. RAMKY Enviro Engineers Ltd., Hyderabad
Page ES.16
� Water Based Mud (WBM) will be used as drilling fluid in exploratory drilling to maintain
hydrostatic pressure control in the well and to lubricate the drill bit.
� Sulfur content in the Diesel which will be used for DG sets is 0.035%. Hence SO2 emissions
will be negligible.
� Noise from DG set shall be controlled by providing acoustic enclosures.
� Process waste e.g. drill cuttings and return mud generated during drilling operations will be
stored and disposed on-site in accordance with GSR 546 (E) regulation under
Environmental (Protection) Act, 1986 specified for onshore oil & gas industry;
� The waste pit after it is filled up shall be covered with impervious liner, over which, a thick
layer of native soil with proper top slope is provided.
� The wastewater from cutting washings around will be sent to waste lined pit for solar
evaporation. Domestic wastewater will be sent to septic tank followed by soak pit at the site.
� Spent oil and loose oil will be sent to Approved Recyclers nearby the proposed drilling well
sites.
9. Conclusions
The exploratory drilling of well is a process of evaluating the potential of the area in terms of oil
and gas production. Additionally, historical background of the area also shows that, the area is a
significant source of oil and gas exploration. The implementation of this drilling activity will
further ensure the presence of oil and gas reserves. The proposed exploratory drilling project
will contribute to economic growth in indirect way and may help in meeting the increasing
demands of oil and gas, if proved to be economically beneficial for future production.
During environmental assessment study, an overall assessment of the potential environmental
impacts likely to arise from the proposed drilling activity. The impact predictions indicate the
maximum GLC levels of PM, SO2, & NOx values were well within the prescribed limits of
MoEF/CPCB standards and the expected impacts are negligible from the release of pollutant
from the DG stacks. The predicted GLC are superimposed on the baseline levels and the post
project levels are found to be within the permissible limits.
The Mitigation measures are proposed to minimize the adverse impacts likely from this activity
in the form of EMP. Various pollution control measures are suggested for Air, Water, Noise , land
& socioeconomic aspects to mitigate any adverse impacts due to the project during
construction, drilling activity and as well as post project monitoring. Proper waste management
practices are also provided for drill cutting waste/Domestic solid waste/hazardous waste
generated. All the effluents and domestic sewage are properly treated in designated waste lined
pit/Septic tanks to the required stipulated standards.
The proposed drilling activity will be operated with the best available pollution abatement
systems with sound environmental management systems with minimal impacts.
Risk Assessment is also carried out for the blow outs anticipated due to drilling. A detailed
disaster management plan is incorporated to mitigate on- site & emergency preparedness plan
for off-site emergencies.
EIA for Exploratory Drilling in Onshore L-II PEL Block of Cauvery Basin,
Tamil Nadu by M/s ONGC
Prepared by M/s. RAMKY Enviro Engineers Ltd., Hyderabad
Page ES.17
Based on the Environment Impact Assessment study conducted the following conclusions are
made:
• The adverse impact due to the proposed drilling activity at Cauvery basin by M/s Oil &
Natural Gas Corporation (ONGC) is reversible and insignificant by adopting the
recommendations followed in the EMP.
• ONGC shall follow the EMP as detailed in the EIA report together with conditions of EC,
NOC etc., for the proposed project.
• All the impacts envisaged during construction stage & operation stage shall be
systematically audited, reported & recorded in adherence with the EMP.
Also, as per the ToR issued by MoEF, ONGC propose to conduct the public hearing at Three
places namely Polagam (Nagapattinam Distrcit), Adiyakkamangalam (Thiruvarur district),
Karambakkudi (Pudukottai District) for the proposed 25 exploratory drilling wells to address
the concerns of local affected people and others, who have plausible stack in the environmental
impacts of the project.
Also, as per the ToR issued by MoEF, ONGC propose to conduct the public hearing at
Adiyakkamangalam (Thiruvarur district) for the proposed 18 exploratory drilling wells, which
are falling under Thiruvarur district are to be addressed for concern of local affected people and
others, who have plausible stack in the environmental impacts of the project.