05 executive summary pel thiruvarur updated · prepared by m/s. ramky enviro engineers ltd.,...

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

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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) .




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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




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Figure 2.1

Location of L-II PEL Block showing wells 18 exploratory drilling wells




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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




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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




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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




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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.




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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




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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




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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




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;




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� 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




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.




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




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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:




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� 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.




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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.

05 executive summary pel thiruvarur updated · prepared by m/s. ramky enviro engineers ltd.,...

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