Block MZ-ONN-2004/1 (Mizoram)
Oil India Limited
Duliajan, Assam
GREEN TECH ENVIRONMENTAL ENGINEER & CONSULTANTS
Guwahati-28Assam
EXECUTIVE SUMMARY
PROJECT HIGHLIGHTS
The On-Shore NELP –VI BLOCK: MZ-ONN-2004/1 located in the Aizwal, Lunglei, and Mamit and Serchhip districts of Mizoram has been allotted by Government of India to Oil India Limited (OIL) and M/S Shiv–Vani Oil & Gas Exploration Services Ltd. for exploration and production of hydrocarbons. OIL is the Operator of the onshore block.
The area of the block MZ-ONN-2004/1 is 3213 sq. km. and has the following coordinates:
Point Latitude, N Longitude, E
A 23040’00.00” 92032’54.85” B 23000’00.00” 92035’58.00” C 23000’00.00” 93000’00.00” D 23040’00.00” 93000’00.00” A 23040’00.00” 92032’54.85”
The Block map is enclosed.
As per the Minimum Work Program (MWP) of the Production Sharing Contract (PSC) signed with the Government of India, OIL is required to Drill 06 (Six) wells .Three locations have been identified for drilling. The other three locations will be selected after further geo scientific studies and results of the drilled wells.
Each drilling location is finalized based on analysis of the seismic and other geo scientific data. Sequential drilling of 06 (six) wells is planned. Tentative time of commencement of drilling is 2012. Drilling and testing of each well is expected to be completed in about 150 days.
In order to obtain the Environmental Clearance (EC) from the Ministry of Environment and Forests (MoEF), OIL is required to carry out an Environmental Impact Assessment (EIA) study in the block to establish present baseline environmental scenario and the likely impact on the same as a result of proposed exploratory drilling and testing of the wells.
EIA report is prepared using primary baseline data collected at the site for nearly 5 weeks in non-monsoon season (March and April, 2011) and secondary data collected from various sources in public domain as well as the project information provided by OIL.
Drilling rig and associated system will be used for drilling of the exploratory wells. Water Based Mud (WBM) will be used as drilling fluid which is intrinsically safe and causes minimum environmental disturbances. Facilities for production testing will be created within each exploratory well site.
The block and adjoining areas belong to warm per-humid eco-region of North-Eastern Hills in Mizoram with red and laterite soils.
Use of WBM for drilling is very eco-friendly and will cause minimum environmental disturbances.
Major liquid effluents during exploratory drilling and testing will be drilling discharges, drainage discharges, used/wasted WBM and domestic waste water.
Drilling discharges will have rock cuttings of sandstone, shale, etc. Wasted WBM will have bentonite clay, barite and other nontoxic ingredients.
Liquid effluents from effluent pits before discharge will be treated in Effluent Treatment Plant (ETP) to meet on-shore discharge limits and treated effluents will be discharged in nearby river/nullah at a controlled rate, if required.
Gaseous emissions will be primarily exhaust gases produced from diesel driven power generators for drilling rig operation and for other uses as well as diesel driven vehicles. These exhaust emissions will primarily contain SO2, NOx, CO, unburnt hydrocarbons etc. Dust will also be generated from
vehicular movement on unpaved roads in the block area.
Formation fluids (Oil/Gas) generated from the exploratory wells will be tested at site for 3 to 4 days to establish the hydrocarbon production potential.
Pollution Control
Liquid effluents will be stored in HDPE lined shallow pits constructed within the exploratory drilling location to prevent contamination of ground aquifers.
On well completion, effluent pits will be filled with drill cuttings and solid debris, covered with HDPE sheet and thick layer of soil to form a small mound with proper slope for rain water drainage.
Organic solid wastes including sewage and food leftovers generated at temporary camp facilities at the exploratory well site will be disposed off as per approved procedure.
Exhaust gases from various power generators will be discharged from stacks of appropriate heights for dispersion in a wider area by atmospheric dispersion process and will result in extremely low incremental ground level concentrations of pollutants in nearby area only.
Formation water (if any) produced with oil during exploratory production testing of oil/gas will be treated in a clarification system and treated effluents meeting the on-shore discharge standards will
Project Benefits
Oil and gas production, if commercially viable, will result in additional revenue generation for the State and Central Governments and will assist in providing energy security to the country. It will also generate some employment potential and lead to infrastructure development of the block area.
BASELINE ENVIRONMENTAL CONDITIONS Physiography and Topography
The block and surrounding area is a undulated forested terrain. Tuirial, Mat Tuikum, Tut and Tuichang rivers flow through or close to the block area. Some agricultural fields are observed in the plains section of the block area along with some thinly populated villages/towns.
Wild life Sanctuaries
Dampa Tiger Reserve forest is outside the block boundary and more than 20km away from the proposed location of OIL 4 & 5.
Tawi Wildlife Sanctuary is about 15 km from the proposed location OIL 2.
Khawnglung Wildlife Sanctuary is more than 40 Km away from the proposed location OIL 8.
Soils
Area has soils derived from siltstones, shales and sandstones having sufficient water holding capacity with relatively low fertility.
Water Resources and Water Quality
Surface water is a perennial source of fresh water. The Tuirial, Mat, Tuikum, Tut and Tuichang rivers flow through the block area.
The monitored water quality indicates that surface water (rivers,streams) and ground water (handpump and spring) samples meet desirable limits for potable water and is fit for drinking.
Climatology and Meteorology
April is the hottest month and January is the coldest month with monthly mean maximum and minimum daily temperatures of nearly 27.2 and 17.90C, and 20.4 and 11.40C, respectively.
Average annual rainfall is 2244.7 mm. June month alone accounts for nearly 21.3% and December to January month’s together account for only 0.6% of annual rainfall at Aizawl.
Ambient Air Quality
National ambient air quality standards for residential rural and other area are always met for PM10,
Terrestrial Fauna
Existence of extensive forest ranges support fairly large variety of wildlife.
Agricultural Crops
Paddy, maize, oil seeds, pulses, vegetables, etc. are grown to limited extent in the block area.
Demographic and Socio-Economic
As per Census 2001, the sex ratio is 958 and literacy rate is 72.29%.
The study area has 47.06% main workers out of which 78.74% are cultivators, 1.94% are agricultural labourers, 1.70% are household industry workers and rest 17.62% are other workers. It is pertinent to note that agricultural activities are the main occupation in the block area.
There is essentially negligible industrial or commercial activity in the block.
ENVIRONMENTAL IMPACT ASSESSMENT Topography and Physiography
Exploratory drilling and testing of the 06 (Six) wells for oil and gas will have negligible impact on topography and physiography of the area.
Soils
There will be no impact on soils of the area except for the collection of rock cuttings, bentonite clay and other non-toxic ingredients of wasted WBM in HDPE lined effluents pits due to drilling of the wells.
Water Resources and Quality
Tuirial, Mat Tuikum, Tut and Tuichang rivers are perennial rivers flowing in and close to the block area. Water requirement is expected to be about 40 m3/d to meet drilling operations and 10 m3/d during testing operation at each well for a limited period. Further, recycling of treated water is likely to reduce the water requirement by about 10 m3/day.
The construction of HDPE lined shallow effluents pits will ensure that there is no adverse impact on ground water or surface water quality of the block area. The discharge, if required, of treated effluents
Ambient Air Quality
Discharge of exhaust gas emissions from the DG Sets of the drilling rig and due to ground flaring of gaseous hydrocarbons produced during exploratory testing for 3 to 4 days at each of the wells using a properly designed flare pit will ensure that the impact of gaseous pollutants in exhaust emissions is insignificant in surrounding area.
Dust generated due to vehicular movement on unpaved roads will settle quickly and will not cause any dust problem in the area.
Noise
Suitable Acoustic enclosure will ensure that the noise levels at the boundary of well site operational area does not exceed 75 dB(A) during exploratory drilling and testing of the wells and this will ensure that there is insignificant impact of drilling on noise levels during day- and night-time in the surrounding village areas, if any .
Land Use
There will be negligible impact on land use of the area because total land requirement for each drilling location is expected to be only about 1.65 hectares. However, some additional land would also be required for making approach road to the drilling site.
Terrestrial Flora and Fauna
There will not be any perceptible adverse impact on the terrestrial flora and fauna of the area due to exploratory drilling and testing activities.
Demographic and Socio-Economic
The demography of the area will not be affected by temporary presence of nearly 40 to 50 persons during drilling and testing operations for about 150 days at each location.
No adverse impact can be expected on socio-economic conditions of the area during exploratory drilling and testing operations. Slight beneficial impact on job opportunity may be expected because some local persons may get temporary employment as unskilled or semi-skilled workers during the drilling phase.
PROJECT ACTIVITY IMPACT
Proposed access Some cutting of trees and earth excavation/filling may be inevitable.
Clearing and timber salvage Cutting of some trees and salvage of timber may be involved for preparation of the drill site and approach road.
Wild life and habitat protection MoEF guidelines will be followed Fuel storage and handling Insignificant impact.
Camps and staging Temporary mobile camp facilities will be used for drilling operations.
Liquid and solid waste disposal Insignificant temporary localized impact Cultural and archaeological
sites
Not applicable
Selection of drilling sites The exploratory well sites will be selected after analysis of seismic & other Geo Scientific data.
Terrain stabilization Not applicable Protection of fresh water
horizons
Not applicable since drilling effluents will be stored in HDPE lined shallow pits and well casing will protect deeper fresh water horizons.
Blowout prevention plan Necessary care will be taken during drilling and blowout preventors (BOP) will be installed at well mouth for any emergency Flaring during completion and
production testing
Separated gases will be flared in suitably designed ground flare pit to minimize adverse impact.
Abandonment of wells Will be applicable only if commercial production of oil/gas is unviable from the exploratory well.
Reclamation for abandonment Not applicable at present
Noise control Necessary measures will be adopted Debris disposal Insignificant localized impact
RISK ANALYSIS AND DISASTER MANAGEMENT PLAN
Occurrence of blowout is the major hazard during drilling. However, Blow out preventer (BOP) shall be installed on well head to prevent the same.
Since only sweet oil and gas is expected in the block area, hazard due to occurrence of H2S is not
likely.
Adequate fire fighting facilities will be deployed and suitable personal protective equipments including breathing masks will be available at the drilling site.
Doctor and First aid facility will be available at drilling site and a 24 hour standby vehicle (ambulance) will also be available at the site for transport of injured persons to nearest hospital.
Quantitative risk assessment indicates that three phase separator during exploratory well testing and HSD storage tanks will have light fire and explosion hazard potential and low toxicity hazard potential.
On-site disaster management plan is suggested for quick and efficient emergency handling even though OIL already has well formulated on-site and off-site emergency plans.
ENVIRONMENTAL MANAGEMENT PLAN
Use of Water Base Mud (WBM) is very eco-friendly as a drilling fluid and does not require any elaborate environmental management plan. Production testing for oil and gas at the exploratory wells will also not require any specific management plan.
Effluents pits will be shallow and HDPE lined to avoid contamination of ground aquifers.
Cutting of some trees and earth cutting/filling, if considered necessary, should be minimized as far as possible for exploratory drilling operational area and for making approach road for the movement of vehicles.
Personal protective equipments for dust and noise should be used whenever required.
Efforts should be made by OIL and its contractors to employ local persons for unskilled and semi-skilled jobs and support activities.
An appropriate environmental monitoring programme during drilling and testing of wells is recommended.
1.2.2 ACTIVITIES OF OIL 1-2
1.3 OBJECTIVE OF EIA STUDY 1-3
1.4 SCOPE OF EIA STUDY 1-4
1.4.1 INTRODUCTION 1-4
1.5 BLOCK AREA/STUDY AREA 1-4
2. POLICY FRAMEWORK
2.1 INTRODUCTION 2-1
2.2 OBJECTIVE OF EIA STUDY 2-1
2.3 PROTECTION OF ENVIRONMENT UNDER NELP / NOMINATION 2-2 2.4 ENVIRONMENTAL CLEARANCE PROCEDURE UNDER EIA 2006 2-3 2.5 STANDARDS FOR EMISSIONS AND DISCHARGE OF
ENVIRONMENTAL POLLUTANTS
2-5
2.5.1 LIQUID EFFLUENTS 2-5
2.5.2 GASEOUS EMISSIONS 2-6
2.5.2.1 DG SETS 2-6
2.5.2.2 ELEVATED / GROUND FLARES 2-6
2.5.3 DISPOSAL OF DRILL CUTTING AND DRILLING FLUIDS 2-6
3. PROJECT DESCRIPTION
3.1 INTRODUCTION 3-1
3.2 BLOCK MZ-ONN-2004/1 3-1
3.3 JUSTIFICATION AND BENEFITS OF THE PROJECT 3-2
3.4 BENEFITS OF THE PROJECT 3-2
3.5 DRILLING OF EXPLORATORY WELLS 3-3
3.6 OIL WELL DRILLING ACTIVITIES 3-4
3.7 RIG SELECTION 3-5
3.8 DRILLING OF OIL/GAS WELL 3-9
3.9 WELL EVALUATION 3-17
3.13 EXPLORATORY DRILLING POLLUTION SOURCES 3-22 3.14 TREATMENT AND DISPOSAL STRATEGY FOR POLLUTANTS 3-24
3.15 ANALYSIS OF ALTERNATIVES 3-26
4. BASELINE ENVIRONMENTAL CONDITIONS: PHYSICAL, BIOLIGICAL,
DEMOGRAPHIC AND SOCIO-ECONOMIC
4.1 INTRODUCTION 4-1
4.2 SAMPLING/MONITORING LOCATIONS 4-1
4.3 PHYSICAL ENVIRONMENT 4-1
4.3.1 TOPOGRAPHY AND PHYSIOGRAPHY 4-1
4.3.2 SOILS 4-2
4.3.3 WATER RESOURCES AND WATER QUALITY 4-4
4.3.3.1 WATER RESOURCES 4-4
4.3.3.2 RAINFALL IN THE STUDY AREA 4-4
4.3.3.3 SURFACE AND GROUND WATER RESOURCES 4-4
4.3.3.4 WATER QUALITY IN STUDY AREA 4-6
4.3.4 CLIMATOLOGY AND METEOROLOGY 4-7
4.3.4.1 INTRODUCTION 4-7
4.3.5 AMBIENT AIR QUALITY 4-8
4.3.5.1 INTRODUCTION 4-8
4.3.5.2 METHODOLOGY OF MONITORING AND ANALYSIS 4-8
4.3.5.3 AMBIENT AIR QUALITY 4-9
4.3.5.4 AMBIENT AIR QUALITY STATUS 4-9
4.3.6 AMBIENT NOISE LEVELS 4-11
4.3.6.1 INTRODUCTION 4-11
4.3.6.2 METHODOLOGY 4-11
4.3.6.3 EQUIVALENT SOUND ENERGY LEVEL OR LEQ 4-12 4.3.6.4 AMBIENT AIR QUALITY STANDARDS IN RESPECT OF NOISE 4-12
4.3.6.5 LAND USE 4-13
4.3.6.6 LAND USE: SCOPE AND LIMITATIONS 4-13
4.4 BIOLOGICAL ENVIRONMENT 4-23
4.4.1 INTRODUCTION 4-23
4.4.2 TERRESTRIAL FLORA 4-24
4.4.3 TERRESTRIAL FAUNA 4-31
4.4.4 AGRICULTURAL CROPS IN THE STUDY AREA 4-39
4.6.3.1 EDUCATIONAL FACILITIES 4-45
4.6.3.2 MEDICAL FACILITIES 4-45
4.6.5 INDUSTRIAL AND COMMERCIAL ACTIVITIES 4-45
5. ENVIRONMENTAL IMPACT ASSESSMENT
5.1 INTRODUCTION 5-1
5.2 TOPOGRAPHY AND PHYSIOGRAPHY 5-1
5.3 SOILS 5-1
5.4 WATER RESOURCE AND WATER QUALITY 5-2
5.5 CLIMATOLOGY AND METEOROLOGY 5-2
5.6 AMBIENT AIR QUALITY 5-3
5.7 NOISE AND VIBRATIONS 5-4
5.8 LAND USE 5-4
5.9 BIOLOGICAL ENVIRONMENT 5-5
5.9.1 TERRESTRIAL FLORA 5-5
5.9.2 TERRESTRIAL FAUNA 5-6
5.10 DEMOGRAPHIC AND SOCIO-ECONOMIC ENVIRONMENT 5-7
5.11 CONCLUSIONS 5-7
6. RISK ASSESSMENT AND CONSEQUENCE ANALYSIS
6.1 RISK ASSESSMENT, CONSEQUENCE ANALYSIS AND OCCUPATIONAL SAFETY DURING DRILLING AND PRODUCTION TESTING
6-1
6.1.1 INTRODUCTION 6-1
6.1.2 IDENTIFICATION OF HAZARDS IN DRILLING AND PRODUCTION
TESTING 6-2
6.1.2.1 MINOR OIL SPILL 6-2
6.1.2.2 MAJOR OIL SPILL 6-2
6.1.2.3 BLOWOUT 6-3
6.1.3.2 CONTROL MEASURES FOR H2S DURING DRILLING 6-7
6.1.3.3 CONTROL MEASURES FOR H2S DURING PRODUCTION TESTING 6-9
6.1.4 FIRE FIGHTING FACILITY 6-9
6.1.4.1 FIRE WATER SYSTEM 6-9
6.1.4.2 FIRST AID FIRE FIGHTING EQUIPMENTS AT DRILLING RIG 6-9 6.2 FIRE FIGHTING EQUIPMENTS FOR PRODUCTION TESTING
FACILITIES
6-11
6.3 MEDICAL FACILITIES 6-12
6.4 QUANTATIVE RISK ASSESSMENT 6-12
6.4.1 FIRE AND EXPLOSION INDEX & TOXICITY INDEX 6-12 6.4.1.1 HAZARDOUS MATERIAL IDENTIFICATION METHODOLOGY 6-13
6.4.1.2 F&EI COMPUTATION 6-14
6.4.1.3 TOXICITY INDEX (TI) 6-14
6.4.1.4 HAZARDS RANKING 6-14
6.4.2 CONSEQUENCE ANALYSIS 6-14
6.4.2.1 CONCLUSIONS 6-15
6.4.2.2 RECOMMENDATIONS FOR RISK REDUCTION 6-15
7 DISASTER MANAGEMENT PLAN
7.1 INTRODUCTION 7-1
7.2 CRISIS MANAGEMENT TEAM OF OIL 7-2
7.3 EMERGENCY CLASSIFICATION 7-2
7.3.1 LEVEL 1 EMERGENCY 7-2
7.3.2 LEVEL 2 EMERGENCY 7-3
7.3.3 LEVEL 3 EMERGENCY 7-3
7.4 METHODOLOGY OF DMP PREPARATION 7-3
7.5 ON-SITE DISASTER MANAGEMENT PLAN 7-4
7.5.1 SITE MAIN CONTROLLER 7-4
7.5.2 THE SITE INCIDENT CONTROLLER TEAM 7-4
7.5.3 THE AUXILIARY TEAM 7-4
7.5.4 RESPONSIBILITIES OF SITE MAIN CONTROLLER (SMC) 7-4 7.5.5 RESPONSIBILITIES OF SITE INCIDENT CONTROLLER (SIC) 7-5 7.5.6 RESPONSIBILITIES OF AUXILIARY TEAM CONTROLLER (ATC) 7-5
7.5.7 RESPONSIBILITIES OF SIC SUPERVISORS 7-6
7.5.8 RESPONSIBILITIES OF ATC SUPERVISORS 7-6
8 ENVIRONMENTAL MANAGEMENT PLAN
8.1 INTRODUCTION 8-1
8.2 MITIGATIVE MEASURES FOR MINIMISING ENVIRONMENTAL IMPACTS
8-1
8.2.1 GENERAL MEASURES REQUIRED DURING DRILLING AND TESTING
8-1
8.2.2 SPECIFIC MEASURES REQUIRED DURING DRILLING AND PRODUCTION TESTING
8-2
8.2.3 ENVIRONMENTAL MONITORING 8-4
8.2.4 OCCUPATIONAL HEALTH SURVEILLANCE PROGRAMME 8-4
TABLE 4.1 SOIL CHARACTERISTICS IN STUDY AREA 4-3
TABLE 4.2 DISTRICT –WISE MONTHLY AVERAGE RAINFALL 4-2
TABLE 4.3 WATER QUALITY AT STUDY AREA 4-7
TABLE 4.4 AMBIENT AIR QUALITY IN MIZORAM BLOCK 4-10
TABLE 4.5 AMBIENT AIR QUALITY IN MIZORAM BLOCK( VOC) 4.11
TABLE 4.5 AMBIENT STANDARDS IN RESPECT OF NOISE 4-12
TABLE 4.6(a) LIST OF FLORA IN STUDY AREA 4-24
TABLE 4.6(b) LIST OF FAUNA STUDY AREA 4-31
TABLE 4.7(a) POPULATION OF STUDY AREA (2001) 4-40
TABLE 4.7(b) HOUSEHOLD AND HOUSEHOLD SIZE OF STUDY AREA (2001) 4-41
TABLE 4.8 EDUCATION LEVEL AND WORK STATUS 4-42
TABLE 4.9 EMPLOYMENT PATTERN 4.43
TABLE 6.1 CHARACTERISTICS OF H2S GAS 6-17
TABLE 6.2 DETERMINATION OF THE FIRE AND EXPLOSION INDEX AND OF THE TOXICITY INDEX
6-18
TABLE 6.3 HAZARD RANKING 6-20
TABLE 6.4 TOLERABLE RADIATION INTENSITIES FOR VARIOUS OBJECTS 6-20
LIST OF PLATES
PLATE 4.1 CARRYING OF WATER IN CART 4-5
PLATE 4.2 HUMAN SETTLEMENT 4-23
PLATE 4.3 OPEN FOREST 4-23
FIG 3.3 WELL BORE DIAGRAM 3-10
FIG 3.4 A TYPICAL BOP STACK 3-16
FIG 4.1 LOCATION MAP OF PROPOSED SITE 4-14
FIG 4.2 ETM 4-15
FIG 4.3 LAND USE CLASSES AROUND THE PROPOSED PROJECT 4-16
FIG 4.4 LOCATION MAP OF LOCATION 4 AND 5 4-17
FIG 4.5 ETM OF LOCATION 4 AND 5 4-18
FIG 4.6 LAND USE CLASSES AROUND LOCATION 4 AND 5 4-19
FIG 4.7 LOCATION MAP OF LOCATION 8 4-20
FIG 4.8 ETM OF LOCATION 8 4-21
CHAPTER 1: INTRODUCTION
1.1 INTRODUCTION
A consortium of Oil India Ltd. (OIL) with 75% participating interest (PI), Shiv-Vani Oil & Gas Exploration Services with 15% PI and Suntera Resources Ltd. with 10% PI has signed a production sharing contract (PSC) with the Government of India for the exploration and production of hydrocarbons in the Exploration Block MZ-ONN-2004/1 falling in Lunglei, Serchhip, Aizawl and Mamit districts in Mizoram under NELP-VI. PSC designates OIL as the Operator of the block. The block is located in central part of Mizoram primarily within Lunglei, Serchhip and Aizawl districts eventhough a small portion falls in Mamit district. The total area of the block is 3213 sq. km and lies towards south of Aizawl, the capital city of Mizoram. To best of our knowledge, exploratory drilling has not been carried at any place in the block so far.
Acquisition, processing and interpretation of 2-D and 3-D Seismic Survey, Gravity Magnetic Survey, Geochemical Survey are in progress for the block MZ-ONN-2004/1. Based on seismic data analysis, OIL is planning to carry out exploratory drilling and testing at 5 promising locations in Phase I within 2007-2012 and at 1 location in Phase II during 2012-15 period within the block area as per the minimum work programme (MWP) outlined in PSC to establish the techno-economic viability for production of hydrocarbons in the block area within a period of 8 years, that is, 2007-15. In addition to these exploratory wells, as per PSC requirement, additional appraisal/delineation wells need to be drilled for commercial production in case of discovery of oil/gas. The location of block MZ-ONN-2004/1 in administrative map of Mizoram, capital city Aizawl and other important town/villages are shown in Fig. 1.1. The Capital city Aizawl is nearly 5 km north of the northern boundary of the block.
1.2 OIL INDIA LTD.
The story of Oil India Limited (OIL) symbolizes and traces the development and growth of India’s petroleum industry. From the first commercial discovery of crude oil in the far east of India at Digboi (Assam) to becoming a fully integrated upstream petroleum company, OIL has traversed a great distance. In the process, it has crossed many a milestone.
In 1889, crude oil was first discovered in the fields of Digboi. On 18th February, 1959, Oil India Private Limited was incorporated to expand and develop the newly discovered
Crude Oil and Natural Gas, Transportation of Crude Oil and Production of LPG. The Company also provides various E&P related services to the industry and holds 26% equity in Numaligarh Refinery Ltd.
1.2.1 Corporate Objectives of OIL
Exploration for new oil and gas reserves.
Development of discovered oil fields and increased recovery from matured and developed fields.
Acquisition of new exploration acreage and oil and gas producing properties. Venturing into oil fields service sector and participation in mainstream activities. Enhanced implementation of EHS measures in operations.
Sustain and promote environmental protection. Optimum utilization of human resources.
Engage in Corporate Social Responsibility activities in operational areas. Ensure reasonable return on capital and optimize cost of production.
1.2.2 Activities of OIL
OIL is operating in 53 blocks and has participating interest in another 16 blocks with a total of over 1,00,000 sq. km of licensed areas. It produces 70,000 bbls/day of crude oil and 260 MMSCFD of natural gas, with a total production of oil and oil equivalent of 1,11,000 bbls/day.
To achieve its vision to be the fastest growing company, the company has realized the need to look beyond the shores of India. Aggressively seeking for overseas business opportunity is one of the strategic goals of OIL. Within a short span of 4-5 years, OIL is already present in 6 countries like Iran, Libya, Gabon, Sudan, Yemen and Nigeria. The focus is also on West Africa, CIS countries, Middle-East countries, etc. With the discovery of heavy oil in Farsi Block in Iran, OIL already has tasted its first success overseas.
1.3 OBJECTIVE OF EIA STUDY
It is recognized that the petroleum operations, such as, exploration for oil and gas and their production, transportation and storage will cause some impact on the environment of the block area and its surrounding area. It is, therefore, expected that the petroleum operations shall be carried out with proper regard to concerns with respect to protection of the environment and conservation of natural resources in the contract and surrounding areas. Accordingly, the Government of India issued guidelines to the contractor of exploration block for execution of environmental work as a part of the production sharing contract (PSC). Briefly these are as follows:
use of advanced techniques, practices and methods of operation to prevent environmental damage;
take measures, in consultation with the Government to minimize adverse impact on the environment where some adverse impact on the environment is unavoidable; prepare contingency plan for oil spills, fires and other emergencies before
commencement of drilling operations; and
remove installation and restore site after the expiry of contract.
OIL desires that the environmental impact assessment (EIA) study should not be limited to areas close to 6 exploratory wells where drilling is likely to commence in the year 2011 but should also include other block area because exact locations are not yet identified and will be finalized only after completion of seismic, gravity magnetic and geochemical data acquisition, processing and interpretation well before the tentative commencement of exploratory drilling in the year 2011. Furthermore, the selection of promising locations is a dynamic process resulting in changes in coordinates of drilling locations on the basis of results of testing of wells already drilled as well as further analysis of seismic and other data. Drilling operation is planned sequentially. EIA study related to exploration drilling and testing operations is required to be completed before commencement of drilling operations under E&P programme and shall be submitted by the Operator and specific approval, that is, environmental clearance (EC) from Ministry of Environment and Forests (MoEF), Government of India, and consent to establish (NOC) and consent to operate under Air and Water Acts from MSPCB will be required as per EIA notification dated 14th September 2006 (EIA 2006).
programme in the block MZ-ONN-2004/1.The EIA Study to be carried out as per TORs F.No.J-11011/877/2007-IA II (I) dated 24th Dec, 2007
1.5 BLOCK AREA/STUDY AREA
Fig. 1.1 shows the administrative map of Mizoram and the location of block
MZ-ONN-2004/1 in Mamit, Aizawl, Serchhip and Lunglei districts.
The block lies in the central part of Mizoram. Mizoram has Bangladesh towards west and Myanmar towards south and east. The block area is well connected by NH-54 and a network of other all weather roads though journey time is quite large due to tortuous undulated forested terrain. The nearest railhead is Silchar in Assam. National Highway (NH-54) runs north-to-south connecting Silchar to Aizawl, Serchhip, Lunglei, Lawngtlai, Saiha and Tuipang V. Aizawl is the capital city of Mizoram and is nearly 5 km north of northern boundary A-D of the block. Aizawl is linked by air to the rest of India and the nearest international airport is located at Kolkata in West Bengal.
Fig. 1.2 shows the lay out map of the block MZ-ONN-2004/1.
The block has a trapezium shape and lies between 23000’00” to 23040’00” N latitude and 92032’54.85” to 93000’00.00” E longitude and is located on Survey of India toposheets 84 A/10, 11, 12, 14, 15 and 16 (all restricted). The block coordinates are as follows:
Point Latitude, N Longitude, E
A 23040’00.00” 92032’54.85”
B 23000’00.00” 92035’58.00”
C 23000’00.00” 93000’00.00”
D 23040’00.00” 93000’00.00”
A 23040’00.00” 92032’54.85”
Agro-ecologically the block area is North-eastern Hills (Purvanchal), warm, perhumid ecoregion, with red and lateritic soils. Soils have been derived from siltstones,
sandstones and shales. The climate is tropical warm and per-humid with an average annual rainfall of nearly 2400 to 3500 mm. However, due to complexity of physiography various microclimates prevail from high elevation to low elevation. Since 2-D and 3-D seismic survey, gravity magnetic survey and geochemical survey are likely to cover the entire block area except area under wildlife sanctuary/national park, if any, the entire block area of 3213 sq. km is considered as the study area. The area is thinly populated undulating forested terrain interspersed with rivers/nullahs with some agricultural fields existing in plains section of the block area.
CHAPTER 2: POLICY FRAMEWORK
2.1 INTRODUCTION
In India, Environment Impact Assessment (EIA) was made mandatory as per Environmental Impact Assessment notification dated 27.01.1994 (EIA 1994). Ministry of Environment and Forests (MoEF) issued a new EIA notification on 14.09.2006 (EIA 2006) which supersedes EIA 1994 under the purview of Environmental (Protection) Act of 1986 with the following objectives: Identify and predict likely impacts based on activities of those components
of project which directly interact with the environment. Find ways and means to reduce adverse impacts. Shape the projects to suit local environment.
Present the predictions and options to the decision-makers or statutory bodies, such as, State Pollution Control Board, Ministry of Environment & Forests (MoEF), Government of India, Director General of Hydrocarbons (DGH), etc.
2.2 OBJECTIVE OF EIA STUDY
The EIA study is expected to cover at least the following matters:
Description of the proposed activities including likely waste generation and measures incorporated to meet environmental standards.
Description of the base environmental and climatic conditions.
Analysis of land use pattern, water consumption (and water balance), power consumption, etc. along with the social and health impacts.
An assessment of likely or potential environmental impacts of the proposed activity (like air, water and soil pollution, noise generation) and the alternatives, including the direct or indirect, cumulative, short-term and long-term effects.
An environmental management plan to mitigate or ameliorate negative effects on environment including post implementation monitoring programme.
The EIA report for all offshore and onshore oil and gas exploration, development and production projects shall be submitted to MoEF for
Licensing Policy (NELP) under Ministry of Petroleum and Natural Gas (MoP&NG) to encourage private sector participation for exploration and production (E&P) of oil and gas both by Indian and foreign E&P operators on Production Sharing Contract (PSC) basis to meet ever rising demand of petroleum products in India. The PSC is a mutual agreement between GOI and an Operator. Article 14 on Protection of Environment is now also applicable to old blocks/areas which were awarded prior to the formulation of NELP for exploration and production of oil and gas and are not under PSC.
As per Article 14 on Protection of Environment, the Government and the Contactor (OIL) recognize that the petroleum operations will cause some impact on the environment in the contract or license area. Accordingly in performance of the contract the operator shall conduct its petroleum operations with due regard to concerns with respect to protection of the environment and conservation of natural resources.
Environmental clearance is now necessary from the regulatory authority (MoEF) for exploratory surveys and drilling as well as production to be undertaken by the Operator. Conditions as applicable under such environmental clearance based on the Environmental Impact Assessment reports are required to be followed by the Operator. GOI monitors the implementation of these conditions. Some of the conditions include:
1. No survey or drilling or production activity can be conducted in national parks, sanctuaries, mangroves, wetlands of national importance, bios-sphere reserves and other biologically sensitive areas.
2. Passage through national parks, sanctuaries, mangroves and wetlands of national importance and biosphere reserves would not be permitted. However, if there is no passage other than through these places to reach a particular point of survey or drilling or production beyond, then the
Operator may obtain the permission of the concerned authorities (Chief Wildlife Warden/ Director of the Biosphere Reserve)
3. In case cutting of trees being involved for survey or drilling or production purpose, compensatory afforestation would be done within a time frame. 4. Approval for diversification of forest land involved, if any, would have to
be obtained specifically in each case.
5. Advanced techniques, practices and methods are to be used to prevent environmental damage.
6. Measures are to be taken in consultation with the Government to minimize adverse impact on the environment where some adverse impact on the environment is unavoidable.
7. Three EIA studies are to be carried out as under:
First EIA study is to be carried out before any field work relating to seismic or other survey;
Second EIA study is to be carried out before commencement of exploration drilling operations; and
Third EIA study is to be carried out before commencement of production operations.
8. Contingency plan for oil spills, fires and other emergencies is to be prepared before commencement of drilling and production operations. 9. Installation is to be removed and site is to be restored after the expiry of
contract.
10. The Government may revoke clearance if implementation of the above conditions is not satisfactory.
11. The above conditions will be enforced inter alia under the provisions of the Water (Prevention and Control of Pollution) Act 1974, Air (Prevention and Control of pollution) Act 1981 and the Environment (Protection) Act, 1986 and the Public Liability Insurance Act, 1991 along with their amendments and rules.
2.4 ENVIRONMENTAL CLEARANCE PROCEDURE UNDER EIA 2006
EIA 2006 categorizes all oil and gas exploration, development and production projects under category A, except for seismic and other exploratory surveys,
draft EIA report by the Expert Appraisal Committee (EAC) of MoEF. Public Consultation, except for seismic and other exploratory, survey will be carried out by the State Pollution Control Board to ascertain the concerns of local affected persons and others who have plausible stake in the environmental impact of the project by making available the Summary of EIA Report and holding a Public Hearing as per the prescribed procedure. EAC will then carry out the appraisal of the application including final EIA report and outcome of public consultation including public hearing proceedings for grant of EC. Environment Impact Assessment Authority (EIAA), that is, MoEF will then consider the recommendation of EAC for the grant of EC. Prescribed time frame for various stages for EC are: 60 days by EAC for finalization of TOR after submission of application on Form 1, 45 days for public consultation after receiving request for the same from project proponent along with EIA report and summary of the EIA report, 60 days by EAC for appraisal after receipt of final EIA report and proceeding of public hearing, and 45 days by MoEF for considering the recommendation of EAC for the grant of EC. It is presumed that the baseline data collection will start after finalization of ToR and time required for the same and for the preparation of draft EIA report as well as that required for preparation of final EIA report after considering material environmental concerns expressed during public consultation will be in addition to the prescribed time frame specified above.
2.5 STANDARDS FOR EMISSIONS AND DISCHARGE OF
ENVIRONMENTAL POLLUTANTS
For the purposes of protecting and improving the quality of the environment and preventing and abating environmental pollution, the standards for emissions and discharge of environmental pollutants from Oil Drilling and Gas Extraction Industry situated on land and away from saline water sink
2.5.1 Liquid Effluents
Industry may opt either for disposal of treated water by on-shore disposal or by re-injection in abandoned well, which is allowed only below a depth of 1000 metres from the ground level. In case of re-injection in abandoned well the effluent have to comply only with respect to suspended solids and oil and grease at 100 mg/l and 10 mg/l, respectively. For on-shore disposal, the permissible limits are given below:
Sl. No.
Parameter On-shore discharge standards
(Not to Exceed) 1. pH 5.5 - 9.0 2. Temperature 400C 3. Suspended Solids 100 mg/l 4. Zinc 2 mg /l 5. BOD 30 mg/l 6. COD 100 mg/l 7. Chlorides 600 mg/l 8. Sulphates 1000 mg/l 9. TDS 2100 mg/l 10. % Sodium 60 mg/l
11. Oil and Grease 10 mg/l
12. Phenolics 1.2 mg/l 13. Cyanides 0.2 mg/l 14. Fluorides 1.5 mg/l 15. Sulphides 2.0 mg/l 16. Chromium (Cr+6) 0.1 mg/l 17. Chromium (Total) 1.0 mg/l 18. Copper 0.2 mg/l 19. Lead 0.1 mg/l 20. Mercury 0.01 mg/l 21. Nickel 3.0 mg/l
2.5.2.2 Elevated/Ground Flares
A. Cold Venting of gases shall never be resorted to and all the gaseous emissions are to be flared.
B. All flaring shall be done by elevated flares except where there is any effect on crop production in adjoining areas due to the flaring. In such cases, one may adopt ground flaring.
C. In case of ground flare, to minimize the effects of flaring, the flare pit at Group Gathering Station (GGS), Oil Collecting Station (OCS) and Group Collection Station (GCS) shall be made of RCC surrounded by a permanent wall (made of refractory brick) of minimum 5 m height to reduce the radiation and glaring effects in the adjoining areas.
D. A green belt of 100 m width may be developed around the flare after the refractory wall in case of ground flaring.
E. If the ground flaring with provision of green belt is not feasible, enclosed ground flare system shall be adopted, and be designed with proper enclosure height, to meet the ground level concentration (GLC) requirement.
F. In case of elevated flaring, the minimum stack height shall be 30 m. Height of the stack shall be such that the maximum GLC never exceeds the prescribed ambient air quality limit.
G. Burning of effluent in the pits shall not be carried out at any stage.
2.5.3 Disposal of Drill Cutting and Drilling Fluids
A. Drill Cuttings (DC) originating from on-shore or locations close to shore line and separated from Water Base Mud (WBM) should be properly washed and unusable drilling fluids (DF) such as WBM, Oil Base Mud (OBM), Synthetic Base Mud (SBM) should be disposed off in a well designed pit lined with impervious liner located off-site or on-site. The
disposal pit should be provided additionally with leachate collection system.
Design aspects of the impervious waste disposal pit; capping of disposal pit should be informed by the oil industry to State Pollution Control Board (SPCB) at the time of obtaining consent.
B. Use of diesel base mud is prohibited. Only WBM should be used for on-shore oil drilling operations.
C. In case of any problem due to geological formation for drilling, low toxicity OBM having aromatic content <1% should be used. If the operators intend to use such OBM to mitigate specific well problem/SBM it should be intimated to Ministry of Environment and Forests/State Pollution Control Board.
D. The chemical additives used for the preparation of DF should have low toxicity i.e. 96 hr LC50 > 30, 000 mg/l as per mysid toxicity or toxicity test
conducted on locally available sensitive fish species. The chemicals used (mainly organic constituents) should be biodegradable.
E. DC separated from OBM after washing should have oil content at < 10 gm/kg for disposal into disposal pit.
F. 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. G. Low toxicity OBM should be made available at installation during drilling
operation.
H. Drilling wastewater including DC wash water should be collected in the disposal pit evaporated or treated and should comply with the notified standards for on-shore disposal.
I. Barite used in preparation of DF shall not contain Hg >1 mg/kg and Cd > 3 mg/kg.
J. Total material acquired for preparation of drill site must be restored after completion of drilling operation leaving no waste material at site. SPCB should be informed about the restoration work.
K. In case, environmentally acceptable methods for disposal of drill waste such as (a) injection to a formation through casing annuals, if conditions allow (b) land farming at suitable location (c) bio-remediation (d)
CHAPTER 3: PROJECT DESCRIPTION
3.1 INTRODUCTION
The On-Shore NELP –VI BLOCK: MZ-ONN-2004/1 located in the Aizwal, Lunglei, Mamit and Serchhip districts of Mizoram has been allotted by Government of India to Oil India Limited (OIL) and M/S Shiv–Vani Oil & Gas Exploration Services Ltd. for exploration and production of hydrocarbons. OIL is the Operator of the block.
As per the Minimum Work Program (MWP) of the Production Sharing Contract (PSC) signed with the Government of India, OIL is required to Drill 06 (Six) wells .Three locations have been identified for drilling. The other three locations will be selected after further geo scientific studies and data gathered from the drilled wells.
Salient features of the project :
Number of wells
Five (05) Nos. in phase I One (01) No. in phase II The above is as per MWP
Name and area of Block MZ-ONN-2004/1 and 3213 Km2
District(s) Aizawl, Mamit, Serchhip and Lunglei
Districts.
State Mizoram
Depth 4000 - 5500m ( tentative)
Estimated drilling Period 150 days (approx) for each well
Type of Hydrocarbon expected Oil/Gas
Cost of Project INR 300 crores (approx) for Six Wells
3.2 BLOCK MZ-ONN-2004/1 AREA
The block covers an area of 3213 km2 in the central part of the state. It starts from about 5 kms South of Aizawl and ends 6 kms. East of Hnahthial Town, covering four districts, viz. Aizawl. Sechhip, Mamit and Lunglei Districts. The coordinates are given below.
C 23 00 00 93 00 00
D 23 40 00 93 00 00
A 23 40 00 92 32 54.85
Drilling Locations
Coordinates of the drilling locations which have been released are as follows:
Sl. No. LOCATIO N
CO-ORDINATES
Easting Northing Longitude Latitude 1 OIL 2 3034138 650176 92o51’06.49” 23o35’00.87” 2 OIL 4 3009334 638426 92o36’23.21” 23o28’55.71” 3 OIL 5 3008350 635893 92o35’46.75” 23o27’33.99” 4 OIL 8 3027949 618948 92o47’04.69” 23o18’10.04”
3.3 JUSTIFICATION OF THE PROJECT
To determine the presence of hydrocarbons and to evaluate the recoverable reserves in the Mizoram Block, 2D seismic surveys and other Geo-scientific studies have been carried out. OIL is now planning to drill six (6) exploratory wells for obtaining more precise estimate of expected total reserves of hydrocarbon and techno-economic viability of Oil/gas production.
3.4 BENEFITS OF THE PROJECT
Commercially viable production of Oil / Gas from the block is likely to render the following benefits
i) Economic assistance to the Govt. of Mizoram from more royalty. ii) Employment potential for local people.
iii) Overall infrastructure development. iv) Increase in business opportunities.
v) More assistance from OIL towards Corporate Social Responsibility (CSR). vi) More cess to central Govt.
3.5 DRILLING OF EXPLORATORY WELL Introduction
To establish the presence of hydrocarbon and evaluate its commercial viability Oil/Gas has to be flown from the underground hydrocarbon bearing reservoir to the surface. This is achieved by drilling an oil well. OIL is planning to drill six (6) wells to determine the hydrocarbon prospects and reserves. Drilling operations will be carried out up to a depth range of 4000m to 5000m (approx). The lithological details at the proposed drilling locations are expected to be as follows:
Tentative Stratigraphy of Mizoram area
Age Group Formation Intervals (m) Lithology M ioc en e S u rm a Upper Bhuban Surface-1200
Thin bedded to massive s.st.
Middle
Buhban 1200-3200
Grossly s.st with
interlaminated silt st & shale.
Lower
Bhuban 3200-4200
Thin bedded shales, s.st & silt st. O li goc en e B ar ai l
Renji 4200-5000 Predominantly shale with
thin beds of s.st & silt st.
Jenam 5000-6200 Dominantly carbonaceous
shales, silt st & s.st.
Laisong 6200-7700
Thin bedded s.st, silt st, shales & carbonaceous shale. Palaeocene-Eocene Disang Group Up. Disang 7700-11000
Predominantly thick unit of dark, indurated shale
interbedded with
occasional bands of s.st & L.st.
Lr. Disang
Pre-cambrian
Geo scientific data acquisition, processing, interpretation / analysis and release of drilling location by Geo-science team.
Site survey and access road alignment (if any) - will be undertaken through consultants/contractors.
Land acquisition and removal of vegetation- Necessary approvals and compensatory afforestation etc through concerned forest department.
Access road and well site preparation by civil contractors. Well design & Planning
Rig Selection Oil well Drilling. Production Testing. Well site restoration. Rig movement
SITE SELECTION
The location of the exploratory wells have been released by Geo-science department of OIL based on the geo-scientific survey/studies. Thereafter, the site survey was carried out by approved consultant/contractor and site was finalized considering the following environmental factors:
At a reasonable distance (minimum 500m) from any river or stream. Minimise cutting of trees and alteration of natural contours.
Avoid National Park/ Wild Life Sanctuary/ Eco-sensitive area. Without affecting drainage
Avoid or minimize detrimental effects on the surrounding environment
The exploratory oil well drilling would be a short duration (about150days) activity at each location.
A flat drilling site of about 2.781 hectares of land which is almost rectangular in shape (175mX140m) would be required to accommodate the drilling rig and allied equipment, effluent pit, flare pit, boiler, office bunk houses etc.Some additional land would also be required for preparation of approach road.
WELL DESIGN & PLANNING
Before commencing drilling operations the following need to be designed and planned taking into consideration the vital geo-scientific information
Type of well- (Vertical or deviated) & Total depth.
Well bore sizes & Casing setting depths, sizes and grades. Drill string confugaration.
Drilling fluid (mud) and Hydraulics programme. Cementing programme
Wire line logging programme. Well testing programme.
Procurement of various consumables like bits, casing pipes, chemicals, cements etc.
3.7 RIG SELECTION
The Drilling Rig and allied equipment are selected as a package on the basis of total depth of the wells to be drilled, geological formations, downhole pressures and complications that are likely to be encountered. OIL is planning to deploy a suitable 2000HP Diesel- Electric AC SCR Rig. Schematic diagram of rig operation is given below:
- Input horse power (HP) rating - 2000 HP (minimum) with nominal depth rating 5500 m (minimum) with 5” OD drill pipes.
- Draw works will be operated by minimum two DC motors of GE-752 make or equivalent.
MAST & SUB-STRUCTURE
Swing lift cantilever type self elevating mast & substructure with minimum clear height of 147 feet. It will have a hook load capacity (derrick capacity) of 1,000,000 lbs (1000 KPS).Casing capacity 800,000lbs(apprx) simultaneously with 550,000lbs of racked pipes. Substructure to have a clearance of minimum25 feet from ground level to underneath of the rotary table beam.
ROTARY SWIVEL
Rotary Swivel to have a minimum API dead load rating of 500 Tons with 5000 Psi working pressure (minimum).
TRAVELLING BLOCK
Unitized traveling block and hook assembly of 500 Tons capacity with 6 sheaves grooved suitable for drill line and with minimum 12 lines operation.
POWER PACK
Engines minimum 4 (four) numbers turbocharged, after cooled, air start, diesel driven, 1010 hp@1500 rpm. Generators – 1500 kVA (each), 600 V, 1500 rpm, 0.7 PF, 50 Hz.
SCR SYSTEM
One RIGHILL electrical SCR system
Two nos of triplex single acting mud pumps with input horse power rating of 1600 (minimum) each driven by 2 DC motors of matching HP rating or equivalent.
DRILL PIPES
A minimum of 6000 m of 5” OD drill pipe consisting of 19.5 PPF Grade ‘G’ flash/friction welded, tapered or square shoulder, in range 2 length.
DRILL COLLARS
Suitable size and numbers of Drill Collars to be used.
BOP CONTROL UNIT
Proper BOP (Blow Out Preventer) stack and associated Well Control Equipment (as per applicable API specification) will be used for the drilling operation to contain any unexpected pressures from the well.
TOTAL TANK VOLUME
A mud system having an active capacity of 220 m3 and gross capacity of about 400 m3, including reserve capacity will be used for drilling operation.
Emergency Systems – this includes fire & other hazard detection and protection equipment. MBBS Doctor and an ambulance will be available at site for emergency medical attention, round the clock.
Safety/protective appliances – all the personnel working in the drill site will be provided with safety & protective appliances like helmet,safety boots,hand gloves ,goggles , etc. as per the OMR and other Govt. regulations.
Environmental Protection – Blow Out Prevention (BOP) system, drill cuttings handling equipment, effluent pit with recycling arrangement and other facilities which may be required for protection of environment will be in place.
SUPPORT SYSTEM
- Portable Living Quarters – to house essential personnel on site on a 24 hour basis. These units are provided with Bath/Washroom.
- Crane-age – cranes for loading/off loading equipment and supplies.
- Vehicle requirement for inter location movement (ILM)- The Drilling rig components including associated equipment etc comprise of about 90 truck/trailer loads.
TYPICAL DRILLING RIG AND ASSOCIATED SYSTEM 3.8 DRILLING OF OIL/GAS WELL
Well construction: Drilling wells are drilled in sections, with the diameter of each section decreasing with increasing depth. The lengths and diameters of each section of the well are determined prior to drilling through well design. The profile of a typical well ( 5000m) is given below.
Hole Size (Inch)
Casing Size (Inch)
Depth of Shoe
(meters below rotary table)
26” 20” 0- 150
17-1/2” 13⅜” 0 - 900
12 -1/4” 9⅝” 0-3000
8-1/2” 7” 3000- 4200
5-7/8” 4-1/2” 4200-5000
Well spudding is the start of drilling activity. Top-hole section will be drilled to a desired depth based on well design. After drilling top-hole section, it will be cased with a pipe called "Casing". The casing provides support to the drill hole wall and secures the hole-section. Other than this, it isolates problematic hole-sections such as loose zones, shale sections, over pressurized formations, etc. After running casing, the space between hole wall and casing (annulus) will be cemented. This process of drilling and casing the hole-sections as per the well design until the final well depth ( target) is achieved.
Drilling Fluid Plan
During drilling operations a fluid known as drilling fluid (mud) is pumped through the drill string down to the drilling bit and returns between the drill pipe and hole / casing annulus up to surface back into the circulation system after separation of drill cuttings / solids through solids control equipment. Drilling fluid is essential to the drilling operation and performs the following functions:
Cleans the bottom of the hole by removing the cuttings and carrying them to surface.
Cools and lubricates drill bit and string.
Continuously builds a wall around the inside of the hole which prevents the hole from caving in.
Counters natural formation pressures, preventing the uncontrolled flow of oil, gas, or water into the borehole.
Holds cuttings and weight material in suspension, when circulation is stopped. Supports part of the weight of drill pipes, casing ,tubing,etc.
Transmits hydraulic horse power to the bit. Acts as medium for electrical well logging.
Ensures maximum information about the formations penetrated. Prevents corrosion of tubulars
TYPE OF DRILLING FLUID (MUD)
An environment-friendly Water-Based Mud (WBM) system will be used for drilling of the proposed wells.It may be noted that a typical WBM may contain nearly 80% water and 20% clay plus chemicals by weight.
Some of the typical chemicals including several bio-degradable chemicals which are planned to be used for the drilling campaign are as follows:
- Guar Gum Bio-degradable - PAC (SL) Bio-degradable - CMC (SL) Bio-degradable - CMC (L) Bio-degradable - PAC (R) Bio-degradable - XC-Polymer Bio-degradable
- Linseed Oil Bio-degradable
- EP-Lube veg-oil lubricant
- Drilling Det Bio Degradable
The above list of drilling fluid chemical requirements may vary considering situations encountered during drilling. During the operation phase however, chemical usage will be monitored and efforts will be made to conserve or reuse chemicals as much as technically possible.
Mud Circulation & Solid Control System
The drilling fluid circulation system consists of several items of equipment as given below:
The mud pumps take drilling fluid from tanks and pump the same to the bit through drill pipes. The mud leaves the well bore through annulus and finally falls over the shale shaker. The mud used during the operation will flush out formation cuttings from the well bore which will be separated from the fluid using solids control system. This will include shale shakers, desanders and. desilters. The process of reusing the drilling fluid during drilling operation is commonly known as “closed loop system”. The system is ideal for drilling operations in sensitive environments as it cuts down immensely on the total water consumption for the formulation of drilling mud and also saves on the consumption of the chemicals.
Special applications of Drilling Fluid
To overcome various types of well problems, specific components are added to the mud to adjust the properties to ensure that following functions are met:
formation. Typical materials include sawdust, groundnut shells, mica etc.
Lubricity: Normally the drilling fluid is sufficient to lubricate and cool the bit. However, under extreme loading, other lubricants such as EP lube, Linseed oil etc are added to prevent the drill string from becoming stuck.
Shale Control: To control caving, sloughing etc of the well bore shale stabilizer (e.g magcoasphasol) is used.
pH control: Caustic Soda is used to control the alkalinity of the drilling fluid in the range of pH of 9 to 10. This ensures the optimum performance of the polymers in the fluid and controls bacterial activity.
Pressure control: Barite is generally used as a weighting material to control down-hole formation pressure and to prevent the ingress of formation fluid into well bore.
The essential ingredients of the WBM are all low toxicity materials, rated either as Grade E products (according to the new OCNS grading system), or Grade O (according to the former OCNS system). These are the two lowest toxicity categories. A variety of other products will be available for various contingencies. Thinners such as chrome free ligno-sulphonates (CFLS) and lignin compounds may be used to control rheology.
CEMENTING PROGRAM
Oilwell cementing is the process of preparing a slurry of API Class G cement with water and various additives in required quantities as accelerators/ retarders, density adjusters, dispersants, fluid loss additives, anti gas migration additives, etc. This slurry is pumped down through steel casing to cover the critical points in the annulus around the casing in the open hole.
Functions of the cementing process
Bond and support the casing strings Isolate oil, gas and water bearing zones.
Prevent Blowouts by quickly forming a seal. Seal off zones of lost –circulation or thief zones. Protect casing from corrosion.
Protect casing from shock loads. DRILLING RIG & EQUIPMENT LAYOUT
Suitable Diesel- Electrical 2000HP Rig will be used for drilling the proposed well. Cellar of the rig will occupy nearly 2m x 2m and overall exploratory well plinth will be nearly 2.781 hectares. Close to the rig, tanks for recycling of the drilling mud, appropriate waste disposal facilities, suitable storage facilities for chemicals and diesel fuel, office bunk houses etc will be arranged. A typical layout plan of OIL drilling rig and associated facilities is enclosed.
WELL CONTROL - BLOWOUT PREVENTION
Well control procedures will be conducted as per API 6A and API RP 53 standards. Well control occurs in two forms, namely, primary and secondary.
Primary: The influx of formation fluids is prevented by maintaining sufficient down
hole pressure with drilling mud of appropriate weight.
Secondary: This is applied when primary control has failed and fluids have entered the
well bore from a formation. The aim of secondary control is to safely discharge the fluids at the surface while preventing further influx down the hole. This is achieved by using blow out preventors (BOPs). A BOP stack is usually formed of three or more separate hydraulically operated preventors, of which there are two main types:
Annular; and Ram type.
The BOP stack arrangement is selected depending on the expected well pressure. Once assembled, the stack is placed on the well mouth and pressure tested before commencement of drilling.
3.9 WELL EVALUATION
Conventional Coring
Conventional cores of sub-surface formations are taken on selective basis to carry out Petrophysical and Geoscientific studies.
Well Logging
Wireline logging operations are undertaken with specialisd equipment mounted on custom built trucks to provide information on the potential type and quantities of hydrocarbons present in the prospective formations.
There are different well logging techniques including electric, electronic, sonic, radioactive logging etc. Logging instruments (sensors) are attached to the bottom of a wire line and lowered to the bottom of the well. They are then slowly brought back, the devices reading different geoscientific parameters as they pass each formation and recording the corresponding data on graphs, which can be interpreted by the exploration team. There are no emissions to the environment associated with wire line logging operations. The radioactive sources required for well logging operations will be kept in specially designed containers, if used.
Well Testing
In the event that presence of hydrocarbons is detected in reasonable quantities, as determined by wire line logs and other geoscientific techniques production testing of well is undertaken. During testing, pressure control Christmas tree at well head is installed and other well testing equipment are lined up to test the well in a controlled manner. The main purpose of testing the exploratory well is to determine the quality, quantity and commercial viability of oil/gas production. This is done by bringing a controlled flow of well fluids (oil,gas,water) to the surface through a nozzle (called Bean) of appropriate diameter in the flowline of the well.
Then the recovered oil/gas along with formation water will be flowed through the piping system to the Separator and other production testing equipment. Hydrocarbon gases will be flared in a suitably designed Flare Pit.
In the event that economic quantities of hydrocarbons are found, the well will be shut in with a wellhead / X-mas tree in place, but all other equipment and materials will be removed from present location to the next drilling site. At the end of well testing at each drilling site, the HDPE Lined Secured Pits for Drill Cuttings and Drilling Mud will be covered with a top HDPE lining. The pit will then be backfilled with minimum 300 mm layer of soil.
ii) Economic Quantities of Hydrocarbons are not Found
In the event that economic quantities of hydrocarbons are not found an abandonment plan will be implemented for the drilling sites in accordance with the applicable Indian regulations, OISD , Oil Mines Regulation(OMR) etc. Plugging requirement of abandoned wells as per Oil Mines Regulation, 1984 are as follows: When it is intended to abandon a well.
1. All permeable formations shall be isolated with cement
2. A cement plug of minimum length of 50 m shall be placed at the bottom of the well 3. A cement plug of a minimum length of 50 m shall be placed across the shoe of
surface casing
4. The cellar pit around the well shall be filled up and the land shall be restored to the original level
5. Cased wells may be abandoned by placing a bridge-plug above the top of perforations capped with three-metre cement plug.
6. Every abandoned well shall be clearly identified at site.
In addition to the above, guidelines as advised by MoEF, New Delhi and SPCB, Mizoram shall also be followed.
The overriding principle is that the environment should, with time be reinstated broadly to its original condition. Until such time as this is achieved, OIL would actively manage the reinstatement process.
3.11 RIG DEMOBILIZATION
Demobilisation would involve dismantling of the drilling rig, all associated equipments, campsite etc and transporting it out of the last drilling location. Demobilisation process is expected to take about 20 to 30days (Approx) and would require about 90 truck/trailer loads.
3.12 MANPOWER AND OTHER REQUIREMENTS
Manpower Requirement
Under normal operation, the project work force will consist of nearly 65 persons distributed as follows:
Location Manpower Total
Technical Non-Technical
Base Office 5 -- 5
Camp Office 20 10 30
Well Site 20 10 30
Total 45 20 65
Workers will be required to work in 2 shifts on 12-hour basis. At any one time there will be nearly 30 persons at the well site and will be accommodatedat the temporary camp/area facilities near the well site. A catering company will be contracted to provide the messing facilities.
Vehicles Requirement
The following type of vehicles will be required during drilling and testing operations for movement of men and material as detailed below:
Sl. No. Vehicle Number Purpose
1. Ambulance 1 Standby at site for emergency.
2. TATA Sumo or
equivalent
1 For meeting domestic requirements of the camp site personnel.
3. Truck 1 For transporting cement, chemicals,
etc to well site as and when required from base camp godown.
4. Trailer 1 For transporting casing pipes,
tubulars, other heavy equipment to well site from base camp godown.
