Techno Economic appraisal of Prospects A Case Study on CB-ONN-2009/8 Block ( Cambay Basin )

Shashank Pandey ( 36 )Vedant Makwana ( 45 )Aditya Harsh

( 03 )

Background

▪ Jay Polychem India Ltd. (JPIL) is an integrated Energy Company having interest in Oil and Gas Exploration.

▪ The concerned block CB-ONN-2009/8 measuring 136 sq. km was awarded to JPIL by Govt. of India under NELP VIII.

▪ The Production Sharing Contract PSC between JPIL and GoI was signed on 30 June 2010.

▪ Block CB-ONN-2009/8 falls in Dholka Taluka of Ahmedabad and Tarapur Taluka of Anand district of Gujarat State.

On site Location

The Project

▪ JPIL has identified 12 wells in Ahmedabad and one in Anand district.

▪ Proposed operation are covered under category 1B of EIA Notification 2006.

▪ JPIL plans to carry out accelerated development programmes on the basis of recent 3D seismic data acquired.

▪ JPIL intends to drill wells to a depth ranging 800 to 2500 metres.▪ There is a possibility of drilling a number of wells from a single

site which is termed as cluster well drilling.▪ Some of the wells may be drilled horizontal to increase sweep

efficiency.

Technical Aspects

The Sedimentary Basin

▪ The Cambay rift basin is a rich petroleum province majorly lying in the state of Gujarat, India

▪ It is a narrow elongated rift grabben extending North to south from Sanchore to Surat.

▪ In the North the basin narrows , tectonically continuing beyond Sanchore to pass into the Barmer Basin of Rajasthan

▪ On the southern side the basin merges with Bombay offshore basin in the Arabian Sea.

▪ Seismic and drilled well data indicate a thickness of about 8 km of tertiary sediments resting over Deccan Volcanic basalt

Geology

▪ Cambay Basin in the western Indian state of Gujarat is a fairly well explored productive basin

▪ The Broach sub block lies in the southern part of the basin. It is bounded on the north by the Mahisagar River and in the south by Narmada River.

▪ It is bounded by basin marginal faults in the east and west. Most of the discovered oil in this block is in Hazad sands of the Ankleshwar Formation, but oil is also produced from deeper pays in the Cambay Shale and Olpad Formation of Paleocene to Early Eocene age.

▪ In a basin with geological history of deltaic sedimentation, entrapment conditions formed in time and space witnesses varying degree of structural and stratigraphic control over hydrocarbon accumulations.

Cont…

▪ Cambay Shale below Hazad base includes the following succession from top to bottom:

– A monotonous fissile shaly interval, occasionally carbonaceous, 100 to 200 m thick deposited in low energy conditions.

– A thickening upward silty interval often associated with a few meters thick coal seam. This interval is widely correlatable in the Jambusar-Broach block.

– Another monotonous shale interval, often carbonaceous, thickening from 50 to 150 m in Nada Malpur area, to 700-800 m in Gandhar and Jambusar wells.

– Deeper, the shales includes 9 to 12 layers of lithic dirty sands, 2 to 10 m thick.

Petroleum Systems

▪ Source Rock– Thick Cambay Shale has been the main Hydrocarbon Source Rock for oil

fields in the Cambay Basin.– The TOC ( Total Organic Carbon ) and maturation studies suggest that Olpad

Formation Shale is organically rich and thermally mature.▪ Reservoir Rock– The reservoir majorly consists of sand sized Basalt fragments although

localised sandstone lenses occur in the Cambay Shale.▪ Cap Rock– Transgressive Shale within the deltaic sequences provide a good cap rock.

Oil Characteristics

▪ Unlike other oil fields of Cambay Basin the oil from the concerned block is heavy and sour.

▪ The API gravity of oil as obtained from discovery samples is approximately 14.0 ( SPGR = 0.95 )

▪ The sulphur content ranges form 1.6 % to 2.2 %.▪ This oil is waxy with pour points ranging from -8 to -3 °C.

Well Testing

▪ While Drilling rock core samples will be taken from the strata.▪ Well log data will be recorded simultaneously.▪ If Hydrocarbons are encountered , composition and reservoir

permeability would be warranted.▪ A production test might proceed through the final completion

valves in place

Economic Aspects

Operations

▪ Drilling of well– Based on the drilling

Methodology adopted by JPIL the size of the Drill bit and other equipment would vary.

– However a schematic cross-section of proposed well is displayed alongside.

– Detail of drilling programme is under finalization , but is expected to follow the general sequence outlined below

Cont…

▪ Spud and Drill 17.5 inch section▪ Run and cement 13.36 inch casing▪ Install and test BOP▪ Drill 12.25 inch section▪ Run and cement 9.62 inch casing▪ Drill 8.5 inch section ▪ Record well logs▪ Run and cement 5.5 inch casing▪ Finally the well will either be completed as producer or plugged and

abandoned.

Drilling Requirements

▪ Drilling Facilities– Drill Bit– Drill String– Drill Collars– Kelly– Top Drive Mechanism– Swivel with high pressure

drilling hose– Diesel Engines– Blow Out Preventer– Storage tanks for Drilling Mud

Raw Materials For Slurries

▪ The main component of Drilling fluid is slurry of inert solids suspended in a liquid phase which will be made up of water.

▪ The anticipated chemicals used in the mud preparation of each well is given in table along side.

▪ JPIL may also explore use of synthetic based mud to achieve higher drilling efficiency.

▪ Schlumberger and Halliburton would be the consultants in case this option is tried.

▪ Another important raw material is cement slurry. On an average 200-250 thousand tonnes of cement is likely to be used for each well.

Sr.No

Chemical Quantity (Tonnes )

1 Bentonite 0.72 Caustic Soda 0.43 Soda Ash 0.054 Lignite 5.055 Barites 120.756 PAC UL 0.67 PAC R 0.58 Spersene 0.99 Aluminium Stearate 0.0310 Chrome Lignite 2.87511 Sulphonated Asphalt 0.5

Economic Aspects

▪ Workforce Arrangement– During the drilling operations and pilot assessment phase about 20-30

people may be working in three shifts of 8 hours each.– 8-10 technical personnel will be present at the site during drilling period.– Once drilling is over no person is required at site except security cover

through contractor.▪ Power Requirement– Diesel Engines shall be utilized as prime movers– Capacity of the engines that shall be used for operating the rig and the

circulation system should be in the range of 440 KVA ( 2 in number , 1 standby ).The Engines would consume high speed diesel at the rate of 20 litre per hour.

– A power generator shall be installed for lighting– The generator shall consume approximately 150 litres per hour.

Cont…

▪ Water Requirement– Water is required for mud preparation , cement preparation , engine

cooling , floor / equipment washing , sanitation , fire fighting storage , and personal uses of crew.

– The emergency fire fighting provision water facility would be initially 150,000 litres.

– According to CGWA ( Central Ground Water Authority ) , Tarapur of Anand District is decided as safe area.

Sr.No

Purpose Water Requirement

1 Construction and Site Preparation 4.7 Kl2 Mud Preparation 10 Kl3 Engine Cooling 0.8 Kl4 Washing 5 Kl5 Fire Fighting Make-up 0.8 Kl6 Domestic Requirements 2.55 Kl

Total 19.5 Kl

Conclusion

The decision of putting in full investment for complete development of the oil fields of the Block CB-ONN-2009/8 depends heavily on the IOIP ( Initial Oil in Place ) assessment

▪ As concluded from the technical aspects the oil is difficult to produce because of low API gravity and supposed to be low flow rate ( No Primary porosity as reservoir rock is basalt )

▪ Hence a lot will depend on the commercial quantities of oil that can be produced.