appraisal of Prospects
A Case Study on CB-ONN-2009/8 Block ( Cambay Basin )
Vedant Makwana ( 45 )
Shashank Pandey ( 36 )
Aditya Harsh ( 03 )
▪ The concerned block CB-ONN-2009/8 measuring 136 sq. km was
awarded to JPIL by Govt. of India under NELPVIII.
▪ Jay Polychem India Ltd. (JPIL) is an integrated Energy Company
having interest in Oil and Gas Exploration.
▪ The Production Sharing Contract PSC between JPIL and GoI was
signed on 30 June 2010.
▪ Block CB-ONN-2009/8 falls in DholkaTaluka ofAhmedabad and
TarapurTaluka of Anand district of Gujarat State.
▪ 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.
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
▪ Seismic and drilled well data indicate a thickness of about 8 km of tertiary
sediments resting over DeccanVolcanic basalt
▪ Cambay Basin in the western Indian state of Gujarat is a fairly well explored
▪ 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 Palaeocene 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.
▪ 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
– 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
– Deeper, the shales includes 9 to 12 layers of lithic
dirty sands, 2 to 10 m thick.
Source : GMRC
▪ Source Rock
– Thick Cambay Shale has been the main Hydrocarbon Source Rock for oil fields in the
– 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.
▪ Drilling of well
– Based on the drilling Methodology
adopted by JPIL the size of the
Drill bit and other equipment
– However a schematic cross-
section of proposed well is
– Detail of drilling programme is
under finalization , but is expected
to follow the general sequence
▪ 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.
▪ 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.
▪ 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
▪ Drilling Facilities
– Drill Bit
– Drill String
– Drill Collars
– 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
▪ 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
Sr.No Chemical Quantity
1 Bentonite 0.7
2 Caustic Soda 0.4
3 Soda Ash 0.05
4 Lignite 5.05
5 Barites 120.75
6 PAC UL 0.6
7 PAC R 0.5
8 Spersene 0.9
9 Aluminium Stearate 0.03
10 Chrome Lignite 2.875
11 SulphonatedAsphalt 0.5
– 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
▪ 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.
▪ 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 Kl
2 Mud Preparation 10 Kl
3 EngineCooling 0.8 Kl
4 Washing 5 Kl
5 Fire Fighting Make-up 0.8 Kl
6 Domestic Requirements 2.55 Kl
Total 19.5 Kl
▪ 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
permeability as reservoir rock is basalt )
▪ Hence a lot will depend on the commercial quantities of oil that can be
1) "Geology of Gujarat" by S.S.Merh published by Geological Society of India
2) "Geology of Gujarat" byV.N.Kulkarni (1985) published by Irrigation, R&B Deptt.
Gujarat State in Journal "NAVNIRMAN" Vol. No.XXVII No.2
3) "Geology and Mineral Resources of Gujarat, Daman and Diu published by
Geological Survey of India. Publication No.30 Part XIV-2001