Cairn India Ltd is readying to drill 55 exploration/appraisal wells in KG-OSN-2009/3 shallow water block offshore India, with option drill nine more wells. The exploration plan comes following the discovery 13 hydrocarbons prospects in Bay of Bengal.

“Detailed planning for the exploration drilling campaign is in progress,” said Cairn India chairman Navin Agarwal.

Cairn India said it intends to take up the exploration works in the offshore block in two phases. The first phase plan comprises drilling the 55 exploration and appraisal wells in 11 hydrocarbons prospects/leads in the southeast part of the block. These prospects lie in the territorial waters within 12 nautical miles from the Andhra coast, according to the company.

“Based on the outcome of the Phase I exploration, further exploration and appraisal in the remaining two leads/prospects lying within the 10 km radius Eco-Sensitive Zone of the Krishna Wildlife Sanctuary will be decided and may be undertaken in the long term. This will constitute the second phase of exploration, i.e. Phase II. A maximum of nine wells may be drilled in these two prospects,” the company said in a proposal submitted to federal environment ministry for clearance.

The Andhra Pradesh provincial government gave a Coastal Regulation Zone (CRZ) clearance for the Phase I drilling plan in April.

According to the proposal, Cairn India would drill 44 of the total 55 exploration/appraisal wells in prospects located in water depth of more than 100 m in southeastern part of the blocks. The remaining 14 wells are to be drilled in water depth of less than 100 m. Each well is to be drilled a maximum depth of 5000 m.

The offshore block is spread over an area of about 1,988 sq km in water depth ranging from five to 1,000 meters below the sea level.

The operator will use independent leg jack up rigs to drill the wells in water depth of up to 120 m and semi-submersibles (semi-subs) or drill ships in water depths of more than 120 m.

The location and number exploration and appraisal wells in the block will be decided after the evaluation of data collected from four exploration wells and of 3-D seismic survey over 1,390 sq m, according to the company.

“Detailed technical evaluation, suitability and optimization studies based on several geo-scientific subsurface data are currently on-going. The number and location of the exploration wells will be finalized on the basis of the results of these studies. The number of appraisal wells will be determined on the basis of exploration success,” the company said.

Initial basin modelling shows that hydrocarbon charge is evident from the Late Jurassic – Early Cretaceous source rock units (Barremian-Aptian-Albian) in the offshore block. The drape features on median basement high making four way dip closure and fault closures are main structural traps, Pinchout and shallow marine fans are main stratigraphic traps in the block.

The geophysical studies indicate that the Cretaceous sequence has potential to generate both oil and gas.

KG-OSN-2009/3 block was awarded to a consortium-led by Cairn India as part of the India’s eighth round bidding in 2010. Operator Cairn India owns 90% participating interest and the rest is held by Cairn Energy India Pty Ltd.

—Contributed by Ravi Prasad