Petroleum Systems of Cambay Basin, India

Neelam Niranjan, J. K. Srivastava, Leena John, Anita Sharma, S. P. Singh, and A. K. Gupta
Regional Geoscience Labs, Oil & Natural Gas Corporation Ltd, Vadodra, India

Cambay basin is a mature basin and needs more efficient and effective exploration methodology to search for undiscovered commercial hydrocarbons. To achieve this objective, petroleum system analysis has been carried out in stratigraphic framework as it allows better relation with depositional processes and sedimentation rates. It also facilitates construction of predictive models.

Two major petroleum systems have been identified:
i) Paleocene, Early and Middle Eocene - Middle Eocene TST (!): This petroleum system identified in South Cambay basin has multicipility of the source rocks. The source rock layers from Paleocene to Middle Eocene have attained peak maturation and all of them have started contributing to the oil accumulations.
ii) Paleocene - Middle Eocene TST (!): This petroleum system is identified in North Cambay Basin and has only one source layer at Paleocene sequence.

Each petroleum system is further divided into assessment units. Detailed folio sheet depicting geographic, stratigraphic and temporal extent of petroleum systems have been prepared.

Total hydrocarbon generated by the source rocks of North and South Cambay basin petroleum systems are estimated to be 27745 MMt and 26574 MMt respectively totaling to 54319 MMt. Hydrocarbons available for entrapment are 1387 and 1329 MMt in North and South Cambay respectively totalling to 2716 MMt in Cambay basin. Approved hydrocarbon resources of Cambay basin computed by areal yield method are 2050 MMt. Total In-place reserves of Cambay basin including Gulf area is 1364 MMt (O+OEG), thus the Generation-Accumulation efficiency of the petroleum systems comes to around 2.5%.

Presentation GEO India Expo XXI, Noida, New Delhi, India 2008©AAPG Search and Discovery