Sequence Biostratigrapahy and Hydrocarbon Source Potential of Mesozoic Sediments, Kutch Basin, India

Kamla Singh¹, H. S. Aswal², S. N. Swamy¹, and L. Phor^1
1PALYNOLOGY, KDMIPE ONGC, Dehradun, India
²Oil & Natural Gas Corp. Ltd., Regional Geoscience Labs, Vadodara, India

Sequence biochronostratigraphic and source potential studies based on microflora has been attempted for Mesozoic sediments in Kutch Basin for sequence stratigraphic and depositional environmental analysis to assist in basin modelling for evaluating hydrocarbon prospects. The high resoulution biostratigraphy has been used as a tool for constructing sequence stratigraphic framework, while organic matter studies integrated with geochemical data helped identification of source rock facies with generation potential.

The studies have been carried out on core and cutting samples from offshore (seven) and onshore (one) wells. The qualitative analysis of the microflora resulted in construction of biochronostratigraphy through dinoflagellate cyst biochronohorizons and identification of hiatusus, while quantitative analysis helped in deciphering depositional environments and sea level fluctuations. Dinocyst species diversity plots helped in identification of twenty three III order depositional sequences while dinocyst events lead to their dating from Hettangian to Maastrichtian (210 -71 Ma)with the presence of four hiatuses of regional/local nature. The microfloral association, absolute pollen frequency plots, along with species diversity and lithological attributes suggest that the sedimentation took place mainly under inner to middle shelf environments.

Pay sands (gas bearing) in well-F occurring within HST is dated as Early Turonian-Coniacian. Hydrocarbon source potential evaluated for the sediments below the Deccan Traps indicates sediments with good source potential to generate hydrocarbon in well B where OM facies is to the order of 850m thick and likely to continue below the drilled depths in wells C, E and D. Searching for narrow regressive sands in the up dip directions would be interesting from the exploration point of view.

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