Integrated Geological Study and Preliminary Hydrocarbon Assessment in Cuddapah Basin, South India

Jatindra K. Samal, A. Mullick, and D. Mitra
KDMIPE, ONGC, Dehradun, India

Understanding the entire geology including evolution, tectonics and structural complexities through compilation of the existing data, field studies and intellectual inputs are the precursors to the decision-making for the exploration strategies of a frontier basin. Proterozoic basins are on the record elsewhere in world to be producing oil and gas, which inspires us to intensify activities in Cuddapah Basin with similar geological set up. In this paper by integrating all the data like high resolution satellite data, geological observations in the field, laboratory analysis results of the samples collected from the field, other information from published literatures, a preliminary hydrocarbon assessment for Cuddapah Basin has been attempted.

Field observations like the lithofacies assemblage, structural interpretation, sedimentary structure of different formations depicts the probable environment of deposition. Favourable rock types and structures do exist in the basin for hydrocarbon generation and entrapment. But the source rock evaluation is not yet conclusive.

Limestones/dolomites, clastics/quartzitic sandstones of Papaghni and Chitravati Groups are likely to have fair secondary and fracture porosity, and can serve as good reservoir rocks. Quartzites with excellent homogeneity and isotropy are capable of producing brittle deformation, has been observed in the field. Therefore, the quartzites can act as fractured reservoir facies. The intervening shale layers, particularly the Nandyal shale can also act as a cap rock in the basin. Numerous doubly plunging folds, domal structures/ upwarps, fault closures are likely structural plays for gaseous hydrocarbon entrapment.