Online Journal for E&P Geoscientists

Misra, Anshuman ^*1; Misra, Kiran S.²
(1) Geology, Kumaun University, Dehradun, India. (2) Petroleum Engineering and Earth Sciences, University of Petroleum and Energy Studies, Dehradun, India.

Unique characteristics of hydrocarbon pools and how they can be utilized for prognostication of areas for detailed exploration are discussed. Pools associated with the rifts and grabens exhibit profound effect of tectonics. In Barmer -Cambay basin, all the pools are trending parallel to the basin forming faults, indicating that the deposition of source rocks, reservoir rocks as well as trapping mechanism are controlled by the basin forming tectonics. In intersectional area of Cambay and Narmada-Tapti tectonic zone, the NW-SE trending pools of Barmer-Cambay basin are obliterated and important pools such as Ambe, Lakshmi, Hazira and Gauri are parallel to the ENE-WSW trending tectonic zone. The Mesozoic sedimentary sequence is separated from Tertiary rock by the Cretaceous volcanics. These volcanics are also forming unique reservoir rocks in many basins such as Rageshwari field in Barmer, Ingoli and Padra in Cambay and Rajol formation in Krishna-Godavari basin. Of these Rageshwari, Ingoli and Padra are prolific producers of gas while Rajol formation produces both oil and gas.

In Bombay offshore basin, Paleocene pools are elongated in N-S direction and seem to have developed due to subsidence along nearly vertical faults in lateral southern continuity of Cambay. The presence of Paleocene rocks and hydrocarbon pools largely in southern part suggests that initiation of rifting started from south to north. This rifting became more rampant in Eocene and continued in the northerly direction, though the Cambay into Barmer region. In Cambay basin, Olpad formation which is mainly trap wash was deposited above the Cretaceous volcanics is also prolific hydrocarbon pool. Oligocene pools comprise cluster of north Tapti, mid Tapti and south Tapti fields which are largely localized in southern part of Gulf of Cambay. These curvilinear pools correspond with submerged sand bars. This suggests that the tectonics responsible for the development of Oligocene pools is still operating and submerged sand bars are manifestation of same tectonic process. The super giant Bombay High hydrocarbon pool is associated with lower Miocene carbonate facies related to development coral reef and marine transgression. In KG basin, Cretaceous hydrocarbon pools are elongated and are largely parallel to geomorphological features, while Tertiary hydrocarbon pools are largely associated with fossilized paleochannel complexes rather irregular and trend mostly in NW - SE direction.