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Identification of Subtle Geobodies and Their Hydrocarbon Entrapment Through 3-D Seismic Volume Based Interpretation in Olpad-Dandi Area, Narmada Block,Western Onshore Basin, India

Kishori Lal, Anima Saikia, Sudhir Vir, and P. B. Pandey
ONGC, Vadodara, India

The strati-structural complexities of Miocene deltaic sequences suggest considerable scope for the interpretation of 3-D seismic data. The merged 3D volume along with available geological data highlights the detailed strati-structural framework of Miocene reservoirs in time & space.

The present study using state-of-art techniques in VRC has helped in delineating subtle strati-structural traps within Early to Late Miocene age.

The study area falls in the southernmost tectonic block of Cambay rift basin. The major hydrocarbon entrapments are due to the results of post inversion that took place during Late Miocene to Early Pleistocene age. As a result significant upliftment caused in the downthrown blocks of major faults. Olpad, a major gas field in this area , discovered on such an upliftment.

Hydrocarbon reservoirs are distributed in different sands separated by persistent clay beds. These sands are well developed and correlatable in the Western onshore as well as offshore, which were deposited under tidally influenced deltaic to estuarine environment.

The integrated analysis of 3-D dataset (PSTM volume) comprises of various Post-stack attribute studies, facies classification using NNT and geobody identification through sub-volume detection method. Pre-stack AVO analysis on selected lines was carried out after calibrating with available well data and hence the geobodies based on anomalous amplitudes were detected.

Present study has emphasized on identification for mapping of partially tested and untested subtle traps in the form of different geobodies within Miocene deltaic facies using different forms of geobody classification, which may add value for future hydrocarbon exploration. Exploratory location has been identified and planned to test hydrocarbon potential of these geobodies.

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