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Abnormal Geo-Pressure in East Coast of India: A Geological Approach to Understand the Anomalies

Kumar, Devendra *1; Shrivastava, Chandramani 2; Singh, Hemant 1
(1) DCS, Schlumberger, Navi Mumbai, India.
(2) Wireline, Schlumberger, Lagos, Nigeria.

A decent understanding of pore pressure is not only essential for well planning but also required for safe and optimized drilling. Modeling the pore pressure and the causative mechanisms becomes imperative for successful campaign.

An attempt has been made to understand the anomalies in the pore pressure profile using geological approach. The re-constructed basin model along with the structural and sedimentation history provide vital clues towards the anomalous pore pressure distribution. In this study, qualitative pore pressure profiles were prepared honoring the wells with reference to evolutionary history of the Eastern offshore India basin. The sequence stratigraphic framework was made use of in conceptualizing the existence of abnormal geo-pressure and the guidelines were compiled for a predictive understanding in the basin.

In this context, lithology and overburden are the key components responsible for generating subsurface formation pressure. The rocks ranging from pre-rift continental and syn-rift shallow marine Mesozoic sediments to the post-rift Tertiary deepwater sediments present a complex picture of tectonic and sedimentation interplay; thereby leading to abnormal pressure profiles along different parts of the basin.

The spatial and temporal facies distribution often leads to compartmentalization and compressive tectonic forces lead to folding/faulting, resulting over pressured formation. Different stratigraphic columns were studied in the basin and a conceptual model has been made for the qualitative pore pressure profiles against different architectural and tectonic elements. The traditional approach towards pore-pressure prediction relies mostly on overburden and tectonics. This study provides an insight into the active role played by sedimentation styles in broad understanding of the expected geo-pressure regimes in the East Coast of India; however, the finer details and surprises still are subject to the drilling.

 

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California