Integration of Borehole Images and Core for Enhancement of Cretaceous Reservoir Facies Model: A Case Study from Eastern Offshore, India

Chandramani Shrivastva¹, Nigel Patrick Machin², and Anil Tyagi^3
1Schlumberger, Mumbai, India
²Schlumberger, Mumbai, India
³Reliance Industries Ltd. Petroleum (E&P), Mumbai, India

This study aims at refining a facies model by integrating the borehole images and cores with the help of other available data and comparison with modern analogues. The Upper Cretaceous fluvial system of Krishna-Godavari Basin, Offshore Andhra Pradesh, India was studied to derive a facies model for the well. The interpretation, drawn from the analyses of conventional wireline logs, borehole images from the Oil Based Micro Imager (OBMI) and interactive dips in the pilot well suggested the depositional environment was consistent with a fine-grained meandering fluvial system with moderate sinuosity.
This study provides an insight into the dynamics of the system with dip interpretation and palaeoflow analysis where stacked channels deposits comprise the majority of the reservoir interval. A detailed interpretation was undertaken to develop the conceptual depositional model for the well and to identify possible modern analogues for the study interval.
Whole core was acquired from the sidetrack well that showed distinct facies variation that was inconsistent with the preliminary interpretation of the main pilot well. The apparent variations required a reassessment of the preliminary facies model to account for the significant lateral heterogeneity exhibited by the sidetrack despite a lateral separation of only several tens of meters.
The fluvial system was re-interpreted to comprise of a medium to coarse-grained braided system developing to a coarse-grained meandering system prior to a major marine transgression that indicated fully marine conditions in the Upper Cretaceous.

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece