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Resolving the Structural Complexities in the Assam-Arakan Fold and Thrust Belt Using Borehole Images: A Case Study from North-East India

Hura, Rajiv 1; Kar, Somenath 2; Roy, Dipanka B.2; Shrivastva, Chandramani 2
1 Hindustan Oil Exploration Co. Ltd, Chennai, India.
2 Schlumberger Asia Services Ltd, Mumbai, India.

A decent understanding of the structural styles and their controls on the hydrocarbon reservoirs is imperative when attempting to decipher the complexities of tectonically active terrains for reservoir characterization. Borehole images provide the much needed avenues of taking the conventional approaches to sub-seismic levels for evaluating the impact of structural complexities in distribution of prospective reservoir facies over the field.

Assam-Arakan basin in the North-Eastern part of India has been a proven petroliferous basin and has been producing for the last seven decades. The recent advances in technology have equipped the explorationists to attempt the characterization of structurally complex oil habitats at sub-seismic scales, which in turn allows for identifying the small compartmentalized reservoirs which were not imaged and interpreted with the conventional methods.

The objective of the present study is to validate the seismic signatures from the field with the well data and once calibrated for the borehole signatures, propagate the high resolution data to the field scale to refine the structural model with finer details. In this study, a reverse fault model was generated from the image log derived dip data. The structural model established exhibits two major structural discontinuity and several inferred minor faults which were further supported by the existence of structural breaks in dip vector plot. The azimuthal variation of bedding dips, associated with the large changes in magnitudes in different structural zones thus identified was compensated to prepare the dip data for sedimentological analysis.

The conceptual model generated from the high resolution borehole image log data is further validated by the existing large scale model in near by well which helps to conclude that this workflow can be used as a standard methodology for high resolution structural evaluation of a complex hydrocarbon reservoir.

 

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009