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Conceptualizing the Structural Architecture and Deformation History in Thrust-and-Fold Belt Using Borehole Images: A Case Study from North-East India

Borthakur, A. N.2; Bharali, Binayananda 2; Kar, Somenath *1; Sikdar, Koushik 1; Roy, Dipanka B.1; Basu, Indrajit 1
(1) Data and Consulting Services, Schlumberger Asia Services Ltd, Navi Mumbai, India. (2) Oil India Ltd, Duliajan, India.

Visualizing and conceptualizing the structural framework and the evolutionary history is indispensable to elucidate the complexity of a tectonically active province for better understanding the reservoir compartmentalization and the spatial distribution of reservoir facies. Resolving the tectonic history is of utmost challenge in this part of structurally disturbed province due to the unavailability of good seismic data and presence of numerous sub-seismic level faults across the field.

The studied extremely complex tectonic province juxtaposed with the Assam-Arakan basin is well known in Indian petroleum economics for its consistent hydrocarbon production and significant amount of reserves still to produce. Increasing demands for oil and gas has forced the petroleum geologist to look for the new technological advancement in conquering the structurally compartmentalized hydrocarbon reservoir at sub-seismic level.

This study illustrates the advanced application of high resolution borehole images in predicting or modeling the structural framework in the vicinity of a well which was not possible with existing seismic data. In the current work a structural model has been generated from the image log derived dip dataset. The model reveals a series of reverse fault zones with an overturned fold towards the top part of the logged interval. The existence and attitudes of the modeled reverse faults/fold zones were further validated from the borehole image. From these different structural zones the mean dip amount and orientation of the bedding surfaces has been computed, which is further compensated for advanced sedimentary analysis, viz, Paleoflow Determination, Paleoenvironement analysis etc.

This study concludes with a hypothetical structural model generated from the high resolution borehole image log data to conceptualize the fault and fold architecture, which can act as competent permeability barrier in hydrocarbon migration and can also lead to compartmentalization of a single reservoir. In a nutshell, this approach shows that borehole images can be used as a standard methodology for high resolution structural evaluation in tectonically disturbed provinces.


AAPG Search and Discovery Article #90141©2012, GEO-2012, 10th Middle East Geosciences Conference and Exhibition, 4-7 March 2012, Manama, Bahrain