--> Abstract: Application of Borehole Imagery to Estimate Paleoflow Directions in Structurally Complex Areas: Case Study from Assam Shelf, India, by Dipanka B. Roy, Aditi Pal, Chandramani Shrivastava, V. Sivarao, and G. J. Rajbob; #90078 (2008)

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Application of Borehole Imagery to Estimate Paleoflow Directions in Structurally Complex Areas: Case Study from Assam Shelf, India

Dipanka B. Roy1, Aditi Pal2, Chandramani Shrivastava1, V. Sivarao3, and G. J. Rajbob3
1Data & Consulting Services, Schlumberger Asia Services Ltd., Mumbai, India
2Data & Consulting Services, Schlumberger, Jakarta, Indonesia
3Logging Section, ONGC, Jorhat, India

Establishing the depositional sedimentary environment is the most important task for exploration geology to model the reservoir heterogeneities. Paleocurrent estimation plays a critical role in understanding the sand body distribution and geometries. Prior to studying the sedimentology, it is always imperative to understand the structural controls in the field. Present study aims at reconstructing the paleoflow directions by negating the structural deformations the sedimentary successions were subjected to.The study well is located in Assam Shelf in northeastern part of India. The area has a highly complex geological history due to tectonically controlled sediment deposition and post-depositional structural modifications. The signatures of these multiple deformation phases are mainly sub seismic in nature and hence a high resolution microresistivity borehole image data was utilised to resolve the subsurface complexity.The image data (FMI) revealed the primary dip direction to be consistently towards southeast and is intersected by several large and small scale faults. The structural cross section developed from the dipset exhibits four major structural events. Based on the structural events different structural zones were identified in the well. Removing the structural dip with respect to the structural model reveals the paleocurrent direction, which exhibits wide variance in the study well. But zoning the distribution of removed dips based on stratigraphy and individual sand bodies identified in the well reveals the sediment transport direction. The palaeoflow direction estimated from this well is consistent with the established paleogeography of the area. The study thus provides a methodology for interpretation of palaeoflow direction to aid in the exploration program from a single well study within the constraints.

 

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas