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Understanding the Architectura of Deepwater Reservoirs: Application of Borehole Images and Core in Krishna-Godavari Basin, Eastern Offshore India

Anil K. Tyagi1, Chandramani Shrivastva2, Samhita Hati1, Deepender Bora2, Rupdip Guha1, and Sandhani Sarmah2
1Reliance Industries Ltd. (E&P Business), Navi Mumbai, India
2DCS, Schlumberger, Mumbai, India

Deepwater sands reservoirs of Krishna-Godavari Basin, Eastern Offshore India have been the focus of recent exploration activities in India. Comprehending these reservoirs for conceptual models is never an easy task for the huge variation in sedimentary facies encountered. Borehole images aid significantly in understanding the depositional environment of such sediments with the help of core and other available dataset.

The major architectural elements of deepwater reservoirs have been interpreted with the help of borehole images. Debris flow, channel sands, levee heterolithics, overbank mud and slide & slump were interpreted in the Mio-Pliocene sediments of this Basin. Process sedimentology has been attempted to understand the role of these architectural changes in controlling the reservoir properties. The extent and orientation of these sand bodies is a direct function of sedimentary processes.

The texture of high energy debris flows leads towards the processes responsible for them. Dips picked in the channelised sands help in estimating the flow direction whereas the image texture, sedimentary structures and facies association suggest the causative flow regime. The heterolithics of sand-shale alternations could possibly be attributed to the architecture of levee elements. The distorted argillaceous facies with high angle dips indicate a slumping, probably in overbank element. The undisturbed hemi pelagic mud facies represents the quiet energy environment. The core data available in a couple of wells has been used to develop and validate the concepts developed by borehole image interpretation.

A number of wells have been studied to understand the process related architectural changes in these deepwater deposits. The integration of borehole images and core is the key towards proper understanding of heterogeneities introduced by these elements in the reservoirs.

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