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Exploration Leads of Deepwater Areas, Mumbai Offshore, India

Venkatramana N. Hegde, Radha Krishan, Rama Paul, and S. Mayor
BRG, KDMIPE, Dehradun, India

The deepwater area is located in the western offshore of India which extends from Kutch-Saurashtra in the north to Kerala-Konkan in the south. Though large hydrocarbon accumulations are discovered in the shelfal part of the Mumbai offshore in the carbonate reservoirs, but the deepwater area remained far from fully understood and explored.
The present study is based on reinterpretation of seismic data with integration of shelf and deepwater sub surface geological information acquired from wells to understand the prospectivity of the area. The time structural, relief and isochronopachs for different horizons have been prepared to understand the structural style and sedimentation pattern.

The systematic mapping of the area revealed the presence of large carbonate build up in the Miocene forming ridge like structure along the shelf edge. The reefal complex stretches about 250 Km trending in NNW-SSE direction parallel to coast line with lateral extent ranging from 15-20 Km. The reefal body is identified on the basis of geological criteria and geophysical interpretation.

The characteristic seismic facies patterns include large drape, discontinuity of reflectors, spurious events and on lapping events. The high energy open sea environment, presence of favourable shelf edge faults, elongated straight coast line and absence of clastic supply favoured the growth of frame builders.

The barrier reef is formed on uplifted block of basement feature during Mid-Eocene to Mid-Miocene. The Oligocene transgression and slow subsidence has helped in continued carbonate buildup till the end of Middle Miocene. The thick Mio-Pliocene clastics derived from Indus and rising sea level brought halt to carbonate sedimentation and acted as seal. The talus derived from reef and debris derived from adjoining areas formed additional exploration targets. The presence of source within and adjacent lows, presence of thick top seal of Mio-Pliocene shale/clay has enhanced the prospectivity of the play. This Block is identified as High Prospective area from exploration point of view.

Presentation GEO India Expo XXI, Noida, New Delhi, India 2008©AAPG Search and Discovery