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ABSTRACT: Imprints of strike-slip movements in the middle eocene-miocene sequence of Western Indian Continental Shelf : Implications for hydrocarbon exploration and production strategy

Verma, N. K., P. S. N. Kutty, and Gautam Sen , Oil & Natural Gas Corporation Ltd, Dehradun, U.P, India

Bombay Offshore Basin developed over western Indian shelf, is characterized by Passive Continental Margin structural affinities. Multicyclic Carbonates of Middle Eocene to Miocene post rift sequence harbouring major part of discovered Indian Petroleum Reserves.

Structural fabric in the basin is characterized by three sets of faults, (i) NW-SE (ii) N-S or NNE-SSW (iii) ENE-WSW, correlatable with ancient structural trends of Dharwar, Aravalli and Narmada respectively. Initial Structural studies inferred rift related block faulting and subsidence as main genetic mechanism for structural evolution. With increasing 3D seismic coverage, imprints of a subtle NNE to ENE -WSW structural trend are evident in almost entire basin including Bombay High field. This trend is characterized by series of tight linear undulations accompanied by numerous small enechelon fault traces. In vertical section these are expressed as space accommodation 'bulges.' Their amplitude and diameter increases upwards and invariably their edges are marked by structural dislocation, depicting typical geometry of proto 'positive flower structures'. In the adjoining structural blocks, similar faults have resulted in moderate to strong positive structural inversion of Eocene-Oligocene strata at number of locales.

This trend, coincides with the transform faults active during the ocean floor spreading in the Arabian Sea, and hence inferred to be related to reactivation of pre-existing fault planes by strike-slip movements during northward movement of Indian plate in Tertiary period.

These faults may have important role in creating the reservoir heterogeneity which could affect fluid migration, entrapment and production behavior.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia