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Structural Growth Related Sand Pinch-Outs and Their Significances in Oil-Gas Exploration in South Cambay Basin, India

Pulin C. Goswami, Santonu K. Bora, and Pss Rao
Oil & Natural Gas Corporation, Ankleshwar, India

Sand pinch-outs belonging to Hazad Member of Ankleshwar Formation of Middle Eocene to Upper Eocene age provide locale for hydrocarbon entrapment in several giant to small sized oil-gas fields in south Cambay basin. The Hazad Member consists of 5 sands in Ankleshwar field and 13 sands in Gandhar field which are further divided into two or more sub-units, each being separated by extensive shale of varying thicknesses; whereas only 2-3 sands are developed in Hazad Member in areas south of Ankleshwar and north of Dadhar River. The geological process for development or genesis of Hazad sand pinch-outs is presently related to deltaic environment of deposition and each sand pinch-out is considered as a deltaic lobe. The geological processes which control preferential development of delta lobes south of Dadhar River and north of Ankleshwar are yet to be understood adequately in light of existing model.

An alternative geological process for genesis of Hazad sand pinch-out is proposed. The Hazad sand pinch-outs are related to structural growth, tectonic control on sedimentation and inability of sedimentation to keep pace with structural growth. The ‘inability of sedimentation to keep pace with structural growth’ is due to low sediment input to growing Broach depression during Middle Eocene to Upper Eocene time. Localized development of sand pinch-outs were governed by growth faults that remained active during sedimentation.

Exploratory efforts for growth related sand pinch-outs is expected to contribute significantly towards reserve accretion in south Cambay and other basins.

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