Hydrocarbon prospects of the western continental slope of India as indicatEd. by surficial enrichment of organic carbon

Abstract

The sediments from the continental mid-slope (150-1500 m depth) of the western margin are highly enriched in organic carbon (upto 16%) occurring as a long and wide band off Bombay to southern tip of India. Organic carbon is essentially of marine origin and is enriched due to its preservation under anoxic conditions causEd. by impingement of oxygen minimum zone. The DSDP data in the southeastern Arabian Sea have revealed the initiation of upwelling and productivity during Early Eocene and establishment of reducing conditions since Mid-Miocene, which continue till today. Under such a reducing environment there is every possibility of retention of higher amount of hydrogen in the kerogen part of organic matter. Published literature has indicated the organic matter is of type 2, the slope sediments have a structural capability for the retention of hydrocarbons and the sediments are significantly thick. All these evidences suggest that sediments from the Indian continental slope can act as source beds for petroleum generation. The continental slope between Ratnagiri-Mangalore and south of Cochin, with gentler topography and appreciable sediments thickness (2-4 km) where surficial organic-rich band is wider, are more potential sites for hydrocarbon exploration