Abstract

The continental shelf off the west coast of India is divided into four sedimentary basins, namely Kutch, Bombay, Konkan and Kerala Offshore Basins. The boundaries of these basins are broadly denned by transverse ridge-type structural features.

In the Kutch Offshore Basin, Mesozoic strata are confined to the eastern part of the shelf. Tertiary sediments are relatively thin in the eastern part and thicken towards the west across a hinge zone. A few drape structures are noted in the Mesozoic rocks.

The Bombay Offshore Basin has only a Tertiary fill with Eocene strata absent on the Bombay High structural uplift. West of the uplift, the Paleogene and Miocene are represented by a thick sequence of limestones and thin shales which are poor in source rock characters. In the southeast, along the Bassein structural trend, the Paleogene consists of limestone and shale. In the northeast, the Paleogene is represented by thick shales, which are considered to be source rocks for the Bombay High (Miocene oil accumulation), Bassein and B-38 fields (Paleogene oil accumulation). The structures of the fields are formed by faulting within the Deccan Trap basement and subsequent rejuvenation. Far to the west of the Bombay High uplift, the Paleogene and Neogene consist of a thick sequence of fine elastics in the shelf margin sedimentary sink.

In the Kerala and Konkan Offshore Basins, Tertiary strata thicken across the hinge zones located within the continental shelf and extend westwards beyond the shelf.

Carbonates may be predominant in the Konkan Offshore Basin, whereas coarse elastics above basaltic sills form the section of the Kerala Offshore Basin. While several carbonate build-up features with drape structures are noted in the Konkan Basin, beyond the continental shelf; gently folded structural features only are noted in the shelf of Kerala Basin.