Tectono–Provenance and Reservoir Rock  Characteristics of the Tipam Sandstones  in Parts of Upper Assam Basin

Dr. Pradip Borgohain

Volume : I, Issue : II, July - 2012

Tectono–Provenance and Reservoir Rock Characteristics of the Tipam Sandstones in Parts of Upper Assam Basin

Dr. Pradip Borgohain

Abstract :

The Tipam Sandstone Formation belongs to Late Miocene to Early Pliocene age and it is one of the main oil producing horizon of Upper Assam Basin. It varies widely in thickness from area to area owing to a major unconformity at the top. The sandstones are composed mainly of quartz, rock-fragments, and mica. The contribution of quartz varies from 43.5% - 57.5%. Both the monocrystalline and polycrystalline quartz are reported. Feldspars varies from 2.2% - 2.5%, rock-fragments varies from 7.0% - 7.5%. The sandstones have undergone all the stages of diagenesis. Dissolution features, quartz overgrowth, transformation of secondary minerals are frequently reported. These diagenetic changes have a direct control on the reservoir quality of the sandstones. The sandstones are mainly subarkosic and wacke type. The sandstones are derived from varied sources however middle rank of metamorphic origin is dominating. Volumetric analysis of major oxides suggests that the sandstones are derived from active continental margins and subordinately from the continental island arc provenance.