Sedimentological Characteristics of the Barail Arenaceous Unit of Makum-North Hapjan Oil Field, Assam

Abstract

Upper Assam Shelf is one of the major on-shore hydrocarbon producing basin in India. It comprises sediments of upper Paleocene to recent and rest unconformably over the Granitic Basement. The Barail Group (Oligocene) of rocks in this basin is characterized by hydrocarbon source rock as well as reservoir rock. The Barail Group of rocks is divided into Arenaceous Unit (lower) and Argillaceous Unit (upper) in Upper Assam basin. The Arenaceous Unit is considered as good reservoir rock, where as the upper Argillaceous Unit is considered as source rock. The aim of the present research work is to characterize the Barail Arenaceous Unit of Makum-North Hapjan oil field with respect to its mineralogical constituents and textural properties. The present study reveals that the Barail reservoir sandstones in Makum- North Hapjan oil field are sublithic-arenite varieties with moderately well sorted texture and deposited in a fluvio-deltaic environment under the intermittent influence of transgressive and regressive effects. The sediments were derived from multiple provenances primarily comprising of reworked sediments and low rank metamorphic rocks.