Petrography of sub-surface Tipam Sandstone Formation of a part of Upper Assam Basin, India

The Tipam Sandstone Formation of Miocene age is one of the prolific hydrocarbon producers of the Upper Assam basin, India. In this paper we report on the petrography of the Tipam Sandstone Formation using subsurface samples of two wells of Oil India Limited from Upper Assam. The petrographic study involved preparation of rock thin section slides from conventional core samples and their study under petrological microscope. This study reveals that the sandstones under study are mainly of sublith-arenite, feldspathic greywacke and lithic greywacke types. However, few of them are also of sub-arkose and arkosic arenite types. The sandstones were derived mostly from middle and upper rank metamorphic sources. The tectonic set up of the source area during the time of deposition of the Tipam Sandstone Formation was of quartzose and transitional recycled types.