Hydrocarbon Potential of the Disang Group of Rocks of the Inner Paleogene Fold Belt of Assam-Arakan Basin Exposed along the Dimapur-Senapati Road Section of Nagaland and Manipur, India

Abstract

Carbonaceous shales of the Upper Disang Formation of the Inner Paleogene Fold Belt of Assam-Arakan Basin, exposed along the Dimapur-Senapati road section of Nagaland and Manipur states of India have been studied for interpreting hydrocarbon potential. The Upper Disang Formation is mostly composed of alteration of shales, sandstones and siltstones. The shales are black coloured and splintery in nature. The shales and associated sandstones show sedimentary structures like bioturbation, cross bedding and ripple marks indicating shallow water origin. The shales contain appreciable amount of pyrites indicating marine influence in the depositional basin. The average TOC of the carbonaceous shale samples is 0.53% indicating poor generative potential. The poor generative potential of the formation is also supported by low S1 (average 0.04 mg/gTOC), S2 (average 0.16 mg/gTOC) and HI (average 36 mg/gTOC). The organic matters are represented dominantly by Type IV kerogens (inertinite) with subordinate amount of Type III kerogens (vitrinite) as shown by both Rock Eval parameters and organic petrography. The dispersed organic matters (DOM) are identified as semifusinite and collotelinite under the microscope. The organic matters are interpreted to be inert/post mature kerogens from the maturity parameters like Rock Eval Tmax (average 563°C), and mean vitrinite reflectance (average 2.0% in oil). The study indicates very poor hydrocarbon potential of the Upper Disang Formation of the Dimapur-Senapati road section.

Unveiling the Presence of Limestone, Chert and Fossil Leaves in Disang Group Exposed in the North- easternmost Part of Assam-Arakan Basin, India: An Integrated Study on Lithology, Petrography, and Clay Mineralogy

“…Krishnan (1968) regarded the Disangs as geosynclinal lithological facies which is well developed to the east and southeast of the Ha ong-Disang Thrust in Nagaland, Manipur and beyond. Earlier studies stated that Disang Group represents deep water turbidite deposit and the shales exhibit high maturity but poor hydrocarbon generation potential (Baruah et al, 2007;Gogoi and Sarmah, 2013;Gogoi et al, 2023). The sandstones are sublithic arenite and lithic wacke type derived from igneous and metamorphic sources in a recycled orogen tectonic setting (Phukon et al, 2010; Gogoi and Sarmah, 2021 and Gogoi et al, 2023).…”