Rock-thin section study, scanning electron microscopy (SEM), X-ray diffraction (XRD), and Rock-Eval pyrolysis have been carried out on the Barail (Oligocene) and Disang (Eocene) groups of rocks of the Naga Schuppen Belt of Assam-Arakan Basin to understand the reservoir properties and hydrocarbon source potential. Analyses show that the Barail Group sandstones are moderately well-sorted, medium-grained, sublithic arenite type, and bear good porosity (avg. 14.48%). In contrast, the Disang Group sandstones are very hard and compact, fine-grained, sublihic arenite, and lithic greywacke types and show medium porosity (avg. 11.3%). The reservoir properties of the sandstones of both groups are controlled by various diagenetic alterations like mechanical compaction, cementation, overgrowth, authigenesis of clay, fracturing, dissolution, and alteration of unstable clastic grains. However, no single diagenetic process could be considered as the main controlling parameter in the evolution of the porosity of the studied sandstones. The Rock-Eval pyrolysis indicates that the carbonaceous shales of both the Barail and Disang groups are characterized by type III and type IV kerogen. A good number of shale samples show TOC (total organic carbon) values ranging from 0.88 to 10.71 wt%, which seems quite good. In most of the samples, S2 is recorded <2 mg HC/g of rock, indicating the potential to generate wet gas. The various binary plots mostly show the gas source potential of shales of both the Barail and Disang groups. Production Index (PI) values vary between 0.04-0.45 for the Barail shales and 0.04-1.0 for the Disang shales, indicating that the studied shale samples are in the last phase of catagenesis.
Terraces are the remains of a river's old floodplain. They are created when a river channel is downcut into its former floodplain, which is then deserted and subjected to lateral erosion. A former floodplain's downcutting, abandonment and lateral erosion can be caused by local or regional tectonic uplift, changes in the climate and changes in the river's discharge or a combination of these. The 1950 Mw 8.6 Great Assam Earthquake, which completely wrecked the region, occurred in the Mishmi Hills. The study area lacks tectonics research, therefore understanding the region's undulations requires a thorough understanding of terraces. Using ArcGIS 10.4, a digital elevation model (DEM) with a 30m resolution and satellite images form Google Earth Pro was superimposed on the Survey of India's topographic map for this investigation. The goal of the study is to use terrace analysis to comprehend the regional tectonic activity of the entire frontal and foothills of the Mishmi Hills. The Lohit, Dibang and Noa Dihing River are the most notable rivers in the research area. The rivers possess incised valleys and tributaries where different level of terraces may be identified. The terraces of the said rivers and tributaries are the subject of this study. Since the terrace levels vary from valley to valley, it is impossible to correlate adjacent valleys. The terraces are typically found where one of these rivers and one of its tributaries converge. The tectonic influence on various features in the studied area is typically defined through the study of terraces.
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