Occurrence of unconventional hydrocarbon deposits and its structural relation in Nepal Himalaya: implication for future exploration

Due to tectonic movement, compressed structures, and mountain upliftment process, several sedimentary basins have evolved in the periphery of the Himalayan orogeny. The evolution of sedimentary basins within the Central Himalaya (i.e., Nepal Himalaya) is quite similar in age (i.e., Eocene–Recent). The sedimentary sequences within this basin are marked by large-scale geological structures (e.g., Main Central Thrust, Main Boundary Thrust, and Main Frontal Thrust). The Lesser Himalayan (Eocene-Miocene) foreland basin in far western Nepal contains various hydrocarbon deposits. Similarly, the shallow marine shale, coal seams numerous fossils, and tight sand layers are the important sources of energy resources. The sedimentary basin, Surkhet Group in the western Nepal, is the prospective area for the unconventional hydrocarbon deposit. Due to active geological structures (such as Ranimatta Thrust, Budar Thrust, Mahabharat Thrust, and Nabi Khola Anticline), oil and gas seem to have migrated upward in the Padukasthan, Nabhisthan, and Sristhan. Therefore, the active oil and gas seepage occur locally in this area. Due to lack of scientific engineering research, the utilization of various energy resources of Central Himalaya (Nepal Himalaya) is important but challenging. There is not much work carried out on this section; the present study discussed about the relationship between the sedimentary structures and the formation of unconventional gas and its prospects in the Nepal Himalaya region.