Analysis of rock reservoir properties in the context of petroleum potential: Emsian-Timanian play in the Kama territory of the Western Urals piedmont

Based on lithofacies analysis, the authors have traced back gross depositional environments and settings for the Takatinsky-Timansky stage of the evolution in the Kama territory of the western Urals piedmont. They demonstrate the features of sedimentation in the Krasnokamsky-Chusovsky paleodepression that plays a leading role in building the potential of source rock sequence. The results of the lithofacies analysis allowed founding that sand bodies of coastal-marine genesis belonging to the zone of the seaside lowland delta plain have the better reservoir properties. Evaluation of reservoir properties of the Pashiisky and Timansky deposits is conducted on the basis of net thickness and net-to-gross maps, as well as section differentiation, reservoir quality, and thickness of the Timansky-Sargaevsky regional impermeable bed. It was found that the Pashiisky deposits are described as mainly medium-capacity medium-permeable reservoirs, while the Timansky - as low-capacity and low-permeable. Fine- and medium-grained sandstone, coarse-grained siltstone in the Permian Arch have the best reservoir properties in the studied interval of the section, where porosity ranges from 12 to 24 %, and permeability reaches 1530 mD (with the mean of 350 mD). The authors delineated zones of maximum interest in the context of petroleum exploration. Resulting from structural and lithofacies analyses, the paleotectonic scheme of the Emsian-Timanian structural stage was created that is the basis of geopetroleum zoning and planning of further trends of exploration and prospecting activities. Main petroleum potential of the Emsian-Timanian terrigenous sequence are associated with the eastern part of the Verkhnekamsky depression, Permsky arch, and Visimsky monocline