Reservoir oil deposits in terrigenous complexes of the Bobrikian horizon of the western slope of the South Tatar arch

Abstract

Oil-bearing terrigenous sections of the Bobrikian horizon of the western slope of the South Tatar arch are considered. It has been established that all oil deposits are confined to thin layers of quartz sandstones screened by dense clayed siltstones and argillites. The sandstones were formed in the coastal-shallow conditions of a desalinated epicontinental marine basin during the active removal of clastic material from the coast of the continent. Similar conditions of accumulation caused a large areal distribution of fine-grained sandstones with a consistent thickness along the lateral. During the period of migration of water-oil fluids, calcite cement was leached from sandstones, due to which their porosity increased to 20-25%, the permeability reached 243.0-359.0 mD. Oils in sandstone reservoirs are characterized by an increased content of light and medium fractions of hydrocarbons, the content of heavy hydrocarbons does not exceed 15-20%. Despite the fact that, according to the results of geophysical studies, the rocks are classified as unpromising, weakly oil-bearing, commercial oil flows are obtained from them in a several of oil-bearing structures.