Mechanism of formation of hydrocarbon basins: the West Siberia, Volga-Urals, Timan-Pechora basins and the Permian Basin of Texas

Abstract

Many authors suggest that a large role in the formation of hydrocarbon basins is played by stretching or thrust loading. Our previous analysis (Artyushkov and Baer, 1983, 1984a,b, 1986) has revealed a large number of deep basins on continental crust in fold belts that were formed by rapid subsidence without significant stretching or thrust loading. This paper shows that the hydrocarbon basins of West Siberia, Volga-Urals, Timan-Pechora and the Permian Basin in Texas pertain to the same basin type. Water-loaded basins, ~ 0.3–0.5 km deep, were produced in these regions by rapid subsidence (in ≲ 1 Ma). Shallow-water and deeper-water strata cover the same area in the basins which precludes significant stretching during the subsidence. There was no folding in the adjacent regions ai the epochs of the subsidence, which precludes thrust loading. A short duration of the subsidence precludes a significant role of thermal relaxation. Rapid subsidence was commonly preceded by slight crustal uplift. In the Volga-Urals and Timan-Pechora it was also preceded by slight volcanism. We suggest destruction of the lower crust under asthenospheric upwelling to the base of the crust as a cause of rapid subsidence. The asthenospheric upwelling strongly increases the heat flow which ensures hydrocarbon maturation at shallow depth. Activization of local tectonic movements from crustal heating occurs after rapid subsidence which produces numerous traps for hydrocarbons. Deposition of highly organic rocks (good source rocks) and the formation of reefs and/or clinoforms (good reservoirs) commonly occur after rapid subsidence. Deposition of shales and evaporites (good seals) takes place in deeper-water basins formed by rapid subsidence. Diapirism of the latter rocks produces additional hydrocarbon traps. The combination of all the above effects associated with rapid subsidence produces very favourable conditions for the generation and preservation of hydrocarbons. Almost all large hydrocarbon fields in the basins considered are located in regions of rapid subsidence. There are no large fields in the adjacent sedimentary basins formed by slow subsidence, although the sediment thickness is commonly high.