Tectonic evolution and hydrocarbon accumulation model in eastern Precaspian Basin

The Precaspian Basin has proved to be one of profilic sedimentary basins in Central Asia. A preliminary study is made in the present paper for the tectonic evolution, source-reservoir-seal associations and migration of hydrocarbons on the eastern margin of the Precaspian Basin. Uralian orogeny is believed to have exerted an important effect on the eastern margin of the Basin. Generally speaking, the suprasalt strata are poor in hydrocarbon accumulation. Instead, the hydrocarbons mainly originated from the subsalt strata. The Carboniferous carbonate rocks KT-I and KT-II beds are interpreted to be the excellent reservoir rocks in the study area. The Lower Permian salt beds appear as the regional cap rocks, and contribute a lot to the local sealing of subsalt hydrocarbons. The salt-associated structural traps are well developed, and the unconformities, faults, pore spaces and fissures constitute a compound oil-gas carrier system. The models for the hydrocarbon accumulation include the "selfgeneration and self-accumulation" type for the subsalt strata, and "lower-generation and upper-accumulation" type for the suprasalt strata.