The geochemistry characteristics of overpressured compartment and its controls on hydrocarbon migration and accumulation: An investigation on the Dongying sag in the Bohaiwan basin, China

Dongying basin represents the continental deposit of faulted-lake and half graben in the eastern China. In the basin the dark mud mainly developed at the Member 4 and Member 3 of Shahejie Formation, and the overpressured systems developed in the dark mud controlled the hydrocarbon migration and accumulation. The formation of the over-pressure was a result of the unequlibrium compaction of source rocks and the hydrocarbon generation. The geochemistry characteristics indicated that the overpressured compartment can be classified into three parts: the edge of compartment (seal), the favorable release zone for hydrocarbon expulsion and the stagnant zone for hydrocarbon expulsion. The geochemistry characteristics demonstrated there were two types of overpressured systems: the open and the closed relatively, and the formation of compartment was a geochemical self-organized course. Influenced by the fluid pressure, the distribution of different types of gas reservoirs were in cyclical.