Comparison of Overpressure System and Hydrocarbon Accumulation between Qaidam Basin and Yinggehai Basin

Abnormal overpressures exist widely in a certain area and depth in the basins of Qaidam basin and Yinggehai basin.Sedimentary and tectonic evolution,feature and origin of overpressure,and hydrocarbon accumulation history are compared to illustrate the relationship between overpressure system and hydrocarbon accumulation in the process of basin evolution.Results show that two basins accepted the rapid deposition of sediments and formed the thick source rock,which is corresponding to the main layer with overpressure system.Depocenter and tectonism at the deposition stage strictly control the distribution of overpressure,and the top interface of overpressure generally represents a trend of being higher in depocenter,gradually decreasing to basin edge,and even disappearing.Hydrocarbons occur near the interface of overpressure and normal pressure system,and it also has a great potential in an enclosed and well preserved deep area.Overpressures provide the force for driving hydrocarbon migration and control the distribution of reservoir in a certain background.The process of hydrocarbon accumulation can seriously influence the formation and evolution of overpressure system.