Structural Effects of Overpressure Fluid Activities in Yinggehai Basin

The characteristics and distribution of faults in Yinggehai basin discussed in this paper reveal the structural effects of the overpressure fluid expulsion. The rapid subsidence and mud-rich intervals of the marine rocks dominate the formation of the overpressure systems and the enormous volumes of the overpressure fluids in the basin. Triggered by some faults,the overpressure fluids were expulsed rapidly from the overpressure compartments to form a series of diapirs in the basin,resulting in the dense fractures or faults and folds in the limbs of diapirs. These fractures and faults provided the migration pathway for the vertical flow of hydrocarbons,so that the gas fields arising from this process might migrate upwards to the sandstone reservoir. Therefore,the hydrocarbon accumulations are usually located in the upper parts of diapiric structures.