Characteristics of Reconstruction Basin in Yanqi Area and Direction Prediction of Oil and Gas Exploration

Yanqi basin is an overlapping and reconstruction basin in Mesozoic and Cenozoic eras, in Mesozoic era it is a foreland-like basin, undergoes thrust, uplift, and erosion at middle and late Yanshan Movement, and reconstructs during Xishanian, while the structural pattern of the basin does not change. Source rock is mainly coal-measure strata with property of early generation and early expulsion. Hydrocarbon generation is mainly at the end of Yanshanian, while hydrocarbon generation during Xishanian is not evident. Many trap patterns exist in the basin, and most of them are related to thrust faulting, which forms during Yanshan period and shapes at Xishanian. Hydrocarbon reservoir forming is favorable for the traps existed at the end of Xishanian, yet the fault of controlled trap during Xishanian determines reservoir preservation formed during Yanshanian. Structural traps and stratigraphic traps formed during Xishanian are poor for oil and gas potential , and forming condition for cap rock and reservoir are unfavorable. Exploration strategy for next step is mainly in structural traps combined with lithologic traps at the end of Yanshan period.