Petroleum accumulation in Ordovician carbonate rocks of Yuqi region in Akekule uplift,Tarim Basin

The Yuqi Block is an important oil and gas exploration play in the Akekule uplift.The hydrocarbon accumulating conditions in the Yingshan Formation are studied and the accumulation model is established using the techniques of basin analysis,reservoir prediction,fluorescence thin section and fluid inclusion.The oil and gas in the Yuqi Block come from the Cambrian to Lower Ordovician source rocks in the southern Akekule uplift.Yingshan Formation reservoirs are of cave,fracture-pore and fracture types,and their physical properties are intermediate.The seal conditions of Lower Carboniferous mudstones are fair,but the late Hercynian structural event is the most important influence element on petroleum preservation.There are at least four oil/gas charges in the Yingshan Formation,and the most important charge periods are Late Hercynian and Himalayan(Cenozoic).The accumulation model is lateral expulsion of hydrocarbon and multistage accumulation,and the evolution has four stages.