Fault Feature and Its Control on Hydrocarbon Accumulation of Paleogene in Qingdong Sag

By using the results of 3Dseismic profile interpretation and combined with the drilling data,the geometry characteristics of fault in Paleogene System were analyzed in detail.The result showed that three main fault types were developed in the study area,including synsedimentary fault types,normal fault types and basement strike-slip fault types.In the plane,the most of faults were distributed nearly in EW,NW and NE directions.In number,the fault of EW was the most,and the fault of NE was the least.According to the combination of the major fault and the sub-fault,the faults were divided into 6types in profile,such as Y type,complex Y type,horsetail shape,dominoes type,pectinate type and cabbage type and 3kinds of systems in plane,such as parallel fault system,oblique fault system and echelon fault system.Based on the analysis of the fault development,the function in the oil and gas generation and accumulation process was clarified.The study shows that the activity of major fault controls the tectonic framework of basin and the distribution of sedimentary and hydrocarbon source rock.The fault distribution in space and tectonic combination style control the types of trap,the faulted anticline,fault block and fault nose traps are the main types.These faults also form a complex three-dimensional conducting network,it provides effective channels for vertical transport of oil and gas accumulation.The northern and southern convex structure areas controlled by the fault formation are the favorable areas of vertical migration of oil and gas.