Definition of the Weihe Single-thrusting Compressional Basin and Its Reservoir-forming Conditions

The basin structure is the foundation for understanding this basin, which not only has an important control to the production, storage, coverage, entrapment, transportation and protection of the oil and gas and its associated resources, but also is a key basis for the exploration and reservoir-forming prognosis. Based on a large number of accurate geophysical exploration and geological data, the structure characters of basin-controlling fracture have been redefined in this paper, and the tectonic units of the Weihe basin have been divided. And then, the structural characteristics of different structural units, reservoir-forming conditions and distribution laws of oil-gas and its associated resources in Weihe basin have been compared. It is found that the northern fault of Qinling Mountain is a huge regional thrust fault, which slopes to north in shallow part and to south in deep. The southern Beishan fault in Weihe basin is not a traditional normal extensional fault, which is effected by the local stress field, with a feature of whole thrust fault. The Weihe basin is not a graben, but a single stamping compressional basin. There are differences in reservoir-forming conditions and distribution laws of oil-gas and its associated resources between different structural units of the basin. The fault belt is a favorable reseivoir zone for ordovician gas, which is mainly controlled by faulted terraces. The monoclinal belt serves as a favorable reseivoir zone for permo-carboniferous gas, which is mainly controlled by the monoclinal structure. The enrichment of the gas in depression belt is related to the development of rollover anticline, faulted nose structure and sandstone rock. The convergence region between fault belt and nose uplift is advantageous to water-soluble helium.