Reservoir Types and Distribution Characteristics of Wurxun-beir Sag

The distribution of Cretaceous lithologic reservoirs in Wurxun-Beir sag of Hailaer Basin is mainly controlled by paleotopography, distribution range of effective reservoirs, and distribution range of effective source rocks, stratigraphic unconformity surface and structure. Oil and gas are mainly concentrated in the margin of sedimentary trough, large gentle slope break zone and low uplift in trough area. The abrupt slope break zone of the belt and the fault type is distributed in a circular shape around the depression trough. On the plane, there are many oil-generating troughs in the Wurxun-Beir depression, which provide abundant and high-quality resource basis for the formation of reservoirs. The hydrocarbon generated from the source bed migrates and accumulates to various types of traps around it through sand bodies, faults or unconformities. Various types of reservoirs, such as structure and lithology, coexist in the depression, forming a transverse superimposed contiguous sheet. The compound oil and gas accumulation zone is mainly distributed in the hydrocarbon generation depression trough or the surrounding fault structural belt. The large area hydrocarbon-generating troughs usually have large oil and gas reserves, such as Surenuoer, Wunan and Beizhong oilfields; the troughs developed in the middle of the depression are easy to form “full depression oil-bearing” oil-rich troughs, such as Beizhong sub-depression reservoirs. Exploration practice has proved that the discovered reservoirs are located in or around the source rock. Therefore, exploration and deployment around the source rock will be the key direction of exploration in the future.