The main body of “Large North” is a small fault block lying in relatively active central Asia intercontinental area, such as Junggar, Alxa and Qaidam. Upper Paleozoic was previously not regarded as the petroleum exploration target in that it was thought to be a metamorphic basement and the Upper Paleozoic strata were lacking:even in Junggar Basin, only a part was considered as the source bed and reservoir. Since the beginning of this century, much new understanding has appeared. There exist huge thick unmetamorphosed marine Upper Paleozoic strata as well as several thousand meters of Upper Paleozoic strata in Mesozoic and Cenozoic cover bed in this area.