New Understandings of Cretaceous Oil Generation Zone in Foreland Basin in Southern Margin of Junggar

The comparison of structural conditions in western and eastern basins of China and geochemical analysis of Lower Cretaceous source rocks in Junggar basin are made. It is considered that in the eastern basins there exist vast distributions of Cretaceous source rocks, better reservoir quality and thickness than those of the western basins on the whole, but the structural and depositional conditions in foothill sag in North Tianshan Mountain of Junggar basin are of a certain similarity with those in the eastern basins, i.e., its Lower Cretaceous strata possesses a capability of hydrocarbon generation, being significant and really existing source rocks for petroleum exploration of southern margin of Junggar basin. The oil-source rock correlation indicates that the crude biomarker features from Tugulu and Horgos areas are similar to those from surface crude and asphalt in Qingshuihe area, and these biomarkers were all coming from the source rock of Lower Cretaceous. Therefore, the Cretaceous source rock can be determined reliably. In this paper, the distribution extension of reservoir with oil source of Cretaceous is delineated. The contribution of the Cretaceous source rock to hydrocarbon accumulation in foothill thrust zone is pointed out, and the major target areas and drilling horizons for oil exploration are suggested in this paper. It is expected that the domain of petroleum prospecting in southern Junggar's foreland basin will be wider and wider.