Hydrocarbon Accumulation Law Research In Chepaizi Area Of Junggar Basin

Chepaizi bulge is a monocline sloping down to the southeast. It is supplied hydrocarbon by two depressions in two periods, and the reservoir includes light oil and heavy oil. The accumulation factors of here are complex. In order to correctly guide the next exploration we have to define the path of oil migration and sum up the law of accumulation and distribution.Conducted by modern theory of petroleum accumulation, we execute the research on the base of conducting system. In this paper, we topically analyze the effectiveness of framework sand body and fault and unconformity and their Space-time configuration. We resumed reservoiring process and confirmed migration path in accumulation period. Consequentially, we summarized hydrocarbon accumulation law and forecasted the favorable area.The light oil in this area originated from the hydrocarbon source rocks of Jurassic in Sikeshu depression in the southern. These reservoirs mostly distributed in N1S2 in the southern and were formed after Neogene. The heavy oil originated from the hydrocarbon source rocks of Permian in Changji depression in the eastern. They distributed from Jurassic to Shawan Formation of Neogene in northeastern.The unconformity and fault and framework sand bodies formed the complex conduit system. The unconformity connected oil source and the fault decided secondary adjustment when oil migrated in the bulge inner, while the framework sand bodies controlled lateral migration distance and whether the oil can accumulate finally. The effective range of the unconformity at the bottom of Cretaceous concentrated in the north, but the effective range of the unconformity in the bottom of the Neogene Shawan Formation is almost all over the bulge. The faults south of P8 and east of P6 and west of P7 were very important for vertical adjustment. The range of the framework sand bodies'lateral connectivity and vertical conduction controlled oil migration. The result is that the upper sand which is conduction with the lower is more beneficial for accumulation. In late Cretaceous, the oil from Permian of Changji depression accumulated along the unconformity at the bottom of Cretaceous. But after Neogene, the oil firstly migrated along the same unconformity then conducted by the fault in the east of P6 which is vertical open and finally accumulated in Shawan Formation. While the oil from the hydrocarbon source rocks of Jurassic in Sikeshu depression firstly migrated along the unconformity at the bottom of Shawan Formation and then was conducted by the fault south of P8 and accumulated in Shawan Formation Sec.The main controlling factors of accumulation include that the configuration of migration background and orientation of source at accumulation periods, and reservoir and cap rocks conditions and the conducting systems connect traps and source.Sand near the unconformity at the bottom of Cretaceous and Shawan Formation and the upper sand of middle and lower Shawan Formation that is in the south of the fault of P8 are the favorable areas for accumulation.