Analysis of burial evolution of stratum and oil-gas reservoirs formation in Ordos basin

Burial conditions of stratigraphy in Petroliferous basins play an important role in the control of hydrocarbon generation and reservoir storage.In this paper,strata burial history and thermal evolution history of hydrocarbon generation in Ordos basin are recovered since later Triassic,and the characteristics of burry and erosion of stratigraphy among are contrasted.We also discuss the impact of the stratigraphic burial characteristics on hydrocarbon accumulation effect.The results show that the depths of burial and burial rate are significantly different among different regions of Ordos basin during four evolution stages of subsidence-uplift(T3,J1,J2,K1).On the one hand,times of hydrocarbon generated from later Triassic Chang-7 Section source rocks in these regions were delayed or advanced due to the difference in stratigraphic burial conditions.It entered into the early hydrocarbon generation during Middle Jurassic(J2) in Gufengzhuang and Baibao area of northern-mid Ordos basin,during Later Jurassic(J3) in Jiyuan,Zhenbei areas of mid,and during early Cretaceous(K1) in Gufengzhuang,Shanbei and Luochuan areas of Ordos basin.The time of large amount stage of hydrocarbon generation all is early Cretaceous(K1) throughout Ordos basin.On the other hand,differences in strata burial lead to changes of closed conditions for reservoir formation in these areas of Ordos basin.Larger depth of stratigraphic burial and higher deposition rate are favorable to the formation of good closed conditions in the northern and south-central Ordos basin,where even early oil and gas generation have been well preserved.