Prospect of primary Palaeozoic oil-gas pools in eastern exploration region,Sinopec

The Lower Paleozoic source rocks in the eastern exploration region of Sinopec are mainly marine carbonates with a low organic content.The rocks in southern Bohai Bay reached early maturation at the end of Mid-Triassic and started secondary hydrocarbon generation at the Mesozoic.To Cenozoic,although subsiding further to more than 10 km,most source rocks in which organic-rich kerogen had already been cracked up were limited in generating hydrocarbon.In the southern North China,the lower Paleozoic source rocks reached primary maturation at late Triassic and the secondary hydrocarbon generation did not occur at the Cenozoic.The Upper Palaeozoic is mainly a set of coal measure sediments with great thicknesses of coal and dark mud beds,which experienced two maturation periods at the end of late Triassic and of early Cretaceous.Based on previous studies,it is concluded that the favorable Upper Paleozoic oil and gas prospects are in the southern Bohai Bay,including Dongpu Sag,Linnan Sub-Sag,southern Dezhou Sag and northern Xinxian Sag.There is risk for the exploration of the Lower Paleozoic proto-petroleum,and the southern Bohai Bay is a preferred place.