Sedimentary facies and hydrocarbon distribution analysis of Shawan formation of Chunguang block in the western margin of Dzungaria basin

It is widely thought that Shawan formation of Chunguang block was developed in a braided river delta sedimen-tary system,however,the author in this paper believes there are conflicts in view of sedimentary facies model.Through careful studies on various sedimentary characteristics and facies marker analysis,the author insists that Shawan formation was developed in a beach bar sedimentary system and then the study on facies classification,sedimentary microfacies belts and sandbody distribution has been carried out in this paper.As a result,the conflicts unable to be explained by delta sedimentary system have been resolved.Based on that,the reasons for large beach bars and 'sand sheet' have been analyzed,and in the end the hydrocarbon accumulation and banding distribution law for isolated beach bars has also been provided.