SEDIMENTARY CHARACTERISTICS OF TWO KINDS OF BEACH-BARS OF OLIGOCENE SHAHEJIE FORMATION IN WESTERN HUIMIN DEPRESSION,CHINA

Two kinds of beach-bars deposited in Member Sha-3 and Member Sha-4 of the Oligocene Shahejie Formation in western Huimin depression,Bohaiwan basin are analyzed in terms of geological,well test,seismic and office analysis.The results have shown that two kinds of beach-bars formed in shallower water environment in weak tectonic activity period and have high degree of compositional maturity and textural maturity.The sandy beach-bars developed in the upper Member Sha-3 of the Shagejie Formation,where terrigenous materials supplied enough,which can be divided into five microfacies.Bioclastic beach-bars mainly developed in upper Member Sha-4 where terrigenous materials supplied insufficiently and was in humid climate period.The reservior quality of sand bodies of two kinds of beach-bars are fine and favorable for oil and gas enrichment.