North-south Differentiation of the Hydrocarbon Accumulation Pattern of Carbonate Reservoirs in the Yingmaili Low Uplift,Tarim Basin,Northwest China

By analyzing the characteristics of development,structural evolution and reservoir beds of the residual carbonate strata,this study shows that the residual carbonate strata in the Yingmaili low uplift are favorable oil and gas accumulation series in the Tabei(northern Tarim uplift)uplift.There are different patterns of hydrocarbon accumulation on the northern and southern slopes of the Yingmaili low uplift.The north-south differentiation of oil reservoirs were caused by different lithologies of the residual carbonate strata and the key constraints on the development of the reservoir beds.The Mesozoic terrestrial organic matter in the Kuqa depression and the Palaeozoic marine organic matter in the Manjiaer sag of the Northern depression are the major hydrocarbon source rocks for the northern slope and southern slope respectively.The hydrocarbon accumulation on the northern and southern slopes is controlled by differences in maturity and thermal evolution history of these two kinds of organic matter.On the southern slope,the oil accumulation formed in the early stage was destroyed completely,and the period from the late Hercynian to the Himalayian is the most important time for hydrocarbon accumulation.However,the time of hydrocarbon accumulation on the northern slope began 5 Ma B.P.Carbonate inner buried anticlines reservoirs are present on the southern slope, while weathered crust and paleo-buried hill karst carbonate reservoirs are present on the northern slope.The northern and southern slopes had different controlling factors of hydrocarbon accumulation respectively.Fracture growth in the reservoir beds is the most important controlling factor on the southern slope;while hydrocarbon accumulation on the northern slope is controlled by weathered crust and cap rock.