Oil Accumulation Conditions And Resources Potential Evaluate In Ordovician Of Northwestern Margin Of Ordos Basin

The northwestern margin of the Erdos basin is located in northwestern of Ordosbason, The northwestern margin Ordovician influence of north china platform, TheHelan trough Qingqi ocean trough in geologic history. Experenced complex tectonicevolution. The region has wide and thick marine facies formation, good hydrocarbonsource rocks and reservoir rocks.In this area,ProsPeeting wells to show gascommonly,It is favorable zone of natural gas accumulation.The research is based on previous research results, author studied in detailanalyzed reservoir forming conditions according to sedimentary facies, source rocksevaluate,reservoir rocks exposition, cap rock, trapping and the play model,bycomprehensively utilizing outcrops, core observation, logging interpretationgeology analysis,etc. Research on reservoir forming. And evaluation of hydrocarbonresources by using genetic method.Through the research of sedimentary facie， rock type and geochemicalbehavior,It is point that the chief source rock of northwestern margin of Ordos Basinincluding coal measure strata in upper Paleozoic and and Pingliang Formation inLower Paleozoic. the other source rock is Majiagou Formation of Ordovician. thekerogen type of Pingliang Formation and Majiagou Formation is I～II1, Theevolutionary phase is medium abundance overcure dry gas phase，The coal series darkmudstone and coal seam in upper Paleozoic, organic carbon content is high, Thelimestone of open marine platform in Majiagou Formation and the dolomite ofplatform margin slope reservoir in Pingliang Formation are the chief reservoir rocksin Lower Paleozoic of northwestern margin of Ordos Basin.The main is thelimestone of Majiagou Formation.The reservoirs mainly have dolomite reservoir，karst pore-cave reservoir and reef-bank reservoir. According to the accumulationfactors and their matching relationship in time and space, the play model in westernmargin of Ordos basin was divide into three types:1.“self-generation andself-accumulation” gas accumulation model,2.“above-generation andbelow-storage”gas accumulation model,3.“mix-generation”(“self-generation andself-accumulation” gas accumulation model and “above-generation andbelow-storage” gas accumulation model) gas accumulation model.Finally,thoughthe evaluation of oil and gas resources. We can reach a conclusion that the quantity of oil and gas resources of the northwestern margin are abundant.