Chang 4 +5 Reservoir In Ordos Basin Sedimentary Facies And Sequence Evolution

Based on mastering field geological data and digesting the research result of predecessors, by means of comprehensive analysis of field geological of outcrops, observation and description of cores, analysis of drilling and logging data, light and heavy minerals in sandstones, observation and identifyication of thin-sections, the outhor analyze the characteristics of sediment resource, sedimentory systems and sedimentory facies ,the relation to evolution of high resolution sequence stratigraphy and source-reservior-cap assemblages of Chang 4+5 oil-bearing bed of the Upper Triassic Yanchang Formation in Ordors Basin .Research on paleocurrent directions and provenances indicate northeast and southwest direction are the two major sediment resources of Chang 4+5oil-bearing bed.Based on lithology type, sedimentary structure, conformation, paleontology, gyration, combination of lithology and electricity, outcrop in the field, information of testing well and many other methods ,the paper consider that sedimentory systems of Chang 4+5 oil-bearing bed can be devided into alluvial fans,lacustring and delta facies,and further sort them into fourteen subfacies and twenty-four microfacies.According to the stratigraphy development characteristics and regional structure of Chang 4+5oil-bearing bed of the research region,at the same time,considering the sequence development's factor including structure,climate,resource,A/S,cornbining Cross's principle, the outhor devide the Chang 4+5 oil-bearing bed into two short-term base-levels and eleven super-short-term base-levels.