Research On Sedimentary Facies And Reservoir Characteristic Of Chang3 And Chang4+5 Member In Jiyuan Area

The thickness of Chang3 and Chang4+5 member of Yanchang formation is from 170m to 210m in Jiyuan Area. In the process of formation analysis ,the marker formation must be ascertained frist, Based on this, the stratum is divided into 5 pieces of member following the principles of formation classification.Based on the sedimentary source direction of the entire basin, heavy and light minerals are used to analyse sedimentary source direction of Chang3 and Chang4+5 formation, In Jiyuan area. Research show that the main formation source of Chang3 and Chang4+5 formation come from the eastnorth of basin.The main sediment was delta facies in Jiyuan area. Based on sedimentology and well logging sign, author think that Chang3 and Chang4+5 member is composed of lake and delta sedimentary system , further researching those sedimentary system ,the formations can be divided into 2 types sediment subfacies and 5 types sediment microfacies ,the sedimentary modes have been put forward.Based on the observation from cast thin section and scanning electron microscope in Jiyuan area, it is held that, chang3 and chang 4+5 reservoir are mainly composed of grey feldspathic sandstone. Filling material mostly include kaolinite. According to porosity type, the intergranular porosity predominate. On the basis of porosity and permeability data, the results show that sandstone reservoir in this area are the typical low porosity and typical low permeability. The research of the clastic reservoir indicates that the dominant diagenesis types are compaction, cementation, replacement and dissolution in the area. These diagenesis process influence pore development of reservoirs.On the basis of the analysis, the favor oilcat area chang3 and chang 4+5 sandstone reservoir is predicted.