The Research On Characteristics Of Chang8 Oil Reservoir Of The Triassic Yanchang Formation In Xunyi Area,Ordos Basin

Chang8 is the one of the main oil reservoirs of YanChang formation in Ordos basin,the research on Chang8 reservoir in Xunyi area of Weibei uplift in the south of Ordos basin is still at a relatively low level.Although the predecessor had done some studies what are more scattered on Chang8,there have been short of systemic research.Based on the petroleum geology and reservoir sedimentology,making comprehensive utilization of kinds of analysis and testing experiments,find out about the petrologic characteristics of reservoir,microscopic pore structure characteristics,physical characteristics,the reservoir heterogeneity and diagenesis and other aspects of Chang8 reservoir in Xunyi area,Summarizing the key factors affecting the reservoir properties,eventually,there will be the classification and evaluation on Chang8 reservoir.The main types of the sedimentary facies of Chang8 in Xunyi area are delta front sub-facies and shallow lake sub-facies,and the two underwater distributary channels are almost distribute from North to South with stable sands distribution,sand-shale alternating layer in vertical,which is main type sand in Chang8 reservoir.The Chang8 reservoir in Xunyi has the feature with mixing source,Chang8 reservoir sandstone are mainly lithic feldspathic sandstone and feldspar lithic sandstone,the content is roughly the same between of quartz,feldspar,and detritus,textural and compositional maturity are both low,with the low porosity and permeability.The average content of interstitial material is 18.16%,including carbonate cement,clay mineral,siliceous cement.The Chang8 reservoir with strong heterogeneity,and heterogeneity in Chang82 is stronger than Chang81.The tight Chang8 reservoir in Xunyi area,the contact among grains can be classified as serrated and linear.The dissolved hole and residual intergranular are main pore space of Chang8 reservoir,microcrack and intercrystalline pore are more less.thin throat is the main types.necking throat and curved lamellar throat are main throat types,there are big differences of connectivity of all throat,what results the strong textural heterogeneity of pore throat.The ? type is main capillary pressure curves with a few III type.The Chang8 reservoir diagenesis in late diagenesis stage A,,the pore decreased by 59%due to the compaction and pressure-solution,because of carbonate cement,clay cement and siliceous cement,the pore decreased by 38%,dissolution and fracture is good to reservoir which could improve the seepage capability of reservoir.Synthesizing the relevant characteristic parameters about reservoir,the Chang8 reservoir can be classified by five kinds of diagenesis facies.Tectonism,sedimentary facies,diagenesis and pore throat are main aspects which had effect on Chang8 reservoir,the physical property of Chang81 is better than Chang 82 as a whole.There are four types reservoir of Chang8 in Xunyi area,and type ? and ?are more developed,furthermore,the type II has better physical property which has big significance to guiding the exploration exploitation in practical work,and it is more developed in Chang81,distribution also increased is obcious.