Research On Jurassic Reservoir Characteristics Of Xishanyao Formation In Baijiahai Bulge Cai31 Area Of Junggar Basin

Tight-gas sandstone reservoir is one of the hot research fields at home and abroad,at present,tight sandstone gas is found in all major basins in China.In particular,two small tight sandstone gas reservoirs were discovered in the Cai 31 area of the Baijiahai bulge in the Junggar Basin.The discovery of tight sandstone gas indicates that the exploration potential of tight sandstone gas in the Junggard Basin is huge.This paper takes the reservoir of Xishanyao Formation in Cai 31 area of CaiNan Oilfield as the target layer.Taking sedimentary petrology and reservoir geology as a theoretical guide,Comprehensive use of core,logging,casting thin sections,scanning electron microscopy,geochemistry,and experimental analysis and other data,from the microscopic and macroscopic perspective of the reservoir,comprehensive study on petrological characteristics,physical properties and diagenesis of reservoirs,analysis of main controlling factors of tight reservoirs,and comprehensive evaluation of reservoirs.The Xishanyao Formation in the study area has developed a set of shallow lakes and meandering river delta deposits,The grain size of the sediment is generally fine,the lithology is mainly medium-fine sandstone,fine sandstone and siltstone.According to the data of 13 wells in Xishanyao formation in the study area,the reservoir rock types of Xishanyao formation are mainly feldspar lithic sandstone and lithic sandstone.The content of cuttings is high,the diagenesis types in the study area are mainly compaction,cementation and metasomatism,dissolution and dissolution.According to the criteria and basis of division of clastic rock diagenetic stage,The diagenetic stage of reservoir can be divided into early diagenetic stage A stage,early diagenetic stage B stage and middle diagenetic stage A.According to the occurrence and dissolution,the reservoir space of the study area is divided.The study area is mainly composed of residual intergranular pores,intra-granular dissolution pores and intergranular dissolution pores.Through the analysis of high pressure mercury experiment,Poor pore throat sorting-medium,Through the physical property experiment statistics of more than 500 samples in the study area,The results show that the average porosity of reservoir in the study area is 7.36%,average permeability is 0.55×10^-3?m².The whole reservoir belongs to low porosity and permeability reservoir.The development of sandstone reservoirs in the study area is influenced by many factors,statistical charts based on oilfield data and previous research data show that:the main factors affecting reservoir physical properties are sedimentary microfacies,diagenesis and tectonic factors,each of these factors has a positive or negative impact on the reservoir.Through the above research,the reservoir can be divided into four types of reservoirs.Type I reservoirs are good reservoirs.Type II reservoirs are effective reservoirs.Type?reservoirs are general reservoirs.Type IV reservoir is non-reservoir.