Tight Sandstone Gas Reservoir-forming Characteristics And Favorable Zones Prediction Of Upper Paleozoic In Linxing Area

The basic characteristics of hydrocarbon geology of Upper Paleozoic source rocks and tight sandstones in Linxing area are thoroughly understood.Based on the theories of sedimentology,reservoir geology and petroleum geochemistry,the characteristics of hydrocarbon source rocks and reservoirs are studied by means of detailed observation and description of core and logging data and laboratory experimental analysis methods.The results are as follows.Based on the quantitative evaluation of source rocks by logging data,the geochemical characteristics of source rocks are combined.The results of application of?Log R method in the study area show that the highest thickness of high quality source rocks is 46.7m,the minimum thickness is 2.3m and the average thickness is 14.8m,which is the best development in the five sections.The average thickness of source rocks in Tai 2 and Ben 1 are14.9 m and 16.8 m,respectively.The average thickness of high-quality source rocks in Tai 1is 12.2 m.The development of high-quality source rocks in four sections is very good.The results of thin section identification and X-ray diffraction analysis show that lithic sandstone is the main rock type of the Upper Paleozoic tight sandstone in Linxing area,followed by feldspar lithic sandstone and lithic feldspar sandstone,containing a small amount of lithic quartz sandstone,feldspar quartz sandstone and quartz sandstone.The main clastic components are quartz,followed by lithic debris and feldspar,with a small amount of fillings.Clay minerals mainly include illite,kaolinite,chlorite,illite/montmorillonite and green/montmorillonite.Coarse and medium-grained sandstones are the main types of sandstones in the study area,followed by fine-grained sandstones,which contain a small amount of giant-grained sandstones.The formation is compact and weathering alteration is deep.Pore cementation is the main type of cementation,and a small amount of pore-base cementation is developed.The main sorting methods are medium and medium-poor,while a few are poor.The roundness of grinding is mostly subcircular and a small amount is subangular.Most of the support types are pore and particle support,and most of the contact modes are concave-convex contact.The reservoir space of the Upper Paleozoic tight sandstone reservoirs in Linxing area is mainly residual intergranular pore,intragranular dissolution pore,dissolution intergranular pore and intergranular pore,with a small number of micro-fractures.The overall pore structure is characterized by small throat,differential separation and high displacement pressure.According to the comprehensive porosity and permeability analysis,the reservoir physical properties of 2 sand groups in Tai 2,2 sand groups in Shan 2,3 sand groups in Shan2,1 sand group in Tai 1,2 sand groups in Shan 1,1 sand group in Shan 1,1 sand group in Shan 2,1 sand group in Tai 2 and 1 sand group in Shan 1 are better.The main reservoir-forming assemblages are self-generation and self-storage,up-generation and down-generation and down-generation and up-storage.The petrological characteristics,pore types and structural characteristics of the Upper Paleozoic reservoirs in Linxing area show strong horizontality.