The Charactercteristics Of Reservoirs And Caprocks,and Their Effects On Gas Accumulation In He8 Member From Southern Of The Sulige Gas Field

Based on the observation and analysis of log interpretation data,cores,casting thin sections,cathodoluminescence,scanning electron microscopy and gas testing data,with the combination of images and pore size analysis,permeability and pore pressure experimental data of mercury injection,this paper studies the reservoir sedimentary microfacies type,sandbody distribution characteristics,diagenesis and pore evolution,caprock characteristics and controlling factors of gas reservoir distribution from reservoir in He8 section of Shihezi Formation on the South Sulige Gas field.Reservoir classification and evaluation and"dessert"prediction are has been studied in this paper.The results show that He-8 section mainly develop the of Braided River Delta front sedimentary facies,and the microfacies include the underwater shunt channel,underwater overflow sand and shunt bay.According to the spatial distribution characteristics of sand bodies,the reservoir sand body configurations can be divided into five types:isolated,discrete lateral stacking,undercut lateral stacking,discrete stacking and tight stacking.The isolated sand bodies are mainly distributed in the He8~1-1 section,the lateral sand bodies are mainly distributed in the He8~1-2 and He8~2-1 section,while the stacked sand bodies are mainly distributed in the He8~2-2 section.The rock types of reservoir in the He-8 section of the study area are mainly quartz sandstone,the second of quartz sandstone and the least proportion of lithic sandstone.Sandstone clastic components have the characteristics of high quartz,high rock fragments and low feldspar in general.The pore types of the small layers are mainly secondary dissolved pores and a small number of residual intergranular pores and kaolinite intergranular pores.The types of reservoir diagenesis in the study area are mainly divided into mechanical compaction,cementation and dissolution.Under the casting thinsection and cathode luminescence,three periods of secondary growth of quartz,two-stage calcite cementing filling and multi-stage dissolution of clay minerals were observed.Through the analysis and calculation of pore evolution,it is concluded that the porosity value of mechanical compaction loss in the study area is 27.7%,and the residual porosity after compaction is 13.5%,and the reservoir is basically dense at this time.The porosity value of cementation loss is 11.8%,the porosity is increased by 2.1%,and the porosity value of dissolution increases is 5.6%.Through the comprehensive study of diagenesis and pore evolution,it is shown that the early mechanical compaction and the cementing filling in the early and late phase two are the main causes of reservoir densification,while the dissolution of two period and the increased pores by authigenic intergranular pore play a certain role in improving the densification of the reservoir.Based on the comprehensive analysis of rock types,pore types and pore permeability on reservoir influencing factors,He-8 segments of the shihezi formation divided into 4 categories.Among them,the characteristics of?and?reservoirs are mainly the development of clastic quartz sandstone and quartz sandstone,the pore combination is intergranular pores-dissolved pores-intergranular pores with better pore-throat connectivity,which is mainly distributed in the He8~1-2 and He8~2-1 section.The analysis of controlling effect of reservoir and caprock characteristics on gas reservoir shows that the high-yield gas wells in the study area are mainly distributed on the underwater distributary channel sand body belt with thicker sand body,higher quartz content,better reservoir physical properties and heterogeneity and better sealing of upper caprock.