Reservoir Characteristics And Diagenetic Evolution Of Silurian Xiaoheba Formation In Southeastern Sichuan

As a important type of unconventional energy,the exploration and development of tight sandstone oil and gas is of great economic value.The Xiaoheba formation of lower Silurian in Southeastern Sichuan is a set of typical marine tight sandstone deposits,which has a good oil and gas prospect.In this paper,the tight sandstone of Silurian Xiaoheba formation in the southeast of Sichuan is selected as the research object,and the detailed petrology study is carried out.The characteristics of sandstone reservoir are summarized and sorted out by combining with rock thin sections,cathodoluminescence,scanning electron microscopy and physical property data.Sandstone types are mainly feldspathic quartz sandstone,followed by lithic quartz sandstone and lithic sandstone.On the whole,the grain size of rock is relatively fine,main of which is very fine sand-coarse sand level.The sandstone reservoir of Xiaoheba formation is a typical tight sandstone reservoir with poor physical properties.The porosity was mainly distributed in 1%?6%,with an average of about 2.5%.The permeability was mainly distributed in 0.01?1m D,with an average of about 0.12 m D.The main types of storage space are micron-scale intergranular dissolution micropores,followed by micron-nanoparticle dissolution micropores and nanoscale intergranular dissolution micropores.The main types of diagenesis are compaction,cementation and dissolution.Compaction is the main type of diagenesis.The development of relatively high-quality reservoir in Xiaoheba formation in the study area is controlled by several factors.The sedimentary environment determines the rock types,physical characteristics.Diagenesis determines the degree of pore secondary transformation,especially dissolution,which plays a positive role in secondary transformation and reservoir physical property improvement.Based on the main parameters of reservoir prediction,the distribution characteristics of sedimentary microfacies and diagenetic facies during sand deposition of the Xiaoheba formation are taken into consideration when the favorable reservoir area of the xiaoheba formation is predicted,and the comprehensive prediction is made in combination with the physical distribution and lithological changes of the reservoir.The relatively high-quality reservoirs in the study area are mainly distributed in compaction-dissolution facies and clay-based hetero-compaction facies,and the corresponding sedimentary microfacies are mainly distributary interbay,sandbank and sheet sand,which are mainly distributed in the areas of Shuangliuba-Lengshuixi,Haokou-Huangcaochang,Rongxi and Hongyanxi.