The Study On Microscopic Pore Structure And Percolation Characteristics Of Tight Sandstone Gas Reservoirs

Tight sandstone gas reservoirs are typical unconventional natural gas reservoirs,and the abundant reserves are the focus of China's large-scale commercial development.Because of the dense features of low porosity and low permeability,special mining techniques are needed to obtain economical scale development.The reservoir microscopic pore structure is one of the key factors for evaluating reservoir quality,influencing flow characteristics and optimizing the mining industry.Exploration and development practices have proved that tight sandstone gas reservoirs have unique pore evolution and genetic characteristics.So this paper focus on the He8 and Shan1 section of the Shan234-235 well zone in the east area of Sulige.Combined with basic geological data and microscopic quantitative experimental data,the microscopic pore structure of tight sandstone gas reservoirs and their influence on gas flow characteristics are quantitatively analyzed,and the accuracy of reservoir quality evaluation and the optimization of development technology are promoted.We can get these follow conclusions:(1)In the genesis aspect,pore types are mainly rock debris dissolved pore,intercrystalline pore,each of these account for more than 2/5,there are little intergranular pore,feldspar dissolved pore,and tuffaceous dissolved pore.(2)According to the conventional mercury injection experiment,The study reservoir including four types of pore structure,each type of pore structure of reservoir space has some differences,and its reservoir permeability is worse.The flow characteristics of tight sandstone reservoirs is controlled by the pore throat structure.(3)The number of effective throat per unit volume and the effective pore throat volume affect the reservoir storage capacity;the effective throat volume per unit volume and the effective number of throats affect the degree of reservoir connectivity,which in turn restricts the reservoir flow characteristics.(4)The movable fluid's saturation is low,it concentrated in the V and IV class.Gas-water have low relative permeability,narrow extent,and strong interference.The structure of microscopic pore control the fluid flow characteristics within the reservoir.(5)Based on the comprehensive micro-experiment and mining characteristics,the Shaan 234-235 well area includes four types of reservoirs: high-yield stable,low-yield stable,low-yield,and non-industrial productivity.Reservoir quality stems from the difference in strength of diagenetic transformation.