Study On Characteristics And Lower Limit Of Physical Property Of Tight Reservoir Of Benxi Formation In The Shaan 295 Well Area Of Ordos Basin

Tight sandstone gas is the unconventional oil and gas with the highest recoverable degree in the existing technology,and it is also an important component of oil and gas resources.Ordos Basin is an important tight sandstone gas producing area in China.Sulige and other large gas fields have been discovered.The main gas producing intervals are Shanxi Formation of Permian and Box 8 of Lower Shihezi Formation,while Benxi Formation of Middle Carboniferous is also a tight reservoir.However,the exploration degree is relatively low,natural gas shows more and industrial gas wells are less.At present,only 64 of 146 wells in the basin have been tested for gas,and only 64have been industrialized.Airflow.Therefore,it is of great significance to study the characteristics and lower limit of physical properties of tight reservoirs in Benxi Formation for deepening the understanding of reservoirs geology in Benxi Formation and providing reference for the selection of favorable exploration zones.Through sample analysis and geological analysis,this paper analyzed the reservoir characteristics and diagenetic evolution of Benxi Formation.On this basis,the lower limit of physical properties of tight reservoir of Benxi Formation was studied by combining physical simulation experiment with numerical simulation experiment.The results show that the reservoir of Benxi Formation in Ordos Basin is generally compact,the rock type is mainly quartz lithic sandstone,the feldspar content is very low,and the secondary pore is relatively developed.According to the stress analysis of natural gas filling process,it is found that the main driving force of natural gas to tight reservoir is gas pressurization,hydrostatic pressure and capillary pressure as the main resistance.Physical simulation experiments show that the higher the porosity,the smaller the resistance of natural gas to tight reservoir filling,and vice versa,the larger the porosity is,the porosity is 11.47%,the critical filling pressure is 310×10^-3 MPa,the porosity is10.31%,and filling is imminent.The boundary pressure is 530×10^-3 MPa,the porosity is 8.49%,and the critical filling pressure is 780×10^-3 MPa.The results of numerical simulation show that the lower limit of physical properties that natural gas can not be filled into tight reservoirs is 1.02%porosity and 0.02×10^-3?m² permeability,and there are differences in different depths.The burial depths of 2100 m,2400 m,2800 m and3500 m correspond to the critical porosity of 11.2%,6.5%,4.2%and 0.9%and the respectively.Therefore,for different burial depth areas of Benxi Formation,the lower limit of physical properties of tight gas exploration,i.e.exploration scope,should be considered separately.