Feasibility of Using Carbon Dioxide as Cushion Gas in Underground Natural Gas Storage
CO2 is used as a cushion gas for underground natural gas storage reservoirs,and during the operation of the gas storage,unreasonable injection and production parameters and other factors lead to the problems of transitional mixing between CO2 and natural gas and a low natural gas recovery rate.The comparison of physical properties of CO2 and CH4,and the visible phase reactor were car-ried out to demonstrate the feasibility of CO2 as cushion gas.A two dimensional model of the gas storage reservoir was established to simulate the process of CO2 as cushion gas injection and production,and the formation parameters and operating parameters affecting the mixing degree of CO2-CH4 were analyzed.The results show that the proportion of CO2 cushion gas is not more than 20％,the molar content of CO2 in produced gas is not more than 3％,the mixing degree of CO2-CH4 and the average reservoir pressure drop are small.The higher the permeability,the more CO2 cushion gas carried by working gas recovery,the smaller the proportion of actual CO2 cush-ion gas,and the insufficient CO2 cushion gas to provide"power"for working gas recovery.Porosity has little effect on the mixing de-gree of CO2-CH4.Reasonable control of gas production rate can effectively inhibit the development of mixed zones.In other words,the gas production rate should be increased at the peak of gas consumption,and the gas production rate should be reduced at the trough to ensure the minimum gas consumption standard.The research results provide theoretical guidance for the engineering practice of using CO2 as cushion gas in underground natural gas storage.
carbon dioxide cushion gasgas mixing experimentproperty differencesmixing zone
万方数据
维普
