Research on Capacity and Influencing Factors of Underground Gas Storage Transformed from Oil Reservoirs

After more than two decades of development, there have been 27 underground gas storage at home. The peak load regulation capacity reaches 14.7 billion m3, occupying 4.4% of the domestic natural gas consumption. The peak load regulation of gas capacity is less than a quarter of the mean level of developed countries around the world. At present, the domestic gas storage are mainly gas reservoirs, accounting for over 80%. Oil reservoirs are transformed into gas reservoirs, which can not only quickly improve China’s peak load regulation capacity for gas storage, but realize the displacement of reservoir oil, so as to increase oil recovery. Combining with interior core test with simulation, this paper artificially simulated the impact of reservoir physical property, gas injection displacement pressure, gas injection displacement direction and gas injection speed on the displacement efficiency of oil reservoirs during the operation of gas storage to analyze the gas-drive reservoir extension mechanism. The experiment confirmed that the higher the reservoir permeability was, the higher the oil displacement efficiency of gas injection was and the more easily the gas reservoir expanded; the higher the injection pressure was, the higher the oil displacement efficiency of gas injection was and the more easily the reservoir capacity formed; the more single the reservoir fluid was, the more easily the gas reservoir expanded; the multi-directional gas injection of oil reservoirs was conductive to increasing the reservoir capacity through gas injection displacement; slow gas injection was beneficial to expanding reservoir capacity through oil displacement. The research results not only have directive significance to the capacity parameter design of underground gas storage transformed from oil reservoirs, and the study of increasing the peak load regulation capacity of gas storage, but have a certain significance to the research on improving the recovery efficiency through gas injection displacement.