Numerical simulation-based correction of relative permeability hysteresis in water-invaded underground gas storage during multi-cycle injection and production

By conducting relative permeability experiments of multi-cycle gas-water displacement and imbibition on natural cores, we discuss relative permeability hysteresis effect in underground gas storage during multi-cycle injection and production. A correction method for relative permeability hysteresis in numerical simulation of water-invaded gas storage has been worked out using the Carlson and Killough models. A geologic model of water-invaded sandstone gas storage with medium-low permeability is built to investigate the impacts of relative permeability hysteresis on fluid distribution and production performance during multi-cycle injection and production of the gas storage. The study shows that relative permeability hysteresis effect occurs during high-speed injection and production in gas storage converted from water-invaded gas reservoir, and leads to increase of gas-water transition zone width and thickness, shrinkage of the area of high-efficiency gas storage, and decrease of the peak value variation of pore volume containing gas, and then reduces the storage capacity, working gas volume, and high-efficiency operation span of the gas storage. Numerical simulations exhibit large prediction errors of performance indexes if this hysteresis effect is not considered. Killough and Carlson methods can be used to correct the relative permeability hysteresis effect in water-invaded underground gas storage to improve the prediction accuracy. The Killough method has better adaptability to the example model.