Gas-water relative permeability variation in multi-cycle injection- production of underground gas storage in flooded depleted gas reservoir

The percolation characteristics of gas-water (two phase) interactive displacement on the gas-water transition zone of the injection-production process have a direct impact on the injection-production capability and storage capacity of the underground gas storage. It is necessary to make experiments on gas-water relative permeability variation in multi-cycle injection-production to identify the gas/water distribution and migration rules during interactive displacement on the gas-water transition zone. The results show that, the gas relative permeability increases, and the water relative permeability decreases after the multi-cycle gas-water interactive displacement, resulting in more severe gas fingering and an increase in the residual water. In addition, with the increase of injection-production cycle, residual gas saturation of gas-water relative permeability increases in the two-phase area, coupling with the residual water saturation itself accounted for the majority, have somehow resulted in the loss of gas storage capacity and active gas quantity. Finally, the bound water has little effect on the gas permeability, while residual gas significantly affects water permeability after the multi-cycle gas-water interactive displacement.