Gas Well Injectivity in Different Regimes of Reservoir Fluid Displacement

The unsteady gas flow from a vertical well to a water-saturated reservoir is investigated in the case of an axisymmetric porous medium. The influence exerted by the shape of the gas zone on the well injectivity index, i.e., in fact, on the maximum gas injection rate, is estimated. It is shown that the well skin factor can be decomposed into two factors, one of which, the shape parameter, characterizes the gas plume shape, and the other describes the growth of the skin factor over time. Numerical simulation of the flow is used to construct diagrams describing the dependence of these factors on similarity parameters. It is shown that, for any parameter values and any gas zone shape, gas injection is accompanied by an increase in injectivity over time and maximum injectivity is reached at high gas injection rates. A skin factor relationship is explicitly obtained for this limiting case. The results of this study can be useful for determining effective ways of applying the Carbon Capture, Utilization, and Storage technology.