Injectivity of a gas well under different modes of reservoir fluid displacement

Unsteady gas flow from a vertical well into a water-saturated reservoir is investigated within the axisymmetric formulation of the filtration problem. The influence of the shape of the gas-saturated zone on the injectivity coefficient of the well, i.e., on the maximum rate of gas injection, is estimated. It isshown that the well skin factor can be decomposed into two multipliers, the first of which – the shape parameter – characterizes the shape of the gas plume, and the second describes the growth of the skin factor with time. With the help of numerical modeling of filtration, diagrams describing the dependence of the noted multipliers on the similarity parameters have been constructed. It is shown that gas injection at any values of parameters and shapes of gas-saturated regions is accompanied by injectivity growth with time, and the maximum values of injectivity coefficients are reached at high rates of gas injection. For this limiting case, the relationship for the skin factor is explicitly obtained. The results of the study can be useful for determining effective ways of application of Carbon Capture, Utilization and Storage technology.