Parametric investigations of a modified simultaneous water-alternating-gas injection technique

The energy of reservoirs gets depleted as production continues. The restoration of reservoir energy involves injection of gas and/or water to support reservoir pressure and to provide a sweeping mechanism. Owing to the unfavorable mobility ratio, gas injection alone results in early breakthrough and poor sweep efficiency. Water and gas might be injected alternatively or together to improve the sweep efficiency. These processes improve the sweep efficiency by stabilizing the displacement front. In this article, a reservoir simulation tool was used to study a new design of simultaneous injection process, in which water is injected at the top of the reservoir and gas is injected at the bottom. The difference in water and gas densities provides a sweeping mechanism in which water tends to sweep hydrocarbons downward and gas tends to sweep the hydrocarbons upward. It is expected that the two displacement mechanisms will work to enhance the overall sweep efficiency. The effects of several design parameters on these drive mechanisms are investigated. Such parameters include the mobility ratio between water and oil phases, the viscosity ratio between gas and oil phases, the lateral aspect ratio, the location of the water and gas injection wells, and the injection rates of water and gas.