Effect of Implementing Three-Phase Flow Characteristics and Capillary Pressure in Simulation of Immiscible WAG
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The effect of including a three-phase representation of the flow parameters and capillary pressure has been investigated using a black oil simulator. The simulation approaches include the complexity of three-phase flow, relative permeability hysteresis, dynamic phase trapping functions and capillary pressure. A WAG simulation case was used to study the effect of three-phase flow parameters and capillary pressure on the size of the three-phase zone, breakthrough time of the injected fluids and oil recovery. Three-phase flow WAG processes are characterised by lower relative permeability of the injected fluids, because of flow path hysteresis and trapping of phases. It is important to incorporate these effects to have a correct description of the physics of multi-phase flow. The results from this study showed that the size of the three-phase zone was considerably larger when a three-phase description of the flow was implemented. The reduced relative permeability of gas and water in the three-phase zone leads to slower segregation of gas and water. The breakthrough time of gas and water was delayed and the oil recovery was increased when hysteresis and trapping functions were included. Including capillary pressure seems to further delay the breakthrough of the injected phases and the result is higher oil recovery. When including capillary pressure effects on the relative permeability, the three-phase zone was further extended and the oil recovery was increased. These studies show the importance of using a more detailed fluid flow description in simulation of immiscible WAG processes.