Two- and three-hydrocarbon phase streamline-based compositional simulation of gas injections

Up to three three-hydrocarbon phases can develop during gas flooding of oil reservoirs at relatively low temperatures. Very few reservoir simulators and none of the published streamline simulators can handle three-hydrocarbon phases. In this work, we have developed a four-phase (including water) compositional streamline module that works with an existing finite-difference simulator to study gas injections. Gravity effects are added using an operator splitting technique. TVD schemes are implemented to construct the numerical solution along streamlines for reducing the impact of numerical dispersion. Two- and three-hydrocarbon phase simulations of gas injections in quarter five-spot models have been demonstrated using this simulator. Breakthrough recovery efficiency increases with the viscous-to-gravity ratio in the range of 1–100. Gas injection simulation of the reservoir oil indicates that three-hydrocarbon phases exist only near the gas–oil displacement front. The gas phase is present in a few grid blocks while the second liquid phase is present in many grid blocks, under the conditions studied.