Multiphase Equilibrium Calculations with Gas Solubility in Water for Enhanced Oil Recovery

In this thesis, we have developed a robust algorithm for three phase compositional simulation of gas injection (especially CO2) in the presence of water. In this work, Henry’s law is applied to calculate component fugacities in the aqueous phase, while an equation of state (EOS) is used for the hydrocarbon vapor and liquid phases.

The basis of the algorithm is stability analysis in combination with phase split calculations. The stability analysis and phase split kernels can be framed as optimization problems. Specifically, stability analysis involves locating the minimum of the tangent plane distance function. The phase split calculation seeks to find the minimum Gibbs free energy of the system.

Successive substitution iteration method, Newton’s method and Trust Region method are applied to ensure robust and efficient computations. We tested two-phase cases and three-phase cases, and compared results with WinProp in CMG. Complex three-phase cases were also tested and phase diagrams were generated to verify our algorithm.