Cubic Equation of State

A Review of Phase Behavior Mechanisms of CO2 EOR and Storage in Subsurface Formations

“…Three-phase VL CO 2 L HC equilibria are very common in the process of CO 2 flooding and CO 2 storage in depleted oil reservoirs. As noted by Pan et al and Li, three concerns must be addressed in order to build a robust three-phase VL CO 2 L HC equilibrium calculation algorithm. First, good initial values of the equilibrium ratios are necessary, especially the one related to the appearance of the second liquid phase.…”

“…First, good initial values of the equilibrium ratios are necessary, especially the one related to the appearance of the second liquid phase. To solve this problem, a robust and efficient stability test must be developed . Second, the two-phase equilibrium calculation results must be checked to prevent yielding the trivial two-phase equilibrium and thereby leading to a trivial three-phase equilibrium.…”

“…Second, the two-phase equilibrium calculation results must be checked to prevent yielding the trivial two-phase equilibrium and thereby leading to a trivial three-phase equilibrium. This requires one to conduct two-phase flash calculations with different initial equilibrium ratios to yield the two-phase equilibrium with the minimum Gibbs free energy. , Third, a hybrid algorithm is required to ensure the robustness of the algorithm. This issue could be solved by using different equation-solving and optimization methods …”

“…This requires one to conduct two-phase flash calculations with different initial equilibrium ratios to yield the two-phase equilibrium with the minimum Gibbs free energy. , Third, a hybrid algorithm is required to ensure the robustness of the algorithm. This issue could be solved by using different equation-solving and optimization methods …”

“…The most important reason is that four-phase equilibrium calculations can be much more complicated than those for the two-phase and three-phase equilibria. As noted by Li, there are four possible types of three-phase equilibria and six types of two-phase equilibria that may appear during the four-phase equilibrium calculations. Although thermodynamic models for four-phase VL CO 2 L HC S equilibrium calculation are still missing, several four-phase VL CO 2 L HC A equilibrium calculation algorithms have been proposed in recent years.…”