Four-Component Gas/Oil Displacements in One Dimension: Part II: Analytical Solutions for Constant Equilibrium Ratios

In this paper we derive closed form solutions for composition paths (integral curves of eigenvectors) for three- and four-component systems with constant equilibrium K-values, and we report example solutions that describe gas injection processes. Extensions to systems with an arbitrary number of components are discussed.Author for correspondence: e-mail:wangy2@bp.com     

Four-Component Gas/Water/Oil Displacements in One Dimension: Part III,Development of Miscibility

The structure of the system of conservation laws in fully compositional three-phase, four-component flow is examined for the first time. Two of the eigenvalues can be found analytically for this flow regime, regardless of the equation of state used to model the phase behavior. A cubic equation of state is used to calculate the gas/oil phase behavior and Henry’s law is used to represent the partitioning of hydrocarbons between the hydrocarbon and water phases. Sample analytical solutions are found for Riemann problems modeling the injection of carbon-dioxide and water into an oil reservoir. Finally, the structure of the solutions at the minimum miscibility pressure (MMP) for the hydrocarbon system is studied. We show that when water is injected simultaneously with gas at the MMP, multicontact miscible displacement of the oil by the injected gas develops only if the fraction of water in the injected fluid is below a critical value. For water fractions above the critical value, water flowing at a high velocity forces the composition path of the solution to remain in the three-phase region in which two hydrocarbon phases are present. We study both condensing and vaporizing gas drives to demonstrate that this result is general.     

Near-critical CO2 liquid–vapor flow in a sub-microchannel. Part I: Mean-field free-energy D2Q9 lattice Boltzmann method

The mean-field free-energy based lattice Boltzmann method (LBM) is developed for the calculation of liquid–vapor flows in channels. We show that the extensively used common bounceback boundary condition leads to an unphysical velocity at the wall in the presence of surface forces that arise from any local forces such as gravity, fluid–fluid and fluid–solid interactions. We then develop a mass-conserving velocity-boundary condition which eliminates the unphysical velocities. An important aspect of the overall LBM model is the inclusion of the correct physics to simulate different wall wettabilities and dynamic contact lines. The model is applied to static and dynamic liquid–vapor interfacial flows and compared to theory. The model shows good agreement with three well established theories of contact line dynamics.