​Abstract: Accurate phase behavior modeling of hydrocarbon and aqueous mixtures plays a critical role in simulation of compositional flow in subsurface reservoirs, such as miscible flooding and CO2 sequestration. In the past four decades, PT flash calculation has been well developed and become the most prevailing algorithm to calculate phase stability and equilibrium amounts and compositions. However, as research interests move to more complicated reservoir fluids, some inherent drawbacks of the PT flash formulation show up and recent research focuses on a promising alternative called VT flash calculation. In the first part, we use VT flash calculation to model phase behaviors of hydrocarbon mixtures. Starting from the second law of thermodynamics, a dynamical model, together with a thermodynamically stable numerical algorithm, is developed to calculate equilibrium phase amounts and compositions which takes into account the capillary effect on phase behaviors of reservoir fluids.In the second part, we extend VT flash calculation to model phase behavior of aqueous mixtures. A salt-based Cubic-Plus-Association equation of state is proposed to model CO2 solubility behavior in single and mixed-salt solutions. This could help us evaluate CO2 sequestration potential in real saline environments through solubility trapping. At the end, we develop an improved two-phase VT-flash compositional simulation algorithm. We apply the multilayer nonlinear elimination method to remove locally high nonlinearities that slows down the convergence. To further improve the computational efficiency, a modified shadow region method is tailored to VT flash calculation and relax the assumption of the original version. Finally, the robustness and efficiency of the proposed compositional flow algorithm is significantly improved and we use it successfully simulate a number of numerical examples with and without gravity.

Location: https://kaust.zoom.us/j/99271514163

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• CONTACTYiteng Li
• EMAILYiteng.Li@kaust.edu.sa