Two- and Three-Phase Compositional Modeling of CO2 Injection with CPA Equation of State

January 31, 2011

Time: January 31, 2011
Lecturer: Prof. Abbas Firoozabadi
Reservoir Engineering research Institute (RERI) and Yale University
Venue: Pfaffenwaldring 61, Raum U1.003 (MML), Universität Stuttgart
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Injection of CO2 in hydrocarbon reservoirs and in saline aquifers may require models based on higher-order numerical methods. For such applications, cubic equations of state (EOS) and Henry's law may not be sufficiently accurate. The association of water molecules and cross-association of water and CO2 molecules affect the phase behavior of CO2-water mixtures and requires a cubic-plus-association (CPA) equation of state (EOS). In this presentation we first present non-equilibrium mixing in open space in a cell at laboratory scale and show that diffusion across the interface and convection in the bulk phases describe the unstable gravity effect.In the second part of the presentation we describe a new higher-order three-phase compositional model with the following features. The mixed hybrid finite element method is used to simultaneously solve for the pressure and the total volumetric flux, and a discontinuous Galerkin approximation is used to update mass transport. We use an efficient solution scheme for the non-cubic equation of state and the two-dimensional bisection method for robust phase amount computations. New approaches are implemented for efficient computations of phase-splitting. We present a number of numerical examples with broad applications in improved oil recovery and for CO2 sequestration. We conclude that the CO2 injection in the subsurface for both improved recovery and sequestration may be more promising than the prevailing belief in the literature.
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