Chemical Reaction Modeling in a Compositional Reservoir-Simulation Framework

Abstract

Abstract The treatment of chemical reactions is required for many simulation applications including in-situ conversion and geological carbon storage. In this work we present a strategy for incorporating chemical reaction modeling into an existing EOS-based compositional simulator. Both kinetic and equilibrium, as well as heterogeneous and homogeneous chemical reactions are included in the implementation. As a first step, the method entails the construction of the Jacobian matrix for a compositional system that does not include any chemical reactions. Then, linear transformations are applied at the level of the Jacobian matrix to account for reaction terms. These transformations act to convert the initial component-based Jacobian matrix to a matrix based on element balances. In so doing, they eliminate all equilibrium reaction rates and reduce the number of kinetic reaction terms that appear. A specialized treatment for handling aqueous-phase components when the aqueous phase disappears (or reappears) is also introduced. Numerical results are presented for CO2 sequestration and in-situ conversion problems. For carbon storage simulations, results demonstrate the robustness of our formulation, even when the aqueous phase disappears in multiple grid blocks. For an idealized in-situ conversion problem, simulation results demonstrate the performance of our modeling strategy over a broad range of Damhkoler number.