A Scalable Parallel Compositional CO2 Geological Storage Simulator

Abstract Storing CO2 in deep saline aquifers is one of the most promising methods for achieving carbon neutrality. Numerical reservoir simulation can assist researchers and engineers in comprehensively understanding and effectively managing the CO2 sequestration process, thereby ensuring its safety and effectiveness. Most of the current CO2 storage simulators use a CO2-brine fluid model which only has water and CO2 components. When impure CO2 is injected, the subsurface fluids form a multi-component gas-brine system, whose phase behavior cannot be accurately described by a CO2-brine fluid model. The current gas-water compositional models include a very limited number of gas components. In this study, we developed a fully implicit parallel CO2 storage simulator for distributed memory computers based on our in-house parallel platform. This simulator uses a fully compositional fluid model which treats water as a component and incorporates it into phase equilibrium calculations. The gas components include not only CO2 but also other common components in captured impure CO2, such as CH4, N2 and H2S. The cubic Peng-Robinson equation of state was used to predict the fugacity and PVT properties of CO2-rich phase. The fugacity in aqueous phase and brine properties are calculated by Henry's law and empirical correlations respectively. Meanwhile, the effect of dissolved gas influence on aqueous viscosity is considered which is ignored by current commercial simulator. The finite difference (volume) method is applied to discretize the compositional fluid model. Numerical experiments show that our simulator is scalable, stable and validated to simulate large-scale CO2 storage problems with hundreds of millions of grid blocks on a parallel supercomputer cluster.