Numerical Simulation of CO2 Sequestration in Aquifers at Nonisothermal Conditions Using Fully Unstructured Dynamic Adaptive Gridding and Higher-Order Discretization

Summary We have advanced numerical simulation of carbon dioxide (CO2) sequestration in subsurface aquifers by incorporating various nonisothermal effects in mass and heat transport. The 11th SPE Comparative Solution Project in the field scale in 2D is selected as an example in this work. We formulate the two-phase, two-component, nonisothermal model describing the system consisting of water (H2O) and CO2. The discretization is based on the combination of the mixed-hybrid finite element method (MHFEM) for pressure and energy equations and the discontinuous Galerkin (DG) method for the species transport. The dynamic adaptive gridding with two and six levels of refinements in 2D is used to provide high resolution and to increase the computational efficiency. Nonisothermal models provide more accurate predictions in the vicinity of the injection wells where the temperature changes significantly with the injection of cold fluid and sinking of CO2 is more pronounced. The heat capacity of the reservoir rock and water limits the reach of the temperature front; the isothermal and nonisothermal models give similar results farther from the injection well where the gravity fingers develop as a result of increase in density of water with dissolved CO2. We also demonstrate the effect of CO2 viscosification in the reduction of CO2 spreading and prevention of reaching the fault zone and leaking.