Sequential coupling of thermal module into the reservoir simulator DMflow

Abstract

In this work, we present a numerical framework for non-isothermal compositional compressible gas-water phase flow simulations in non-fractured and fractured porous media on structured and unstructured meshes. The framework is implemented as the simulator “DMflow”. The discretization of the mass conservation equations is based on the fully-implicit scheme and cell-centered finite-volume control-volume distributed multipoint flux approximation (CVD-MPFA) coupled with a lower dimensional fractured model. Similarly, the discretization of the energy equation is also based on the same method. The recent newly developed enthalpy model of CO2−CH4-H2S-N2-O2-brine system (Guo et al., 2019), which is validated within a wide temperature and pressure range, is used in the energy equation. Here, we present a sequential implicit method for the non-isothermal flow and avoid the simultaneous solution of the fluid flow primary variables and the temperature. We present the validation cases where the 1D and 2D results for non-isothermal carbon dioxide (CO2) injection into water obtained by the new implemented numerical framework are in agreement with the CMG-GEM. The simulation results of the injection of the CO2 into an aquifer shows the robustness of the method to produce gas phase behavior and temperature distribution in agreement with the literature. We also present a simulation case to demonstrate the capability of our simulator to model non-isothermal CO2 injection process into a fractured water saturated reservoir using an unstructured grid. The method is also then applied to simulate and compare the isothermal and the non-isothermal cases of injection of pure CO2 and impure CO2 into water reservoir with heterogeneity in porosity and permeability.