Investigation of the Accuracy and Efficiency of Advanced Linearization and Discretization Schemes for Reservoir Simulation

We improve an advanced fully-implicit parallel framework for reservoir simulation with the application of discretization and linearization methods. The multipoint flux approximation (MPFA) scheme is used with full tensor permeability and unstructured grids. Moreover, the main challenge in reservoir simulation is to have a complex phase behavior, as it leads to high nonlinearity. Operator-based linearization (OBL) has been introduced lately which simplifies residual & Jacobian assembly and also minimizes computational time furthermore. In OBL, the mass-based formulation is implemented in a fully implicit scheme to assure the constancy of solutions and flexibility of the framework for general-purpose reservoir simulation. In this work, we illustrate a complete investigation of the accuracy and efficiency of the OBL. There are three new points in this simulator first is the advanced parallel framework. We develop an advancing parallel framework for general-purpose reservoir simulation; it allocates a huge workload to multiple processors on a cluster. In this work, we use a multipoint linearization scheme that can deliver accurate, robust, and convergent solutions for reservoir simulation. We have a mimetic finite difference scheme (MFD) method and multipoint flux approximation method, which help in enhancing the simulation accuracy and efficiency. Besides, we compare the numerical solution with the analytical solution by running simulations with different resolutions. Moreover, we present several benchmark cases to thoroughly determine the accuracy, convergence, and robustness of the framework. We investigate the effect of grid resolution on simulation results by running several models with different grid sizes. We also investigate the robustness of the OBL by running simulations with different oil viscosities. Moreover, we run multi filed cases to illustrate the performance of the OBL method for reservoir simulations. Finally, MPFA-O helps to guarantee convergence solution when we apply full tensor permeability and unstructured grid. Also, MPFA-O could provide accurate solutions and better solutions than that TPFA. The MFD enhances the modeling capabilities of the framework for the cases with full tensor permeability in unstructured grids so it can take the challenging cases for reservoir simulation. OBL is a reliable method, but high resolutions are needed to model multiphase flow problems accurately. The OBL drastically reduces the programming work and the computational cost related to property evolution. As a result, by coupling MFD and OBL in a parallel framework, QASR can provide accurate and efficient solutions for challenging reservoir simulation cases.