In this paper we describe the OpenGeoSys (OGS) project, which is a scientific open-source initiative for numerical simulation of thermo-hydro-mechanical-chemical processes in porous media. The basic ...concept is to provide a flexible numerical framework (using primarily the Finite Element Method (FEM)) for solving multifield problems in porous and fractured media for applications in geoscience and hydrology. To this purpose OGS is based on an object-oriented FEM concept including a broad spectrum of interfaces for pre- and postprocessing. The OGS idea has been in development since the mid-eighties. We provide a short historical note about the continuous process of concept and software development having evolved through Fortran, C, and C++ implementations. The idea behind OGS is to provide an open platform to the community, outfitted with professional software-engineering tools such as platform-independent compiling and automated benchmarking. A comprehensive benchmarking book has been prepared for publication. Benchmarking has been proven to be a valuable tool for cooperation between different developer teams, for example, for code comparison and validation purposes (DEVOVALEX and CO
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BENCH projects). On one hand, object-orientation (OO) provides a suitable framework for distributed code development; however, the parallelization of OO codes still lacks efficiency. High-performance-computing efficiency of OO codes is subject to future research.
Prediction about reservoir temperature change during carbon dioxide injection requires consideration of all, often subtle, thermal effects. In particular, Joule–Thomson cooling (JTC) and the viscous ...heat dissipation (VHD) effect are factors that cause flowing fluid temperature to differ from the static formation temperature. In this work, warm-back behavior (thermal recovery after injection completed), as well as JTC and VHD effects, at a multi-layered depleted gas reservoir are demonstrated numerically. OpenGeoSys (OGS) is able to solve coupled partial differential equations for pressure, temperature and mole-fraction of each component of the mixture with a combination of monolithic and staggered approaches. The Galerkin finite element approach is adapted for space discretization of governing equations, whereas for temporal discretization, a generalized implicit single-step scheme is used. For numerical modeling of warm-back behavior, we chose a simplified test case of carbon dioxide injection. This test case is numerically solved by using OGS and FeFlow simulators independently. OGS differs from FeFlow in the capability of representing multi-componential effects on warm-back behavior. We verify both code results by showing the close comparison of shut-in temperature profiles along the injection well. As the JTC cooling rate is inversely proportional to the volumetric heat capacity of the solid matrix, the injection layers are cooled faster as compared to the non-injection layers. The shut-in temperature profiles are showing a significant change in reservoir temperature; hence it is important to account for thermal effects in injection monitoring.
Performance of Oxidative Coupling of Methane (OCM) reactor using the research benchmark Mn-Na2WO4/SiO2 catalyst under various sets of operating conditions was experimentally investigated. In ...particular, the impacts of varying the operating parameters (630 combination-sets) namely; reactor set-temperature (in 6 levels in the range of 750–875 °C), feed flow-rate (in 5 levels in the range representing GHSV -Gas Hourly Space Velocity- of 9600-19200 cm3 g−1 h−1), methane-to-oxygen ratio (CH4/O2 in 7 levels in the range of 1.5–10), and inert gas dilution (in 3 levels at 0%, 25% and 50%) on the recorded trends of methane-conversion and selectivity and yield of the desired products (C2: C2H4&C2H6) were systematically reviewed. The performed experimental analysis enabled determining the impact of each investigated parameter as well as their interactive impacts through a carefully designed set of experiments. The novel proposed contour graphs visualized how the temperature and methane-to-oxygen ratio for instance directly influence the contribution of the catalyst or indirectly affect the reactor performance in synergy with the variation of dilution and feed flow due to their thermal impacts via affecting the intensity of the gas-phase and catalytic reactions in reactor-scale. It was demonstrated that in wide ranges of variation of these operating parameters, the recorded OCM reactor performance for instance in terms of the observed selectivity represent the interactive impacts of the intrinsic characters of the catalyst and the reactor's characteristics such as its dimension and thermal capacity. Therefore, these aspects should be carefully considered in design of experiments and in the interpretation of the experimental observations for the research purposes as well as in the design and operation of large-scale reactors.
The paper presents a modeling strategy as well as simulation results of a designed conservative tracer test in the depleted Altensalzwedel natural gas reservoir in order to know the tracer ...concentration and breakthrough time at the production wells. Krypton is considered as a suitable tracer. The production wells are located in several hundred meters to a few kilometers away from the injection well. The numerical simulation has been performed by using the newly implemented compositional gas flow module of OpenGeoSys (OGS), a scientific open-source simulator for calculation of coupled geohydraulic (single and multiphase flow), transport (heat and mass transfer), geomechanical and geochemical processes. The tracer breakthrough curves at the production wells show that the breakthrough times vary between 2 and 3 years. The model verification is presented by comparing the OGS results with a one-dimensional analytical solution. The numerical results have been verified by code comparison, additionally.
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•Comprehensive OCM reactor performance analysis was conducted and reported.•Impacts of four operating parameters on the OCM reactor performance were analyzed.•Results of a ...comprehensive experimentation for 630 sets of conditions were reported.•Novel visualization approach enabled tracking the interactive impacts of parameters.
Performance of Oxidative Coupling of Methane (OCM) reactor using the research benchmark Mn-Na2WO4/SiO2 catalyst under various sets of operating conditions was experimentally investigated. In particular, the impacts of varying the operating parameters (630 combination-sets) namely; reactor set-temperature (in 6 levels in the range of 750–875 °C), feed flow-rate (in 5 levels in the range representing GHSV -Gas Hourly Space Velocity- of 9600-19200 cm3 g−1 h−1), methane-to-oxygen ratio (CH4/O2 in 7 levels in the range of 1.5–10), and inert gas dilution (in 3 levels at 0%, 25% and 50%) on the recorded trends of methane-conversion and selectivity and yield of the desired products (C2: C2H4&C2H6) were systematically reviewed. The performed experimental analysis enabled determining the impact of each investigated parameter as well as their interactive impacts through a carefully designed set of experiments. The novel proposed contour graphs visualized how the temperature and methane-to-oxygen ratio for instance directly influence the contribution of the catalyst or indirectly affect the reactor performance in synergy with the variation of dilution and feed flow due to their thermal impacts via affecting the intensity of the gas-phase and catalytic reactions in reactor-scale. It was demonstrated that in wide ranges of variation of these operating parameters, the recorded OCM reactor performance for instance in terms of the observed selectivity represent the interactive impacts of the intrinsic characters of the catalyst and the reactor’s characteristics such as its dimension and thermal capacity. Therefore, these aspects should be carefully considered in design of experiments and in the interpretation of the experimental observations for the research purposes as well as in the design and operation of large-scale reactors.
In this paper, conceptual modeling as well as numerical simulation of two-phase flow in deep, deformable geological formations induced by CO2 injection are presented. The conceptual approach is based ...on balance equations for mass, momentum and energy completed by appropriate constitutive relations for the fluid phases as well as the solid matrix. Within the context of the primary effects under consideration, the fluid motion will be expressed by the extended Darcy's law for two phase flow. Additionally, constraint conditions for the partial saturations and the pressure fractions of carbon dioxide and brine are defined. To characterize the stress state in the solid matrix, the effective stress principle is applied. Furthermore, the interaction of fluid and solid phases is illustrated by constitutive models for capillary pressure, porosity and permeability as functions of saturation. Based on this conceptual model, a coupled system of nonlinear differential equations for two-phase flow in a deformable porous matrix (H2M model) is formulated. As the displacement vector acts as primary variable for the solid matrix, multiphase flow is simulated using both pressure/pressure or pressure/saturation formulations. An object-oriented finite element method is used to solve the multi-field problem numerically. The capabilities of the model and the numerical tools to treat complex processes during CO2 sequestration are demonstrated on three benchmark examples: (1) a 1-D case to investigate the influence of variable fluid properties, (2) 2-D vertical axi-symmetric cross-section to study the interaction between hydraulic and deformation processes, and (3) 3-D to test the stability and computational costs of the H2M model for real applications.
CO2 capture and storage technology is often hampered by CO2 leakage through natural occurring fractures in the overlying caprock. This work suggests a two-dimensional test case of typical CO2 ...injection with possible leakage into freshwater resource. By using this test case in combination with a 1D verification example, the effects of sorption and decay processes are evaluated. Leakage value and buoyancy number reveal that buoyancy is the main mechanism for leakage, and the sorption process delays the arrival of CO2 at the fracture. The volume translated Peng-Robinson (VTPR) equation of state (EoS) has been modified for accurate material properties of CO2 and water in a multi-componential flow model.
Developing further the substructure models proposed by Mandel and Dafalias a thermodynamically consistent system of differential and algebraic equations is derived to describe anisotropic ...elasto-plastic material behavior at finite deformations. Based on the multiplicative split of the deformation gradient an appropriate material law is formulated applying the principle of the maximum of plastic dissipation. Generalized basic relations of this material model containing a relation of hyperelasticity, evolutional equations for the internal variables describing different kinds of hardening, and the yield condition are presented. The capacity of the proposed material model is demonstrated on the example of a sheet with a hole. Presenting the evolution of yield surfaces the capability of the model to describe anisotropic hardening behavior is shown.
The aim of this contribution is the presentation of an adaptive finite element procedure for the solution of geometrically and physically non-linear problems in structural mechanics. Within this ...context, the attention is mainly directed on the error estimation and hierarchical strategies for mesh refinement and coarsening in the case of finite elasto-plastic deformations. An important but sensitive aspect of adaptation approaches of the space discretization is the calculation of mechanical field variables for the modified mesh. Procedures of mesh refinement and coarsening imply the determination of strains, stresses and internal variables at the nodes and the Gauss points of new elements based on the transfer of the required data from the former mesh. In order to improve the efficiency as well as the convergence behaviour of the adaptive FE process an approach of data transfer primarily related to nodal values is presented. It is characterized by solving the initial value problem not only at the Gauss points but additionally at the nodes of the elements.
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