Modeling of multiphase-multicomponent processes for the sequestration of CO2 in the subsurface

Focal point of research IWS LH2

The storage of CO2 in the subsurface can potentially mitigate the increase of greenhouse gas concentrations in the atmosphere. It is currently an intensive field of research both in Germany (funded, for example, by the German Ministry for education and research BMB+F and the German Research Foundation DFG within the programme GEOTECHNOLOGIEN ( www.geotechnologien.de)) and worldwide. The Chair of Hydromechanics and Modelling of Hydrosystems (LH2) is contributing to the research in this field within several project, at present mainly within the GEOTECHNOLOGIEN programme.

The main focus of recent work at LH2 was first of all on the development of physical-mathematical modell concepts for the simulation of CO2 injection in geological formations within a DFG-funded project. Therefore it is essential to transfer the basic thermodynamic processes into mathematical equations and numerical algorithms, like variations of density, viscosity, and phase compositions dependent on pressure, temperature, and concentrations, etc. The implementation of such concepts is done within the program system MUFTE-UG. Recently - since 2008 - the CO2-related model concepts and algorithms are transferred step by step onto the newly developed numerical software package DuMux.

The application of the above-mentioned model concepts is of great interest to address different kind of problems and questions related with CO2 storage, such as issues of feasibility, risks, storage capacities, sensitivities, etc. This is done, for example, within the EU funded project CO2SINK which is coordinated by the Geoforschungszentrum Potsdam (GFZ). The work of LH2 within CO2SINK deals with large-scale modelling of processes during and after injection of CO2 in the reservoir including the usage of state-of-the-art mesh generators for the complex 3D geometry of the Ketzin storage site. The development of model concepts for the simulation of processes during underground CO2 storage is still a relatively young field of research. That is why there is a high demand, particularly for modellers, to assess the reliability and accuracy of their models. In order to address this issue, LH2 worked on the project BENCHMARKS (funded by GEOTECHNOLOGIEN) and set up problem-specific benchmark problems that are aimed at improving the understanding of the complex coupled processes on the one hand and to be used for code/model intercomparison on the other hand.

Further work in the field of modelling underground CO2 storage at LH2 deals with the spatial and temporal coupling of models of different complexity (within the GEOTECHNOLOGIEN project CO2-MoPa) and with risk assessment and sensitivity studies for site-specific case studies (planned within the GEOTECHNOLOGIEN project COAST, beginning of project not yet (January 2009) clear). Likewise related to CO2 storage is the work Modelling of biofilm growth and its influence on CO2 and water (two-phase) flow in porous media within the international research training group NUPUS. In this project a model concept is developed that is capable of simulating the growth of biofilms and their influence of hydraulic properties in the underground. The biofilms are aimed at sealing potential leakage pathways in the cap rocks and and overlying formations.

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