Brine migration along vertical pathways due to CO<sub>2</sub> injection – a simulated case study in the North German Basin with stakeholder involvement

Abstract

Abstract. Brine migration into potential drinking water aquifers due to the injection of CO 2 into deep saline aquifers is one of the potential hazards associated with the Carbon Capture and Storage technology (CCS). Thus, in any site selection process, an important criterion should be the evaluation of brine migration resulting from the injection. We follow an interdisciplinary approach using participatory modeling to incorporate stakeholder opinion at an early stage in order to discuss and evaluate model conception and relevant scenarios for brine migration. The basis for this approach is a realistic (but not real) on-shore 5 site in the North German Basin with characteristic geological features for that region. Our model fully couples flow in shallow and in deep saline aquifers including variable-density transport of salt and a realistic description of the top surface boundary conditions with groundwater recharge and rivers. We investigate different scenarios to identify relevant system components. Further, different model simplifications are compared and discussed with respect to the relevant physical processes and the expected data availability, i.e. to find a model as complex as necessary and as simple as possible. It becomes clear that the 10 initial salt distribution plays a key role as to where noticeable concentration changes may occur. Also the boundary conditions are important for determining the amount of vertically displaced brine. Simplifications in the model setup, such as neglecting variable-density flow or simplifying the complex geometry may prove valid options given sparse data availability.

Modelling of CO2 storage in geological formations with DuMux, a free-open-source numerical framework. A possible tool to assess geological storage of carbon dioxide in Romania

“…Since 2008, DuMu x was used and developed in 22 PhD theses. CO2 storage sites A number of numerical studies using DuMu x were conducted to assess the storage efficiency in North German Basin and are described in [28], [29]. DuMu x was applied to model the CO2 storage at the Ketzin pilot site located in Brandenburg, Germany, which is the longestoperating on-shore CO2 storage site in Europe [30], [31].…”