Brine migration along vertical pathways due to CO2 injection – a simulated case study in the North German Basin with stakeholder involvement
Brine migration into potential drinking water aquifers due to the injection of CO<sub>2</sub> 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
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
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.