23.03.2016: The storage of gases and liquids in the deeper subsurface bears the risk of highly saline water intrusion into shallow groundwater. A team of GFZ scientists, section Fluid Systems Modelling, showed that based on numerical simulations, the higher risk of salinisation results from the existence of short geologic faults in the subsurface.
When gases or liquids are injected into the subsurface (e.g. for CO2 storage) the existing salt water (brine) is displaced. This brine can under certain circumstances enter potable groundwater bearing aquifers. In a new study the risk of salinisation was simulated for different geological boundary conditions. Higher potential of salinisation was shown to come from the existence of short geological fault segments in the subsurface. Long fault segments bear a much smaller potential for salinisation.
Short geological fault segments only provide a small area for water to pass. The resulting excess pressure in the storage formation causes displacement of water from greater depth with higher salinity (salinity increases with depth). Salinisation is in this case more localized. This may be a problem, if groundwater is extracted here. In contrary, for long fault segments the displaced water comes from shallower depth with lower concentration and the salinisation is more widespread.
