Reducing risk of CO2 storage in regional aquifers – plume migration in flat layer

Abstract In order to show that in certain circumstances the presence of a structural trap is not required for CO₂ storage, a set of conceptual models for CO₂ injection in a deep saline aquifer represented by a horizontal, laterally infinite layer, i.e., without structural or stratigraphic trap, was developed. This is theoretically supported by the assumed gravitational migration of a CO₂ plume towards cap-rock. The hypothesis was tested by varying injection depths and rock permeability to analyse the influence of these parameters on time and radius of CO₂ plume lateral spreading. After running 30 simulation cases, an analytical term has been proposed and it was found that a logarithmic function is satisfactory for describing the relationship between time and maximum spreading radius from the injection well. Subsequently, a generalized analytical multi-parameter correlation was found to describe CO₂ plume movement with time within the spread radius. After establishing such a fitted correlation, it is possible to predict the extent of the CO₂ saturation zone, justifying less frequent 4D seismic measurements.