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.