Patent ID: 8532954

Claim:
A method of monitoring a CO 2 geological storage site, from a first set of seismic data imaging a subsoil zone which are acquired before a CO 2 injection in an underground formation of the zone, and from a second set of seismic data imaging the subsoil zone which are acquired after CO 2 injection, to locate a free CO 2 plume formed after the injection comprising: constructing by using stratigraphic inversion for each seismic data set a P-wave seismic impedance cube and an S-wave seismic impedance cube; constructing a density variation cube from the P-wave and S-wave seismic impedance cubes before and after CO 2 injection wherein the density variation cube discretizes the subsoil zone into a set of cells; constructing an incompressibility modulus variation cube from the P-wave and S-wave seismic impedance cubes before and after CO 2 injection wherein the incompressibility modulus variation cube discretizes the subsoil zone into a set of cells; and locating the free CO 2 plume in the zone by identifying cells where the density variation is negative and the incompressibility modulus variation is negative and has an absolute value greater than a positive threshold.