Patent ID: 8793072

Claim:
A method of monitoring an underground formation into which a gas is injected, from a first set of seismic data imaging a subsoil zone acquired before gas injection into an underground formation of the zone, and from a second set of seismic data imaging the subsoil zone acquired after the gas injection, comprising: constructing a pre-injection P-wave seismic impedance cube by a computer programmed with software which when executed performs stratigraphic inversion of the first set of seismic data with the cube discretizing the subsoil zone into a set of cells; defining an anamorphosis function α by a function comprising a positive lower limit B 1 , an upper limit B 4 , and an identity interval defined between limits B 2 and B 3 , with B 1 <B 2 <B 3 <B 4 ; associating with each cell of the cube a value for each limit B 1 , B 2 , B 3 and B 4 ; associating with each cell of the cube a post-injection P-wave seismic impedance by a computer programmed with software which when executed performs stratigraphic inversion of the second set of seismic data wherein the anamorphosis function α is applied to the post-injection P-wave seismic impedance; and locating the gas within the zone by comparing the post injection P-wave seismic impedance with the seismic pre-injection P wave impedance.