Time-lapse VSP Monitoring of Shallow Gas Injection at the Maguelone Experimental Site (Languedoc, France)

The Maguelone experimental site has been the subject of surface and downhole geophysical monitoring of gas injection experiments in a shallow subsurface reservoir. In particular, vertical seismic profiles (VSP) were conducted in two holes located within meters of the gas injection hole, before, during and after a series of injections. The times of first-arrival were obtained by picking and interpreted in terms of seismic velocity models. Before injection, the lateral variability of seismic velocities at the site is underlined. The comparison of seismic velocities between experiments for a single hole brings out the impact of gas injection on the elastic properties of the porous clastic sediments at the injection site.