TotalEnergies conducted a pilot project of CO₂ capture and storage (CCS) in the south-west of France between Lacq and the old Rousse gas field, both located few kilometers apart. Microseismic monitoring goal was to monitor reservoir seal integrity and supply all seismological metrics and attributes necessary for seismic risk management and population information.

During seven years of the monitoring, 2637 events have been detected and 717 were located inside the surveillance perimeter. Magnitude of events ranged between -2.6 and +1.1 in two distinct clusters: one in the vicinity of the injection point (reservoir perimeter) and another one close to the “Meillon/Saint-Faust” fault complex, located 2 Km north of the injection site (local perimeter) (figure below).

The seismic monitoring on this CO2 storage pilot shows a strong influence of the injection in the reservoir perimeter (≈1 Km around the injection point). At a larger scale (local perimeter), this study did not enable to assess reliably eventual seismicity rate changes during injection operations. Nevertheless, this “multi-scale” seismic network design perfectly achieves the goals assigned in terms of risk management, population information and injection mapping.