Présentations Colloques

Geologic carbon storage (GCS) has emerged as an option to significantly reduce carbon dioxide (CO2) emissions and thus, mitigate anthropogenic climate change. Several questions related to GCS remain open and some of them have been controversial lately, such as the likelihood of GCS to induce large seismic events and the potential for CO2 to leak. In spite of the fact most of the modeling studies suggest that a proper pressure management may lead to a safe CO2 storage, i.e., without inducing earthquakes and without causing CO2 leakage, demonstration projects are required to turn GCS into a reality. The In Salah Gas Project, in Algeria, was an industrial scale GCS project that permitted to test the geomechanical response of the subsurface to CO2 injection at high pressure. Furthermore, the injected CO2 reached the storage formation at a temperature around 45 OC colder than the rock. We numerically investigate the thermo-hydro-mechanical (THM) couplings that take place during cold CO2 injection at In Salah. Simulation results show that cooling decreases fracture stability, which may be the cause of a portion of the induced microseismic events that were measured, most of them occurring within the storage formation or below it. The region affected by cooling is much smaller than the CO2 plume and concentrates around the injection well. Cooling causes the contraction of the rock matrix, which opens up existing fractures, leading to an increase in injectivity. We found that the solution of coupled THM processes is required to explain some of the observations reported at In Salah.