Geomechanical modeling of CO2 storage in deep saline aquifers – A review

Geological CO2 storage (GCS), particularly in deep saline aquifers, is considered to be a promising technology to reduce the CO2 emissions into the atmosphere due to the burning of fossil fuels. Large-scale and long-term CO2 sequestration is a significantly coupled thermal-hydraulic-mechanicalchemical (THMC) process, which may cause a series of mechanical issues, including ground surface deformation, reduced integrity of the cap-rock and wellbore and the reactivation of fault or seismic events (Rutqvist 2012, Li et al. 2006). For example, in a GCS project in Salah, Algeria, an uplift of 2.5 cm at a rate of 5 mm per year has been observed. In addition, at Weyburn, approximately 100 micro-seismic events with magnitudes ranging from −1 to −3 have been detected since 2004. Fortunately, no grave security issues associated with CO2 storage systems have yet been reported. However, serious accidents caused by the injection of fluid into a deep geologic formation have been reported. For instance, a geothermal project in Basel was shut down after a 3.4 magnitude seismic event was induced by a water injection. Water injection is similar to CO2 injection; hence, the potential for a large-scale CO2 injection to cause serious accidents in the future cannot be ruled out. Thus, it is vital to comprehensively assess the geomechanical issues associated with CO2 sequestration (Rutqvist 2012).