Microseismic monitoring of CO2 storage

Geomechanical deformation, if it creates and/or reactivates faults and fractures, can provide a leakage pathway for CO2 to escape the reservoir. By monitoring microseismicity in and around the reservoir, the risks of leakage can be assessed. Although it is a mature technology for monitoring hydraulic fracturing in tight gas reservoirs, microseismic monitoring is still an experimental technique for CCS. To be of use for CCS sites, arrays must be capable of detecting events must across a wider area than typical frac-jobs. This poses a challenge to design suitable arrays within engineering and cost constraints. Another key issue is to determine how microseismic observations should be best interpreted with respect to leakage risks. So far we have found that linking event observations with geomechanical models - comparing predictions from various geomechanical scenarios with field observations - is an important aspect of event interpretation. In this paper we use a case example from the Weyburn CCS project, although our discussions have general application.