Monitoring carbon dioxide storage using passive seismic techniques

Carbon dioxide stored in geological reservoirs to reduce anthropogenic emissions must be monitored to ensure that no leakage is occurring. One leakage risk is that injection-induced pressure increases may generate fractures in the caprock, providing a pathway for buoyant carbon dioxide to penetrate the reservoir seal. Geophones can be deployed to detect fracturing events. The rates and magnitudes of seismicity, and their hypocentres, can be used to characterise geomechanical deformation induced by injection, and thereby assess the risks of leakage through fractures. In this paper synthetically modelled data are used to show how surveys should be designed to maximise the potential for this technique within the specific remits of carbon dioxide capture and geological storage (CCS), before discussing several case examples where passive seismic monitoring has been used to monitor subsurface injection of carbon dioxide. Recommendations and suggestions are given for the deployment of passive seismic monitoring as CCS moves from pilot to full-scale demonstration and commercial projects.