Keywords:carbon dioxide, saline aquifer, well logging, seismic survey, trap mechanism, monitoring
A major challenge in geological sequestration is to map the movement of CO2 in the subsurface and to demonstrate that the CO2 is safely contained within the reservoir. When CO2 is injected into an aquifer, the existing formation water in pore spaces of the reservoir rock will be partially displaced by the CO2. This process will change the compressibility and density of the reservoir rock. These changes will in turn affect propagation characteristics of seismic waves. Recent research shows that seismic methods are among the most promising monitoring methods. Time-lapse 2D/3D seismic survey has been widely used in CO2-EOR fields, particular in North America. Achievements in CO2-EOR strongly suggest effectiveness of seismic survey in monitoring CO2 migration in an aquifer. Other technologies such as well-based monitoring (VSP, logging, crosswell seismic and EM tomography) are also useful in monitoring the injected CO2 around the wells with high resolution compared to seismic survey.
Several key questions need to be answered when CO2 geological storage is to be undertaken worldwide. How should CO2 be stored underground? Can trapping be assumed in saline formations and can CO2 be retained for long periods safely in the subsurface? This presentation will give a review on CO2 monitoring carrying out at the injection sites particular in North America and also provide information on what kind of technology works well and what did not work. Pilot and demonstration CO2 injection projects provide unique data to develop economically viable, environmentally effective options for reducing carbon emissions in the near future.