Tracking CO2 Migration in Storage Aquifer

Monitoring technologies for CO2 in geological carbon sequestration are based upon the physico-chemical and electromagnetic properties of the CO2-water/brine and rock system as well as the induced events such as micro-seismicity. As CO2 migrates in the subsurface, its interactions with elements like rock, water/brine can be used to track its presence and direction. For deep subsurface storage of CO2, methods like electrical resistivity tomography (ERT), seismicity, capillary pressure and relative permeability as well as geochemical measurements can be reliably employed in monitoring CO2. Other methods like membrane-sensor technique and gas accumulation chamber are mainly suitable for shallow geological sequestration. However, prior to the full-scale deployment, it is necessary to understand the principles of operations and limitations of the adopted technologies as well as obtain experimental and practical information from them. In the field application, pre-injection baseline assessment is necessary followed by critical assessments during the storage process and post-injection period. Accuracy in leakage quantification and identification of sinks are also important. Factors that can influence the results of these technologies include fluctuations of pressure, temperature, initial salinity level, initial pH level, porosity, fluid properties, porosity, tortuosity, pore size distribution, wettability, reservoir mineralogy and surface chemistry.