MONITORING CARBON DIOXIDE INJECTIONAND STORAGE IN AQUIFERS AND DEPLETEDOILFIELDS USING CARBON AND SULFURISOTOPE TECHNIQUES

摘要

Fluid and gas monitoring can be used to confi rm the security and integrity ofgeological CO2 storage. The distinct carbon isotopic composition of CO2 from manyindustrial sources that process or combust hydrocarbons allows the use of isotopic andchemical analyses of produced fl uids and gases to trace the injected CO2 and quantifyCO2 storage processes in the subsurface. Our four year monitoring programme atthe International Energy Agency Weyburn CO2 Monitoring and Storage Project inSaskatchewan, Canada, featured frequent chemical and isotopic measurements ofproduced fl uids and gases from around forty wells. Over the four year period, over fourmillion tonnes of CO2 were injected for storage and enhanced hydrocarbon recoveryin the Weyburn oilfi eld. CO2 concentration and carbon isotopic measurements ofproduced fl uids and gases trace CO2 , and confi rm that the order of magnitude increasein the amount of CO2 in the subsurface resulted from CO2 injection. The amount ofCO2 stored as HCO3 – can be quantifi ed using HCO3 – concentration and carbon isotopicmeasurments, while concentration and isotope data for SO4 2 – and H2 S indicate thatbacterial sulfate reduction was not a major source of HCO3 – . To allow widespreadapplication of geological CO2 storage, reliable, cost effective monitoring of storageintegrity will be essential. The produced fl uid and gas monitoring techniques describedhere are based on chemical and isotopic techniques that are already widely employedand well understood by environmental isotope hydrologists, and have the potenital toplay an essential role in future geological CO2 storage monitoring programmes.