| Excessive Carbon Dioxide (CO2) emission has become a serious issue and caused lots of environmental problems. Carbon Capture and Storage (CCS) program has been developed to reduce the CO2 content in the atmosphere. CO2 storage has been targeted mainly on depleted oil or gas reservoirs and deep saline aquifers. However, leakage could occur through wellbores, cap rocks, formation faults, and fractures during and after CO2 injection. To minimize the risk, different types of sealants have been investigated to prevent CO2 leaks. The aim of this thesis is to provide a comprehensive review of the materials which could be used as CO2 sealants. Based on the difference of materials components, this research has classified the sealants into seven types, including cements, geopolymers, foams, gel systems, resin systems, biofilm barriers, and nanoparticles. For each type of sealants, its chemical components, physical properties, stabilities, impact factors, applied environments, advantages and limitations were summarized. The most commonly used sealant for CO2 leakage control from wellbore is still cement, and the aluminate-calcium based cement has the best properties. It is very challenging to seal the fractures and faults, far from wellbore due to the difficulty to deliver plugging materials into the in-depth of a reservoir. The thermo-stability is also a great challenge for most materials and should be evaluated under supercritical CO2 condition. |
