CO2 breakthrough and leak-sealing - Experiments on shale and cement

The long-term storage of CO2 in deep geological formations would lose effectiveness if CO2 leaks through the cap rock, joints, and improperly grouted wells. Plug tests conducted on shale and cement specimens highlight the importance of hairline cracks in otherwise intact small-pore materials. Crack sealing is attempted under pressure by injecting suspensions of bentonite and kaolin; the sub-micron particles successfully fill cracks, and the CO2-breakthrough pressure increases significantly above initial values. The sealing strategy can be optimally engineered for field applications during or after CO2 injection in order to prevent CO2 leakage.