CO2 Sequestration Wellbore Sealing and Enhancement Method
Considering the service environment of the CO2 sequestration wellbore,a wellbore model containing a cement corrosion layer was developed.Based on the finite element method,the development process of micro-annu-lus at the cement plug-formation interface was simulated,the mechanism of micro-annulus expansion and the main controlling factors under the fluid drive were clarified,and the method of wellbore sealing enhancement was pro-posed.The simulation results show that the supercritical CO2 accumulation will cause a change in the stress at the cement bonding surface.When the stress at the interface changes from compressive to tensile,and the stress value is higher than the bonding strength,micro-annulus will be generated in the wellbore.If the cement stiffness and bonding strength decrease after corrosion,the wellbore sealing decreases;the expansive additive can increase the initial compressive stress of the bonding surface and then enhance the wellbore sealing.When the expansion rate is 0.5‰,the micro-annulus propagation pressure rises by 43.7％,the micro-annulus length decreases by 42.7％,and the wellbore sealing is significantly enhanced.
CO2 sequestration wellboresealingmicro-annuluscement plugenhancement method
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