Abstract

Carbon sequestration in abandoned oil fields and deep saline aquifers are being considered effective solutions for reducing CO2 emissions to the atmosphere. These deposits permit the storage of large amounts of CO2. The reservoir requires high porosity, which would allow good injectivity, and a caprock with very low permeability to prevent CO2 leakage through it. While drilling, the zone near the well is damaged, and it could provide leakage paths of supercritical CO2 to upper environments. Within the triple interface of the intervening materials (reservoir rock, caprock, and cement), the cement glass G used in the oil industry is chemically unstable against CO2 and much less against scCO2. This work presents the microstructural and mechanical behavior of G-cement under supercritical carbonation. Uniaxial tests (UCS), mercury intrusion porosimetry (MIP), and X-ray diffraction (XRD) characterized the cement carbonated for 28 days at 20 MPa pressure and 90°C temperature. The results indicate a decrease in its mechanical strength despite the reduction in its capillary porosity. These experimental studies were simulated using a coupled chemo-hydro-mechanical model. The model simulates the carbonation front advance in cement subjected to supercritical CO2 and the changes generated by the chemical reactions, using the classic balance equations of porous continua based on conservation of mass and momentum.

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