To investigate the mitigation of high-pressure CO2-induced degradation of wellbore cement sheath in Carbon Capture, Utilization, and Storage–Enhanced Oil Recovery applications (CCUS-EOR), conventional Class G oil well cement and modified cement systems incorporating graphene, waterborne epoxy resin, and a composite of waterborne epoxy resin with graphene were formulated. This study presents the original comparative investigation on the long-term carbonation resistance of graphene-modified, waterborne-epoxy-modified, and their composite-modified oil well cements under 130 °C and 7 MPa CO2 partial pressure, filling the research gap of unclear synergistic effects of the two modifiers in high-temperature CCUS environments. The specimens were subjected to simulated downhole conditions, and key properties, including compressive strength and permeability, were evaluated. The underlying mechanisms were elucidated through material characterization techniques such as X-ray diffraction, X-ray computed tomography, and scanning electron microscopy. Results indicated that the waterborne epoxy resin–modified cement system exhibited superior long-term carbonation resistance, achieving a 90 d compressive strength retention rate of 84%. The graphene-modified cement showed a 90 d compressive strength retention rate of 65%, while the waterborne epoxy–graphene composite system only retained 39.7% of its compressive strength at 90 d due to negative synergistic effects. The enhanced durability of the waterborne-epoxy-modified cement is attributed to the formation of a continuous polymeric film, which acts as a protective barrier against CO2 penetration. This study provides valuable insights for the design of CO2-resistant cement systems in CCUS-EOR environments.
Cao et al. (2026) studied this question.