Research on the characteristics of aluminate cement stone under ultra-high temperature environment

High-temperature conditions during heavy oil thermal recovery and in-situ extraction pose challenges to the sealing integrity of oil well cement sheaths. Aluminate cement exhibits superior heat resistance, fire resistance, and corrosion resistance compared to Portland cement, along with rapid hydration and high early strength. Therefore, a pressurized curing chamber and a high-temperature furnace were used to simulate the conditions of heavy oil thermal recovery and in-situ extraction, respectively, to conduct research on the thermal damage characteristics of aluminate cement stone under hydrothermal conditions at 350°C and dry heat conditions at 600°C. The study assessed the long-term changes in the compressive strength, permeability parameters, microstructure, and hydration products of the cement stone. The results indicated that after hydrothermal curing at 350°C, the hydration products of the cement stone transformed from gibbsite and katoite to boehmite, calcite, and calcium aluminum, predominantly featuring blocky and loosely granular structures, with enlarged pore throats and decreased strength; The incorporation of quartz sand can inhibit the strength decline of aluminate cement, promoting its stable growth, at 350°C, the products transformed into dmistcimbergite, boehmite, and bicchulite, with interlocking blocky and platy structures in tight arrangement. After dry heat curing at 600°C, the products shifted to mayenite and a small amount of lime, with an increase in corundum content. The strength of the cement stone initially increased and then gradually decreased, with enhanced permeability, predominantly featuring blocky and granular structures. The addition of quartz sand did not effectively modify the aluminate cement stone, resulting in poor bonding and higher permeability. However, it improved the microstructure and reduced porosity. The study reveals the evolutionary patterns of aluminate cement stone characteristics in ultra-high temperature environments, aiming to provide a reference for the development of aluminate cement systems under ultra-high temperature conditions for heavy oil thermal recovery and in-situ extraction.