Research and application of ultra-high temperature resistant functional materials for ultra-deep wells cementing

Deep and ultra-deep formations have become key areas for oil and gas reserve and production growth. Cementing is a vital engineering technology to ensure the safe and efficient exploration and development of oil and gas resources. However, it is confronted with a series of engineering and technical challenges, including ultra-deep (6,000-11,000m), ultra-high temperature (UHT, 200-240°C), ultra-high pressure (120-200MPa), and long cementing intervals (over 7,000m). These conditions pose severe challenges to the temperature resistance and long-term stability of key materials and cement slurry systems. Moreover, under UHT conditions, cementing materials are prone to performance degradation and system instability, which severely compromise both the operational safety of cementing for ultra-deep wells and the long-term sealing integrity of cement sheaths. To address these challenges, key functional materials—such as retarder, fluid loss additive, stabilizer, and strength decline inhibitor—capable of withstanding temperatures up to 240 °C were developed. A UHT cement slurry system suitable for cementing in ultra-deep wells was constructed, and its properties were characterized. Results indicate that the UHT cement slurry system has a temperature resistance of up to 240°C, with a settlement stability below 0.03g/cm 3 , fluid loss volume less than 50mL, and thickening time exceeding 500 minutes, showing a good linear relationship with temperature and retarder dosage. At 240°C, the 28-day compressive strength of set cement slurry exceeds 30 MPa, with no significant long-term degradation observed. This system effectively addresses the three major technical bottlenecks—material failure, slurry instability, and strength degradation— under UHT conditions, thereby meeting the requirements for safe construction and long-term sealing in ultra-deep well cementing. The developed UHT cementing materials and slurry system have been successfully applied in over 100 ultra-deep well operations across basins such as Tarim, Sichuan, Junggar, and Bohai Bay. Notably, they were successfully applied in Well SDTK-1 with depth of 10910 m, Asia's deepest vertical well and the world's second deepest, setting a global record for the deepest cementing. The cementing quality was excellent, with ultrasonic Lamb wave imaging logging results showing a 100% qualification rate and an 88.6% high-quality rate. This research provides critical technical support for the exploration and development of deep and ultra-deep oil and gas resources.