关键词: 深井, 大温差, 高温缓凝剂, 两亲聚合物, 固井水泥浆, 稠化时间, 水化机制

Abstract: Cementing in long sealing section of deep wells requires high performance cement slurry system, which needs to ensure not only safe pumping at high temperature, but also a rapid early strength development in the top cement stone for shortening the cycle of well construction. However, the retardation effect of existing retarders becomes weaker as temperature increases, and increases as temperature decreases, which may lead to an unfavorable phenomenon that cement slurry does not solidify for a long time. Therefore, an amphiphilic polymer high-temperature intelligent retarder TRAP is innovatively designed and synthesized, which possesses self-assembly and temperature response properties. At low temperature, hydrophobic group molecules are self-assembled into well-arranged conformation to wrap the retarding groups, which can prevent retarding groups from adsorbing on the surface of cement particles and reduce the side effects of the retarder at low-temperature. At high temperature, the molecular conformation changes from being ordered to being unordered, for which more retarding groups are adsorbed on the surface of cement particles. This demonstrates a complete high-temperature retarding effect, which has achieved intelligent regulation of retarding effect with temperature change, thus providing a new method for solving the difficulty in deep well cementing due to large temperature difference. The research results show that TRAP has excellent high temperature resistance, which can prolong hydration induction period and effectively prolong the thickening time of cement slurry at 30 ℃ to 200 ℃. Within the temperature range of 130 ℃ to 190 ℃, the retardation performance of TRAP can increase significantly with the increase of temperature, and the thickening time difference between maximum and minimum temperatures is only 69 minutes, which witnesses the regulation characterized by intelligent enhancement of retarding effect with temperature increase. By simulating the conditions of high-temperature cycle cementing at 180 ℃ at the well bottom, it is found that the early strength of top returning cement slurry develops rapidly, 24 h compressive strength of cement slurry can reach 16.3 MPa at 90 ℃, which has greatly shortened the waiting-on-cement time to 24 h. In conclusion, the retarder has unique intelligent temperature response characteristics, which is different from and significantly superior to existing retarders with a large temperature difference in terms of regulation laws and effects, providing a new approach for solving the problem of thickening time at high temperature and early strength regulation at low temperature in long sealing section of deep wells.

Key words: deep well, large temperature difference, high-temperature retarder, amphiphilic polymer, cement slurry, thickening time, hydration mechanism