In view of the cementing problem that the sedimental stability of cement slurry is difficult to guarantee under high temperature and ultra-high temperature conditions, a hydrophobically associating high-temperature suspension agent BCJ-Z was invented by introducing hydrophobic groups into hydrophilic polymer chains through molecular structure design. IR analysis showed that the monomers were involved in the polymerization reaction; TG analysis showed that BCJ-Z had good heat resistance, and the heat resistance reached 278 °C. The performance evaluation experiments of cement slurry show that the suspension agent does not thicken at low temperature, does not dilute at high temperature, and has good suspension performance. The maximum use temperature can reach 200 °C. The comprehensive performance of cement slurry containing the suspension agent is good. The suspension agent has been used in more than 30 wells of high temperature complex deep wells in Tarim and Liaohe Oilfields. The high-temperature sedimental stability of cement slurry is good, and the site construction is successful. The high-pressure brine in the salt paste layer is effectively sealed, and the negative pressure channeling test of the target layer is qualified.
Cementing suspension agent is a kind of oil well cement additive used in cement slurry to prevent particle sedimentation and increase system stability. Free liquid and solid phase settlement caused by unstable cement slurry has a great influence on the cementing quality, which is more obvious in large slope section and horizontal section cementing. Free liquid and solid phase settlement can cause excessive permeability of cement stone in the upper part of the well section, and even produce micro clearance, resulting in interlayer connected channeling.
At present, the mature cement suspension agents abroad are mainly synthetic polymer materials with high temperature resistance, such as latex suspension agents and polymer suspension agents. The temperature resistance can reach about 180 °C, but the comprehensive performance needs to be improved. There are few cement suspension products in China, mainly composed of compound products with limited temperature resistance. The stability of these products at low temperature can still be guaranteed; however, at high temperature, due to the degradation, desorption, shear dilution and other factors of polymer additives in the system, as well as the intensification of Brownian motion, the settlement of solid particles is accelerated and the stability is deteriorated, and the temperature resistance can only reach 160 °C. At the same time, the suspension agent products are basically mixed with a certain amount of metakaolin, resulting in excessive thickening of cement slurry at low temperature and excessive dilution at high temperature. Therefore, it is necessary to develop cement suspension agents with strong temperature resistance and wide application scope to improve the stability of cement slurry and ensure the safety and quality of cementing in high-temperature deep wells.
