新型两性离子固井缓凝剂合成与性能评价

Synthesis and Performance Evaluation of a New Amphoteric Well Cement Retarder

针对目前常用的缓凝剂在长封固段固井中存在高温失效,顶部水泥石强度发展缓慢,温度、加量敏感等问题,以丙烯酸(AA)、衣康酸(IA)、2丙烯酰胺-2甲基丙磺酸(AMPS)和一种新型阳离子单体(X)为原料,合成一种高温缓凝剂CXT-1。得到最佳合成条件:单体物质的量比为37∶8∶8∶6,反应温度为60℃,溶液pH值为4,反应时间为4h,引发剂加量为0.3%。通过红外光谱、核磁共振和热失重分析对其进行表征,同时评价了添加缓凝剂CXT-1水泥浆体系的综合性能。实验结果表明,CXT-1中含有4种单体的特征官能团,330℃之前未出现明显质量损失,热稳定性高。缓凝剂CXT-1在90~180℃下可延长水泥浆稠化时间,180℃下稠化时间可达368min,加量敏感系数最小为0.48,最大为1.73,温度敏感性系数最大为6.2%,均低于行业标准要求。60~100℃下24h顶部水泥石强度最低可达10.6MPa,满足现场施工要求。电导率、XRD、SEM分析表明,缓凝剂的作用机理为多点吸附控制水化作用、抑制Ca(OH)2晶体生长以及络合作用共同作用的结果。

In cementing long openholes, cement retarders sometimes lose their effectiveness because of high temperatures. Slow development of the strength of the top cement slurry, sensitivity of cement slurry to temperature and to the dosage of cement additives are problems encountered during well cementing. To address these problems, a high temperature retarder CXT-1 has been developed with acrylic acid (AA), itaconic acid (IA), 2-acrylamide-2-methylpropane sulfonic acid (AMPS) and a new cationic monomer (X). The optimum synthetic conditions obtained through orthogonal experiment are as follows: molar ratio of the monomers is 37∶8∶8∶6, reaction temperature is 60 ℃, pH of the reaction solution is 4, time of reaction is 4 h, and the concentration of initiator is 0.3%. CXT-1 was characterized with IR spectroscopy, NMR and thermogravimetric analysis, and evaluated in laboratory. It was found that the molecules of CXT-1 contains the characteristic functional groups of the four monomers. CXT-1 has good thermal stability, and no obvious mass lose of CXT-1 was found when temperature is less than 330 ℃. Using CXT-1, the thickening time of a cement slurry can be prolonged at temperatures between 90 ℃ and 180 ℃. At 180 ℃, the thickening time is 368 min. The concentration sensitivity coefficient of CXT-1 is in a range of 0.48 - 1.73, and the maximum temperature sensitivity coefficient of CXT-1 is 6.2%, all satisfying the needs of the relevant industrial standards. The 24 h compressive strength of the top cement slurry at temperatures between 60 ℃ and 100 ℃ is at least 10.6 MPa, satisfying the needs of field operations. Analyses of conductivity, XRD and SEM show that the working mechanisms of the retarder are the combined action of multipoint adsorption which controls the hydration of cement, inhibition of the growth of Ca(OH)2 crystals and complexation.