耐高温抗盐固井降失水剂的制备及性能研究

针对目前聚合物降失水剂耐高温性能不佳、抗盐能力差以及低温增黏、高温稀释严重的问题，通过在分子结构上引入特殊阳离子功能单体，采用自由基水溶液聚合方法，制备了一种抗温可达210℃的两性离子型耐高温抗盐降失水剂DRF-4L。采用红外光谱、热失重分析以及环境扫描电镜对聚合物分子结构和耐温性进行了表征，并对其应用性能进行了评价。结果表明，DRF-4L适用温度范围广（30~210℃），降失水性能优异；210℃（BHCT）时，掺4% DRF-4L的水泥浆API失水量为42 mL；抗盐能力强，可使饱和盐水水泥浆API失水量控制在50 mL以内；此外，DRF-4L低温不增稠、高温弱分散，对改善水泥浆初始流变性能和提高水泥浆高温稳定性具有明显优势；含DRF-4L的水泥石早期强度发展快，90℃下12 h抗压强度高于14 MPa，且后期强度发展正常。同时，以DRF-4L为主剂的低密度、常规密度、高密度水泥浆以及胶乳水泥浆体系等综合性能良好，能够满足高温深井超深井的固井技术需求。 

Development and Study on a High Temperature Salt Resistant Filter Loss Reducer for Well Cementing

A high temperature salt resistant zwitterionic filter loss reducer DRF-4L has been developed to deal with problems encountered in filtration control of drilling fluids, such as poor resistance to high temperature, poor resistance to high salinity, viscosifying the mud at low temperatures as well as severe thinning at high temperatures. DRF-4L has special cationic groups in its molecules and is synthesized through free radical water solution polymerization. The molecular structure and temperature tolerance of DRF-4L were characterized using IR spectroscopy, thermogravimetric analysis and ESEM. The performance of DRF-4L was evaluated. It was found that DRF-4L has wide work temperatures (30-210℃) and excellent filtration control ability. at 210℃ (BHCT), a cement slurry treated with 4% DRF-4L had API filter loss of 42 mL. Saturated salt cement slurries treated with DRF-4L had API filter loss less than 50 mL. Cement slurries treated with DRF-4L do not thicken at low temperatures and only very slightly disperse at elevated temperatures. DRF-4L is very beneficial to improving the initial rheology and to enhancing the high temperature stability of cement slurries. Cement slurries containing DRF-4L has fast developed early strength, the 12 h compressive strength of the set cement at 90℃ is at least 14 MPa, and the late strength of the set cement develops normally. Cement slurries with low density, normal density and high density, or latex cement slurries, if treated with DRF-4L as the major treatment agent, have good overall properties, and are able to satisfy the needs of cementing high temperature deep and ultra-deep wells.