新型耐高温油井降失水剂的合成与性能评价

以丙烯酰胺(AM)、丙烯酸(AA)和一种具有特殊结构的磺酸基单体(TS)为原料,过硫酸氨为引发剂,合成了新型抗高温抗盐油井水泥降失水剂FR。利用红外光谱、核磁共振、热重分析表征降失水剂FR的结构及热稳定性,评价了含降失水剂FR的水泥浆的降失水性能、抗温性能、抗盐性能、稠化时间等工程性能。结果表明:丙烯酰胺(AM)、丙烯酸(AA)和磺酸基单体(TS)有效聚合到降失水剂FR中;该降失水剂耐温性能和控制失水性能良好,可在90~200℃内使用,当温度为200℃、FR质量分数为1.0%时,水泥浆体系失水量为48 mL;降失水剂FR耐盐性能良好,可在含有25%NaCl的水泥浆体系中使用,并控制其失水量为24 mL;降失水剂FR适应性良好,可应用于不同品牌的水泥中,对水泥浆流变性、水泥石抗压强度等无不良影响。采用化学分析、扫描电镜等手段研究了降失水剂FR的黏弹性吸附层理论的作用机理:高分子通过电荷作用吸附到带正电的水泥颗粒上,形成一层可压缩的黏弹性吸附层,在失水的压差作用下,吸附层被挤压并填充到水泥颗粒间的空隙中,从而有效、牢固地堵塞了失水通道、降低了滤饼渗透率。该理论能合理解释吸附增黏类降失水剂的作用机理。

Synthesis and performance evaluation of novel high-temperature-resistant fluid loss additive for oil wells

By taking acrylamide (AM), acrylic acid (AA) and a sulfonic monomer (TS) with special structure were as materials, and ammonium persulfate as an initiator, a novel high-temperature-resistant fluid loss additive (FR) for oil wells is synthesized in this study. The structure and thermostability of FR are characterized using infrared spectrum, nuclear magnetic resonance and thermogravimetric analysis, so as to evaluate the fluid loss, temperature resistance, salt tolerance, thickening time and other engineering performances of the cement slurry with FR. The results show that acrylamide (AM), acrylic acid (AA) and sulfonic monomer (TS) are effectively polymerized to the fluid loss reducer FR; FR has good fluid loss control ability and high-temperature resistance ability, and can be used in the temperature range of 90-200℃. When the temperature is 200℃ and FR mass fraction is 1.0%, the fluid loss of cement slurry is 48 mL, indicating excellent ability to resistant water loss. In the 25% NaCl salt-water cement slurry system, the fluid loss is 24 mL, proving a good salt resistance performance. Moreover, FR shows good applicability to different brands of cement and multiple oil well cement additives with little impact on the rheological property of the cement slurry and compressive strength of the cement stone. Then the mechanism of viscoelasticity adsorption layer theory regarding FR is studied based on chemical analysis, SEM and other means. The macromolecules are adsorbed to positively charged cement particles by charge effect, thus forming a compressible viscoelasticity adsorption layer. Under the pressure difference function of fluid loss, the adsorption layer is compressed to fill the interspace of cement particles, so as to block the fluid loss channel effectively and stably as well as reduce the permeability of filter cake. This theory can give a rational explanation to the mechanism of fluid loss additives through adsorption and viscosity increasing.