适用于大温差固井用一种新型耐温耐盐缓凝剂(PMC-180)的合成及性能评价

Synthesis and performance evaluation of a new type of temperature and salt resistant retarder(PMC-180)for large temperature difference cementing

摘要:

针对深井超深井长封固段固井时水泥浆柱顶部强度发展缓慢、缓凝甚至超缓凝的问题，笔者采用溶液聚合原位插层法，以2-丙烯酰胺基-2-甲基丙磺酸(AMPS)、丙烯酸(AA)、二烯丙基二甲基氯化铵(DMDAAC)为单体，以改性蒙脱土为活性聚合填料，合成了一种新型有机-无机复合型大温差缓凝剂(PMC-180)，采用红外光谱、X射线衍射及热重分析等方法分别表征了其结构和热稳定性能，并对其相关应用性能进行了评价，探讨了其在水泥浆中的缓凝作用机理。结果表明，所合成共聚产物(PMC-180)为目标产物且具有插层剥离复合结构，初始热解温度为267.27℃，具有良好的耐热稳定性。含PMC-180的水泥浆具有良好高温缓凝性能和抗盐性能，淡水基和盐水基水泥浆均可通过调整其加量调节水泥浆的稠化时间，且稠化曲线平稳无“鼓包”等异常现象；含PMC-180的水泥浆在顶部低温下强度发展良好，可应用于长封固段大温差固井且有效缓解了顶部水泥浆超缓凝的问题；与不同水泥浆体系及外加剂具有良好的配伍性，综合性能良好，易于调整和控制。通过化学分析、X射线衍射、电镜扫描等表征手段，讨论了缓凝剂PMC-180的缓凝机理及大温差适应机理，认为缓凝现象的发生，是因为PMC-180吸附于水泥颗粒表面形成水化吸附层及与Ca2 络合抑制了Ca(OH)2晶核、晶体的正常生长，进而达到缓凝效果；温度的变化控制PMC-180中片层间距变化实现有效缓凝基团的束缚释放，同时分子结构中的阴阳两性离子产生竞争吸附，从而达到高温下具有较强缓凝效果，低温下具有部分缓凝效果，使得PMC-180具有良好的大温差适应性。

Abstract:

Aimed at the problems of strength’s slow development, slow setting and even super retarding happening at the top of cement slurry in deep and ultra-deep wells with long cementing intervals,a new type of polymer/inorganic composite retarder(PMC-180)was prepared by in-situ intercalated polymerization method.2-acrylamido-2-methylpropanesulfonic acid(AMPS),acrylic acid(AA),two diallyl dimethyl ammonium chloride(DMDAAC)were used as monomer,Modified montmorillonite was used as active polymerization filler,the structures and the thermal stability of PMC-180 were characterized by Fourier transform infrared spectroscopy(FT-IR),X-ray diffraction(XRD) and thermogravimetric analysis(TGA).Then, the application performance was evaluated and the retarding mechanism in cement slurry was discussed.The results show that the synthesized copolymer (PMC-180) is the target product with intercalation/exfoliation composite structure,The initial pyrolysis temperature of which reaches 267.27℃ and has good thermal stability.The cement slurry containing PMC-180 has good retarding property and salt/temperature resistance performance,the thickening time of the freshwater or brine cement slurry can be regulated effectively by adjusting the additives amount of PMC-180,moreover, the thickening curve of different kinds of cement paste is stable and no abnormal phenomenon such as bulging. The compressive strength of slurry containing PMC-180 is well developed at low temperature,which can be applied to long sealing and large temperature difference cementing and effectively alleviates super retarding phenomenon at the top of cement slurry.The slurry with PMC-180 which is easy to regulate and control has good compatibility with different cement slurry system and additives,and has good comprehensive performance.the retarding mechanismand temperature adaptation mechanismof PMC-180 were discussed by characterization methods of chemical analysis, X ray diffraction and scanning electron microscope:(1)PMC-180 is adsorbed on the surface of cement particles to formed a layer of hydration adsorption and the complexation reaction between PMC-180 and Ca2 is inhibiting the normal growth of Ca(OH)2 crystal nucleus or crystal, so the retarding effect is achieved finally;(2)the binding or release of effective retarding groups were controlled by the change of lamellar spacing being related to temperature in PMC-180,at the same time, the anions and cations in the molecular structure compete to adsorb each other on the surface of cement particles,therefore,The PMC-180 has good adaptability to large temperature difference,which mainly shows that it has a strong retarding effect at high temperature, and has a partial retarding effect at low temperature.