高温多功能防气窜水泥浆体系在四川盆地海相超深井中的成功应用

针对四川盆地海相高温、高压、高含硫超深气井所面临的高温水泥浆沉降、气窜、水泥石强度衰退等主要固井技术难题，基于高温高压稠化仪模拟沉降稳定性评价方法、颗粒级配原理优选体系稳定材料，采用直接测定气窜和塑性态渗透率为辅助手段的防气窜评价方法优选防气窜材料，基于乌氏黏度计法的聚合物耐温能力评价方法来优选高温缓凝剂，采用正交法测试、热重法辅助分析180℃高温养护后水泥石抗压强度，优选高温稳定剂石英砂粒径和加量，研究出水泥浆和水泥石性能良好的胶乳弹韧性和低渗透防窜水泥浆体系。结果表明，①水泥浆体系在密度为1.90~2.30 g/cm3、温度为150~180℃范围内具有良好的工程性能和应用前景，为解决该类固井技术难题奠定了基础；②加砂可缓解水泥石强度衰退，高温下，加砂量与抗压强度呈正向关系，相同加砂量下，只加细砂强度表现更优，但长期强度增加幅度不如粗砂；建议150℃和180℃时，硅砂加量分别大于35%和45%；③基于乌氏黏度计法的聚合物耐温能力评价方法能有效评价降失水剂和缓凝剂的抗高温能力，是快速筛选高温井关键处理剂的重要辅助手段；④建议进一步开展H₂S介质等酸性气体对水泥石的腐蚀评价，有利于合理设计防气窜防腐水泥浆体系。 

Successful Application of High Temperature Multi-Functional Gas Channeling Preventing Cement Slurry in Marine Ultra Deep Wells in Sichuan Basin

In cementing ultra-deep gas wells with high temperature, high pressure and high sulfide content in marine Sichuan basin, settling of cement slurry at high temperatures, gas channeling and decline of the strength of set cement were the main technical problems that need to be addressed. In the development of a latex cement slurry with high elasticity, high toughness, low permeability and anti-channeling performance, different methods were used to optimize the cementing additives. The stabilizing agent was selected by settling stability evaluation performed on an HTHP thickening instrument and by particle sizing principles. By directly measuring the gas channeling permeability and the permeability of the set cement under plastic conditions, the gas channeling agent was selected. The high temperature retarder was selected using Ubbelohde viscometer which evaluates the thermal stability of polymers. The particle size and concentration of a quartz sand as high temperature stabilizer were optimized by analyzing the compressive strength of the set cement cured at 180 ℃ through orthogonal test method and thermogravimetry. It was found in these experiments that: 1) at temperatures between 150 ℃ and 180 ℃, the cement slurries of 1.90 g/cm3-2.30 g/cm3 all had good engineering performance, laying the foundation of solving the well cementing difficulties as mentioned above. 2) Adding sand into the cement slurry can mitigate strength decline of the set cement. At elevated temperatures, sand concentration has a positive relationship with compressive strength of the set cement. At the same sand concentration, sand of finer particle sizes is better than sand of coarse particles, but from the long run, addition of coarse sand is more beneficial to the strength development of the set cement. It was thus suggested that at temperatures between 150 ℃ and 180 ℃, the silica sand concentration should be greater than 35% and 45%, respectively. 3) Ubbelohde viscometer can be used to evaluate the high temperature resistance of filter loss reducer and retarder, and is therefore an important auxiliary means to fast screening of key additives for high temperature wells. 4) Further evaluation on the corrosion by acidic gases such as H₂S, to set cement should be carried out, and this will be beneficial to the design of cement slurries with anti-gas-channeling and corrosion resistance capacities.