Abstract:

The problems of low temperature and shallow water-gas flow are concerned in deepwater cementing.The properties of the composite deepwater cementing system combining sulfoaluminate cement with Class-G oil well cement were tested,including the static gel strength,thickening time,compressive strength,long-term compressive strength and volume expansion of cement stone.The hydration products and the long-term products under different temperature were characterized by X-ray diffraction.The results demonstrate that the ettringite(AFt) produced in the early hydration of sulfoaluminate cement can enable the cement slurry to have the favorable behaviors of low temperature and early strength,right-angle-set property and short transition time of static gel strength,as well as the cement stone showing negligible volume expansion.During the latter hydration period,the calcium silicate gel(C₂SH₂) and Ca(OH)₂ are created from the hydration of C₃S and C₂S.C₂SH₂ is closely packed in the AFt crystals to compact the structure of cement stone and promotes strength continuously.The main stable hydration products of AFt and C₂SH₂ can guarantee the long-term mechanical stability of cement stone.

Key words: deepwater cementing, cement, static gel strength, right-angle-set property, compressive strength, hydration mechanism

摘要：

针对深水固井中出现的低温、浅层水—气流动问题,测试了G级油井水泥—硫铝酸钙复合深水固井水泥体系的稠化时间、静胶凝强度、抗压强度、长期抗压强度和水泥石体积膨胀率,利用XRD手段表征了不同温度下水化产物和长期水化产物。结果表明:早期主要为硫铝酸钙矿物熟料水化生成钙矾石AFt,使水泥浆具有优异的低温早强、"直角稠化"、静胶凝强度"过渡时间"短和水泥石体积微膨胀的优点;后期主要为C₃S、C₂S水化生成水化硅酸钙凝胶C₂SH₂和Ca(OH)₂,水化硅酸钙凝胶C₂SH₂填充在钙矾石AFt晶体间,使水泥石结构致密,促进水泥石强度持续增长。体系中主要水化产物AFt、C₂SH₂凝胶稳定保证了水泥石力学性能的长期稳定。

关键词: 深水固井, 水泥, 静胶凝强度, 直角稠化特性, 抗压强度, 水化机理