松科2井超高温水泥浆固井技术

Cementing Technology for Ultra-high Temperature Well Songke-2

针对中国大陆科学钻探松科2井超高温固井难点,采用四元共聚型抗高温降失水剂和三元共聚复合膦酸盐类缓凝剂,提高了水泥浆的耐温稳定性,避免了"热稀释"现象带来的风险,通过调整这2种耐高温外加剂的加量,满足了超高温下控制水泥浆失水量和调整稠化时间的要求。同时,根据颗粒级配及紧密堆积原理,对硅砂的粒径和加量进行优化,使硅钙比接近于1,防止超高温下水泥石后期强度的衰退,另外,优选了由颗粒和纤维共同组成的弹韧性材料,提高水泥石的弹韧性。通过合理配比设计出了抗260℃超高温的水泥浆体系,浆体稳定性好,水泥浆上、下密度差不大于0.03g/cm3,稠化时间为200~420 min,失水量小于100 m L,48 h抗压强度大于20 MPa,后期强度不衰退,7 d抗压强度大于38 MPa。优化尾管悬挂固井工艺,严格控制水泥浆密度,确保不压漏地层,采用耐高温高效冲洗隔离液,提高顶替效率,保证施工安全和固井质量。该体系在井底静止温度为260℃,循环温度为210℃的松科2井四开尾管固井中应用,现场施工顺利,保证了固井质量。

A cement slurry used to deal with difficulties cementing the exploratory well Songke-2 in main land China, has been formulated with a quadripolymer filter loss reducer and a terpolymer phosphonate retarding agent to improve its thermal stability and avoid the risks of ＂thermal thinning＂ of the cement slurry. The filter loss and thickening time of the cement slurry were controlled to satisfy the needs of cementing ultra-high temperature wells by adjusting the concentrations of the two additives. Meanwhile, based on particle sizing and the close-packing principle, the particle sizes and concentration of silica sand were optimized, adjusting the ratio of silicon over calcium closing to 1, thereby preventing the decaying of the late-stage strength of set cement at ultra-high temperatures. Furthermore, an elastic tough material developed with particles and fibers was used to enhance the elasticity and toughness of the cement slurry. By optimizing the ratio of these additives, a cement slurry able to tolerate 260 ℃ well temperature was designed. This cement slurry has good stability, density difference between the upper and the lower parts of the cement slurry less than 0.03 g/cm3, thickening time between 200 min and 420 min, filter loss less than 100 m L, 48 h compressive strength greater than 20 MPa, and 7 d compressive strength greater than 38 MPa. The late-stage strength of the set cement is not declining. By optimizing the liner hanging and cementing techniques, and strictly controlling cement slurry density, the integrity of the formations penetrated by the well was maintained, without being fractured during cementing operations. Using high temperature high efficiency flushing spacers, the displacing efficacy was increased, and job safety and cementing job quality were ensured. Well cementing has been performed successfully with high job quality on the Well Songke-2, whose static bottom hole temperature is 260 ℃, and circulating bottom hole temperature 210 ℃.