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针对南海莺琼盆地地质条件复杂,钻探井深在5000m以上,井下温度高,地层压力大,压力层系多,易发生气窜等问题。以丁苯胶乳、发气剂作为防气窜外加剂,以1200目铁矿粉作为加重剂,以硅粉控制水泥石强度衰退,研究出了一种新型抗高温防气窜高密度水泥浆体系。结果表明:所研制的水泥浆密度可达2.35g/cm3、抗温可达180℃(BHCT)、失水量可降至70mL/30min左右,早期抗压强度高达14MPa以上,易于保证封固质量;水泥浆的流变性好,稠化时间可调,且稠化时间受温度波动、水质变化以及前置液污染的影响在可控范围内。因此,该水泥浆能够满足现场施工要求;水泥浆的自由水小于0.5%,养护后水泥石没有发生体积收缩且上下密度差较小,具有良好的浆体稳定性和凝结固化稳定性;水泥浆凝固过程,稠化过渡时间短(t100Bc-t30Bc<15min),稠度阻力系数值小于0.110,气窜阻力达2.28MPa,能有效防止气窜。
In view of the complicated geological conditions in Yingqiong Basin of the South China Sea, drilling wells with a depth of more than 5000 m, high downhole temperature, large formation pressure, multiple pressure beds and gas channeling easily occur. With styrene-butadiene latex and gas-generating agent as anti-gas channeling additive and 1200-mesh iron ore powder as weighting agent, the strength of cement stone was controlled by silica fume. A new type of high-temperature anti-gas channeling high-density cement slurry system . The results show that the density of cement slurry developed can reach 2.35g / cm3, the temperature can reach 180 ℃ (BHCT), the water loss can be reduced to about 70mL / 30min and the early compressive strength can reach 14MPa, which is easy to ensure the sealing quality. The rheology is good, the thickening time is adjustable, and the thickening time is affected by the temperature fluctuation, the change of the water quality and the pollution of the precursor liquid within the controllable range. Therefore, the cement slurry can meet the requirements of on-site construction; the free water of the cement slurry is less than 0.5%; after curing, the cement shrinkage does not shrink in volume and the density difference between the upper and lower sides is small; the slurry has good slurry stability and solidification stability; Solidification process, the thickening of the transition time is short (t100Bc-t30Bc <15min), the consistency of resistance coefficient is less than 0.110, gas channeling resistance of 2.28MPa, can effectively prevent gas channeling.