摘要:
调整井固井质量往往不高,这是由于长期大量的注水采油,使地层压力、温度和水泥浆的吸热环境发生了变化。再由于固井工艺的特点,决定了返至环空水泥浆的温度最高点不在井底油层段,而在距井底一定距离的地方。返至环空后,温度高的水泥浆优先进入初凝期,并开始失重,使下部未凝固的水泥浆吸纳较高压力地层的流体,同时加速向低压层失水,这就是水泥浆的"异位吞吐",结果使水泥浆固井质量不高。文中分析了水泥浆"异位吞吐"的原因,并提出了预防措施。经数十口井试验,只要采取优选水泥浆降失水剂的类型和剂量的措施,对提高固井质量十分有效。
Abstract:
Generally the cementing of adjustment well is of bad quality because longterm water injection made the formation pressure, temperature and heat absorption environment of cement slurry change. The characteristics of cementing technology determined that the highest point of temperature of cement slurry that returned to the annulus was in the certain distance away from the bottomhole instead of bottomhole reservoirs. The cement slurry with higher temperature had priorlty to enter the initial setting period and began to loss weight after returning to the annulus. Thls made the lower cement slurry without being solidified absorbed into fluid from higher pressure formation and began to discharge into the lower pressure formation,, it was defined as "fluid loss and suction with inverted sequence"for cement slurry. So the cementing of slurry is always from bad quality. This paper analyzed the reason for "fluid loss and suction with inverted sequence" and gave precautions.With the field test of some wells, the optimlzation of types and dosages of filtrate loss reduction additive for cement slurry is beneficial for improving cementing quality.
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