海上超高温高压探井弃井水泥塞技术

莺琼盆地超高温高压探井高密度弃井水泥塞面临着流动性与沉降稳定性矛盾突出，水泥石强度易衰退，封固段长，温差大，顶部强度发展缓慢，安全密度窗口窄，水泥浆漏失与气窜风险并存等难题。通过使用球形微锰矿加重水泥浆，改善高密度水泥浆流变性，同时提高其沉降稳定性，优选高温成膜防气窜剂，降低气窜风险，优化硅粉加量，提高水泥石高温抗压强度，强化隔离液防漏性能，配合挤入式固井注水泥塞工艺，形成了一套莺琼盆地超高温高压弃井水泥塞技术。该技术在莺琼盆地应用最高井底静止温度达213℃，水泥浆最高密度达2.50 g/cm3。现场应用表明，弃井水泥塞流动性及沉降稳定性好，高温强度发展快且不衰退，稠化时间稳定，具有良好的防窜及防漏能力，均成功封固住高压气层。 

The Technology of Setting Cement Plug for Offshore Ultra High Temperature and Ultra High Pressure Abandoned Wells

High density abandonment well plugs are set for ultra high temperature ultra high pressure exploratory wells drilled in Yingqiong Basin. Several problems, such as the conflict between mobility and sedimentation stability of the cement slurry, deterioration of the strength of the set cement, long section of cementing, big temperature difference, slow strength development at the top of cement, narrow safe drilling windows, loss of cement slurry and gas channeling etc., were encountered when setting the abandonment plugs. Several measures were taken to resolve these problems. First, spherical manganese ore powder was used to weight the cement slurry and to improve the rheology and sedimentation stability of the cement slurry. Second, a high temperature filming anti gas channeling agent was used to mitigate the risk of gas channeling. Third, an optimized amount of micro silica was used to increase the high temperature compressive strength of the set cement. Fourth, the quality of the spacer was optimized to enhance its ability to prevent loss of cement slurry. Finally, the cement slurry was squeezed into the hole to eliminate potential downhole problems. These measures have been successfully used in cement wells with maximum static bottom hole temperature of 213℃, and the highest density of cement slurry used was 2.50 g/cm3. Field operation showed that the cement slurry for setting abandonment plug has good mobility and sedimentation stability. The high temperature strength of the set cement developed fast and did not deteriorate. The cement slurry had stable thickening time, good anti-channeling and cement slurry loss preventing performance. All high pressure gas zones were successfully sealed off.