美国页岩气水平井水基钻井液研究与应用进展

 水平井钻井是推动美国页岩气大规模开发的核心技术之一，美国在页岩气水平井初期使用油基钻井液成功钻探页岩水平井。迫于油基钻井液环保和成本高的压力，美国对页岩气水平井水基钻井液进行了研究并推广应用。介绍了美国典型的3个页岩气区块水基钻井液研究情况。Haynesville地区选用更接近井下环境1.38 MPa分压的CO₂侵、12%低密度固相污染和204℃、48 h条件评价钻井液抗污染能力；通过模拟钻井液流入、井底静止和流出过程中井温和压力变化的新方法测试钻井液在井眼中的流变性。而Fayetteville和Barnett地区采用扫描电子显微镜（SEM）分析浸泡后岩石的形貌研究钻井液与岩石的作用机理，进而研究水基钻井液配方。Haynesville地区现场应用时，在CO₂侵和井底204℃高温条件下，机械钻速比使用油基钻井液的邻井提高8.5%；Fayetteville和Barnett地区应用钠米硅醇封堵水基钻井液时，滑动钻速分别是9.2~15.4 m/h和7.4~24.6 m/h，复合钻钻速30.8~77.0 m/h。

Advances and application of horizontal-well water-based mud in US shale gas reserviors

Horizontal drilling is one of the core technologies in US shale gas large scale exploration. Oil based mud (OBM) was applied successfully at the beginning, however, due to its environmental reason and high cost, water based mud (WBM) was developed and applied. Three typical WBM cases for shale gas are introduced in this article. In the Haynesville area, a condition close to downhole environment is used to evaluate drilling fluid anti-contamination properties, including 1.38 MPa CO₂, 12% solid and hot rolling at 204℃ for 48 h. Rheological properties are tested by stimulating well temperature and pressure variations during the processes of fluid flowing in, staying static in bottom hole, and flowing out. In Fayetteville and Barnett areas, the interaction mechanism between WBM and shale is investigated to form drilling fluid formulation using SEM so as to analyze the morphology of soaked rocks. In Haynesville, with CO₂ contamination and 204℃ temperature, the ROP increases by 8.5%, compared with adjacent OBM well. In Fayetteville and Barnett, the sliding drilling speeds are 9.2-15.4 m/h and 7.4-24.6 m/h, respectively and the rotating speed is 30.8-77.0 m/h when using nano-silica-alcohol WBM. The development and application of US shale gas horizontal well WBM are worth learning by China.