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.

shale gas  /  horizontal well  /  water based drilling fluid  /  drilling fluid formula  /  SEM analysis