The phenomenon of self-cleavage of coal and rocks leads to poor continuity and a high degree of heterogeneity of the coal-rock matrix, causing the wellbore in the process of drilling. The problem of wellbore stability in the drilling process of the coal strata has become one of the key scientific problems. To solve the problem, single-agent optimization and compounding tests of surfactants have been carried out. Based on the test results, the surfactant compounding composition has been selected, which can effectively reduce the surface tension of the drilling fluid and increase the contact angle between the drilling fluid and the coal and rock surface. To evaluate the effect of the drilling fluid wettability on wellbore stability of the coal measures strata, the expansibility test, rolling recovery test, and shale pressure transfer test have been carried out, combined with the basic performance tests of the water-based drilling fluid. The results show that the composite surfactant can effectively reduce the surface tension of the drilling fluid by 80.83% and increase the contact angle with coal by 54.17%. The recovery rate of the composite surfactant water-based drilling fluid is as high as 96.2%. The compound surfactant drilling fluid can significantly slow down the transfer rate of shale pore pressure, reduce the invasion degree of the drilling fluid to coal and rock matrix, prevent hydration erosion, and effectively enhance the stability of coal and rock sidewall.

煤和岩石的自解理现象导致煤岩基质的连续性差和高度异质性，从而在钻井过程中造成井眼。煤层钻进过程中的井筒稳定性问题已成为关键的科学问题之一。为了解决该问题，已经进行了表面活性剂的单剂优化和配合测试。根据试验结果，选择了表面活性剂配混组合物，可以有效降低钻井液的表面张力，增加钻井液与煤岩表面的接触角。为了评估钻井液的润湿性对煤系地层井眼稳定性，膨胀性测试，滚动采收率测试的影响，进行了页岩压力传递试验，并结合了水基钻井液的基本性能试验。结果表明，该复合表面活性剂可有效降低钻井液的表面张力80.83％，与煤的接触角增加54.17％。复合表面活性剂水基钻井液的回收率高达96.2％。复合表面活性剂钻井液可以显着降低页岩孔隙压力的传递速度，降低钻井液对煤和岩石基质的侵入程度，防止水合侵蚀，有效增强煤岩侧壁的稳定性。结果表明，该复合表面活性剂可有效降低钻井液的表面张力80.83％，与煤的接触角增加54.17％。复合表面活性剂水基钻井液的回收率高达96.2％。复合表面活性剂钻井液可以显着降低页岩孔隙压力的传递速度，降低钻井液对煤和岩石基质的侵入程度，防止水合侵蚀，有效增强煤岩侧壁的稳定性。结果表明，该复合表面活性剂可有效降低钻井液的表面张力80.83％，与煤的接触角增加54.17％。复合表面活性剂水基钻井液的回收率高达96.2％。复合表面活性剂钻井液可以显着降低页岩孔隙压力的传递速度，降低钻井液对煤和岩石基质的侵入程度，防止水合侵蚀，有效增强煤岩侧壁的稳定性。