适用于页岩气井的强抑制防塌高性能水基钻井液体系

High inhibition and anti-sloughing water-based drilling fluid system for shale gas horizontal wells

威远地区M井区页岩气水平井钻井过程中易出现井壁失稳、坍塌等问题,而采用油基钻井液时钻屑含油量高、难处理,并且环保压力大。因此,以新型阳离子复合抑制剂DY-Ⅱ为主要处理剂,结合优选的封堵剂、润滑剂,形成一套适合于页岩气井的强抑制防塌高性能水基钻井液体系,并对体系性能进行了评价。室内实验结果表明:钻井液体系具有优良的抑制性和润滑性,页岩滚动回收率达99.2%,极压润滑系数和泥饼黏附系数与油基钻井液体系相当;体系在140℃下老化后流变性能稳定,具有良好的抗温性;采用高效铝基微纳米聚合物封堵剂,能够较好地封堵地层微裂缝,提高井壁稳定性;加入20%钻屑后,体系性能稳定,抗污染能力较强。现场试验结果表明,该体系性能稳定,具有较强的抑制防塌能力,施工过程中未发生井下复杂情况,作业顺利,说明该高性能水基钻井液体系能够满足威远地区M井区页岩气井的钻井需要。

With the problems of wellbore instability and wellbore collapse during drilling process of shale gas horizontal wells in M Well area of Weiyuan area, using oil-based drilling fluid will bring large amount of oil in particle debris and cause difficulties to be dealt with, resulting great pressure on environment. Therefore, the new cationic compound inhibitor DY-Ⅱ is used as the main treatment agent, combined with the preferred plugging agents and lubricants, forming a set of strong inhibition, anti-sloughing and high performance water-based drilling fluid system suitable for shale gas wells, and the performance of the system was evaluated. The results show that the drilling fluid system has inhibitory and excellent lubricating properties, shale recovery rate reaches 99.2%, and the coefficient of lubrication and the adhesion coefficient of mud cake are equivalent to the oil based drilling fluid system; after aging at 140℃, the rheological properties of the system are stable and have good temperature resistance; high efficiency aluminum based micro nano polymer plugging agent can be used to block the micro cracks and improve the stability of the wellbore; after adding 20% drilling chips, the system has stable performance and strong anti-pollution ability. Field experiment results show that the system has stable performance, strong inhibition and anti-collapse ability; no downhole trouble happened in the construction process suggests that this high performance water-based drilling fluid system can meet the Weiyuan shale gas drilling in M Well area.