【摘要】 利用物理或化学方法强化封堵页岩微纳米尺度裂缝是解决页岩气地层井壁失稳与井漏问题的技术关键。在研究页岩气地层井壁失稳机理基础上,探讨了通过钻井液物理-化学协同封堵强化页岩井壁稳定的机理。采用乳液聚合方法,研制了一种微纳米聚合物微球封堵剂,并利用压力传递实验、核磁共振等评价了微纳米聚合物微球封堵剂与化学封堵剂的协同封堵作用效果。研究表明,微纳米聚合物微球"吸附-架桥-可变形填充"、化学封堵剂"封堵-固结"两种封堵机理协同作用,能够在井壁周围形成连续、致密的承压封堵层,阻止压力传递与滤液侵入,实现物化协同封堵强化井壁的目的。进一步优化了页岩气地层强化井壁水基钻井液体系,密度达2. 0 g/cm~3时仍具有良好的流变、滤失及润滑性能,可有效地封堵页岩微纳米尺度缝隙、抑制页岩水化效应,为页岩气钻探开发提供了钻井液技术支撑。更多还原

【Abstract】 Using physical or chemical methods to seal micro-scale and nano-scale fractures in shale is the key to solve the problem of wellbore instability and lost circulation of shale gas wells. The mechanism of enhancing shale wellbore stability through physical-chemical co-sealing of drilling fluid is discussed on the basis of studying the mechanism of shale gas formation wellbore instability. A micro nano polymer microsphere plugging agent was developed by emulsion polymerization. The synergistic plugging effect of the micro nano polymer microsphere plugging agent and chemical plugging agent was evaluated by pressure transmission experiment and nuclear magnetic resonance. The results show that,the synergistic effect of the " adsorption-bridging-deformable filling" mechanism of the micro nano polymer microsphere plugging agent with the " plugging-consolidation" mechanism of chemical plugging agent can form a continuous and compact plugging layer on well wall to prevent pressure transmission and filtrate invasion,and achieve the goal of strengthening the well wall. The addition of the micro nano polymer microsphere plugging agent further optimizes the comprehensive performance of water-based drilling fluid system. When the density of the drilling fluid reaches 2. 0 g/cm~3,it still has good rheological,filtration and lubrication properties. It can effectively plug micro-and nano-scale cracks in shale and inhibit the hydration effect of shale,and provides drilling fluid technical support for drilling development of shale gas.更多还原