【摘要】 硬脆性泥页岩地层井壁失稳问题是一个十分复杂的难题。外来流体侵入后,岩石内部将会产生一系列的微观物理化学变化而影响地层的稳定性。采用CT成像技术,微观揭示硬脆性泥页岩水化过程中裂缝的发展规律及其对岩石的破坏,并结合扫描电镜等测试手段,分析其机理和对井壁失稳的影响,进而制定出井壁稳定技术对策,为硬脆性泥页岩井壁稳定性研究提供一种新的思路。结果表明,硬脆性泥页岩具有较显著的毛细管效应,岩石矿物颗粒间微孔缝自吸水后产生较强的水化作用,促使次生微裂纹的产生、扩展与连通,微裂纹不断发展成裂缝直至贯通,岩石发生宏观破坏。自吸水化产生次生裂缝破坏是硬脆性泥页岩地层井壁失稳的主要原因之一。强化封堵、控制滤失量和降低滤液表面张力是防止硬脆性泥页岩地层自吸水化破坏的有效措施。更多还原

【Abstract】 The borehole wall instability of hard-brittle shale formations is a very complex problem because after the invasion of foreign fluids,rocks will have a series of internal microscopic physical and chemical changes that affect the stability of formations.Here we proposed a new approach to studying the borehole wall instability of hard-brittle shale formations,which can microcosmically reveal the development law of cracks and the damage to rocks during a hydration process of hard-brittle shales by means of CT imaging technology,analyze its mechanism of and effects on the borehole wall instability with a combination of scanning electron microscope and other instrumentations,and then set down a practicable countermeasure for wall stabilization.The results show that hard-brittle shale has a notable capillary effect,by which spontaneous imbibition of micropores among particles of rock matrix will result in a strong hydration that promotes the generation,expansion and connectivity of secondary micropores.The continuous development of micropores into cracks till penetrated fracturing through rocks will bring about macroscopic damage to rocks.Therefore,one of the major causes that lead to the instability of brittle shale formations is the damage of secondary micropores generated from the hydration by spontaneous imbibition.Thus,intensifying plugging,controlling filter loss and reducing the surface tension of filtrate are effective measures to prevent hard-brittle shale formations from the hydration damage by spontaneous imbibition.更多还原