龙马溪组硬脆性页岩水化实验研究

硬脆性页岩水化对页岩气开发井壁稳定有重要的影响，为此，对龙马溪组硬脆性页岩进行水化实验研究，包 括矿物组成、微观结构、水化应力、自吸吸水率及岩芯浸泡等方面实验研究，探讨分析了硬脆性页岩水化过程与机理。 研究结果表明，页岩黏土矿物以伊利石为主，黏土矿物呈片状且定向排列，层理和微裂纹发育，为水化提供作用空间 和流动通道；页岩水化应力和自吸吸水率随浸泡时间增加而先上升后趋于稳定，页岩组构对上升速率或幅度有重要影 响；浸泡过程中，岩样表面主要形成平行层里面的裂缝，随着浸泡时间增加，岩样保持完整性或水化剥落成碎块，页岩 组构和胶结程度对页岩水化程度有重要影响；页岩水化是物理化学作用和力学作用相互耦合结果，前者使岩石断裂韧 性下降，后者使I 型裂纹应力强度因子增大，当应力强度因子大于岩石断裂韧性时，裂纹将扩展或增宽，逐渐形成宏观 裂纹，可进一步扩展成裂缝。

Hydration Experiment of Hard Brittle Shale of the Longmaxi Formation

The hydration of hard brittle shale has an important influence on the borehole stability. Therefore，the hydration experiments was done for different types of shale from the Longmaxi formation in the south region of Sichuan Basin，observations were made to mineral composition，microstructure，hydration swelling stress，water absorption by self-priming and core immersion. And based on observations，the paper discusses the hard brittle shale hydration process and hydration mechanism. The result shows that the main clay mineral of shale is illite，the shape of the clay mineral particles is flake and directional alignment. There are lots of bedding and micro-crack in the shale，which provide the operation-space and flow channel for the hydration of shale. The hydration swelling stress and water absorption by self-priming of shale tend to ascent first before becoming stable. The fabric of the shale has an important influence on the ascend velocity or extent. The fractures in the surface of sample are parallel plane of bedding in the process of immersion. With the increase of immersion time，the sample would keep its integrality or spall to pieces. The fabric and cementation type of the shale have an important influence on the hydration swelling. The hydration of the shale is a result of coupling of physical-chemical action and mechanical action，the former decreasing the rock fracture toughness，and the later increasing the stress intensity factor for mode-I fracture. When the stress intensity factor is greater than the rock fracture toughness，the crack will extend or broaden.