中文摘要：

页岩地层裂纹扩展对页岩气井井壁稳定有重要影响，而钻井液与页岩间相互作用（毛细管效应和水化作用）将对页岩地层裂纹扩展产生影响。选择四川盆地龙马溪组露头及井下岩心开展室内实验研究页岩润湿性和水化作用，基于断裂力学理论，考虑水化作用和润湿性（毛细管效应），建立页岩裂纹裂缝扩展模型，分析了水化作用和润湿性对页岩裂纹扩展的影响。研究结果表明，龙马溪组页岩表面既亲油又亲水，且页岩表面更倾向于油湿；页岩浸泡在水中，水化应力随着时间增加而先上升后趋于稳定，而先浸泡在白油中、后浸泡在水中或浸泡在10％KCl溶液中测试膨胀应力，水化应力上升速度减慢；页岩浸泡在水中，岩样表面形成的裂缝主要平行于层理面，随着时间增加，岩样保持完整或剥落成碎块，而页岩浸泡在10％KCl中，岩样表面形成裂缝数量少且破裂程度轻；水化作用和润湿性对应力强度因子增量影响较大及对页岩裂纹扩展有重要影响，钻井液体系应减小钻井液滤失量及钻井液界面张力、增加黏土矿物水化抑制剂和增大钻井液与页岩表面接触角，减小自吸作用，抑制水化作用。油基钻井液与页岩表面接触角小，但其界面张力小，造成毛细管力小，因此页岩地层钻井中，采用油基钻井液能在一定程度上抑制裂纹扩展，使井壁不易失稳。

英文摘要：

The shale formation cracks have an important influence on the borehole stability of shale well, and the interaction between drilling fluidand shale （ capillary effect and hydration swelling ） would impact on the propagation mechanism of shale formation crack. In this thesis, experiments were done for the outcrop and well core of the Longmaxi Formation shale of the southern Sichuan Basin to determine shale wettability and hydration swelling. Based on fracture mechanics, the propagation model of shale formation crack was established with the hydration swelling stress and capillary force, and the effects of hydration swelling and wettability on the propagation mechanism of shale formation crack were studied. The result shows that the wettability of the Longmaxi Formation shale is both waterwet and oilwet, and is more likely to be oilwet. The hydration swelling stress of the shale tend to ascent first and then become stable with the increase in time. For the shale rocks first soak in oil or KCl, the rise velocity of hydration swelling stress would decrease.The fractures on the sample surface are parallel plane of bedding in the process of immersing in water. With the increasing of immersion time, the sample would keep its integrality or spall to pieces. While the number of the fractures soaking in KCl is less and the cracked degree of the rocks is lighter. The hydration swelling has a great influence on the increment of the stress intensity factor, and the drilling fluid systems need to decrease the drilling fluid filter loss and increase the clay minerals hydrate inhibitor. The wetting behavior has a great influence on the propagation mechanism, and the drilling fluid systems need to reduce the drilling fluid interfacial tension and enlarge the wetting angle between drilling fluid and rock medium. The contact angles of oilbased drilling fluids and shale surface and the interfacial tension are little, which result in small capillary force. Therefore, the oilbased drilling fluid is used to inhibit crack propagatio