石油实验地质Issue(6)：780-786,7.DOI:10.11781/sysydz201406780
水化作用和润湿性对页岩地层裂纹扩展的影响
Effects of hydration swelling and wettability on propagation mechanism of shale formation crack
摘要
Abstract
The shale formation cracks have an important influence on the borehole stability of shale well, and the in⁃teraction 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 Long⁃maxi 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 forma⁃tion crack were studied. The result shows that the wettability of the Longmaxi Formation shale is both water⁃wet and oil⁃wet, and is more likely to be oil⁃wet. 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 num⁃ber 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 drill⁃ing 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 oil⁃based drilling fluids and shale sur⁃face and the interfacial tension are little, which result in small capillary force. Therefore, the oil⁃based drilling fluid is used to inhibit crack propagation, hence the wellbore will be easy to maintain stable.关键词
龙马溪组页岩/润湿性/水化作用/毛细管效应/应力强度因子/裂纹扩展Key words
Longmaxi Formation shale/wettability/hydration swelling/capillary effect/stress intensity factor/crack propagation分类
能源科技引用本文复制引用
梁利喜,熊健,刘向君..水化作用和润湿性对页岩地层裂纹扩展的影响[J].石油实验地质,2014,(6):780-786,7.基金项目
国家自然科学基金联合基金重点项目“页岩气低成本高效钻完井技术基础研究”（ U1262209）和国家自然科学基金面上项目“硬脆性泥页岩地层井周裂缝形态调控岩石力学基础研究”（51274172）联合资助。 （）
