Abstract：Microcrack growth induced by water imbibition and hydration in hard-brittle shale has consistently posed a challenge to wellbore stability during drilling. While most current studies rely on modeling assumptions of constant crack width and hydration driving force, as well as semi-quantitative experimental characterizations, they fail to sufficiently reveal the chemical fracture mechanisms underlying hydration cracking in hard-brittle shale. To address these limitations, this work establishes a mathematical model applicable to the nucleation and subcritical crack growth (SCG) of hydration cracking in illite-rich hard-brittle shale, based on the principles of physical equivalence and the framework of linear elastic fracture mechanics (LEFM). The asymptotic solutions of stress fields near the tips of hydration microcracks, under variable crack width and nonlinear hydration stress conditions, were derived, and the long-term stability was also evaluated, clarifying the evolution mode of SCG dominated by intrinsic multi-processes. Additionally, an innovative indoor double torsion test was developed for the first time, wherein water was instantaneously introduced to the tip of a stress-loaded crack to simulate water-rock interactions after wellbore formation. The dynamic behavior of hydration cracking evolution in hard-brittle shale from the Gulong Qingshankou formation was quantitatively characterized. Furthermore, a critical criterion for the transition time from hydration cracking to sudden instability failure was proposed. Results indicate that the double torsion program, which incorporates instantaneous water introduction to the crack tip, is reliable and repeatable. The hydration of illite crystal layers in hard-brittle shale can significantly enhance the rate of SCG by 1 to 2 orders of magnitude, reaching rates of μm/s, and increase the length of SCG to 4 to 13 times that of the original length. Moreover, the model predictions provided by the iterative algorithm align well with experimental results, exhibiting a maximum mean relative error not exceeding 8.2% and achieving rapid convergence under varying initial stress levels, thereby confirming the reliability and robustness of the proposed model. This study clarifies the microscopic origins and progressive evolution behaviors of hydration cracking in illite-rich hard-brittle shale from the perspective of chemical fracture mechanics, highlighting a hierarchical regulation strategy that enhances blockage at the crack mouth, obstructs flow within the crack, and inhibits growth at the crack tip, thereby ensuring overall wellbore stability. The experimental results and theoretical model offer methodological references and data for both indoor expanded tests and on-site engineering practices.
张亚洲，金 衍*，陈 勉，卢运虎. 硬脆性页岩伊利石晶层水化诱发开裂的化学断裂力学机制与试验研究[J]. 岩石力学与工程学报, 2026, 45(10): 3047-3064.
ZHANG Yazhou, JIN Yan*, CHEN Mian, LU Yunhu. Chemical fracture mechanism and experimental study on cracking induced by hydration in illite crystal layers of hard-brittle shale. , 2026, 45(10): 3047-3064.
[1] 金 衍，张亚洲，卢运虎. 力学化学耦合的硬脆性泥页岩微裂纹扩展机制研究进展与思考[J]. 石油科学通报，2023，8(5)：577–587.(JIN Yan，ZHANG Yazhou，LU Yunhu. Progress and reflections on the microcrack growth mechanism of hard-brittle shale under chemical-mechanical couplings[J]. Petroleum Science Bulletin，2023，8(5)：577–587.(in Chinese))
[2] 金 衍，薄克浩，张亚洲，等. 深层硬脆性泥页岩井壁稳定力学化学耦合研究进展与思考[J]. 石油钻探技术，2023，51(4)：159–169.(JIN Yan，BO Kehao，ZHANG Yazhou，et al. Advancements and considerations of chemo-mechanical coupling for wellbore stability in deep hard brittle shale[J]. Petroleum Drilling Techniques，2023，51(4)：159–169.(in Chinese))
[3] CHENEVERT M E. Shale alteration by water adsorption[J]. Journal of Petroleum Technology，1970，22(9)：1 141–1 148.
[4] 邱正松，李健鹰. 硬脆性页岩坍塌机理的实验研究[J]. 钻井液与完井液，1989，6(2)：26–31.(QIU Zhengsong，LI Jianying. Experimental study on caving mechanism of hard and brittle shale[J]. Drilling Fluid & Completion Fluid，1989，6(2)：26–31.(in Chinese))
[5] 石秉忠，夏柏如，林永学，等. 硬脆性泥页岩水化裂缝发展的CT成像与机制[J]. 石油学报，2012，33(1)：137–142.(SHI Bingzhong，XIA Bairu，LIN Yongxue，et al. CT imaging and mechanism analysis of crack development by hydration in hard-brittle shale formations[J]. Acta Petrolei Sinica，2012，33(1)：137–142.(in Chinese))
[6] 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，2014，36(6)：780–786.(LIANG Lixi，XIONG Jian，LIU Xiangjun. Effects of hydration swelling and wettability on propagation mechanism of shale formation crack[J]. Petroleum Geology & Experiment，2014，36(6)：780–786.(in Chinese))
[7] 卢运虎，梁 川，金 衍，等. 高温下页岩水化损伤的各向异性实验研究[J]. 中国科学：物理学 力学 天文学，2017，47(11)：138–145.(LU Yunhu，LIANG Chuan，JIN Yan，et al. Experimental study on hydration damage of anisotropic shale under high temperature[J]. SCIENTIA SINICA (Physica，Mechanica & Astronomica)，2017，47(11)：138–145.(in Chinese))
[8] ZHANG S F，SHENG J J. Study of the propagation of hydration-induced fractures in mancos shale using computerized tomography[J]. International Journal of Rock Mechanics and Mining Sciences，2017，95：1–7.
[9] 康毅力，杨 斌，李相臣，等. 页岩水化微观作用力定量表征及工程应用[J]. 石油勘探与开发，2017，44(2)：301–308.(KANG Yili，YANG Bin，LI Xiangchen，et al. Quantitative characterization of micro forces in shale hydration and field applications[J]. Petroleum Exploration and Development，2017，44(2)：301–308.(in Chinese))
[10] 隋微波，田英英，姚晨昊. 页岩水化微观孔隙结构变化定点观测实验[J]. 石油勘探与开发，2018，45(5)：894–901.(SUI Weibo，TIAN Yingying，YAO Chenhao. Investigation of microscopic pore structure variations of shale due to hydration effects through SEM fixed-point observation experiments[J]. Petroleum Exploration and Development，2018，45(5)：894–901.(in Chinese))
[11] 李 宁，金之钧，张士诚，等. 水/超临界二氧化碳作用下的页岩微观力学特性[J]. 石油勘探与开发，2023，50(4)：872–882.(LI Ning，JIN Zhijun，ZHANG Shicheng，et al. Micro-mechanical properties of shale due to water/supercritical carbon dioxide-rock interaction[J]. Petroleum Exploration and Development，2023，50(4)：872–882.(in Chinese))
[12] 杨 斌，张 浩，杨 建，等. 基于裂缝亚临界扩展理论的页岩吸水起裂微观力学机制[J]. 天然气工业，2025，45(2)：105–113. (YANG Bin，ZHANG Hao，YANG Jian，et al. Micro-mechanical mechanism of water imbibition inducing fracture initiation in shale based on subcritical fracture propagation theory[J]. Natural Gas Industry，2025，45(2)：105–113.(in Chinese))
[13] ZHUANG Y，ZHANG T T，LIU X J，et al. Intrinsic mechanisms of shale hydration-induced structural changes[J]. Journal of Hydrology，2024，637：131433.
[14] ALAM A B，FUJII Y，HASAN N，et al. Hydration-induced fractures in shale with silt layers: A perspective on slope stability[J]. Geohazard Mechanics，2025，3(2)：136–146.
[15] NAKAKURA C，DUREE J，STEPHENS K，et al. Atomic force microscopy monitoring of subcritical slow crack growth in soda lime silicate glass[J]. Journal of the European Ceramic Society，2024，44(13)：7 927–7 935.
[16] GEORGE M，NZIAKOU Y，GOERKE S，et al. In situ AFM investigation of slow crack propagation mechanisms in a glassy polymer[J]. Journal of the Mechanics and Physics of Solids，2018，112：109–125.
[17] GURGUREWICZ J，MÈGE D，SKI?CIM M，et al. Nanotopographic characterization of microfractures in rocks by Atomic Force Microscopy[J]. Journal of Structural Geology，2019，124：70–80.
[18] ATKINSON B K. Fracture mechanics of rock[M]. London：Academic Press，1987：111–115.
[19] WIEDERHORN S M. Influence of water vapor on crack propagation in soda-lime glass[J]. Journal of the American Ceramic Society，1967，50(8)：407–414.
[20] FREUND L B. Dynamic fracture mechanics[M]. Cambridge：Cambridge University Press，1998：152–158.
[21] HARRELLSON S G，DELAY M S，CHEN X，et al. Hydration solids[J]. Nature，2023，619(7970)：500–505.
[22] BROBERG K B. Cracks and fracture[M]. London：Academic Press，1999：90–95.
[23] FETT T，MUNZ D. Stress intensity factors and weight functions[M]. Southampton：Computational Mechanics Publication，1997：78–80.
[24] WIEDERHORN S M，BOLZ L H. Stress corrosion and static fatigue of glass[J]. Journal of the American Ceramic Society，1970，53(10)：543–548.
[25] LIU X J，ZENG W，LIANG L X，et al. Experimental study on hydration damage mechanism of shale from the Longmaxi Formation in southern Sichuan Basin，China[J]. Petroleum，2016，2(1)：54–60.
[26] DING X X，YOU Q，WU J F，et al. Hydration characteristics and mechanism study of artificial fracture surface in illite rich shale gas reservoir: A case study of Longmaxi formation shale in Yongchuan District[J]. Energy Reports，2023，9：4 174–4 186.
[27] 张保平，单文文，田国荣，等. 泥页岩水化膨胀的实验研究[J]. 岩石力学与工程学报，2000，19(增1)：910–912.(ZHANG Baoping，SHAN Wenwen，TIAN Guorong，et al. Testing study on the hydration of shale[J]. Chinese Journal of Rock Mechanics and Engineering，2000，19(Supp.1)：910–912.(in Chinese))
[28] 徐加放，邱正松，韩丰欣. 泥页岩水化应力实验方法与实验装置[J]. 钻井液与完井液，2008，25(4)：13–15.(XU Jiafang，QIU Zhengsong，HAN Fengxin. Methods and apparatus for shale hydration experiments[J]. Drilling Fluid & Completion Fluid，2008，25(4)：13–15.(in Chinese))
2026, Vol. 45 
