Abstract Mode I fracture mechanics tests of mostly calcareous Vaca Muerta shale rocks were performed in a new experimental device. A hydraulic system allows the injection of pressurized fluids inside of cracks to generate applied KI and measure fracture toughness in room pressure and temperature conditions. Multi-notched 1.5″ plugs were tested with different polar and non-polar fluids (water-based fluids and organic solvents). Some samples were subject to previous saturation in order to activate multiple micro crack initiation via various embrittlement mechanisms. The methodology allows to test a large number of plug samples with low cost and times, and with a comparatively low uncertatinty and scatter of results with respect to other techniques. Results are discussed in terms of the two stress terms at the crack tip: Stress Intensity Factor (KI) and T-stress, and according to the Extended Maximum Tangencial Strain criterion (EMTSN). The variation of toughness in dry and saturated samples are discussed in terms of damage mechanisms, as well as in terms of the stochastic nature of toughness results in these rocks. The convenience of repeating these tests at reservoir pressure and temperature conditions is recognized.

中文翻译：

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页岩韧性测试的改进技术

摘要 以钙质为主的Vaca Muerta 页岩的I 型断裂力学试验在新的实验装置上进行。液压系统允许在裂缝内注入加压流体以产生应用的 KI 并测量室温和室温条件下的断裂韧性。使用不同的极性和非极性流体（水基流体和有机溶剂）测试了多槽口 1.5" 塞子。为了通过各种脆化机制激活多个微裂纹萌生，一些样品经历了先前的饱和。该方法允许以低成本和时间测试大量塞样品，并且相对于其他技术，结果的不确定性和分散性相对较低。结果根据裂纹尖端的两个应力项进行讨论：应力强度因子 (KI) 和 T 应力，并根据扩展最大切向应变准则 (EMTSN)。根据损伤机制以及这些岩石韧性结果的随机性质，讨论了干燥和饱和样品中韧性的变化。人们认识到在储层压力和温度条件下重复这些测试的便利性。