Abstract This work examines the susceptibility of methane hydrate in sand to fracture. The task is made difficult because of two challenges: (1) the means to conduct hydraulic fracturing experiments under high pressure and low temperature conditions, and (2) the formation of high saturation hydrate-bearing sand. The apparent fracture toughness ( K Q ) of a material is usually determined via conducting standard tests such as three-point bend on notched beams or pull test on compact specimens. In Part I, Too et al. (2018) , hydraulic fracturing in a penny-shaped crack was found able to determine K Q and estimate the tensile strength of frozen sand. As such, experiments were conducted using the similar approach on the synthesized high saturation methane hydrate-bearing sand specimens (approximately 50–75%) with sample size of 80 mm in diameter and 150 mm in length. The range of K Q determined is between 0.3 and 1.4 MPa√m while the tensile strength estimated ranges between 6 and 12.5 MPa for the hydrate saturation range. The possibility of creating artificial fractures in synthetic methane hydrate-bearing sand may present an opportunity to improve the gas production from natural occurring hydrate-bearing sand.

中文翻译：

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便士形裂缝中的水力压裂。第二部分：测试含甲烷水合物砂的可压裂性

摘要 这项工作研究了砂中甲烷水合物对破裂的敏感性。由于两个挑战，这项任务变得困难：(1) 在高压和低温条件下进行水力压裂实验的方法，以及 (2) 高饱和度含水合物砂岩的形成。材料的表观断裂韧性 (KQ) 通常通过进行标准测试来确定，例如在缺口梁上进行三点弯曲或对紧凑试样进行拉力测试。在第一部分中，Too 等人。(2018)，发现在便士形裂缝中进行水力压裂能够确定 KQ 并估计冻砂的抗拉强度。因此，使用类似方法对合成的含高饱和甲烷水合物的砂岩样品（约 50-75%）进行了实验，样品直径为 80 毫米，长度为 150 毫米。确定的 KQ 范围在 0.3 到 1.4 MPa√m 之间，而水合物饱和度范围的拉伸强度估计范围在 6 到 12.5 MPa 之间。在含甲烷水合物的合成砂中形成人工裂缝的可能性可能为提高天然含水合物砂的天然气产量提供机会。