Cloud-fracture networks as a means of accessing superhot geothermal energy
Cloud-fracture networks as a means of accessing superhot geothermal energy
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DOI：
10.1038/s41598-018-37634-z
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发表时间：
2019-01
影响因子：
4.6
通讯作者：
N. Watanabe;K. Sakaguchi;Ryota Goto;T. Miura;K. Yamane;T. Ishibashi;Youqing Chen;T. Komai;N. Tsuchiya
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文献类型：
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作者：
N. Watanabe;K. Sakaguchi;Ryota Goto;T. Miura;K. Yamane;T. Ishibashi;Youqing Chen;T. Komai;N. Tsuchiya
超高温地热环境（高于ca。400 °C）代表了一个新的地热能源前沿。然而，能够储存和传输流体的渗透性裂缝网络可能在大陆花岗岩地壳中不存在。在这里，我们报告了有史以来第一个实验结果，包括在温度≥400 °C的真三轴应力下将低粘度水应用于花岗岩。这项工作证明了渗透性微裂缝网络的形成，这些微裂缝密集地分布在整个岩体中，代表了所谓的云裂缝网络。压裂被认为是在一个相对较低的注射压力之间的中间和最小的主应力和传播根据预先存在的微裂缝的分布，独立的主应力的方向。这项研究证实了油井增产的可能性，以创造良好的裂缝模式，应允许有效提取热能。
Superhot geothermal environments (above ca. 400 °C) represent a new geothermal energy frontier. However, the networks of permeable fractures capable of storing and transmitting fluids are likely to be absent in the continental granitic crust. Here we report the first-ever experimental results for well stimulation involving the application of low-viscosity water to granite at temperatures ≥400 °C under true triaxial stress. This work demonstrates the formation of a network of permeable microfractures densely distributed throughout the entire rock body, representing a so-called cloud-fracture network. Fracturing was found to be initiated at a relatively low injection pressure between the intermediate and minimum principal stresses and propagated in accordance with the distribution of preexisting microfractures, independent of the directions of the principal stresses. This study confirms the possibility of well stimulation to create excellent fracture patterns that should allow the effective extraction of thermal energy.