Creating Cloud-Fracture Network by Flow-induced Microfracturing in Superhot Geothermal Environments
Creating Cloud-Fracture Network by Flow-induced Microfracturing in Superhot Geothermal Environments
复制标题
DOI：
10.1007/s00603-021-02416-z
复制
发表时间：
2021-03
影响因子：
6.2
通讯作者：
Ryota Goto;N. Watanabe;K. Sakaguchi;T. Miura;Youqing Chen;T. Ishibashi;Eko Pramudyo;Francesco Parisio;K. Yoshioka;Kengo Nakamura;T. Komai;N. Tsuchiya
中科院分区：
文献类型：
--
作者：
Ryota Goto;N. Watanabe;K. Sakaguchi;T. Miura;Youqing Chen;T. Ishibashi;Eko Pramudyo;Francesco Parisio;K. Yoshioka;Kengo Nakamura;T. Komai;N. Tsuchiya
深度约2-4公里、温度约400-500°C的超热地热环境作为新型地热资源而备受关注。为了通过建立增强型地热系统（超热EGS）来有效地开发超热地热资源，水力压裂是一种很有前景的技术。实验室规模的花岗岩水力压裂实验最近证明，在水的超临界温度或接近温度下，整个岩体形成了密集的渗透性裂缝网络，称为云裂缝网络。尽管该过程被认为涉及低粘度水连续渗透到预先存在的微裂缝中，然后形成和合并后续裂缝，但云裂缝网络形成的合理标准仍有待澄清。格里菲斯破坏准则的适用性得到了水力压裂实验的支持，并对花岗岩在 400°C 真三轴应力下和 450°C 传统三轴应力下进行声发射测量。本研究首次为建立超热EGS水力压裂程序提供了所需的理论基础。
Superhot geothermal environments with temperatures of approximately 400–500 °C at depths of approximately 2–4 km are attracting attention as new kind of geothermal resource. In order to effectively exploit the superhot geothermal resource through the creation of enhanced geothermal systems (superhot EGSs), hydraulic fracturing is a promising technique. Laboratory-scale hydraulic fracturing experiments of granite have recently demonstrated the formation of a dense network of permeable fractures throughout the entire rock body, referred to as a cloud-fracture network, at or near the supercritical temperature for water. Although the process has been presumed to involve continuous infiltration of low-viscosity water into preexisting microfractures followed by creation and merger of the subsequent fractures, a plausible criterion for cloud-fracture network formation is yet to be clarified. The applicability of the Griffith failure criterion is supported by hydraulic fracturing experiments with acoustic emission measurements of granite at 400 °C under true triaxial stress and at 450 °C under conventional triaxial stress. The present study provides, for the first time, a theoretical basis required to establish the procedure for hydraulic fracturing in the superhot EGS.