High-temperature and high-pressure rheology of rock fractures: impacts on hydrothermal fluids circulation in magmatic systems.

岩石裂隙高温高压流变学：对岩浆系统热液循环的影响。

• 批准号: 416615483
• 负责人: Dr. Keita Yoshioka, since 9/2021
• 金额: --
• 依托单位: Montanuniversität Leoben
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/416615483?language=en
• 关键词: temperature; pressure; rheology; rock; fractures

Watanabe et al.’s (2017a) work published in Nature Geoscience critically challenges the scientific community’s hypothesis of a significant reduction in the formation permeability below the Brittle Ductile Transition (BDT) depth and argues in favour of perspectives of exploitable supercritical geothermal resources in the ductile crust. A subsequent Thermo-Hydro-Mechanical (THM) experimental study (Watanabe et al. 2017b) shows a drastic change in the fracture network morphology from planar to dendritic in supercritical conditions, which again supports the earlier argument. However, despite the significant implications of these findings, an adequate conceptual framework that describes these phenomena is yet to be conceived. The formulation of such a model can in turn be based on previous work by the German team on the constitutive model of rocks spanning the brittle-ductile transition. The mentioned model has been successfully employed to explain previously contrasting precursory seismic and gravimetric signals of volcanic eruptions as related with high-temperature rheology of rocks. A successful extension to describe the above mentioned experimental phenomena requires addressing several open questions relating fluid and rock rheology to fracture morphology and permeability evolution. This study will unravel the complex mechanisms behind natural fracture formation beyond the brittle condition in the earth crust. To this purpose, further experiments will be conducted first at Tohoku University, decoupling each component thought to play a role in the dendritic fracture development, which are pore space, supercritical fluid rheology, and ductile rock rheology, in order to assess their individual impacts. Based on the experimental results, the constitutive model developed by the German partners will be further extended towards supercritical pore fluids and implemented into the open-source multi-physics code OpenGeoSys. Finally, the explanatory capabilities of the newly developed concepts towards intricate dynamical processes in the earth’s crust (e.g., supercritical hydro-thermal flows with evolving rock permeability, low-frequency earthquakes, dyke propagation, etc.) will be assessed in simulations of selected large-scale scenarios to be conducted by the German-Japanese team utilizing High Performance Computing (HPC) capabilities at the partner institutions.

Watanabe等人“的（2017年a）发表在《自然地球科学》上的工作对科学界关于在脆韧性转变（BDT）深度以下地层渗透率显著降低的假设提出了严峻的挑战，并主张在韧性地壳中可开采的超临界地热资源的前景。随后的热-水力-机械（THM）实验研究（Watanabe等人，2017 b）显示，在超临界条件下，裂缝网络形态从平面到树枝状发生了急剧变化，这再次支持了先前的论点。然而，尽管这些研究结果的重大影响，一个适当的概念框架，描述这些现象还有待构思。这样一个模型的制定，可以反过来基于以前的工作，由德国队的岩石本构模型跨越脆-韧性转变。上述模型已成功地用于解释以前对比的火山爆发的地震和重力信号与高温流变岩石。一个成功的扩展，以描述上述实验现象，需要解决几个悬而未决的问题有关的流体和岩石流变裂缝形态和渗透率的演变。这项研究将揭示地壳脆性条件下天然裂缝形成背后的复杂机制。为此，首先将在东北大学进行进一步的实验，将被认为在树枝状裂缝发育中发挥作用的每个成分（孔隙空间、超临界流体流变学和韧性岩石流变学）分开，以评估它们各自的影响。根据实验结果，德国合作伙伴开发的本构模型将进一步扩展到超临界孔隙流体，并实施到开源多物理场代码OpenGeoSys中。最后，新发展的概念对地壳复杂动力学过程的解释能力（例如，超临界水热流与岩石渗透率的变化、低频地震、堤坝扩展等）将在选定的大规模情景模拟中进行评估，由德国-日本团队利用合作机构的高性能计算（HPC）能力进行。