Abstract The behavior of fluid flow through rock fractures at varying temperatures is a critical issue in many subsurface geo-energy projects. Previous work has considered the thermal effects on fracture permeability, but not in isolation of the chemical effects as well. Therefore, to quantitatively assess the mechanical influences on fracture permeability, we present results from permeability tests of five cylindrical Beishan granite samples, each with a single artificial fracture, at different temperatures. Three samples were tested at a constant confining pressure of 5 MPa and temperatures of 22 °C, 90 °C and 150 °C for 22 days, to examine creep-induced changes in fracture permeability. Fracture permeability decreases with time until about 10 days, and the eventual magnitudes of fracture permeability reduction are much greater at 90 °C and 150 °C than at 22 °C. Two samples were subjected to three heating cycles (30 °C to 150 °C) at a constant confining pressure of 5 MPa. Fracture permeability decreases as temperatures increase from 30 °C to 150 °C, and then slight changes in permeability occur as the sample is cooled to 30 °C. A similar tendency appears in subsequent temperature cycles, while the magnitude of fracture permeability reduction decreases with increasing heating-cooling cycles. A coupled thermal-mechanical model considering asperity damage is developed to describe the thermally-induced changes in fracture permeability, which properly predicts the experimental results. The residual deformation of asperities and temperature dependent Young's modulus play an important role in thermally-induced changes in fracture permeability.

中文翻译：

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单个花岗岩裂缝中热效应对渗透率的影响：实验和理论模型

摘要 在许多地下地质能源项目中，流体在不同温度下通过岩石裂缝的流动行为是一个关键问题。以前的工作已经考虑了热对裂缝渗透率的影响，但也没有孤立地考虑化学影响。因此，为了定量评估对裂缝渗透率的机械影响，我们提供了五个圆柱形北山花岗岩样品在不同温度下的渗透率测试结果，每个样品都有一个人工裂缝。在 5 MPa 的恒定围压和 22 °C、90 °C 和 150 °C 的温度下测试了三个样品 22 天，以检查蠕变引起的裂缝渗透率变化。裂缝渗透率随时间降低，直至约 10 天，90 °C 和 150 °C 时裂缝渗透率降低的最终幅度比 22 °C 时大得多。两个样品在 5 MPa 的恒定围压下进行三个加热循环（30 °C 至 150 °C）。随着温度从 30 °C 升高到 150 °C，裂缝渗透率会降低，然后当样品冷却到 30 °C 时，渗透率会发生轻微变化。类似的趋势出现在随后的温度循环中，而裂缝渗透率降低的幅度随着加热-冷却循环的增加而减小。开发了一种考虑粗糙损伤的热力耦合模型来描述热致裂缝渗透率的变化，从而正确地预测了实验结果。凹凸不平的残余变形和温度相关的 Young'