Geothermal systems consisting of fractures in impermeable rocks are difficult to characterize by in situ methods. In an effort to link characteristics of small-scale and large-scale fractures, this study investigated possible relations between their geophysical parameters. We upscaled the relationship between fracture permeability and formation factor in a laboratory specimen to larger fracture dimensions. Microscopic flow characteristics indicate that this relationship is related to the tortuosity of flow paths. We derived an empirical formula that directly predicts changes in fracture permeability from changes in formation factor. This relation may make it possible to monitor subsurface hydraulic activities through resistivity observations.

由不渗透岩石中的裂缝组成的地热系统很难通过原位方法表征。为了将小规模和大型裂缝的特征联系起来，本研究调查了其地球物理参数之间的可能关系。我们将实验室样品中的裂缝渗透率和形成因子之间的关系放大到更大的裂缝尺寸。微观流动特性表明这种关系与流动路径的曲折性有关。我们得出了一个经验公式，该公式可以根据形成因子的变化直接预测裂缝渗透率的变化。这种关系可能使通过电阻率观测监测地下水力活动成为可能。