Defining the fracture network and the active fluid pathways are fundamental to characterizing a fractured reservoir. With this goal, we chose the Saint Pierre Bois quarry (Vosges Massif, France) as a natural analogue for the Permian-Stephanian cover (arkoses)/Hercynian basement (granite) transition that serve as geothermal reservoirs, for example at Rittershoffen, Landau and Insheim, where geothermal plants exploit this kind of reservoir within the Upper Rhine Graben (URG). During our study, along walls of the quarry, we measured fracture orientation on multiple 1D scanlines, sampled fracture fills and associated wall rock, and measured porosity. Our interpretation of the fracture dataset and associated mineral deposits and alteration indicates a large unmapped fault zone (displacement around 10m) we infer to cross the quarry. This fracture zone comprises a core zone (>50 m thick), which is the most highly altered-fractured zone in the quarry. In the transition zone (20–25m thick), some E-W faults cross and displace the arkose/granite transition. The two major fracture sets (E-W and NNE-SSW strikes) are present in the damage zone (>100m thickness) and are typically randomly distributed, but sometimes are grouped in clusters (defined by high spacing coefficient of variation). The E-W fractures and faults are the result of local tectonic inheritance in relation to the Villé basin formation at the end of the Hercynian orogen. Based on rock alteration, these structures constitute good pathways for fluid, first of all for the meteoric fluid during the E-W fault zone creation associated to the Villé basin opening, and then for the hot brine, which clogged the system by quartz precipitation during the burial of the basin.

定义裂缝网络和有效流体通道是表征裂缝储层的基础。为了实现这一目标，我们选择了圣皮埃尔·博瓦斯采石场（法国，孚日地区）作为二叠纪-斯蒂芬阶盖（arkoses）/海西期基底（花岗岩）过渡的天然类似物，这些过渡地热库例如在Rittershoffen，Landau和因斯海姆（Insheim），地热发电厂在上莱茵河格拉本（URG）内利用这种储层。在我们的研究中，沿着采石场的墙壁，我们测量了多条一维扫描线上的裂缝方向，采样了裂缝填充物和相关的围岩，并测量了孔隙度。我们对裂缝数据集以及相关的矿藏和蚀变的解释表明我们推断要穿越采石场的是大的未映射断层带（位移约10m）。该断裂带包括一个核心区（> 50 m厚），这是采石场中变化最大的断裂带。在过渡带（20–25m厚）中，一些EW断层横穿并取代了阿科斯/花岗岩过渡带。损坏区（厚度大于100m）中存在两个主要裂缝组（EW和NNE-SSW走向），通常是随机分布的，但有时会成簇分组（由高间距变异系数定义）。EW断裂和断层是与海西造山带末期的Villé盆地形成有关的局部构造遗传的结果。基于岩石蚀变，这些结构构成了良好的流体通道，首先是与维莱盆地开口有关的EW断层带形成期间的陨石流体，然后是热盐水，