The Muschelkalk, composed of Triassic limestones, marls, dolomites, and evaporites, forms part of the Permo-Triassic cover of sedimentary rocks that directly overlies the fractured granitic reservoir used for geothermal energy exploitation in the Upper Rhine Graben. Petrophysical data for this lithostratigraphic unit are sparse, but are of value for reservoir prospection, stimulation, and optimisation strategies at existing and prospective geothermal sites throughout the Upper Rhine Graben. To this end, we present here a systematic microstructural, mineralogical, and petrophysical characterisation of the Muschelkalk core (from the Middle to Lower Muschelkalk; from a depth of ~ 930 to ~ 1001 m) from exploration borehole EPS-1 at Soultz-sous-Forêts (France). First, we assessed the microstructure and mineral content of samples from six depths that we consider represent the variability of the available core. The majority of the core is composed of fine-grained, interbedded dolomites and marls; however, anhydrite and a dolomitic sandstone bank were found in the Upper and Lower Muschelkalk core, respectively. A larger suite of samples (from fifteen depths, including the six depths chosen for microstructural and mineral content analysis) were then characterised in terms of their petrophysical properties. The matrix porosity of the measured Muschelkalk samples is low, from ~ 0.01 to ~ 0.1, and their matrix permeability is below the resolution of our permeameter (≪ 10−18 m2). P-wave velocity, thermal conductivity, thermal diffusivity, specific heat capacity per unit volume, Young’s modulus, and uniaxial compressive strength range from 2.60 to 5.37 km/s, 2.42 to 5.72 W/mK, 1.19 to 2.46 mm2/s, 1.63 to 2.46 MJ/m3 K, 9.4 to 39.5 GPa, and 55.1 to 257.6 MPa, respectively. Therefore, and despite the narrow range of porosity, the petrophysical properties of the Muschelkalk are highly variable. We compare these new data with those recently acquired for the Buntsandstein unit (the Permo-Triassic unit immediately below the Muschelkalk) and thus provide an overview of the petrophysical properties of the two sedimentary units that directly overly the fractured granitic reservoir.

中文翻译：

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来自Soultz-sous-Forêts地热站点（法国）的Muschelkalk的岩石物理性质，这是上莱茵河Graben地热开发的重要岩石地层学单元

Muschelkalk由三叠纪的石灰岩，泥灰岩，白云岩和蒸发岩组成，形成了沉积岩的Permo-Triassic覆盖层的一部分，该覆盖层直接覆盖了上游莱茵Graben地热能源开采中破碎的花岗岩储层。该岩石地层学单元的岩石物理数据稀疏，但对于整个上莱茵-格拉本地区现有和潜在地热站点的储层勘探，增产和优化策略具有价值。为此，我们在这里介绍了Soultz-sous-soul的勘探井EPS-1的Muschelkalk岩心（从中部到下部Muschelkalk；深度约930至1001 m）的系统微观结构，矿物学和岩石物理特征。福雷斯（法国）。第一，我们从六个深度评估了样品的微观结构和矿物质含量，我们认为这些深度代表了可用岩心的变异性。岩心的大部分由细粒，夹层的白云岩和泥灰岩组成。然而，在Muschelkalk上部和下部岩心分别发现了硬石膏和白云质砂岩。然后根据岩石物理特性对一大批样品（从15个深度中选择了包括用于显微组织和矿物含量分析的6个深度）进行了表征。所测量的Muschelkalk样品的基质孔隙度很低，从〜0.01到〜0.1，并且它们的基质渗透率低于我们的渗透仪的分辨率（≪ 10-18 m2）。P波速度，导热系数，热扩散系数，每单位体积的比热容，杨氏模量，单轴抗压强度分别为2.60至5.37 km / s，2.42至5.72 W / mK，1.19至2.46 mm2 / s，1.63至2.46 MJ / m3 K，9.4至39.5 GPa和55.1至257.6 MPa。因此，尽管孔隙率范围狭窄，但Muschelkalk的岩石物理性质却高度可变。我们将这些新数据与最近从Buntsandstein单元（Muschelkalk下方的Permo-Triassic单元）获得的数据进行比较，从而概述了直接位于裂缝性花岗岩储层上方的两个沉积单元的岩石物性。Muschelkalk的岩石物理性质是高度可变的。我们将这些新数据与最近从Buntsandstein单元（Muschelkalk下方的Permo-Triassic单元）获得的数据进行比较，从而概述了直接位于裂缝性花岗岩储层上方的两个沉积单元的岩石物性。Muschelkalk的岩石物理特性是高度可变的。我们将这些新数据与最近从Buntsandstein单元（Muschelkalk下方的Permo-Triassic单元）获得的数据进行比较，从而概述了直接位于裂缝性花岗岩储层上方的两个沉积单元的岩石物性。