Database of Petrophysical Properties of the Mid-German Crystalline High

Abstract

Abstract. Petrophysical properties are a key element for reservoir characterization but also for interpreting the results of various geophysical exploration methods or geophysical well logs. Furthermore, petrophysical properties are commonly used to populate numerical models and are often critically governing the model results. Despite the common need of detailed petrophysical properties, data is still very scarce and often not available for the area of interest. Furthermore, both the online research for published property measurements or compilations, as well as dedicated measurements campaigns of the selected properties, which requires comprehensive laboratory equipment, can be very time-consuming and costly. To date, most published research results are often focused on a limited selection of parameters only and hence, researching various petrophysical properties, needed to account for the thermal-hydraulic-mechanical behavior of selected rock types or reservoir settings, can be very laborious. Since for deep geothermal energy in central Europe, the majority of the geothermal potential or resource is assigned to the crystalline basement, a comprehensive database of petrophysical properties comprising rock densities, porosity, rock matrix permeability, thermal properties (thermal conductivity and diffusivity, specific heat capacity) as well as rock mechanical properties as compressive and shear wave velocities, unconfined compressive strength, Young’s modulus, Poisson’s ratio, tensile strength and triaxial shear strength was compiled by measurements conducted at the HydroThermikum lab facilities of the Technical University of Darmstadt. Analyzed samples were mostly derived from abandoned or active quarries and natural or artificial outcrops such as road cuts, river banks or steep hill slopes. Furthermore, samples of the cored deep wells Worms 3 (samples from 2175–2195 m), Stockstadt 33R (samples from 2245–2267 m), Weiterstadt 1 (samples from 2502–2504 m), Tiefbohrung Groß-Umstadt/Heubach, B/89–B02 and the cored shallow wells Forschungsbohrung Messel GA 1 and 2 as well as GWM17 Zwingenberg, GWM1A Zwingenberg, Langenthal BK2/05, EWS267/1 Heubach, and archive samples of the Institut für Steinkonservierung e.V. in Mainz originating from a comprehensive large scale sampling campaign in 2007 were investigated. The database (Weinert et al. 2020b, https://doi.org/10.25534/tudatalib-278) aims to provide easily accessible petrophysical properties of the Mid-German Crystalline High, measured on 224 locations in Bavaria, Hesse, Rhineland-Palatinate and Thuringia and comprising 26,951 single data points. Each data point is addressed with the respective metadata such as sample identifier, sampling location, petrography and if applicable stratigraphy and sampling depth (in case of well samples).

Integrated 3D geological modelling of the northern Upper Rhine Graben by joint inversion of gravimetry and magnetic data

“…In comparison, the less suitable mafic and metamorphic rocks occupy a rather subordinate area. Additionally, Weinert et al (2020a) found a direct relationship between bulk density and thermal conductivity for the rock samples of the MGCH. The petrophysical models can therefore be used to infer the spatial distribution of thermal properties in the basement, allowing again more realistic potential estimates and heat flow simulations.…”

“…While the highest values are measured in granites due to the increased concentration of radioactive elements, the heat production of mafic rocks is on average almost one magnitude smaller (Vilà et al, 2010). Likewise, the thermal conductivity of granites is by a factor of 1.3 higher than in gabbros (Weinert et al, 2020a). In addition, also the hydraulic conductivity of the basement is strongly influenced by the lithology.…”

“…(Brun et al, 1992;Meier and Eisbacher, 1991;Meissner and Bortfeld, 1990). Key information is therefore mainly provided by the crystalline outcrops at the graben borders, which for example allow the conduction of analogue studies (Bär, 2012;Dezayes et al, 2021;Weinert et al, 2020a;Welsch et al, 2014).…”

Techno-Economic Assessment of Geothermal Resources in the Variscan Basement of the Northern Upper Rhine Graben

“…2c). Petrophysical data, mainly the specific heat capacity, were adapted from the databases of Ba ¨r et al (2020) and Weinert et al (2020). Information on the 3D stress tensor in the Northern URG, provided by Ahlers et al (2021), was used to determine the reactivation potential of fault zones (see details below).…”

Comment on se-2021-118

“…the approach of Oda (1985). The undisturbed rock matrix is considered impermeable (Jing and Stephansson, 2007;Weinert et al, 2020), implying that fluid flow occurs exclusively through connected fractures. The directional permeability is related to the size, orientation, opening and connectivity of the fractures.…”