Thermal tracking of upper crustal fluid flow in the Rhine graben

Abstract

Abstract. More than 52,000 temperature values from almost 10,000 boreholes in Germany have been incorporated into a data base since 1977. Due to petroleum-oriented drilling, a large quantitity of temperature data (both German and French) is available for the Rhine Graben. A horizontal temperature contour map for 800 m depth and a vertical cross section support the concept that thermal anomalies in the Rhine Graben are caused by convection in the upper crust. At the local scale of a borehole, large changes of the temperature gradient to depths of 5 km can roughly be related to different hydraulic conditions of the formations. A better means to qualitatively characterize the convective regime, however, is the observed thermal equilibration in a well after drilling disturbances. The data base is well suitable for an application of temperature as a tracer for fluid flow.

How do permeable fractures in the Triassic sediments of Northern Alsace characterize the top of hydrothermal convective cells? Evidence from Soultz geothermal boreholes (France)

“…However, this radiogenic production is insufficient to explain the geothermal anomalies (Stussi et al 2002). Temperature data from various oil and geothermal wells reveal a concentration of hot zones along Soultz or Kutzenhausen normal faults (Benderitter and Elsass 1995;Pribnow and Clauser 2000;Pribnow and Schellschmidt 2000). These geothermal anomalies at the local scale are attributed to buoyancy-induced hydrothermal circulation within the crystalline basement and the sandstones.…”

“…The so-called 'Soultz geothermal anomaly' is one of the most important temperature anomalies and has been the subject of numerous studies. Soultz granites exhibit a maximum variation in radiogenic production of 5.5 to 6.5 μW/m 3 measured in core samples from GPK-1 (Rummel et al 1988) and a more important vertical variation of 2 to 7 μW/m 3 in GPK-2 (Pribnow and Schellschmidt 2000). However, this radiogenic production is insufficient to explain the geothermal anomalies (Stussi et al 2002).…”

“…This profile can be divided into three parts. The uppermost part from 0-to 1.0-km depth is composed of sedimentary formations from Tertiary and Mesozoic (Jurassic and Upper Trias) and features a geothermal gradient of 110°C/km, which indicates a conductive heat transport mechanism (Pribnow and Schellschmidt 2000). This geological section acts as a cap rock, i.e., an impermeable layer that insulates the hydrothermal system active below.…”

“…Triassic sediments above it (Schellschmidt and Clauser 1996;Pribnow and Schellschmidt 2000;Pribnow and Clauser 2000). The interpretation of seismic reflection profiles identifies major large-scale faults extending across the Cenozoic and Mesozoic sedimentary cover and originating in the Paleozoic fractured basement (Cautru 1988) (Figure 1).…”

Structure and nature of the Palaeozoic basement based on magnetic, gravimetric and seismic investigations in the central Upper Rhinegraben

“…The extensive geological, geophysical and deep drilling data collected in the Soultz and Rittershoffen geothermal wells have led to a better understanding of the deep-seated geothermal resources located at the interface between the sediments and the basement of northern Alsace (Baujard et al 2017;Dezayes et al 2010, Ledésert et al 1999Pribnow and Schellschmidt 2000;Sanjuan et al 2016;Sausse et al 2010;Vidal et al 2016Vidal et al , 2017.…”