Spring Water Geochemistry: A Geothermal Exploration Tool in the Rhenohercynian Fold-and-Thrust Belt in Belgium

Abstract

Spring water geochemistry is applied here to evaluate the geothermal potential in Rhenohercynian fold and thrust belt around the deepest borehole in Belgium (Havelange borehole: 5648 m MD). Fifty springs and (few) wells around Havelange borehole were chosen according to a multicriteria approach including the hydrothermal source of “Chaudfontaine” (T ≈ 36 °C) taken as a reference for the area. The waters sampled, except Chaudfontaine present an in-situ T range of 3.66–14.04 °C (mean 9.83 °C) and a TDS (dry residue) salinity range of 46–498 mg/L. The processing methods applied to the results are: hierarchical clustering, Piper and Stiff diagrams, TIS, heat map, boxplots, and geothermometry. Seven clusters are found and allow us to define three main water types. The first type, locally called “pouhon”, is rich in Fe and Mn. The second type contains an interesting concentration of the geothermal indicators: Li, Sr, Rb. Chaudfontaine and Moressée (≈5 km East from the borehole) belong to this group. This last locality is identified as a geothermal target for further investigations. The third group represents superficial waters with frequently high NO3 concentration. The application of conventional geothermometers in this context indicates very different reservoir temperatures. The field of applications of these geothermometers need to be review in these geological conditions.

Editorial of Special Issue “Enhanced Geothermal Systems and Other Deep Geothermal Applications throughout Europe: The MEET Project”

“…The inputs and difficulties of studying surface analogues were investigated [12]. Fluid flow laboratory experiments were conducted within slate samples from the Harz Mountains [13] and water samples collected from springs around a very deep borehole in Belgium were analyzed [14]. The fluid flow pathways were investigated through the use of the Mohr diagram [15] and the experimental determination of hydraulic properties of fractures [16].…”

“…Cabidoche et al [14] characterized water samples collected in 50 springs to evaluate the geothermal potential around the Havelange (Belgium) deep borehole, within the Rhenohercynian fold and thrust belt. They based their work on a heat map as well as on hydrogeochemistry and geothermometry analyses to define the main water types, and produced the paper entitled "Spring Water Geochemistry: A Geothermal Exploration Tool in the Rhenohercynian Fold-and-Thrust Belt in Belgium".…”

“…During the four years of the project, two main types of exploitations were investigated: Enhanced Geothermal Systems (EGS) and oil-to-geothermal conversion or co-production. The following topics were addressed: the upscaling of thermal power production and optimized operation of EGS plants (papers [1][2][3][4][5]); variscan geothermal reservoirs in granitic and metamorphic rocks (papers [6][7][8][9][10][11][12][13][14][15][16][17]); and technical, economic and environmental assessment for oil-to-geothermal fields and EGS integration into energy systems (papers [18][19][20]). These 20 papers give an overview of some of the work performed in the MEET project, but they are not exhaustive of all the results obtained in this frame.…”