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Michel Brach - One of the best experts on this subject based on the ideXlab platform.
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Major geochemical characteristics of Geothermal Brines from the Upper Rhine Graben granitic basement with constraints on temperature and circulation
Chemical Geology, 2016Co-Authors: Bernard Sanjuan, Romain Millot, Chrystel Dezayes, Christophe Innocent, Julia Scheiber, Michel BrachAbstract:This paper is the first to present the main geochemical characteristics of the native Brines collected from all the Geothermal wells penetrating the granite basement underlying the sedimentary cover, in the Upper Rhine Graben. These deep wells (from 2580 to 5000 m) were only drilled in four Geothermal sites (Soultz-sous-Forêts and Rittershoffen in France; Landau and Insheim in Germany). The Na-Cl Geothermal Brine samples collected from the granite returned TDS values ranging from 99 to 107 g/l with pH values close to 5, along with Cl and Br concentrations and delta D, delta 18O and delta 34S values that indicate a multiple origin with mixing between primary Brine formed by advanced evaporation of seawater (probably until the stage of halite precipitation) and dilute meteoric water, plus contributions from halite dissolution following successive marine transgression-regression cycles from the Triassic to the Oligocene. Chemical, isotopic and gas geothermometers indicate concordant reservoir temperatures close to 225 ± 25°C for all the fluids, even though the maximum temperature so far measured on site is 200°C. An exhaustive literature review has indicated that only the Geothermal Brine from the deep Cronenbourg well (2870 m) ending in the Buntsandstein has similar chemical and isotopic compositions (apart from Br and Ca) to the fluids from the granite, with an identical estimation of reservoir temperature from geothermometry. Geothermal Brine from the deep Bruchsal well (2540 m), drilled down to the junction of the Buntsandstein and the Saxo-Thuringian formations, has a higher TDS value (120-125 g/l) with its chemical and isotopic compositions giving a lower estimation of reservoir temperature (190 ± 25°C). By contrast, Geothermal Brine from the Bühl well (2655 m) ending in the Buntsandstein has an even higher TDS value of about 201 g/l and a lower temperature-at-depth estimation of 110 ± 25°C, close to the temperature measured on site (115°C). The above results indicate that the Geothermal fluids collected from the granite probably originate from Triassic sedimentary formations located at great depth (≥4 km) with temperatures close to 225 ± 25°C in the centre of the Rhine Graben, but that their different TDS and Cl/Br values reflect the presence of several distinct Geothermal reservoirs. Many discrepancies due to high-temperature water-rock interactions are revealed on comparing the chemical and isotopic compositions of the hot Brines with those of cooler Brines from Bühl and the Landau Eocene-Oligocene oilfield wells, among others. The hottest Brines are much enriched in K, Ca, SiO2, Li, Rb, Cs, As, Sr, Ba, Mn, Nd, U and in metals such as Zn, Pb, Cu, Co, Cd, Sb, but are depleted mainly in Mg, SO4 and B and have much lower isotopic Li and B signatures. The He isotopic signatures of the gases associated with these fluids (R/Ratm. = 0.128 at Bruchsal and 0.252 at Insheim) confirm that the thermal anomalies are mainly crustal and not mantle-derived (1.46% and 2.88% of mantellic He, respectively, for the two sites). Thus it is concluded that the thermal anomalies are associated mainly with the convective circulation of hot fluids along probable NE-SW faults between the graben’s deep sedimentary centre and the fractured granite basement at its edges. Moreover, the western part of the Upper Rhine Graben (the Landau, Insheim, Soultz, Rittershoffen and Cronenbourg sites) seems to be hotter than the eastern part (Bruchsal and Bühl). According to the U-Th isotope system, the minimum transit time of these deep Geothermal Brines would be about 1000 years.
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main characteristics of the deep Geothermal Brine 5 km at soultz sous forets france determined using geochemical and tracer test data
Comptes Rendus Geoscience, 2010Co-Authors: Bernard Sanjuan, Chrystel Dezayes, Romain Millot, Michel BrachAbstract:Three deep wells (5000 m) have been drilled into a fractured granite basement at Soultz-sous-Forets, within the Tertiary Rhine Graben, in order to develop a heat exchanger and produce electricity after the creation of an EGS reservoir. Very few analyses representative of the deep Geothermal fluids are available because of frequent contamination by drilling fluids or injected waters. These indicate similar chemical and isotopic compositions (NaCl fluids) and high salinities (about 100 g/l) suggesting a common sedimentary origin and identical water–rock interaction processes at equilibrium temperatures close to 230 °C in a sedimentary rather than a granite reservoir. The latter would be situated closer to the Graben centre where the Triassic Buntsandstein formation is deepest and hottest. Tracer tests conducted after 2000 show that the deep native Geothermal Brine is omnipresent in the fluids discharged during the production and circulation tests. Its natural convective flux was estimated at 1–1.2 m3/h.
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Fluid origin and circulation in the heat exchanger of Soultz-sous-Forêts (France) estimated using geochemical and tracer test data.
2008Co-Authors: Bernard Sanjuan, Chrystel Dezayes, Romain Millot, Michel BrachAbstract:In the framework of the European Hot Dry Rock Energy (HDR) Program, three deep wells (5000 m) have been drilled into a fractured granite basement at Soultz-sous-Forêts, located within the Rhine Graben, in order to develop a deep heat exchanger (GPK-3 as injector and GPK-2/GPK-4 as producers) and produce electricity after the creation of an EGS reservoir. Despite very few representative analyses of deep Geothermal fluids, often contaminated by drilling fluids or injected waters, the geochemical data provide new and interesting information on the nature, origin, circulation and deep temperature of these fluids (Sanjuan et al., 2006a and c). They indicate similar chemical and isotopic compositions (NaCl fluids) and high salinity values (TDS about 100 g/l) which suggest a common sedimentary origin and identical water-rock interaction processes. The chemical and gas geothermometers suggest that the native Geothermal Brine and associated gases are equilibrated with a mineralogical assemblage at temperatures close to 220-240°C (> 200°C measured at the bottom-hole; Sanjuan et al., 2006a and c). According to the Na/Li geothermometer and the 7Li values, these equilibrium reactions would occur in a sedimentary rather than granite reservoir (Fig. 1). Given the location of the Soultz site and these constraints, this reservoir would be situated more eastern, towards the Graben centre where the Triassic sedimentary formations are the deepest and hottest (Fig. 2). From tracer tests carried out after 2000, the natural flux of the native Geothermal Brine was estimated at 1-1.2 m3/h, which is identical to that calculated for the fluid flux parallel to the Graben strike, based on a convection model and numerical 3D modeling (Bächler, 2003; Sanjuan et al., 2006b and c). During all the production and circulation tests, the tracer tests and geochemical data showed the omnipresence of the native Geothermal Brine in the discharged fluids even after injection of large amounts of external water into the wells. The existence of at least three fluid flow pathways between the wells GPK-2 and GPK-3 with different effective fluid velocities, which contrasts with a poor hydraulic connection between GPK-3 and GPK-4 (Fig. 3), was highlighted during the fluid circulation loop and the associated tracer test using fluorescein, carried out between July and December 2005 (Sanjuan et al., 2006b and c).
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TRACER TESTING AT SOULTZ-SOUS-FORÊTS ( FRANCE ) USING NA-BENZOATE , 1 , 5 AND 2 , 7-NAPHTHALENE DISULFONATE
Twenty-Ninth Workshop on Geothermal Reservoir Engineering, 2004Co-Authors: Sanjuan Bernard, Jean-claude Foucher, Michel Brach, Peter Rose, Gilles BraibantAbstract:A hydraulic stimulation was conducted in well GPK-2, at Soultz-sous-Forêts (France), in July 2000, one year after its deepening from a depth of 3,500 m to 5,100 m. During this operation, two organic tracers (Na-benzoate and 1,5-naphthalene disulfonate) were continuously injected at a controlled concentration of about 2 mg/l into GPK-2 with around 26,800 m3 of fresh water. The chemical composition of this water is very different from that of the Geothermal Brine (NaCl fluid with a TDS close to 100 g/l). Four short- term production tests were carried out between December 2000 and April 2002. The fluid produced from GPK-2 was geochemically monitored during these tests. This paper presents the main results of that fluid monitoring. Comparison with natural tracers such as chloride indicated that the organic tracers were remarkably stable during more than 2 years at around 200°C. At each production test, the mass proportions of injected fresh water and Geothermal Brine could be estimated; the recovered fresh water could also be calculated (less than 7% relative to the total volume of fresh water injected into GPK-2). It was observed that the injected fresh water was internally replaced by the Geothermal Brine in the reservoir. The mean flow rate of the Geothermal Brine circulation could be estimated at 1-1.2 m3/h. Between January and March 2003, and during another operation of hydraulic stimulation, a third tracer (2,7-naphthalene disulfonate) was injected into GPK-2 at a controlled concentration of about 3 mg/l, with about 24,000 m3 of fresh water. The detection of 1,5-nds, almost 3 years after its injection into GPK-2, and that of 2,7-nds in the fluid discharged from GPK-3, have shown that the recently drilled GPK-3 well (depth of 5,100 m) is directly connected to GPK-2.
Bernard Sanjuan - One of the best experts on this subject based on the ideXlab platform.
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Main geochemical characteristics of the deep Geothermal Brine at Vendenheim (Alsace, France) with constraints on temperature and fluid circulation
2020Co-Authors: Bernard Sanjuan, Gabrielle Negrel, Morgan Le Lous, Ewan Poulmarch, Frédérick Gal, Pierre-clément DamyAbstract:The first analytical results relative to the native Geothermal Brine discharged from the two deep wells drilled at Vendenheim, in the Rhine Graben, in Alsace (France), obtained within the framework of the Vendenheim FONROCHE Geothermal project and the H2020 European DEEP-EGS project, suggest the geochemical composition of this Brine is very similar to that of the fluid which was discharged from the neighboring Cronenbourg deep well, in the past. It is also close to that of the Brines discharged from the other deep wells located in more northern areas of the Rhine Graben, such as Soultz-sous-Forêts, Rittershoffen, in France, and Landau, Insheim, in Germany. This Na-Cl Brine has a TDS value around 100 g/l and a pH value close to 5, before cooling and degassing. Except for the calcium and strontium concentration values, which are much lower than those in the Soultz-sous-Forêts, Rittershoffen, Landau and Insheim Brines, the other concentration values of major and trace species are comparable. Given the similarity of the geochemical composition of all these waters, their origin is probably similar but also multiple, because it results from processes of mixing between primary Brines formed by advanced evaporation of seawater (probably until the stage of halite precipitation) and meteoric freshwaters, plus contributions from halite dissolution following successive marine transgression-regression cycles from the Triassic to Oligocene. As for the other deep Brines, the main solute cation geothermometers give estimations of reservoir temperature close to 225 ± 25°C for the Vendenheim native Brine. This estimation probably corresponds to the temperature of equilibrium at which this Brine acquires its chemical composition by interaction with the reservoir rocks. The mineralogical assemblage in equilibrium with the Brine at this temperature was described in previous studies. The concordant estimations of reservoir temperature, using thermometric relationships such Na-Li and Mg/Li, especially developed for oilfield and sedimentary basin Brines, and existing thermal gradients from 40 to 60°C/km, suggest that the deep Brines discharged from the granite basement could probably originate from Triassic sedimentary formations (Buntsandstein, for example) located at great depth (≥ 4 km), in the centre of the Rhine Graben, in which they acquire their high salinity and chemical composition at temperatures close to 225 ± 25°C. This assumption seems to be also supported by their Li, B and Sr isotopic signatures. These hot Brines would then migrate through a complex, but still poorly defined system of deep faults (probably NE-SW but also NW-SE faults), from the sedimentary centre of the Rhine Graben to the granite-fractured basement and the Graben's NW borders.
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Major geochemical characteristics of Geothermal Brines from the Upper Rhine Graben granitic basement with constraints on temperature and circulation
Chemical Geology, 2016Co-Authors: Bernard Sanjuan, Romain Millot, Chrystel Dezayes, Christophe Innocent, Julia Scheiber, Michel BrachAbstract:This paper is the first to present the main geochemical characteristics of the native Brines collected from all the Geothermal wells penetrating the granite basement underlying the sedimentary cover, in the Upper Rhine Graben. These deep wells (from 2580 to 5000 m) were only drilled in four Geothermal sites (Soultz-sous-Forêts and Rittershoffen in France; Landau and Insheim in Germany). The Na-Cl Geothermal Brine samples collected from the granite returned TDS values ranging from 99 to 107 g/l with pH values close to 5, along with Cl and Br concentrations and delta D, delta 18O and delta 34S values that indicate a multiple origin with mixing between primary Brine formed by advanced evaporation of seawater (probably until the stage of halite precipitation) and dilute meteoric water, plus contributions from halite dissolution following successive marine transgression-regression cycles from the Triassic to the Oligocene. Chemical, isotopic and gas geothermometers indicate concordant reservoir temperatures close to 225 ± 25°C for all the fluids, even though the maximum temperature so far measured on site is 200°C. An exhaustive literature review has indicated that only the Geothermal Brine from the deep Cronenbourg well (2870 m) ending in the Buntsandstein has similar chemical and isotopic compositions (apart from Br and Ca) to the fluids from the granite, with an identical estimation of reservoir temperature from geothermometry. Geothermal Brine from the deep Bruchsal well (2540 m), drilled down to the junction of the Buntsandstein and the Saxo-Thuringian formations, has a higher TDS value (120-125 g/l) with its chemical and isotopic compositions giving a lower estimation of reservoir temperature (190 ± 25°C). By contrast, Geothermal Brine from the Bühl well (2655 m) ending in the Buntsandstein has an even higher TDS value of about 201 g/l and a lower temperature-at-depth estimation of 110 ± 25°C, close to the temperature measured on site (115°C). The above results indicate that the Geothermal fluids collected from the granite probably originate from Triassic sedimentary formations located at great depth (≥4 km) with temperatures close to 225 ± 25°C in the centre of the Rhine Graben, but that their different TDS and Cl/Br values reflect the presence of several distinct Geothermal reservoirs. Many discrepancies due to high-temperature water-rock interactions are revealed on comparing the chemical and isotopic compositions of the hot Brines with those of cooler Brines from Bühl and the Landau Eocene-Oligocene oilfield wells, among others. The hottest Brines are much enriched in K, Ca, SiO2, Li, Rb, Cs, As, Sr, Ba, Mn, Nd, U and in metals such as Zn, Pb, Cu, Co, Cd, Sb, but are depleted mainly in Mg, SO4 and B and have much lower isotopic Li and B signatures. The He isotopic signatures of the gases associated with these fluids (R/Ratm. = 0.128 at Bruchsal and 0.252 at Insheim) confirm that the thermal anomalies are mainly crustal and not mantle-derived (1.46% and 2.88% of mantellic He, respectively, for the two sites). Thus it is concluded that the thermal anomalies are associated mainly with the convective circulation of hot fluids along probable NE-SW faults between the graben’s deep sedimentary centre and the fractured granite basement at its edges. Moreover, the western part of the Upper Rhine Graben (the Landau, Insheim, Soultz, Rittershoffen and Cronenbourg sites) seems to be hotter than the eastern part (Bruchsal and Bühl). According to the U-Th isotope system, the minimum transit time of these deep Geothermal Brines would be about 1000 years.
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main characteristics of the deep Geothermal Brine 5 km at soultz sous forets france determined using geochemical and tracer test data
Comptes Rendus Geoscience, 2010Co-Authors: Bernard Sanjuan, Chrystel Dezayes, Romain Millot, Michel BrachAbstract:Three deep wells (5000 m) have been drilled into a fractured granite basement at Soultz-sous-Forets, within the Tertiary Rhine Graben, in order to develop a heat exchanger and produce electricity after the creation of an EGS reservoir. Very few analyses representative of the deep Geothermal fluids are available because of frequent contamination by drilling fluids or injected waters. These indicate similar chemical and isotopic compositions (NaCl fluids) and high salinities (about 100 g/l) suggesting a common sedimentary origin and identical water–rock interaction processes at equilibrium temperatures close to 230 °C in a sedimentary rather than a granite reservoir. The latter would be situated closer to the Graben centre where the Triassic Buntsandstein formation is deepest and hottest. Tracer tests conducted after 2000 show that the deep native Geothermal Brine is omnipresent in the fluids discharged during the production and circulation tests. Its natural convective flux was estimated at 1–1.2 m3/h.
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Fluid origin and circulation in the heat exchanger of Soultz-sous-Forêts (France) estimated using geochemical and tracer test data.
2008Co-Authors: Bernard Sanjuan, Chrystel Dezayes, Romain Millot, Michel BrachAbstract:In the framework of the European Hot Dry Rock Energy (HDR) Program, three deep wells (5000 m) have been drilled into a fractured granite basement at Soultz-sous-Forêts, located within the Rhine Graben, in order to develop a deep heat exchanger (GPK-3 as injector and GPK-2/GPK-4 as producers) and produce electricity after the creation of an EGS reservoir. Despite very few representative analyses of deep Geothermal fluids, often contaminated by drilling fluids or injected waters, the geochemical data provide new and interesting information on the nature, origin, circulation and deep temperature of these fluids (Sanjuan et al., 2006a and c). They indicate similar chemical and isotopic compositions (NaCl fluids) and high salinity values (TDS about 100 g/l) which suggest a common sedimentary origin and identical water-rock interaction processes. The chemical and gas geothermometers suggest that the native Geothermal Brine and associated gases are equilibrated with a mineralogical assemblage at temperatures close to 220-240°C (> 200°C measured at the bottom-hole; Sanjuan et al., 2006a and c). According to the Na/Li geothermometer and the 7Li values, these equilibrium reactions would occur in a sedimentary rather than granite reservoir (Fig. 1). Given the location of the Soultz site and these constraints, this reservoir would be situated more eastern, towards the Graben centre where the Triassic sedimentary formations are the deepest and hottest (Fig. 2). From tracer tests carried out after 2000, the natural flux of the native Geothermal Brine was estimated at 1-1.2 m3/h, which is identical to that calculated for the fluid flux parallel to the Graben strike, based on a convection model and numerical 3D modeling (Bächler, 2003; Sanjuan et al., 2006b and c). During all the production and circulation tests, the tracer tests and geochemical data showed the omnipresence of the native Geothermal Brine in the discharged fluids even after injection of large amounts of external water into the wells. The existence of at least three fluid flow pathways between the wells GPK-2 and GPK-3 with different effective fluid velocities, which contrasts with a poor hydraulic connection between GPK-3 and GPK-4 (Fig. 3), was highlighted during the fluid circulation loop and the associated tracer test using fluorescein, carried out between July and December 2005 (Sanjuan et al., 2006b and c).
Akira Ueda - One of the best experts on this subject based on the ideXlab platform.
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u shaped polymer cladding and hetero core fiber optic sensors for monitoring scale formation in Geothermal Brine
Analytical Letters, 2020Co-Authors: Takuya Okazaki, Ryuichi Seto, Tomoaki Watanabe, Akira Ueda, Hideki KuramitzAbstract:In the development of fiber optic sensors for monitoring scale formation in Geothermal Brine, high sensitivity and easy handling are desirable features. These characteristics have already been succ...
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observation of silica nanoparticle growth in saline Geothermal Brine from the yamagawa Geothermal power station japan using dynamic light scattering
Geothermics, 2019Co-Authors: Ui Mori, Yuji Osaka, Takumi Yanaze, Minoru Kusakabe, Takushi Yokoyama, Katsuo Tsukamoto, Shigeko Unami, Katsumi Marumo, Akira UedaAbstract:Abstract Silica nanoparticle growth during the polymerization of silicic acid in saline Geothermal Brine from the Yamagawa Geothermal power station, Japan, was examined using dynamic light scattering (DLS). Two types of polysilicic acid particles (large and small) were found to grow simultaneously after vapor–Brine separation at the surface. The DLS results seemed to indicate that the average particle size increased over the initial 70 min and then decreased, however this is most likely due to the larger particles settling out. The small particles gradually increased to 200 nm over 180 min. As deduced from the change in the numbers of the two types of polysilicic acid particles, the small particles were absorbed by the large particles.
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experimental field investigations of inhibitors for controlling silica scale in Geothermal Brine at the sumikawa Geothermal plant akita prefecture japan
Geothermics, 2017Co-Authors: Risa Ikeda, Akira UedaAbstract:Abstract A number of Geothermal Brine column flow tests were conducted at the Sumikawa Geothermal power plant to evaluate inhibitors for the prevention of silica scaling. The silica concentration of the Brine was 1150 mg/L and nine inhibitors were examined at concentrations up to 25 mg/L. The most effective inhibitors and concentration were found to be polyacrylic and phosphinocarboxylic acid salts and 1 mg/L, respectively that higher concentrations were not necessarily better in suppressing scaling and generally the inhibiters were better than acidification. The projected cost associated with this inhibition method is close to that of the standard pH adjustment method.
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silica removal from mokai new zealand Geothermal Brine by treatment with lime and a cationic precipitant
Geothermics, 2003Co-Authors: Akira Ueda, Koichi Kato, Katsumi Mogi, Ed Mroczek, Ian A ThainAbstract:Abstract Preliminary experiments using two chemicals (CaO, a quicklime, and a cationic nitrogen-bearing precipitant, EC-004) to remove silica from Geothermal Brine were undertaken at the Mokai Geothermal plant, New Zealand. The Brine was mixed with the reagent (CaO or EC-004). The reaction was studied from the start of the experiment (NRT, 0 min, no retaining time) and after 15 min (15RT) at 90 °C. The concentration of silica in the Brine was initially 954 mg/l, and decreased linearly with increasing reagent concentration. When CaO is added, the silica concentration at 15RT was 200 mg/l lower than at NRT and became almost zero on addition of 1.5 g/l. In contrast, when EC-004 is added, the total silica concentration nearly reaches the solubility of amorphous silica at 90 °C. In order to prevent silica scaling in Mokai Brines cooled to 90 °C, the CaO and EC-004 added should be individually adjusted to 0.5 g/l and 80 mg/l, respectively.
Chrystel Dezayes - One of the best experts on this subject based on the ideXlab platform.
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Major geochemical characteristics of Geothermal Brines from the Upper Rhine Graben granitic basement with constraints on temperature and circulation
Chemical Geology, 2016Co-Authors: Bernard Sanjuan, Romain Millot, Chrystel Dezayes, Christophe Innocent, Julia Scheiber, Michel BrachAbstract:This paper is the first to present the main geochemical characteristics of the native Brines collected from all the Geothermal wells penetrating the granite basement underlying the sedimentary cover, in the Upper Rhine Graben. These deep wells (from 2580 to 5000 m) were only drilled in four Geothermal sites (Soultz-sous-Forêts and Rittershoffen in France; Landau and Insheim in Germany). The Na-Cl Geothermal Brine samples collected from the granite returned TDS values ranging from 99 to 107 g/l with pH values close to 5, along with Cl and Br concentrations and delta D, delta 18O and delta 34S values that indicate a multiple origin with mixing between primary Brine formed by advanced evaporation of seawater (probably until the stage of halite precipitation) and dilute meteoric water, plus contributions from halite dissolution following successive marine transgression-regression cycles from the Triassic to the Oligocene. Chemical, isotopic and gas geothermometers indicate concordant reservoir temperatures close to 225 ± 25°C for all the fluids, even though the maximum temperature so far measured on site is 200°C. An exhaustive literature review has indicated that only the Geothermal Brine from the deep Cronenbourg well (2870 m) ending in the Buntsandstein has similar chemical and isotopic compositions (apart from Br and Ca) to the fluids from the granite, with an identical estimation of reservoir temperature from geothermometry. Geothermal Brine from the deep Bruchsal well (2540 m), drilled down to the junction of the Buntsandstein and the Saxo-Thuringian formations, has a higher TDS value (120-125 g/l) with its chemical and isotopic compositions giving a lower estimation of reservoir temperature (190 ± 25°C). By contrast, Geothermal Brine from the Bühl well (2655 m) ending in the Buntsandstein has an even higher TDS value of about 201 g/l and a lower temperature-at-depth estimation of 110 ± 25°C, close to the temperature measured on site (115°C). The above results indicate that the Geothermal fluids collected from the granite probably originate from Triassic sedimentary formations located at great depth (≥4 km) with temperatures close to 225 ± 25°C in the centre of the Rhine Graben, but that their different TDS and Cl/Br values reflect the presence of several distinct Geothermal reservoirs. Many discrepancies due to high-temperature water-rock interactions are revealed on comparing the chemical and isotopic compositions of the hot Brines with those of cooler Brines from Bühl and the Landau Eocene-Oligocene oilfield wells, among others. The hottest Brines are much enriched in K, Ca, SiO2, Li, Rb, Cs, As, Sr, Ba, Mn, Nd, U and in metals such as Zn, Pb, Cu, Co, Cd, Sb, but are depleted mainly in Mg, SO4 and B and have much lower isotopic Li and B signatures. The He isotopic signatures of the gases associated with these fluids (R/Ratm. = 0.128 at Bruchsal and 0.252 at Insheim) confirm that the thermal anomalies are mainly crustal and not mantle-derived (1.46% and 2.88% of mantellic He, respectively, for the two sites). Thus it is concluded that the thermal anomalies are associated mainly with the convective circulation of hot fluids along probable NE-SW faults between the graben’s deep sedimentary centre and the fractured granite basement at its edges. Moreover, the western part of the Upper Rhine Graben (the Landau, Insheim, Soultz, Rittershoffen and Cronenbourg sites) seems to be hotter than the eastern part (Bruchsal and Bühl). According to the U-Th isotope system, the minimum transit time of these deep Geothermal Brines would be about 1000 years.
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main characteristics of the deep Geothermal Brine 5 km at soultz sous forets france determined using geochemical and tracer test data
Comptes Rendus Geoscience, 2010Co-Authors: Bernard Sanjuan, Chrystel Dezayes, Romain Millot, Michel BrachAbstract:Three deep wells (5000 m) have been drilled into a fractured granite basement at Soultz-sous-Forets, within the Tertiary Rhine Graben, in order to develop a heat exchanger and produce electricity after the creation of an EGS reservoir. Very few analyses representative of the deep Geothermal fluids are available because of frequent contamination by drilling fluids or injected waters. These indicate similar chemical and isotopic compositions (NaCl fluids) and high salinities (about 100 g/l) suggesting a common sedimentary origin and identical water–rock interaction processes at equilibrium temperatures close to 230 °C in a sedimentary rather than a granite reservoir. The latter would be situated closer to the Graben centre where the Triassic Buntsandstein formation is deepest and hottest. Tracer tests conducted after 2000 show that the deep native Geothermal Brine is omnipresent in the fluids discharged during the production and circulation tests. Its natural convective flux was estimated at 1–1.2 m3/h.
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Fluid origin and circulation in the heat exchanger of Soultz-sous-Forêts (France) estimated using geochemical and tracer test data.
2008Co-Authors: Bernard Sanjuan, Chrystel Dezayes, Romain Millot, Michel BrachAbstract:In the framework of the European Hot Dry Rock Energy (HDR) Program, three deep wells (5000 m) have been drilled into a fractured granite basement at Soultz-sous-Forêts, located within the Rhine Graben, in order to develop a deep heat exchanger (GPK-3 as injector and GPK-2/GPK-4 as producers) and produce electricity after the creation of an EGS reservoir. Despite very few representative analyses of deep Geothermal fluids, often contaminated by drilling fluids or injected waters, the geochemical data provide new and interesting information on the nature, origin, circulation and deep temperature of these fluids (Sanjuan et al., 2006a and c). They indicate similar chemical and isotopic compositions (NaCl fluids) and high salinity values (TDS about 100 g/l) which suggest a common sedimentary origin and identical water-rock interaction processes. The chemical and gas geothermometers suggest that the native Geothermal Brine and associated gases are equilibrated with a mineralogical assemblage at temperatures close to 220-240°C (> 200°C measured at the bottom-hole; Sanjuan et al., 2006a and c). According to the Na/Li geothermometer and the 7Li values, these equilibrium reactions would occur in a sedimentary rather than granite reservoir (Fig. 1). Given the location of the Soultz site and these constraints, this reservoir would be situated more eastern, towards the Graben centre where the Triassic sedimentary formations are the deepest and hottest (Fig. 2). From tracer tests carried out after 2000, the natural flux of the native Geothermal Brine was estimated at 1-1.2 m3/h, which is identical to that calculated for the fluid flux parallel to the Graben strike, based on a convection model and numerical 3D modeling (Bächler, 2003; Sanjuan et al., 2006b and c). During all the production and circulation tests, the tracer tests and geochemical data showed the omnipresence of the native Geothermal Brine in the discharged fluids even after injection of large amounts of external water into the wells. The existence of at least three fluid flow pathways between the wells GPK-2 and GPK-3 with different effective fluid velocities, which contrasts with a poor hydraulic connection between GPK-3 and GPK-4 (Fig. 3), was highlighted during the fluid circulation loop and the associated tracer test using fluorescein, carried out between July and December 2005 (Sanjuan et al., 2006b and c).
Romain Millot - One of the best experts on this subject based on the ideXlab platform.
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Major geochemical characteristics of Geothermal Brines from the Upper Rhine Graben granitic basement with constraints on temperature and circulation
Chemical Geology, 2016Co-Authors: Bernard Sanjuan, Romain Millot, Chrystel Dezayes, Christophe Innocent, Julia Scheiber, Michel BrachAbstract:This paper is the first to present the main geochemical characteristics of the native Brines collected from all the Geothermal wells penetrating the granite basement underlying the sedimentary cover, in the Upper Rhine Graben. These deep wells (from 2580 to 5000 m) were only drilled in four Geothermal sites (Soultz-sous-Forêts and Rittershoffen in France; Landau and Insheim in Germany). The Na-Cl Geothermal Brine samples collected from the granite returned TDS values ranging from 99 to 107 g/l with pH values close to 5, along with Cl and Br concentrations and delta D, delta 18O and delta 34S values that indicate a multiple origin with mixing between primary Brine formed by advanced evaporation of seawater (probably until the stage of halite precipitation) and dilute meteoric water, plus contributions from halite dissolution following successive marine transgression-regression cycles from the Triassic to the Oligocene. Chemical, isotopic and gas geothermometers indicate concordant reservoir temperatures close to 225 ± 25°C for all the fluids, even though the maximum temperature so far measured on site is 200°C. An exhaustive literature review has indicated that only the Geothermal Brine from the deep Cronenbourg well (2870 m) ending in the Buntsandstein has similar chemical and isotopic compositions (apart from Br and Ca) to the fluids from the granite, with an identical estimation of reservoir temperature from geothermometry. Geothermal Brine from the deep Bruchsal well (2540 m), drilled down to the junction of the Buntsandstein and the Saxo-Thuringian formations, has a higher TDS value (120-125 g/l) with its chemical and isotopic compositions giving a lower estimation of reservoir temperature (190 ± 25°C). By contrast, Geothermal Brine from the Bühl well (2655 m) ending in the Buntsandstein has an even higher TDS value of about 201 g/l and a lower temperature-at-depth estimation of 110 ± 25°C, close to the temperature measured on site (115°C). The above results indicate that the Geothermal fluids collected from the granite probably originate from Triassic sedimentary formations located at great depth (≥4 km) with temperatures close to 225 ± 25°C in the centre of the Rhine Graben, but that their different TDS and Cl/Br values reflect the presence of several distinct Geothermal reservoirs. Many discrepancies due to high-temperature water-rock interactions are revealed on comparing the chemical and isotopic compositions of the hot Brines with those of cooler Brines from Bühl and the Landau Eocene-Oligocene oilfield wells, among others. The hottest Brines are much enriched in K, Ca, SiO2, Li, Rb, Cs, As, Sr, Ba, Mn, Nd, U and in metals such as Zn, Pb, Cu, Co, Cd, Sb, but are depleted mainly in Mg, SO4 and B and have much lower isotopic Li and B signatures. The He isotopic signatures of the gases associated with these fluids (R/Ratm. = 0.128 at Bruchsal and 0.252 at Insheim) confirm that the thermal anomalies are mainly crustal and not mantle-derived (1.46% and 2.88% of mantellic He, respectively, for the two sites). Thus it is concluded that the thermal anomalies are associated mainly with the convective circulation of hot fluids along probable NE-SW faults between the graben’s deep sedimentary centre and the fractured granite basement at its edges. Moreover, the western part of the Upper Rhine Graben (the Landau, Insheim, Soultz, Rittershoffen and Cronenbourg sites) seems to be hotter than the eastern part (Bruchsal and Bühl). According to the U-Th isotope system, the minimum transit time of these deep Geothermal Brines would be about 1000 years.
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main characteristics of the deep Geothermal Brine 5 km at soultz sous forets france determined using geochemical and tracer test data
Comptes Rendus Geoscience, 2010Co-Authors: Bernard Sanjuan, Chrystel Dezayes, Romain Millot, Michel BrachAbstract:Three deep wells (5000 m) have been drilled into a fractured granite basement at Soultz-sous-Forets, within the Tertiary Rhine Graben, in order to develop a heat exchanger and produce electricity after the creation of an EGS reservoir. Very few analyses representative of the deep Geothermal fluids are available because of frequent contamination by drilling fluids or injected waters. These indicate similar chemical and isotopic compositions (NaCl fluids) and high salinities (about 100 g/l) suggesting a common sedimentary origin and identical water–rock interaction processes at equilibrium temperatures close to 230 °C in a sedimentary rather than a granite reservoir. The latter would be situated closer to the Graben centre where the Triassic Buntsandstein formation is deepest and hottest. Tracer tests conducted after 2000 show that the deep native Geothermal Brine is omnipresent in the fluids discharged during the production and circulation tests. Its natural convective flux was estimated at 1–1.2 m3/h.
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Fluid origin and circulation in the heat exchanger of Soultz-sous-Forêts (France) estimated using geochemical and tracer test data.
2008Co-Authors: Bernard Sanjuan, Chrystel Dezayes, Romain Millot, Michel BrachAbstract:In the framework of the European Hot Dry Rock Energy (HDR) Program, three deep wells (5000 m) have been drilled into a fractured granite basement at Soultz-sous-Forêts, located within the Rhine Graben, in order to develop a deep heat exchanger (GPK-3 as injector and GPK-2/GPK-4 as producers) and produce electricity after the creation of an EGS reservoir. Despite very few representative analyses of deep Geothermal fluids, often contaminated by drilling fluids or injected waters, the geochemical data provide new and interesting information on the nature, origin, circulation and deep temperature of these fluids (Sanjuan et al., 2006a and c). They indicate similar chemical and isotopic compositions (NaCl fluids) and high salinity values (TDS about 100 g/l) which suggest a common sedimentary origin and identical water-rock interaction processes. The chemical and gas geothermometers suggest that the native Geothermal Brine and associated gases are equilibrated with a mineralogical assemblage at temperatures close to 220-240°C (> 200°C measured at the bottom-hole; Sanjuan et al., 2006a and c). According to the Na/Li geothermometer and the 7Li values, these equilibrium reactions would occur in a sedimentary rather than granite reservoir (Fig. 1). Given the location of the Soultz site and these constraints, this reservoir would be situated more eastern, towards the Graben centre where the Triassic sedimentary formations are the deepest and hottest (Fig. 2). From tracer tests carried out after 2000, the natural flux of the native Geothermal Brine was estimated at 1-1.2 m3/h, which is identical to that calculated for the fluid flux parallel to the Graben strike, based on a convection model and numerical 3D modeling (Bächler, 2003; Sanjuan et al., 2006b and c). During all the production and circulation tests, the tracer tests and geochemical data showed the omnipresence of the native Geothermal Brine in the discharged fluids even after injection of large amounts of external water into the wells. The existence of at least three fluid flow pathways between the wells GPK-2 and GPK-3 with different effective fluid velocities, which contrasts with a poor hydraulic connection between GPK-3 and GPK-4 (Fig. 3), was highlighted during the fluid circulation loop and the associated tracer test using fluorescein, carried out between July and December 2005 (Sanjuan et al., 2006b and c).