Journal: Geothermal Energy

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SpringerOpen

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2195-9706

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2019 - 201922020 - 20253
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Publications 1 - 5 of 5
  • Numerical modeling of the geothermal hydrology of the Volcanic Island of Basse-Terre, Guadeloupe
    Item type: Journal Article
    Raguenel, Margaux; Driesner, Thomas; Bonneau, François (2019)
    Geothermal Energy
    This study investigates the thermo-hydraulic implications of three geologic scenarios for characterizing the geothermal hydrology of Basse-Terre Island, Guadeloupe. Despite newly acquired magnetotelluric, petrophysical, and geologic data, flow patterns and heat sources have remained elusive. Our simulations were performed in 2D, on a cross section going from La Soufrière volcano in the south to the operating Bouillante geothermal field near the west coast. Simulation results are compared to geologic constraints such as the temperature profile measured at Bouillante and the timing of volcanic activity in the area, which may be indicative of new heat sources at depth. The simulations indicate that during lateral flow from La Soufrière, geothermal fluids would cool too much to explain the temperature at Bouillante. Two other scenarios were found to explain the current thermal structure of the Bouillante geothermal system: a young (ca. 5000 years) and more local magmatic intrusion at depth, or vertical corridors of enhanced permeability that tap hot and porous formations at a few km depth. Without further geologic evidence, neither of these two scenarios can be preferred. The second magma chamber scenario would indicate a more complex magmatic history of the island than previously established. The study shows that geologically constrained scenarios of regional geothermal hydrology can be meaningfully tested with current numerical simulation techniques, providing further insights for geothermal exploration.
  • Integrative analysis of the Aachen geothermal system (Germany) with an interdisciplinary conceptual model
    Item type: Journal Article
    Gómez‑Díaz, Esteban; Balza Morales, Andrea; Kukla, Peter A.; et al. (2025)
    Geothermal Energy
    The comprehension of geothermal systems involves the efficient integration of geological, geophysical and geochemical tools that are crucial in unraveling the distinct features inherent in geothermal reservoirs. We provide a first approach to comprehending the geologically complex geothermal system in the Aachen area, which has been known for its natural thermal spring occurrences since Roman times. Through a comprehensive analysis involving geochemical interpretation of water samples, a review of 2D seismic profiles, stress analysis, and surface geology, a dynamic model has been built, which serves as a conceptual framework providing a clearer understanding of the system. The model characterizes a non-magmatic, detachment fault-controlled convective thermal system, wherein the reservoir exhibits mixed properties of the mainly Devonian carbonate rocks. NW-SE directed fault lines play a pivotal role in fluid transport, enabling the ascent of thermal waters without the need for additional energy. We additionally conducted magnetotelluric (MT) surveys and analyzed apparent resistivity and impedance values obtained through forward modeling, along with an assessment of noise levels. These findings contribute to evaluating the potential use of MT methods in further evaluating the study area and for geothermal energy exploration in general.
  • A fracture flow permeability and stress dependency simulation applied to multi-reservoirs, multi-production scenarios analysis
    Item type: Journal Article
    Lepillier, Baptiste; Daniilidis, Alexandros; Gholizadeh Doonechaly, Nima; et al. (2019)
    Geothermal Energy
    The use of the subsurface and the exploitation of subsurface resources require prior knowledge of fluid flow through fracture networks. For nuclear waste disposal, for the enhancement of hydrocarbon recovery from a field, or the development of an enhanced geothermal system (EGS), it is fundamental to constrain the fractures and the fracture network. This study is part of the GEMex project, an international collaboration of two consortia, one from Europe and one from Mexico. The research is based on exploration, characterization and assessment of two geothermal systems located in the Trans-Mexican volcanic belt, Los Humeros and Acoculco. In Acoculco, two wells reached very high temperatures, but did not find any fluids. For that reason, the Acoculco Caldera is foreseen as an EGS development site, hoping to connect existing wells to a productive zone. This implies that the fluid flow through the geothermal reservoir would be mainly fracture dominated. This study investigates the dependency of fracture permeability, constrained by fracture lengths and apertures, with stress field conditions. Simulations are computed in 2D, using COMSOL Multiphysics® Finite Elements Method Software, populated with mechanical data obtained in the rock physics laboratory and with dense discrete fracture networks generated from 1D scanline surveys measured in Las Minas analogue outcrops for Acoculco reservoir. The method offers a prediction for multiple scenarios of the reservoir flow characteristics which could be a major improvement in the development of the EGS technology.
  • Laboratory tests simulating corrosion in geothermal power plants: influence of service conditions
    Item type: Journal Article
    Vallejo Vitaller, Ana; Angst, Ueli; Elsener, Bernhard (2020)
    Geothermal Energy
    One of the main challenges associated with the operation and maintenance of binary geothermal power plants is the degradation of construction materials. In this sense, it is crucial to apply appropriate preventive maintenance in critical components (such as the wellheads, heat exchangers, or pipes), while reducing shutdown times. Based on electrochemical measurements performed in an autoclave corrosion testing setup, we studied the corrosion mechanism of API L80 steel grade as a function of operational and/or maintenance procedures. We used a test fuid representative for a site in Switzerland, but the main observations made may be applicable in a wider context. We found that changes in the fuid temperature (from 200 to 100 °C) or temporary oxygen ingress signifcantly infuenced the corrosion behavior of this carbon steel and increased its corrosion rate (from approx. 20 µm/year to>120 µm/year). After a few days, the corrosion rate was found to decrease and stabilize around values of 50–70 µm/year, as a result of a porous corrosion product layer formed on the metal surface (approx. 250 µm thick). Electrochemical impedance spectroscopy indicated an increase in capacitance of the double layer over time, most likely due to an increase in the efective surface area of the steel sample, as a consequence of surface roughening due to corrosion. The results from this study may be implemented in the design and operation of future power plants in Switzerland and elsewhere to ensure reliable and cost-efective energy production from geothermal resources.
  • Controls of low injectivity caused by interaction of reservoir and clogging processes in a sedimentary geothermal aquifer (Mezőberény, Hungary)
    Item type: Journal Article
    Marko, Abel; Brehme, Maren; Pedretti, Daniele; et al. (2024)
    Geothermal Energy
    Low injectivity is often experienced in geothermal doublets installed in sandstone reservoirs. This even led to a shutdown of the Mezbereny (Hungary) geothermal site. An on-site campaign was carried out in January 2021 to prepare a stimulation aiming to enhance the transmissivity of the sedimentary reservoir and the near-wellbore zone of this site. Previous studies have concluded that insufficient injectivity may be linked to a high skin effect in the near well-bore zone and pore clogging in combination with the low net sandstone content of the fluvio-deltaic reservoir. A chemical soft stimulation based on the injection of hydrochloric acid (HCl) was successfully used to unclog and recover the well injectivity. Despite such empirical evidence, the geochemical mechanisms leading to both, detrimental formation of clogging and the HCl-driven transmissivity restoration, have not yet been elucidated. This work presents the results of a novel analysis aiming at (a) predicting the dominant type of clogging forming in the near-well bore zone; (b) quantifying the drop in hydraulic conductivity as clogging occurs; and (c) supporting the optimization of the HCl dosage during the chemical soft stimulation. The study is supported by new experimental datasets never presented before from the Mezbereny site and a geochemical model set-up simulating the main mechanisms involved in the clogging and unclogging processes. It is concluded that the biofilm formation was the dominant, while the precipitation of calcite and amorphous ferrihydrite-later reduced to magnetite by microbes-was the secondary clogging mechanism: In the long-term (yearly scale) simulating the hydraulic conductivity showed a decline with forming scales; therefore, biofilm was presumably responsible for the experienced rapid (1 month) clogging. When modelling the chemical stimulation, the estimated amount of precipitated minerals was dissolved already with 2.5 mol of HCl per liter of water (similar to 10 m/m%). Therefore, the 20 m/m% of HCl chosen during the field campaign might had a beneficial effect dissolving the potentially higher amount of scaling and/or the carbonate minerals of the matrix near the wellbore. Overall, it is concluded that the chemical and the microbial analyses together with the geochemical model were critical to tailor the remediation attempts and to propose further development or reconstruction of the surface system before going into operation to prevent recurrent impairments. Our findings highlight the importance of interactions of various clogging mechanisms with each other as well as with the reservoir processes and provide approaches to tackle the issue of injectivity drop by characterizing and quantifying their effects.
Publications 1 - 5 of 5