Geothermal Energy最新文献

This study investigates petrological and thermophysical properties of rocks from the Estopanyà and Boix synclines (salt basins) to evaluate their potential as analogues for geothermal reservoir. A total of 45 samples were collected, including 26 carbonates, 16 arenites, and 3 altered carbonates (chalky limestones and calcitized dolomites). These samples were classified into eight distinct rock types based on 106 thin sections. Thermophysical measurements revealed mineral densities ranging from 2.64 to 2.72 g cm⁻³ and variable connected porosity (0.50–17.63%), permeability (< 0.001 to 15.30 mD, equivalent to < 10⁻¹⁸ to 10⁻¹⁴ m²), P-wave velocities (1.8–6.6 km s⁻¹ in dry and 2.7–6.3 km s⁻¹ in water-saturated samples), thermal conductivity (2.1–4.7 W m⁻¹ K⁻¹), and specific heat capacity (724–860 J kg⁻¹ K⁻¹). Correlations between thermophysical properties suggest that connected porosity predominantly influences permeability, P-wave velocity, and specific heat. In contrast, thermal conductivity is more dependent on rock composition. Key diagenetic processes such as dissolution, cementation, brecciation, and dolomitization significantly alter rock texture and composition, impacting critical thermophysical properties (e.g., thermal conductivity, permeability, and porosity), essential for geothermal reservoir potential. These alterations are particularly pronounced near the Estopanyà salt wall, indicating that fluid flow along diapir margins intensifies rock alteration. Away from the diapir margin, these effects diminish, underscoring the localized influence of salt diapirism. Results indicate that natural fluid convection likely occurred in two sedimentary units within the Estopanyà and Boix synclines. The first unit, composed of diapir-margin breccias, probably had high permeability in the past, as suggested by its present-day intense cementation. Similarly, the ongoing dedolomitization of these breccias also hints for a past dolomitization in them, which should have enhanced the thermal conductivity of this unit in the past, making it a favorable geothermal target prior to cementation and dedolomitization. The second unit consists of arenites from the Tremp Group, which exhibit sufficient permeability for fluid storage but lack the necessary permeability for natural fluid convection, in the absence of open fractures. These surface data underscore the value of outcrop analogues, demonstrating how petrological insights can reveal past geological processes that influence the thermophysical properties and reservoir potential of salt basins.

In the context of the heat transition in Germany, the decarbonization of the heating and cooling industry via renewable energy sources requires the usage of comprehensive strategies and novel engineering solutions. With regard to district heating in urban areas, middle-deep geothermal resources offer a great potential which has not been fully utilized yet due to the required minimum temperature of district heating networks, leading to the additional employment of industrial and high-capacity-power heat pumps. However, the controlling factors on the optimal and sustainable development of those middle-deep geothermal resources are not fully elucidated yet. By evaluating numerical approaches against analytical model solutions, this work systematically analyzes the impact of reservoir quality and operational controlling factors on the performance of Mesozoic sandstone reservoirs in the North German Basin (NGB) targeted by multi-well arrangements. For the first time, we compare in a comprehensive manner previous analytical model results with our numerical findings to characterize more broadly the quantitative influence of different controlling factors on the thermal breakthrough occurrence time, the maximum cooling rate after the occurrence of the thermal breakthrough and the end production temperature. Moreover, we especially focus and illustrate the controls on the behavior of the production temperature after the thermal breakthrough has occurred and conduct a one-factor-at-a-time (OAT) parametric sweep analysis with regard to the thermal utilization time or life span of a geothermal facility. Based on our numerical results, we set up a ranking scheme showing the influence of varying controlling parameters on the considered performance parameters. One of the striking findings of our scenario analysis relates to the thermal breakthrough occurrence time, which is 17 ± 3% higher for a geothermal doublet array compared to a single doublet. Yet, the maximum cooling rate of the production temperature after the thermal breakthrough is higher for the array layout, depending on the number of neighboring injection wells. Our comprehensive numerical study, therefore, illustrates in detail the complex thermo-hydraulic interaction of geothermal doublet arrays, the controls on the defined thermal lifetime as well as the optimization possibilities of middle-deep geothermal resources.

As a crucial solution to the challenge of limited urban underground space development, the assembled shaft offers extensive structure–soil contact surfaces and meantime holds significant potential for shallow geothermal energy exploitation. In this paper, we propose an assembled energy shaft, i.e. a novel geothermal development system, in which the heat exchanger could be easily installed in the shaft concrete with extensive soil–contact area and can have superior protection without extra pre-drilling. This paper establishes a heat transfer model for energy shafts in soft soil areas. By comparing the heat transfer efficiency and additional thermal stress of the energy tunnel in Beijing, the practical feasibility of constructing energy shafts in coastal cities is demonstrated. By proposing the characterization parameters of heat exchange capacity per unit lining surface area and heat exchange per unit length of pipe, it is revealed that thermal interference is minimized when the heat exchange pipe spacing of the energy shaft is 0.25–0.3 m. The heat exchange efficiency is increased when the fluid flow rate is 0.6 m/s ~ 0.9 m/s. According to the deformation characteristics of the lining, the maximum tensile and compressive stresses occur near the inlet of the heat exchange pipe. To minimize stress concentration, it is advisable to position the inlet of the heat exchange pipe at the center of the segment. The research findings confirm the substantial potential of assembled energy shafts in shallow geothermal development and provide valuable insights for the design of such shafts in coastal cities.

Geothermal energy could be used to reduce or replace diesel for heating in remote northern communities. Geothermal development has primarily focused on shallow, high-temperature resources, but interest in low-temperature and deep geothermal resource exploration has increased as energy costs and climate change policy have evolved. Here, we evaluated the low-temperature geothermal favourability in southwestern Yukon by adapting Play fairway analysis to data-scarce regions. Play fairway analysis is a spatial statistical tool that uses a layered data approach to model favourability and risk assessments for resource exploration. Previous Play fairway analyses concentrate on the physical aspects of geothermal favourability: heat, permeability, and fluid availability. This study presents an overview of potential direct and indirect physical parameters that could be used in a geothermal Play fairway analysis in data-scarce regions and introduces the importance of considering socio-economic data in the exploration phase. The socio-economic controls are grouped into quantitative and qualitative parameters that describe population trends and community interests. The framework presented is then applied to a Play fairway analysis for southwestern Yukon. Based on the physical and socio-economic analysis, there is interest in exploring geothermal potential along the Denali fault near Duke River to support the community of Burwash Landing.

The thermal properties of grouting materials characterise the heat transfer around borehole heat exchangers (BHE). However, these properties are typically determined in the laboratory. Thus, this study aims to assess the properties of grouting materials in the field. Two BHE grouted with two different grouting materials within unsaturated loess and limestone were excavated up to a depth of 15 m. Collected field samples show higher thermal conductivities by 13% (W/S = 0.3) and 35% (W/S = 0.8) than laboratory samples of the same material. These differences in thermal properties are mainly related to the filtration of the grouting suspension. In addition, with a short-time enhanced thermal response test (ETRT), 17% lower in-situ thermal conductivities are determined than in comparison with the field samples. The deviations are attributed to the geometry of the borehole, the trajectory of the BHE pipes and the heating cable. Thereby, this study shows the limitations when transferring laboratory-derived properties to a field site and emphasises the importance of considering site conditions, such as geology and hydrogeology.

The North Alpine Foreland Basin in Bavaria is one of Europe’s most important deep reservoirs for hydrogeothermal energy utilization for district heating. Most of the plants are located in the Munich metropolitan region, where there are both favorable geological conditions and a high demand for heat due to the urban character. However, the region's potential is far from fully utilized and extensive geothermal development is thus planned in the city of Munich and the surrounding municipalities. Reliable productivity prognoses help to ensure that this development is sustainable and efficient. We use the dense and comprehensive drilling data set in the region to derive a productivity zonation using multivariate methods. To do this, we derive geophysical and hydraulic parameters from the existing borehole measurements and combine them with hydrochemical, historical and technical data to derive a set of 24 individual parameters. For this parameter set, we carry out a principal component analysis (PCA) and single linkage hierarchical cluster analysis (HCA). The PCA reduces the data set to six main factors, which explain 80% of the data set variability. Of those, the most important factors fa1, fa2, and fa3, which explain 53% of the data set variability, contain mainly geological (fa1), hydrochemical (fa2), and technical parameters (fa3). The HCA reveals four main clusters, with clusters 3 and 2 in the north, 1 in the center of the study area, and 4 in the south. The spatial location of these clusters fits very well with the zoning assumed in the previous assessment analysis ‘Masterplan Geothermal Energy‘. Cluster 2 behaves very similar to cluster 3, but is separated from it by a different hydrochemistry (fa2). In addition, two outliers were identified at two doublets in the north of the study area, which are distinguished from the main clusters in one case by differing hydrochemistry and in the other case by differing hydraulic and thermal conditions. Furthermore, a sub-cluster of cluster 4 is the only one that scatters across the entire study area. However, this can be explained by factors that do not directly influence the productivity of the boreholes concerned. Our results indicate that we can divide the reservoir from north to south into three productivity types A to C, where we derive different outflow temperatures and porosities from regression equations of depth trends.

Graphical Abstract

Hot springs in the southern Qinghai-Xizang Plateau show anomalous lithium (Li) and cesium (Cs) enrichment, but the mechanisms driving this enrichment remain poorly constrained. Using multi-isotope tracers (H, O, Li, Sr), we investigate the Semi-Dazi geothermal field, which hosts the Plateau’s highest recorded geothermal Cs concentrations. The system comprises two geographically separated geothermal areas: Semi and Dazi, spaced ~ 15 km apart, displaying distinct hydrogeochemical signatures. Semi hot springs show significantly higher Li (34.2 to 35.6 mg/L) and Cs (49.8 to 52.7 mg/L) concentrations than Dazi (Li: 11.4 to 21.1 mg/L; Cs: 21.5 to 37.7 mg/L). Isotopic contrasts further differentiate the areas: Semi exhibits elevated δ⁷Li (1.53 to 1.91 ‰) and lower ⁸⁷Sr/⁸⁶Sr (0.739 to 0.741), whereas Dazi shows δ⁷Li values of − 0.25 to 1.24 ‰ and ⁸⁷Sr/⁸⁶Sr ratios of 0.742 to 0.759. Two key processes govern enrichment: (1) atmospheric recharge infiltrates Li–Cs-rich strata, where high-temperature water–rock interactions (217 °C at Semi and 197 °C at Dazi reservoirs) mobilize these elements into geothermal waters; (2) phase separation during ascent causes differential steam loss (Semi: 24%, concentration factor 1.32; Dazi: 8 to 21%, 1.08 to 1.26). Secondary processes (cold water mixing, conductive cooling, mineral adsorption) further modify surface hot springs geochemistry. Semi-Dazi geothermal field illustrates how a shared geothermal system can yield chemically distinct fluids from separate reservoirs characterized by differing hydraulic connectivity and circulation pathways. Geyserite deposits and high reservoir temperatures suggest that a crustal partial melt layer adds extra heat, intensifying water–rock reactions. The occurrence of Li–Cs-rich springs on the Plateau is intrinsically linked to elevated concentrations of these elements in underlying crustal source rocks and spatially associated with deep, extensive fault systems, particularly at fault convergences. These findings underscore the necessity of multi-isotope models for interpreting geothermal Li–Cs anomalies in continental collision zones, with implications for strategic mineral exploration.

The Upper Pannonian (UP) sandstone formation in Hungary has been utilized for thermal water production without reinjection since the 1960s. However, there is an increasing need for setting up geothermal doublets or triplets, where used water is expected to be reinjected into the same formation. Sustainable injection into porous sandstone rock formation is not straightforward. Thus, the Hungarian research and development project “Development of a well completion technology for sustainable and cost-effective reinjection of thermal water” aims at designing a methodology for sustaining the injectivity of geothermal wells in UP sandstone reservoirs. In this case study, we present an intervention approach of an old geothermal production well for reinjection at the Szentes Geothermal Field. Based on the evaluation of well conditions, the injectivity decline may be associated with reservoir characteristics, i.e., low transmissibility, mineral precipitation or local particle migration. Thus, a stimulation program was designed, where various techniques such as hydraulic fracturing, acid treatment and skin frac experiment were conducted. The novelty of this study is that to the best of our knowledge, the skin frac technique has been applied for the first time in a geothermal injection well worldwide. Based on the comparison of the various stimulation experiments, the injectivity reduction is related to phenomena in the near-wellbore area, i.e., mechanical clogging due to fines migration in the reservoir. The largest injectivity enhancement was observed due to skin frac experiment and pump lift, which was not part of the original stimulation program. The skin frac method has the potential for providing injectivity enhancement of recompleted wells in poorly cemented sandstone formations, but further field demonstration with optimized design is required. The results of this well treatment, such as regular conduction of pump lift and recommendations for proper design of skin frac treatment can be used in designing long-term reinjection tests in loose sandstone formations in geothermal reservoirs. Furthermore, future study should focus on the investigation of the link between pressure depletion due to overexploitation, subsequent compaction and land subsidence as well as injectivity problems.

Enhanced geothermal systems (EGS) are a new technology with the potential to expand renewable energy generation. Understanding how information about EGS affects people’s opinions and support for its development is critical for its implementation. The present study examines how social endorsement cues (SEC; e.g., number of likes and shares) and perceived familiarity with EGS might influence audience considerations. We found that SEC significantly influenced perceived credibility of a blog post. Perceived familiarity with EGS moderated the relationship between perceived credibility and support for regulation of academic and commercial EGS research. However, there were differences in the mediating effect of perceived credibility for support for regulation of commercial, compared to academic, research. If producers of commercial EGS want greater public support, engaging SEC on public platforms could be a promising path forward.