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The Status and Development Trend of Geothermal Resources

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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "H2: Geothermal".

Deadline for manuscript submissions: closed (25 April 2025) | Viewed by 13026

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Special Issue Editors

Dr. Yilong Yuan

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Guest Editor

Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun 130021, China
Interests: geothermal energy; enhanced geothermal system; geothermal development; energy efficiency; numerical modeling; multi-phase flow; rock mechanics; water-rock reaction

Dr. Guanhong Feng

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Guest Editor

College of New Energy and Environment, Jilin University, Changchun 130021, China
Interests: supercritical geothermal; CO₂ geological sequestration; multiphase flow numerical modeling

Dr. Yibin Huang

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Guest Editor

College of Water Conservancy and Transportation, Zhengzhou University, Zhengzhou 450001, China
Interests: development and utilization of geothermal energy; energy geotechnical engineering
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Special Issue Information

Dear Colleagues,

With the continuous increase in the human population，environmental pollution and the shortage of resources is gradually becoming a problem all over the world. Therefore, environmental protection and energy conservation and new energy development and utilization are becoming the development strategies of all countries. In addition, the goal of carbon neutrality and carbon peak requires major system changes in the energy supply. As a clean, low-carbon, and stable non-carbon-based renewable energy, geothermal energy is to have a guaranteed used in achieving this realization. A geothermal project utilizes a natural resource in the form of a flow of geothermal fluid as water and/or steam, at an elevated temperature, capable of providing energy to consumers in the form of electricity or as heat and cooling for buildings, greenhouses, aquaculture ponds, and industrial processes. Thus, governments and research institutes around the world have shown a high degree of recognition and attention to the development and utilization of geothermal energy.

Geothermal energy development and utilization is a comprehensive technology involving multiple disciplines, fields, and industries, including resource exploration and evaluation, drilling and completion, reservoir fracturing, tail water recharge, cascade utilization, heat exchange and insulation, corrosion and scale prevention, heat pump and power generation, ground engineering, operation management, and other technologies. Therefore, the development of geothermal resources requires the collaboration of scientists from different fields to achieve the goal of carbon neutrality.

This Special Issue aims to investigate the status and development trend and utilization technology of geothermal resources. Based on the analysis of the development status and trend of geothermal resources, it is helpful to promote the development of geothermal resources to facilitate new breakthroughs.

Dr. Yilong Yuan
Dr. Guanhong Feng
Dr. Yibin Huang
Guest Editors

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Keywords

geothermal development
energy systems
geothermal utilization
geothermal heating
geothermal cooling
geothermal power generation
numerical modelling
sustainability
renewable energy
heat transfer
multi-phase flow
geothermal recharge

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Published Papers (11 papers)

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Research

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16 pages, 11135 KiB

Open AccessArticle

High-Quality Heat Flow Determination from Coastal Areas of Fujian Province, China

by Yaqi Wang, Yibo Wang, Guangzheng Jiang, Jie Hu and Shengbiao Hu

Energies 2025, 18(7), 1735; https://doi.org/10.3390/en18071735 - 31 Mar 2025

Viewed by 182

Abstract

The coastal region of Fujian is part of the southeastern hilly and coastal geothermal anomaly zone and is a significant high-heat-flow area in mainland China. However, existing heat flow data suffer from low quality due to insufficient calculation depth and inadequate corrections; this hinders theoretical research and geothermal resource exploration in the region. This study obtained high-quality geothermal heat flow data through steady-state temperature measurements in six boreholes and thermal conductivity tests on 79 core samples collected in situ. The results indicate that the average heat flow values from four newly analyzed representative boreholes (HDR1, LJSZ, JM-1, DS) are 65.2 mW/m², exceeding the mainland Chinese average of 60.5 mW/m², highlighting the region’s high heat flow characteristics. This finding corroborates previous high-heat-flow measurements in the coastal area of Fujian and aligns with earlier studies. The research fills a gap in providing high-quality heat flow data for the region, enhances our understanding of its thermal state, and is significant for studying the distribution and development of geothermal resources in the area. Full article

(This article belongs to the Special Issue The Status and Development Trend of Geothermal Resources)

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20 pages, 3947 KiB

Open AccessArticle

Potential Enhanced Geothermal Systems in Western Poland—Petrothermal and Geochemical Issues

by Krzysztof Labus, Rafał Moska and Małgorzata Labus

Energies 2025, 18(4), 876; https://doi.org/10.3390/en18040876 - 12 Feb 2025

Viewed by 768

Abstract

This study evaluates the potential of enhanced geothermal systems (EGSs) in Poland, focusing on formations composed by igneous rocks, such as crystalline rocks of the Karkonosze pluton and volcanic rocks of the Gorzów Block. A total of 57 rock samples, including granites and rhyolites from these formations, were analyzed for their thermal and geochemical properties to assess their suitability for EGS development. The results highlight the importance of thermal parameters, such as conductivity and diffusivity, in optimizing geothermal exploitation. The measurements reveal that Karkonosze granite exhibits high thermal diffusivity and conductivity, making it a prime candidate for heat extraction. Although the Gorzów Block rhyolites show slightly lower values, their high initial temperatures still promise long-term geothermal viability. Geochemical modelling indicates that mineral precipitation that causes permeability damage is unlikely in these reservoirs. Instead, minor increases in porosity due to mineral dissolution can reduce hydraulic resistance, potentially affecting the performance of the system. Full article

(This article belongs to the Special Issue The Status and Development Trend of Geothermal Resources)

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25 pages, 9319 KiB

Open AccessArticle

Experimental Investigation of Deposition of Silica Nanocolloids by Depressurizing Supercritical Water Vapor

by Silje Bordvik, Morten Tjelta and Erling Næss

Energies 2025, 18(4), 813; https://doi.org/10.3390/en18040813 - 10 Feb 2025

Viewed by 477

Abstract

This article presents the results of an experimental investigation of silica deposition from depressurized supercritical steam. The case investigated is relevant for supercritical geothermal reservoirs with high temperature and pressure, where silica content is significant and deposition occurs rapidly upon depressurization. The purpose of the presented experiments is to accurately measure the deposited mass in two different areas in a flow tube and mathematically relate the measurement to particle formation behavior. In addition, SEM analysis permits valuable insight into the morphology of the scale formed under these conditions. The measured deposition is caused by silica solids formed when depressurizing supercritical fluids from around 350 bar and 500 °C by an isenthalpic valve to a state of superheated steam and pressures ranging from 60 to 150 bar. A test rig was designed, fabricated, and used for this purpose. The deposition mechanisms differ from silica particle formation in the water phase and the limited experimental research for the investigated conditions makes the gathered data highly interesting. The measured results are compared to validated models for deposition in straight pipes. The knowledge obtained on silica solidification and deposition can be used to optimize steam treatment of high-temperature pressurized geothermal sources for maximum power utilization by aiding in the development of advanced prediction tools for scaling and mineral extraction. Full article

(This article belongs to the Special Issue The Status and Development Trend of Geothermal Resources)

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20 pages, 6214 KiB

Open AccessArticle

Flowing Salt Solution Thin Film Vaporization and Heat Transfer Mechanisms: A Molecular Dynamics Study

by Dayuan Yuan, Chao Li, Liuyang Zhang and Shengqiang Shen

Energies 2024, 17(24), 6286; https://doi.org/10.3390/en17246286 - 13 Dec 2024

Viewed by 738

Abstract

Geothermal energy offers a sustainable way, through heating a salt solution, to generate electricity and extract salt, minimizing environmental impact while supporting clean energy needs. The thermal behavior and vaporization mechanisms of flowing salt solution thin films are investigated in this study using molecular dynamics (MD) simulations. The research focuses on the evaporation dynamics of NaCl solutions at various temperatures (450 K and 550 K) and under different flow conditions, providing insights into the microstructural evolution and the role of ionic interactions. The simulations reveal critical aspects of evaporation, such as the formation and behavior of ion clusters, the impact of temperature on evaporation rates, and the effects of flow on heat transfer efficiency. Key findings include the observation that higher temperatures accelerate the evaporation process and promote ion clustering, while flow conditions enhance heat and mass transfer, leading to more efficient vaporization. These results contribute to a deeper understanding of the thermal dynamics in saline solutions, with implications for industrial processes such as desalination, crystallization, and thermal management. Full article

(This article belongs to the Special Issue The Status and Development Trend of Geothermal Resources)

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15 pages, 4612 KiB

Open AccessArticle

Process Modeling and Optimization of Supercritical Carbon Dioxide-Enhanced Geothermal Systems in Poland

by Paweł Gładysz, Leszek Pająk, Trond Andresen, Magdalena Strojny and Anna Sowiżdżał

Energies 2024, 17(15), 3769; https://doi.org/10.3390/en17153769 - 31 Jul 2024

Cited by 2 | Viewed by 1592

Abstract

This paper presents a comprehensive analysis of supercritical carbon dioxide (sCO₂)-enhanced geothermal systems (EGSs) in Poland, focusing on their energetic performance through process modeling and optimization. EGSs harness the potential of geothermal energy by utilizing supercritical carbon dioxide as the working fluid, offering promising avenues for sustainable power generation. This study investigates two distinct configurations of sCO₂-EGS: one dedicated to power generation via a binary system with an organic Rankine cycle and the other for combined power and heat production through a direct sCO₂ cycle. Through accurate process modeling and simulation, key parameters influencing system efficiency and performance are identified and optimized. The analysis integrates thermodynamic principles with geological and operational constraints specific to the Polish context. The results highlight the potential of sCO₂-EGSs to contribute to the country’s energy transition, offering insights into the optimal design and operation of such systems for maximizing both power and thermal output while ensuring economic viability and environmental sustainability. Full article

(This article belongs to the Special Issue The Status and Development Trend of Geothermal Resources)

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16 pages, 5179 KiB

Open AccessArticle

The Feasibility of Heat Extraction Using CO₂ in the Carbonate Reservoir in Shandong Province, China

by Xiao Liu, Feng Zhang, Shuailiang Song, Xianfeng Tan and Guanhong Feng

Energies 2024, 17(12), 2910; https://doi.org/10.3390/en17122910 - 13 Jun 2024

Cited by 3 | Viewed by 804

Abstract

CO₂ is being considered as an effective alternative working fluid for geothermal applications due to its superior fluid dynamics and heat transfer properties compared to water. Utilizing sedimentary rocks for geothermal energy recovery through a CO₂-plume geothermal system, especially in carbonate reservoirs, has been shown to be a practical approach that eliminates the need for hydraulic fracturing. However, uncertainties remain regarding the thermal and hydraulic behavior, particularly the chemical interactions between CO₂ and carbonate rocks. This study develops a comprehensive wellbore–reservoir coupling reactive transport model based on specific information obtained from the Ordovician limestone geothermal reservoir in Shandong, China. The model aims to assess the feasibility of heat extraction in carbonate reservoirs by evaluating the heat extraction performance and fluid–rock interaction. The results indicate a rapid temperature drop after CO₂ breakthrough due to the Joule–Thomson effect. Simultaneously, the fluid transitions into and maintains a two-phase state throughout the operation. Chemical reactions within the reservoir are not aggressive since complete mixing between unsaturated water and CO₂ only occurs in the vicinity of the production well, highlighting the potential of utilizing carbonate reservoirs for efficient heat extraction in geothermal systems. Further research is needed to optimize the performance of CO₂-based geothermal systems in carbonate reservoirs. Full article

(This article belongs to the Special Issue The Status and Development Trend of Geothermal Resources)

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10 pages, 533 KiB

Open AccessCommunication

Thermodynamics of Halite Scaling in Superhot Geothermal Systems

by Lodin Ellingsen and Tore Haug-Warberg

Energies 2024, 17(12), 2812; https://doi.org/10.3390/en17122812 - 7 Jun 2024

Viewed by 839

Abstract

Over the past decades, considerable research has been conducted on extracting energy from superhot geothermal reservoirs, where temperatures are higher than at the critical point of water. A major challenge when operating wells under such conditions is managing scaling in an effective manner. [...] Read more.

H_{2} O

–

NaCl

system as a proxy. Phase diagrams in pressure–enthalpy and pressure–entropy coordinates are used to illustrate how scaling occurs in idealized processes, such as the isenthalpic expansion of geothermal fluid to the wellhead or the isentropic power generation of a steam turbine. Particular emphasis is placed on explaining the non-trivial graphical composition of these phase diagrams in an accessible manner. A wellhead sample and an estimate of the downhole conditions are used as points of reference in the discussion of scaling. All thermodynamic properties, including the solubility of

NaCl

in water vapor, are calculated using a newly developed equation of state by the same authors as in this article. Full article

(This article belongs to the Special Issue The Status and Development Trend of Geothermal Resources)

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17 pages, 4010 KiB

Open AccessArticle

Fluid Chemical and Isotopic Signatures Insighting the Hydrothermal Control of the Wahongshan-Wenquan Fracture Zone (WWFZ), NE Tibetan Plateau

by Tingxin Li, Rui Lu, Wenping Xie, Jinshou Zhu, Lingxia Liu and Wenjing Lin

Energies 2024, 17(11), 2715; https://doi.org/10.3390/en17112715 - 3 Jun 2024

Cited by 2 | Viewed by 828

Abstract

Compared to the southern Tibetan Plateau, the northern part has been regarded as relatively lacking geothermal resources. However, there is no lack of natural hot springs exposed in beads along large-scale fracture systems, and research on them is currently limited to individual hot springs or geothermal systems. This paper focuses on the Wahongshan-Wenquan Fracture Zone (WWFZ), analyzes the formation of five hydrothermal activity zones along the fracture zone in terms of differences in hot water hydrochemical and isotopic composition, and then explores the hot springs’ hydrothermal control in the fracture zone. The results show that the main fractures of the WWFZ are the regional heat control structures, and its near-north–south- and near-east–west-oriented fractures form a fracture system that provides favorable channels for deep hydrothermal convection. Ice and snow meltwater from the Elashan Mountains, with an average elevation of more than 4,500 m above sea level, infiltrates along the fractures, and is heated by deep circulation to form deep geothermal reservoirs. There is no detectable mantle contribution source heat to the hot spring gases, and the heat source is mainly natural heat conduction warming, but the “low-velocity body (LVB)” in the middle and lower crust may be the primary heat source of the high geothermal background in the area. The hot springs’ hydrochemical components show a certain regularity, and the main ionic components, TDS, and water temperature tend to increase away from the main rupture, reflecting the WWFZ controlling effect on hydrothermal transport. In the future, the geothermal research in this area should focus on the hydrothermal control properties of different levels, the nature of fractures, and the thermal contribution of the LVB in the middle and lower crust. Full article

(This article belongs to the Special Issue The Status and Development Trend of Geothermal Resources)

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16 pages, 3427 KiB

Open AccessArticle

Heat Production Performance from an Enhanced Geothermal System (EGS) Using CO₂ as the Working Fluid

by Wentao Zhao, Yilong Yuan, Tieya Jing, Chenghao Zhong, Shoucheng Wei, Yulong Yin, Deyuan Zhao, Haowei Yuan, Jin Zheng and Shaomin Wang

Energies 2023, 16(20), 7202; https://doi.org/10.3390/en16207202 - 23 Oct 2023

Cited by 4 | Viewed by 2311

Abstract

CO₂-based enhanced geothermal systems (CO₂-EGS) are greatly attractive in geothermal energy production due to their high flow rates and the additional benefit of CO₂ geological storage. In this work, a CO₂-EGS model is built based on the available geological data in the Gonghe Basin, Northwest China. In our model, the wellbore flow is considered and coupled with a geothermal reservoir to better simulate the complex CO₂ flow and heat production behavior. Based on the fractured geothermal reservoir at depths between 2900 m and 3300 m, the long-term (30-year) heat production performance is predicted using CO₂ as the working fluid with fixed wellhead pressure. The results indicate that the proposed CO₂-EGS will obtain an ascending heat extraction rate in the first 9 years, followed by a slight decrease in the following 21 years. Due to the significant natural convection of CO₂ (e.g., low viscosity and density) in the geothermal reservoir, the mass production rate of the CO₂-EGS will reach 150 kg/s. The heat extraction rates will be greater than 32 MW throughout the 30-year production period, showing a significant production performance. However, the Joule–Thomson effect in the wellbore will result in a drastic decrease in production temperature (e.g., a 62.6 °C decrease in the production well). This means that the pre-optimization analyses and physical material treatments are required during geothermal production using CO₂ as the working fluid. Full article

(This article belongs to the Special Issue The Status and Development Trend of Geothermal Resources)

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16 pages, 13609 KiB

Open AccessArticle

Three-Dimensional Geological Modeling and Resource Estimation of Hot Dry Rock in the Gonghe Basin, Qinghai Province

by Guilin Zhu, Linyou Zhang, Zhihui Deng, Qingda Feng, Zhaoxuan Niu and Wenhao Xu

Energies 2023, 16(16), 5871; https://doi.org/10.3390/en16165871 - 8 Aug 2023

Cited by 2 | Viewed by 1568

Abstract

The Gonghe Basin, situated on the northeastern margin of the Qinghai–Tibet Plateau, is a strike-slip pull-apart basin that has garnered considerable attention for its abundant high-temperature geothermal resources. However, as it is located far from the Himalayan geothermal belt, research on the geothermal resources in the Gonghe Basin has mainly focused on the heat source mechanism, with less attention given to the distribution and resource potential of hot dry rock. In this project, a comprehensive approach combining geological surveys, geophysical exploration, geochemical investigations, and deep drilling was employed to analyze the stratigraphic structure and lithological composition of the Gonghe Basin, establish a basin-scale three-dimensional geological model, and identify the lithological composition and geological structures within the basin. The model revealed that the target reservoirs of hot dry rock in the Gonghe Basin exhibit a half-graben undulation pattern, with burial depths decreasing from west to east and reaching a maximum depth of around 7000 m. Furthermore, the distribution of the temperature field in the area was determined, and the influence of temperature on rock density and specific heat was investigated to infer the thermal properties of the deep reservoirs. The Qiabuqia region, situated in the central-eastern part of the basin, was identified as a highly favorable target area for hot dry rock exploration and development. The volume method was used to evaluate the potential of hot dry rock resources in the Gonghe Basin, which was estimated to be approximately 4.90 × 10²² J, equivalent to 1.67 × 10¹² t of standard coal, at depths of up to 10 km. Full article

(This article belongs to the Special Issue The Status and Development Trend of Geothermal Resources)

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18 pages, 3201 KiB

Open AccessFeature PaperReview

Research Progress on CO₂ as Geothermal Working Fluid: A Review

by Lianghan Cong, Shuaiyi Lu, Pan Jiang, Tianqi Zheng, Ziwang Yu and Xiaoshu Lü

Energies 2024, 17(21), 5415; https://doi.org/10.3390/en17215415 - 30 Oct 2024

Cited by 4 | Viewed by 1464

Abstract

With the continuous increase in global greenhouse gas emissions, the impacts of climate change are becoming increasingly severe. In this context, geothermal energy has gained significant attention due to its numerous advantages. Alongside advancements in CO₂ geological sequestration technology, the use of CO₂ as a working fluid in geothermal systems has emerged as a key research focus. Compared to traditional water-based working fluids, CO₂ possesses lower viscosity and higher thermal expansivity, enhancing its mobility in geothermal reservoirs and enabling more efficient heat transfer. Using CO₂ as a working fluid not only improves geothermal energy extraction efficiency but also facilitates the long-term sequestration of CO₂ within reservoirs. This paper reviews recent research progress on the use of CO₂ as a working fluid in Enhanced Geothermal Systems (EGS), with a focus on its potential advantages in improving heat exchange efficiency and power generation capacity. Additionally, the study evaluates the mineralization and sequestration effects of CO₂ in reservoirs, as well as its impact on reservoir properties. Finally, the paper discusses the technological developments and economic analyses of integrating CO₂ as a working fluid with other technologies. By systematically reviewing the research on CO₂ in EGS, this study provides a theoretical foundation for the future development of geothermal energy using CO₂ as a working fluid. Full article

(This article belongs to the Special Issue The Status and Development Trend of Geothermal Resources)

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