Geothermal Energy Production Research Articles

Modeling of Chemical Tracers for Two-Phase Flow in Advective-Dominated Porous Media at Core Scale

Summary Chemical tracer modeling in porous media plays a key role in subsurface applications including oil recovery, aquifer remediation, and geothermal energy production. In oil reservoirs, chemical tracers are critical to quantifying the remaining oil saturation in porous media after displacing processes, enabling the correct evaluation of the sweep efficiency of recovery methods at the field scale. Even though the transport of solutes under single-phase flow has been modeled extensively with numerous solutions, there are no existing mathematical approaches to examine the displacement of solutes in two-phase flow conditions. Therefore, we present in this research work the first analytical solutions derived to model the transport of ideal and partitioning tracers in porous media with mobile water and oil phases. The models presented are derived from the classic study of fluid displacement by viscous forces and the analysis of dynamic phase distribution in porous media, where key transformation variables are introduced to simplify the nonlinear advection-dispersion equation (ADE) into a conventional partial differential expression. In our derivation process, it is recognized that the dispersion effect can be superimposed onto an ideal concentration front via a singular perturbation expansion, resulting in practical solutions that do not require complex numerical calculations or inversion methods. The solutions derived are verified with numerical simulations and validated with experimental data under different flow conditions for the transport of ideal and partitioning tracers, demonstrating that the complex mechanisms of hydrodynamic dispersion, partitioning, and adsorption are accurately modeled under two-phase flow. Thus, our solutions can be used to rapidly evaluate tracer transport under the existing flow conditions in porous media, significantly reducing the number of experiments and simulations to characterize and select the correct tracer to be used in field applications.

Acceleration of Deep Subsurface Fluid Fluxes in the Anthropocene

AbstractThe Anthropocene has been framed around humanity's impact on atmospheric, biologic, and near‐surface processes, such as land use and vegetation change, greenhouse gas emissions, and the above‐ground hydrologic cycle. Groundwater extraction has lowered water tables in many key aquifers but comparatively little attention has been given to the impacts in the deeper subsurface. Here, we show that fluid fluxes from the extraction and injection of fluids associated with oil and gas production and inflow of water into mines likely exceed background flow rates in deep (>500 m) groundwater systems at a global scale. Projected carbon capture and sequestration (CCS), geothermal energy production, and lithium extraction to facilitate the energy transition will require fluid production rates exceeding current oil and co‐produced water extraction. Natural analogs and geochemical modeling indicate that subsurface fluid manipulation in the Anthropocene will likely appear in the rock record. The magnitude and importance of these changes are unclear, due to a lack of understanding of how deep subsurface hydrologic and geochemical cycles and associated microbial life interact with the rest of the Earth system.

Assessing the hazard of fault triggering by deep geothermal energy production in an active fault system via a 1D stress model and 3D fault mapping

Borehole image data and a 1D-stress model built on open hole logs, leak-off tests (LOT) and image logs are used to evaluate the potential of seismicity caused by fault triggering during geothermal heat production in the city of Vienna. Data were derived from a 4220 m deep geothermal exploration well that investigated the geothermal potential of fractured carbonates below the Miocene fill of the Vienna Basin. The well penetrated several normal faults of the Aderklaa Fault System (AFS) that offset Pleistocene terraces at the surface and hence are regarded as active. Stress-induced borehole failures and 1D geomechanical modeling proves that the potential reservoirs are in a normal fault stress regime with Sv > SHmax > Shmin. While stress magnitudes in the upper part of the well (down to about 2000 m) are significantly below the magnitudes that would trigger the rupture of critically oriented faults including the AFS, stresses in the lower part of the drilled section in the pre-Neogene basement (below about 3300 m) are not. Data evidence a rotation of SHmax for about 45° at a fault of the AFS at 3694 m to fault-parallel below the fault suggesting that the fault is active. Critical or near-critical stressing of the fault is corroborated by the stress magnitudes calculated from the 1D geomechanical model. The safety case to exclude unintended triggering of seismic fault slip by developing geothermal reservoirs in close vicinity to one of the branch faults of the AFS may therefore be difficult or impossible to make.Graphical

Unlocking Geothermal Energy: A Thorough Literature Review of Lithuanian Geothermal Complexes and Their Production Potential

Lithuania is located on the East of Baltic sedimentary basin and has a geothermal anomaly situated in the southwestern region of the country. There are two primary geothermal complexes within the anomaly, composed of Cambrian and Devonian aquifers. The Cambrian formation is composed of sandstones that have a reservoir temperature reaching up to 96 °C (depth > 2000 m). The Devonian aquifer is composed of unconsolidated sands of Parnu–Kemeri and has a reservoir temperature of up to 46 °C (depth > 1000 m). Historically, both formations have been investigated for geothermal energy production. In this article, we present a detailed literature review of the geothermal work carried out on both formations, including past, present, and some possible future studies. The study presented in this paper highlights the key findings of previous research work, summarizes the research gaps, and then elaborates on the possible applications of emerging technologies to bridge the research gaps and improve our understanding of geothermal complexes in Lithuania. Although it is not the main aim of this article, this article also touches upon the important need to develop 2D/3D numerical models, to quantify uncertainties, in the evaluation of the geothermal potential in Lithuania for commercial development. This study also highlights possibilities of extending geothermal development to depleted hydrocarbon reservoirs through repurposing the high-water-production wells. Moreover, from the literature review, it can be concluded that the Lithuanian geothermal aquifers are hyper-saline in nature and temperature changes lead to the deposition of salts both upstream and downstream of the reservoir. Therefore, there is a need for developing multiphysics thermo-mechanical–chemical (THMC) models for evaluation of reservoir behavior. The literature also describes the potential use and development of the THMC model as a part of future work that must be carried out.

Pore Fluid Pressure in St. Gallen Geothermal Field (Switzerland) Based on Earthquake Focal Mechanisms

AbstractInduced seismicity represents a negative drawback during subsurface exploitation for geothermal energy production. Understanding the triggering mechanisms of induced earthquakes can help implement effective seismic hazard mitigation actions. Among the triggering mechanisms, the pore fluid pressure is of primary importance. Here we provide a static picture of the excess pore fluid pressure at the hypocenters of a seismic sequence induced at the deep geothermal field in St. Gallen, Switzerland, in July 2013. We find that in addition to the Coulomb static stress change, fluids play a key role in promoting the sequence. The estimated excess pore fluid pressure for approximately half of the earthquakes is higher than the injection pressure necessary during the well control phase to fight the unexpected gas kick, that accidently occurred during field operations when a trap of overpressured gas was broken.

Detection of Land Surface Temperature anomalies using ECOSTRESS in Olkaria geothermal field

Geothermal systems can be used to produce low-emission energy throughout the day and night, regardless of the weather conditions. These features make geothermal systems a sustainable and reliable energy source, which can be exploited on a much larger scale than it is now. Remote sensing techniques can support detecting areas potentially suitable for geothermal energy production, thereby reducing the costs of preliminary exploration. The Ecosystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) can provide nighttime thermal imagery, which can be used for geothermal anomaly detection. This paper presents a method for automated detection of geothermal anomalies using nighttime ECOSTRESS data of the study area in Olkaria, Kenya. The proposed detection method is a kernel-based one, and includes adaptions of kernel size for the cases of large geothermal anomalies. The accuracy of the method is verified with reference data acquired during field work. A producer’s accuracy of 82% is achieved, which is on average 56% points better than in randomised anomaly maps. The possible sources of errors in detection are heat capacity of surfaces, terrain features and vegetation masking the thermal signatures. The high producer’s accuracy proves potential for application in global mapping of geothermal anomalies.

Study Explores Retrofitting Abandoned Petroleum Wells for Geothermal Production

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 210861, “An Overview of Retrofitting Abandoned Petroleum Wells for Geothermal Energy Production,” by Rahman Ashena, SPE, Asia Pacific University of Technology and Innovation. The paper has not been peer reviewed. _ The complete paper presents a comprehensive overview and analysis of 20 global case studies in which abandoned petroleum wells were retrofit for geothermal applications, followed by important downhole and surface parameters. Good potential exists for producing geothermal energy from abandoned and nonactivated petroleum wells. Introduction In retrofitted geothermal projects, the bottomhole temperatures are usually much lower than conventional geothermal wells. Given the low temperatures of these projects, optimization should be achieved in all respects. While the complete paper details the effect of the concepts investigated by the authors in the 20 case studies, this synopsis mainly offers a higher-level summary of these concepts rather than a discussion of the case studies themselves. Overview All case studies mentioned in the complete paper are simulation works except for one. Table 1 of the complete paper lists general information including the regional locations and investigators of these case studies, while Table 2 of the complete paper provides comprehensive design and production information about the cases provided.

Technology Focus: Geothermal Energy (March 2024)

As the world seeks transformative solutions to ensure a sustainable energy future, there is a growing interest in geothermal energy because of its versatility and evolving technologies that enable the application of low-enthalpy fluids. One area where the untapped potential of geothermal energy has been realized is in harnessing thermal energy from abandoned or inactive oil and gas wells. Such wells could be exploited for electricity generation or direct use through well repurposing. Three innovative papers elucidate the challenges, complexities, applicability, and key operational considerations associated with repurposing abandoned or idle oil and gas wells for geothermal energy. The first paper offers a comprehensive overview of 20 case studies from various countries, including actual and simulated cases. Downhole and surface parameters, including production scenarios, heat exchangers, circulation fluids, and power-generation efficiency, are meticulously examined. The investigation concludes with a positive outlook, highlighting the potential of producing geothermal energy from underused oil and gas wells. The second paper delves into the technical and economic feasibility of repurposing oil and gas wells specifically for community heating through geothermal energy. The multidisciplinary approach involves a thorough analysis of physical, technical, economic, and environmental aspects. The results showcase the potential benefits of repurposing low-temperature wells for community heating, emphasizing the cost-effectiveness and sustainability of this approach. The third paper introduces a geothermal assessment project conducted in an operational high-pressure/high-temperature field on the UK Continental Shelf. This innovative project uses a novel integrated work flow to assess the geothermal energy potential of offshore oil and gas assets and provides insights into CO2 emission reduction. The life of oil and gas wells can be extended through repurposing for geothermal energy production. The findings underscore the technical viability, economic feasibility, and environmental benefits of oil and gas well repurposing, providing a promising avenue for transforming existing oil and gas resources and infrastructure into contributors to a cleaner and greener energy future. Recommended additional reading at OnePetro: www.onepetro.org. SPE 213068 A Robust Screening Tool To Repurpose Hydrocarbon Wells to Geothermal Wells in Oklahoma by Esteban R. Ugarte, University of Oklahoma, et al. SPE 215554 A Feasibility Study of Geothermal Energy Extraction in the Baram Basin, Sarawak, Using Numerical Reservoir Simulation Based on Analog Data by M. Bataee, Curtin University Malaysia, et al. SPE 212075 Geothermal Energy in the Caspian Region: Study of Heat-Extraction Methods From Deep Wells by Dmitriy Abdrazakov, SLB

Study Outlines Challenges of Repurposing Oil and Gas Wells for Geothermal Applications

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 215751, “Challenges for Repurposing Oil and Gas Wells for Geothermal Applications,” by Livio Santos, SPE, and Arash Dahi Taleghani, SPE, The Pennsylvania State University. The paper has not been peer reviewed. _ This work provides insights into the technical and economic viability of repurposing oil and gas wells for geothermal energy production for direct heating. The potential benefits—especially for areas that are highly dependent on fossil fuels for heating—and challenges of this approach are assessed, while technical, market, and policy barriers for future development are identified. Repurposing oil and gas wells for geothermal energy requires a multidisciplinary approach that involves expertise in geology, engineering, and regulatory affairs. Introduction Repurposing abandoned wells for power generation in geothermal energy projects can present challenges because of the low temperatures associated with these wells. The low temperature gradients and thermal energy available in such wells have been found to limit overall power-generation potential. The same low-temperature geothermal resources can still be used effectively, however, for community heating applications. Community heating systems have lower temperature requirements compared with those necessary for power generation and are compatible with available heat from low-temperature geothermal sources. In particular, closed-loop geothermal systems, specifically designed for community heating, offer several advantageous features. The closed-loop design ensures that the fluid remains contained within the system. These systems are environmentally compatible because they do not extract or discharge water from natural sources. Additionally, with better control over the working fluid and heat-exchange process, closed-loop systems deliver optimized system performance, energy efficiency, and cost savings. They also require less maintenance and feature lower operational risks because of the closed circuit. Closed-loop systems offer fluid-selection flexibility and streamlined regulatory compliance. Not all abandoned wells are suitable for repurposing, however. Thorough feasibility assessments and well-integrity evaluations are necessary to ensure that the abandoned well is structurally sound, has the appropriate depth and geological characteristics, and can extract geothermal heat effectively. The condition of the well casing, cementing, and any potential wellbore damage also must be evaluated. An economic analysis is performed to assess the financial viability and cost-effectiveness of the geothermal community heating system. Finally, an environmental impact assessment evaluates the environmental consequences of the geothermal community heating system.

Assessment of the effect of heat storage on the production of clean geothermal energy using the medium and deep U-type borehole heat exchanger system

Heat storage is a critical measure to realize the utilization of waste heat and to enhance the heating capacity of the medium-deep U-type borehole heat exchanger (MDUBHE) system. However, the effects of heat storage on the operation of the MDUBHE system remain unclear. The effects of heat storage measures on the building and the environment have not been assessed. In this paper, the effects of heat storage measures on system performance are revealed and assessed using the numerical heat transfer model. The results show that heat storage measures are particularly necessary in severe cold regions of China. The minimum value of the storage inlet temperature in this study should be more than 42.25 °C, and the flow rate is recommended at no more than 15 kg/s. Although increasing the inlet temperature of heat storage enhances the MDUBHE system's heating performance, the storage system's energy and exergy efficiencies are attenuated. Heat is mainly stored in the underground region within 6 m from the MDUBHE and at a depth of up to 2000 m, and the shape of the thermal plume is an inverted funnel. After adopting heat storage measures, the heating area supplied to buildings by the MDUBHE system increases, and reduces environmental pollution. Compared with the no heat storage measure, the heating area of the MDUBHE system is increased by 6770 m2 when the storage inlet temperature is 80 °C, and the corresponding solar collector area needs to be 756.1 m2. When Tins increases from 45 °C to 80 °C, the reduction of CO2 emissions increases by 12.43 tons, 21.05 tons, 38.26 tons, 55.41 tons, and 72.50 tons, respectively. This study could promote the application of the MDUBHE system and the heat storage system in severe cold regions.

Assessing Geothermal Energy Production Potential of Cambrian Geothermal Complexes in Lithuania

Lithuania has a geothermal anomaly situated in the southwestern region of the country. This anomaly is comprised of two primary geothermal complexes located in western Lithuania. The first complex is characterized by the Pärnu–Kemeri Devonian sandstone aquifers, which exhibit exceptionally good flow properties. However, the reservoir temperatures in this complex only reach up to 45 °C. The second complex encompasses Cambrian sandstone reservoirs. Although these Cambrian sandstone reservoirs exhibit high temperatures, with the highest reservoir temperatures reaching up to 96 °C, these Cambrian sandstone reservoirs have less favorable petrophysical properties. This study focuses on the high temperature Cambrian Geothermal sandstone reservoirs. The study aims to conduct a geological screening of the existing and depleted hydrocarbon reservoirs with high water production rates. After initial data gathering, numerical modeling is employed with the help of mechanistic box models to evaluate the geothermal potential of the selected sites for commercial development. Ultimately, the study identifies the top five screened sites, which could be developed further for techno-economical modelling.

Integrated Raw Material Approach to Sustainable Geothermal Energy Production: Harnessing CO2 for Enhanced Resource Utilization

Integrated Raw Material Approach to Sustainable Geothermal Energy Production: Harnessing CO2 for Enhanced Resource Utilization

Power generation prediction of a geothermal-thermoelectric hybrid system using intelligent models

This study focuses on the most effective use of energy resources, which is the main goal of sustainable energy systems. The first contribution of the research is to ensure that the waste and geothermal fluids generated during the geothermal energy production process are evaluated in the most efficient way and reused for energy production. For this purpose, a geothermal-thermoelectric hybrid experimental system has been designed to produce electrical energy through heat exchange and how waste thermal energy could be reused in this process has been examined. Experimental tests have been performed under electrical load and in the presence of real-time uncertainties such as temperature changes, thermal conductivity, electrical noise, heat losses and random variations in thermal interaction. The second main contribution of the study is to predict and evaluate different power generation performances in the Thermoelectric Generator (TEG) system, which is affected by the mentioned experimental limitations based on artificial intelligence models. In addition, the optimal prediction performance of artificial intelligence models using hyper-parameter optimization has also been compared. Experimental results have shown that intelligent models are a successful tool for energy prediction in geothermal power generation. As a result of the hyper-parameter optimization, each model is improved by ∼5 % to ∼30 % in various error metrics. However, it was observed that the decision tree-based learning techniques resulted in ∼46 % to ∼96 % less inaccurate predictions on various error metrics compared to other methods. Power production predictions obtained using intelligent models have been obtained with 98.7 % accuracy with LightGBM learning algorithms. Most of the models used to classify different hot and cold water levels exhibit very high classification performance. The results show the successful integration of artificial intelligence models in effectively utilizing waste thermal energy and adopting a sustainable approach to energy production.

Lithuania’s geo-energy landscape: a brief overview of CCUS, hydrogen, and geothermal

Lithuanian energy landscape is changing because of a strong push to reduce carbon emissions and reliance of fossil-based energy production. EU climate directive promotes investments into carbon capture and storage technologies along with renewable energy resource development. CCUS, hydrogen and geothermal are some technologies which could promote reduction in carbon emissions and along with reducing dependence on fossil-based energy sources. Lithuania already has large potential for carbon and hydrogen storage and in past had a working geothermal power plant for district heating. In this work we revisit the carbon storage potential in Lithuania subsurface and provide a high-level estimate of potential of generating hydrogen energy from depleted hydrocarbon fields using in-situ methods. We also evaluate the prospects of development of geothermal energy production from deep Cambrian reservoirs where temperature above 85 °C has been documented.

Heat Extraction Evaluation of CO2 and Water Flow through Different Fracture Networks for Enhanced Geothermal Systems

Enhanced geothermal system (EGS) technologies have been developed to improve geothermal energy production from hot dry rock (HDR). In this study, discrete fracture network models for geometric topological networks that consider different parameters (the fracture density and the fracture length index) were built on the basis of fractal geometry theory. The heat extraction processes of CO2 and water as the working fluid through different discrete fracture networks were simulated with the application of the thermal–hydraulic–mechanical (THM) coupled method. A series of sensitivity analyses were carried out to reveal the influences of fracture parameters on heat transfer processes. Based on the simulation results, heat extraction efficiencies and temperature distributions in the reservoir of CO2 and water as the working fluid were compared, which showed that CO2 as the working fluid can bring a faster thermal breakthrough. It was found that the fracture length index a = 2.5 and the fracture density I = 5.0 can provide the highest heat extraction rate compared with other cases. This study provides a detailed analysis of fracture parameters and working fluids, which will contribute to the optimized management of geothermal energy production.

Social acceptance of geothermal technology on a global view: a systematic review

BackgroundThe role of geothermal technology in the context of global efforts toward carbon-free and clean energy production is becoming increasingly important. Social acceptance is a decisive factor in the successful implementation of geothermal projects.Main textThis systematic review summarizes the major aspects and evaluates the crucial outcomes of recent research on community acceptance as a dimension of social acceptance of geothermal technology since 2011, on a global scale. From the literature, we identified and grouped researched acceptance factors into five main acceptance categories, namely ‘project organization and process’, ‘environment’, ‘municipality’, ‘technology’, and ‘governance’. Each category comprises a number of specific acceptance factors addressed by different survey methods (e.g., interviews, questionnaires, content analyses) in the relevant publications. The acceptance factor categories ‘technology’ and ‘governance’ are remarkably underrepresented, whereas the acceptance factors combined in the categories ‘project organization’ and ‘municipality’ are frequently mentioned in the literature. Acceptance factors combined within the category ‘environment’, ‘trust in key actors’, and ‘information about the project’ are expectedly the most dominant ones in the papers studied. Interestingly, acceptance categories and number of mentions of acceptance factors are comparable in all survey methods applied in the various studies. Besides the acceptance factors combined in the categories ‘environment’ and ‘project organization and process’, ‘knowledge about geothermal technology’ (an acceptance factor from the category ‘municipality’) represents the predominant acceptance factor of geothermal technology.ConclusionsDeeper knowledge, in particular about the technical aspects of geothermal energy generation, might enable a more comprehensive and holistic view on geothermal technology. Furthermore, the integration of all relevant groups of stakeholders in the process of implementation of geothermal projects strongly influences their social acceptance. Following the results of our systematic literature review, we propose these aspects should be addressed in more detail in future research on the community acceptance of geothermal technology and energy production.

Induced Seismicity Forecasting with Uncertainty Quantification: Application to the Groningen Gas Field

Abstract Reservoir operations for gas extraction, fluid disposal, carbon dioxide storage, or geothermal energy production are capable of inducing seismicity. Modeling tools exist for seismicity forecasting using operational data, but the computational costs and uncertainty quantification (UQ) pose challenges. We address this issue in the context of seismicity induced by gas production from the Groningen gas field using an integrated modeling framework, which combines reservoir modeling, geomechanical modeling, and stress-based earthquake forecasting. The framework is computationally efficient thanks to a 2D finite-element reservoir model, which assumes vertical flow equilibrium, and the use of semianalytical solutions to calculate poroelastic stress changes and predict seismicity rate. The earthquake nucleation model is based on rate-and-state friction and allows for an initial strength excess so that the faults are not assumed initially critically stressed. We estimate uncertainties in the predicted number of earthquakes and magnitudes. To reduce the computational costs, we assume that the stress model is true, but our UQ algorithm is general enough that the uncertainties in reservoir and stress models could be incorporated. We explore how the selection of either a Poisson or a Gaussian likelihood influences the forecast. We also use a synthetic catalog to estimate the improved forecasting performance that would have resulted from a better seismicity detection threshold. Finally, we use tapered and nontapered Gutenberg–Richter distributions to evaluate the most probable maximum magnitude over time and account for uncertainties in its estimation. Although we did not formally account for uncertainties in the stress model, we tested several alternative stress models, and found negligible impact on the predicted temporal evolution of seismicity and forecast uncertainties. Our study shows that the proposed approach yields realistic estimates of the uncertainties of temporal seismicity and is applicable for operational forecasting or induced seismicity monitoring. It can also be used in probabilistic traffic light systems.

Geological controls on lithium production from basinal brines across North America

With increasing lithium (Li) demands for electric car batteries and grid storage, additional Li beyond traditional continental brines and hard-rock sources might be necessary. Elevated Li concentrations have been reported in select oil field brines. Li could be extracted from the large volumes of saline fluids produced by oil and gas wells or from new wells dedicated to Li production. However, the spatial distribution of Li+ concentrations, the rates at which fluids can be produced in areas with elevated Li+ concentrations, and potential sources of Li enrichment are not well characterized. To help identify additional sources of Li, this study investigates the concentration, origin, and potential production rates of Li from sedimentary basin brines across North America. New Li data from brines in various stratigraphic units in the Paradox Basin are combined with existing datasets from the basin and others across North America. New Li analyses of organic-rich shales in the Paradox Basin are also examined to provide insights into the origins of Li. Results from this study show the median Li+ concentration in oil and gas produced waters across North America is ~5 mg/L; these generally low concentrations are unlikely to support Li production. However, higher Li+ concentrations (>65 mg/L) are found in select basins and strata containing deep saline fluids, associated with evaporation of paleo-seawater and precipitation of halite and potash salts, that have not been flushed by meteoric recharge. High Li content of organic-rich shales (range: 20–440 ppm; median: 60 ppm) interbedded with evaporites in the Paradox Basin suggest fluid-rock interactions with diagenetically-altered shales and organic matter are one potential source of Li-enrichment in basinal brines. Observed fluid production and injection rates indicate that Li production will likely be highest in sandstone and carbonate formations with relatively high permeability. Potential Li production rates can vary by orders of magnitude even within these strata due to heterogeneity in both Li concentrations and permeability, as well as recovery efficiencies between 40 and 70 % with current technology. Targeted Li production wells, rather than relying on existing oil and gas wells, would likely be necessary to produce brines at sufficient volumes to support Li production at these low concentrations. Co-recovery of other critical elements or combination with other subsurface developments, such as geothermal energy production, may make Li production from sedimentary basin fluids more viable.

Unlocking geothermal energy for sustainable greenhouse farming in arid regions: a remote-sensed assessment in Egypt’s New Delta

This study introduces a novel approach for assessing geothermal potential in arid regions, specifically Egypt’s New Delta Agriculture Mega Project area. The challenge of limited sub-soil temperature profile data was addressed by integrating Global Land Data Assimilation System (GLDAS) weather data. Using the Earth-to-Air Heat Exchanger (EAHE) model, the extracted air and sub-soil temperature profiles the potential for geothermal energy production was estimated. We modeled the annual sinusoidal soil surface periodic heating pattern by utilizing GLDAS ambient air temperature (AAT) and land surface temperature (LST). Using either AAT or LST yielded a Root-Mean-Square Error (RSME) of 0.2°C. The generated sub-soil profiles for the New Delta region showed a temperature variation of no more than 1.5°C at a 4-m depth, making it an optimal depth for EAHE installation. One-pipe EAHE demonstrated a cooling/heating capacity ranging from 400 W (cooling) to −300 W (heating). The study highlights the New Delta region’s strong geothermal potential for greenhouse cooling and heating, underlining its suitability as a sustainable energy source in arid areas. It also offers a practical guide for the EAHE application and it emphasizes the global potential for geothermal energy exploration, using innovative GLDAS data to expand sub-soil temperature profile accessibility.

Heat transfer characterizations of water flow through a single fracture with integrating water dissolution effects for the Enhanced Geothermal Systems

The Enhanced Geothermal Systems (EGS) is the technology that generates connected fracture networks in the Hot Dry Rock (HDR) reservoir with the application of water as the working fluid for hydraulic fracturing and geothermal energy production. A good understanding of water flow behaviors in the single fracture is critically important because connected fracture networks are composed of individual fractures. It should be noticed that the dissolution reaction between the reservoir rock and the working fluid (water) will change the fracture surface directly and consequently affect the mass and heat transfer process of water through the rock fracture in the HDR reservoir. In this study, the heat transfer process of water flow in the single fracture by considering dissolution reactions between water and fracture surfaces of reservoir rock have been investigated under high pressure and temperature conditions. The experiments of dissolution reaction and convective heat transfer have been performed separately for different temperature conditions with the rock sample of 0.2 mm fracture aperture. The influences of reaction duration, mass flow rates and initial temperature have been presented and analyzed. It is found that mass flow rates and temperature have significant effects on measured temperature of fracture surfaces. The effects of dissolution reaction on fracture surface morphology exists but it is extremely small for heat transfer. Based on experimental and simulation data, a modified correlation that integrates reaction duration, mass flow rates and changes of thermophysical properties has been proposed and its maximum error that compares with experimental results is less than 7%. The results of this study provided an accurate correlation for simulations and characterizations of the Hot Dry Rock reservoirs, which is of great importance for geothermal energy production and optimization.