Geothermal Resources Research Articles

Application of a Novel Temperature-Sensitive Polymer PNA-SiO2 as a Rheological Agent in Geothermal Drilling.

In geothermal drilling, the significant rheological deterioration of biopolymer drilling fluids can lead to decreased cutting-carrying efficiency and fluctuations in annulus pressure, which can easily result in unpredictable downhole accidents. To address the challenges, this study innovatively introduces temperature-sensitive monomers (NIPAM) and nanosilica into molecular chains based on temperature response effects and adsorption stability to counteract the negative effects of temperature and salt ions, aiming to develop a rheological agent (PNA-SiO2) that is resistant to high temperature and salt. The molecular structure and thermal stability of PNA-SiO2 were characterized by FT-IR and TGA, and it was demonstrated to have the stability of the molecular main chain within 317 °C. According to rheological and filtration studies, PNA-SiO2 effectively addresses the issues of high-temperature viscosity attenuation and a sharp rise in the filtration volume of bentonite mud by aggressively adsorbing, creating a stable thixotropic network, and enhancing molecular repulsion. After aging at 60-180 °C, the drilling fluid with 2-4% PNA-SiO2 has excellent rheology (AV ≥ 57.5 mPa·s, PV ≥ 42 mPa·s, Gel10min ≥ 1.533 Pa) and filtration (FLAPI ≤ 9.6 mL) properties that fully satisfy API requirements. The H-B model is the preferred model to accurately describe the rheology behavior of PNA-SiO2 drilling fluids. Moreover, under the comprehensive influence of Na+ on the interlayer spacing of bentonite and the thickness of the diffusion bilayer, PNA-SiO2 has applicability in high-temperature saturated saline water. After aging at 150 °C and 5-36% NaCl, the PNA-SiO2 drilling fluid exhibits stable viscosity (AV ≥ 55 mPa·s, PV ≥ 44 mPa·s) and low filtration volume (≤9.6 mL). In conclusion, PNA-SiO2 is used as a rheological and fluid loss agent, offering a cost-effective solution to the technical issues of severe leakage and inadequate cutting-carrying capacity encountered by geothermal drilling, which enables the safe and quick exploration of geothermal resources.

A Simulation-Optimization Approach of Geothermal Well-Doublet Placement in North China Using Back Propagation Neural Network and Genetic Algorithm

The well-doublet production model has far-reaching implications for the sustainable utilization of geothermal resources. The position of the injection well in the geothermal production process is closely connected to the emergence of thermal breakthroughs and the production lifespan. Thus, it is necessary to optimize the well placement. However, traditional simulation and optimization approaches require a long time and have a high computing burden. In this paper, a surrogate model based on the back propagation neural network (BPNN) is trained to improve the drawbacks of previous approaches, and it is combined with the genetic algorithm (GA) to develop a simulation-optimization approach to find the optimal well placement of a well-doublet geothermal production system. To guarantee that the training data have appropriate physical significance, the TOUGH2 program is used for the hydro–thermal model development of the geothermal reservoir of the Minghuazhen Formation in Tianjin, China. A sensitivity analysis is used to select the series of samples used for training, which includes temperature and pressure variation, heat extraction rate (Wh), and economic cost. The results reveal that the surrogate model has excellent prediction accuracy and efficiency for physical processes, and the genetic algorithm optimization outcomes are consistent with predictions, which is of practical importance.

The Current Status of Wellbore Stability Research in Geothermal Drilling

Wellbore stability is crucial in geothermal drilling as it guides the setting and selection of many parameters, such as drilling fluid density, fracture pressure, drill bit speed, and well trajectory. However, it is unfortunate that research on wellbore instability in geothermal drilling is limited. The future large-scale development of higher temperature geothermal resources will require further study of wellbore instability, particularly under harsh conditions in different regions and rock layers. Additionally, improving and predicting wellbore instability is essential for enhancing efficiency and reducing costs during the drilling process.

Geothermal Water Component of Land-Based Fish Farm—A Case Study of the Sustainable Blue Economy Architecture

Geothermal water, as a by-product of renewable energy generation, can be appreciated as part of a sustainable Blue Economy in terms of resource effectiveness. This could be part of urban geothermal resource parks in the near future. City aquaculture integrated with urban farms running in a cascading model of energy and material consumption can provide an advanced energy-water-food nexus in densely populated areas, evolving into a refined Nature 4.0 habitat. This case study of the world’s first climate-controlled, closed salmon farm based on geothermal resources presents inclusive, water-sensitive design principles and resilient urban planning, where architecture brings aquatic ecosystems indoors. This is also an example of how to reduce investment risk and integrate geothermal development with sustainable, innovative fish farming based on water circulation systems (RAS) and digital technologies to sustain life-support systems. This greenfield project on Poland’s Baltic coast highlights the potential for geothermal investments, demonstrating that even low-temperature extracted water can serve as both a renewable energy source and a valuable resource. Having operated successfully for over a decade with positive certification, this model of efficient geothermal resource utilization appears to be well-suited for replication and broader implementation.

Investigation and Evaluation of Geothermal Resources in Northern Shanxi Province, China

In this study, survey methods including seismic techniques and controlled-source audio-frequency magnetotelluric, drilling, and pumping tests were employed to investigate the geothermal systems and their formation mechanisms in northern Shanxi Province, China. The following characteristics were observed: (1) Geothermal resources in northern Shanxi Province are primarily located in Archean metamorphic rocks and fracture zone aquifer groups. The direct heat source is likely uncooled magma chambers in the middle-upper crust, whereas the overlying layers consist of Quaternary, Neogene, and Paleogene deposits. (2) The high-temperature geothermal system is of the convective-conductive type: atmospheric precipitation and surface water infiltrate pore spaces and fault fractures to reach thermal storage, where they are heated. Hot water then rises along the fracture channels and emerges as shallow hot springs, and ongoing extensional tectonic activity has caused asthenospheric upwelling. The partial melting of the upper mantle forms basic basaltic magma, which ascends to the middle-upper crust and forms multiple magma chambers. Their heat is transferred to the shallow subsurface, causing geothermal anomalies. (3) Borehole YG-1 findings revealed that these geothermal resources are primarily static reserves. Our findings provide a foundation for further geothermal development in the region, including the strategic deployment of wells to improve geothermal energy extraction.

Hydrochemical Processes, Mineral Scaling and Water Quality of Geothermal Waters in Sichuan Basin, Southwestern China

Geothermal resources are significant natural resources for achieving carbon neutrality. In this study, we collected eight groups of geothermal water samples from a Sichuan sedimentary basin. Major and trace elements were measured for hydrochemical analysis. SO42− and Ca2+ are the major anion and cation, respectively, in geothermal waters with the hydrochemical type Ca–SO4. The dissolution of calcite and gypsum, silicate weathering and positive cation exchange were responsible for hydrochemical processes. Saturation indices showed the unsaturated affinity of geothermal waters. Carbonate scaling would be the main problem during geothermal exploitation. The water quality index indicated that most of the geothermal water samples, except G3 and G8, were suitable for drinking purposes. The poor water quality of the G3 and G8 samples was attributed to elevated Na+ and K+ concentrations. The weights of affecting factors followed the order of NH4+ (3.803) > Cl− (2.823) > Na+ (2.677) > pH (2.224) > Ca2+ (1.506) > SO42− (1.169) > F− (1.127) > Mg2+ (0.850) > TDS (0.808). The results of this study provide an important insight for geothermal exploitation in sedimentary basins worldwide.

Impacts of Temperature and Pressure on the Thermophysical Properties of Granites

The thermophysical properties of rocks are identified as basic physical parameters for the exploitation and utilization of hot dry rock (HDR) geothermal resources. Given that reservoirs in a HDR system are subjected to a certain temperature and pressure, investigating the impacts of temperature and pressure on the thermophysical properties of rocks holds great significance. This study investigated the granite samples from the Tengchong area, Yunnan Province, China. Using laboratory tests combined with simulations, this study explored the impacts of temperature, pressure, and the combination of both on the thermal conductivity and diffusivity of granites. The results indicate that in the uniaxial pressure range of 0 to 42.2 MPa, as the uniaxial pressure increases, the thermal conductivity of the granites tends to increase nonlinearly, while their thermal diffusivity has no obvious correlation with the pressure. In the temperature range of 25 to 300°C, as the temperature increases, both the thermal conductivity and diffusivity of the granites tend to linearly decrease, with a linear relationship existing between the thermal conductivity and diffusivity. Using these findings, this study developed a prediction model for the thermal conductivity of granites under the combined effects of temperature and pressure. Additionally, based on the computed tomography (CT) scans, this study established core-scale heat transfer models focusing on minerals using the COMSOL Multiphysics finite element analysis (FEA) software. The model has a certain reliability in the prediction of thermal conductivity at 25∼300°C, and the error is less than 15% at 25∼200°C.

Prospect of comprehensive utilization of geothermal resources during the construction and operation of railway

PurposeThis study is dedicated to systematically collating the distribution and utilization circumstances of geothermal resources in China. Moreover, it endeavors to formulate a comprehensive utilization scheme for geothermal resources during the construction and operation phases of the railway, thereby furnishing robust support and valuable reference for the holistic utilization of geothermal resources along the railway corridor.Design/methodology/approachThrough an in-depth analysis of the extant utilization of geothermal resources in China, it is discerned that the current utilization modalities are relatively rudimentary, bereft of rational planning and characterized by a low utilization rate. Concurrently, by integrating the practical requisites of railway construction and operation and conducting theoretical dissections, a comprehensive utilization plan for the construction and operation periods of railway is proffered.FindingsIn light of the railway’s construction and operation characteristics, geothermal utilization models are categorized. During construction, comprehensive modalities include tunnel illumination power generation, construction area heating, tunnel antifreeze using shallow geothermal energy, tunnel pavement antifreeze and construction concrete maintenance. During operation, they comprise operation tunnel antifreeze, railway roadbed antifreeze, railway switch snow melting and deicing, geothermal power station establishment and railway hot spring health tourism planning.Originality/valueAccording to the characteristics and actual needs of railway construction and operation, it is of great significance to rationally utilize geothermal resources to promote the construction and operation of green railways.

Exploring Geochemical Characteristics of Composite Geothermal Reservoirs for Sustainable Utilization: A Case Study of the Northwestern Shandong Geothermal Area in China

Presently, geothermal resources have been globally recognized as an indispensable component of the energy system due to their sustainability. However, previous studies on geothermal reservoirs focus primarily on single reservoirs, lacking a systematic investigation of composite geothermal reservoirs. The geothermal reservoirs in the northwestern Shandong geothermal area in China are primarily of sandstone and karst types, characterized by extensive distributions, shallow burial depths, high water temperatures, and high water abundance, holding considerable potential for exploitation. This study explored the hydrochemical, isotopic, and circulation characteristics of geothermal fluids in the composite geothermal reservoirs in the study area using methods like hydrogeochemistry and geothermal geology. The purpose is to determine the geochemical differences in geothermal fluids across the composite geothermal reservoirs and provide scientific support for subsequently efficient and sustainable exploitation and utilization of geothermal resources in the study area. The composite geothermal reservoirs in the study area are composed of porous sandstone geothermal reservoirs (also referred to as sandstone reservoirs) in the upper part and karst-fissured geothermal reservoirs (also referred to as karst reservoirs) in the lower part. The results show that the geothermal fluids in the sandstone and karst reservoirs are primarily of Na-Cl-SO4 and Na-Ca-Cl-SO4 types, respectively. The hydrochemical composition of geothermal fluids in the karst reservoirs is principally influenced by the precipitation–dissolution equilibrium of carbonate and sulfate minerals, while that in the sandstone reservoirs is predominantly influenced by the precipitation–dissolution equilibrium of carbonate and silicate minerals, as well as cation exchange reactions. The temperatures of the karst reservoirs were calculated at 52.9–82.09 °C using geothermometers. Given the cold-water mixing ratios range from 89% to 96%, the corrected reservoir temperatures vary from 200 to 225 °C. In contrast, the temperatures of the sandstone reservoirs were calculated at 60.54–85.88 °C using geothermometers. These reservoirs exhibit cold water mixing ratios ranging from 85% to 90%, and their corrected reservoir temperatures vary from 150 to 200 °C accordingly. The circulation depths of geothermal fluids in the karst and sandstone reservoirs range from 1107.28 to 1836.69 m and from 1366.60 to 2102.29 m, respectively. The study area is primarily recharged by meteoric water from Mount Tai and the Lushan and Yishan mountains (collectively referred to as the Tai-Lu-Yi mountains) to the southeast of the study area. Investigating the differences in geochemical characteristics of geothermal fluids in composite geothermal reservoirs in the study area is significant for balancing the exploitation and supply of geothermal resources, optimizing the exploitation and utilization modes, and promoting the efficient and sustainable exploitation and utilization of geothermal resources in the study area.

Study Examines Thermal Effects on Drilling Performance in Hot Dry Rock

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 217718, “Thermal Effects on Drilling Performance in Hot Dry Rock,” by Aleksandr Vetsak, SPE, Eavor Technologies; Laurent Gerbaud, Mines Paris Tech; and Roman J. Shor, SPE, University of Calgary, et al. The paper has not been peer reviewed. _ High-temperature geothermal resources at a distance from tectonic boundaries or geologic hotspots can be accessed by the drilling of deep wells through significant sections of basement rock. This paper evaluates the effect of rapid cooling on the rock-cutting process and incorporates this effect into a drilling-performance optimization approach. Introduction Construction of deeper wells for geothermal heat involves drilling into the basement of the continental crust. Accessing geothermal resources in impermeable igneous or metamorphic rock is referred to as drilling hot dry rock (HDR). HDR, characterized by low permeability, minimal porosity, and negligible initial water saturation, maintains high temperatures through conductive heat exchange. Accessed from the surface by conventional rotary-drilling technologies, HDR fails in compression under axial loading of roller-cone drill bits and fails in compression shear under axial and tangential loading of polycrystalline-diamond cutters (PDC) in fixed-cutter drill bits. During HDR drilling, circulated drilling fluid exits through the bottomhole assembly (BHA) into the annulus. If the static formation temperature is higher than the temperature rating of the BHA, then the colder drilling fluid is used to cool down and keep the BHA within its temperature limit. When such colder fluid exits the drill bit, it cools down the rock surface in front of the bit and around the BHA. Combined with rotary drilling, the circulation of the colder drilling fluid creates a temperature difference at the bit/rock interaction surface by cooling the thin layer of hot rock in front of the drill bit in milliseconds, later to be removed by rotary cutting. Thermal conductivity affects heating or cooling rates. High angular velocities of the drill bit and low depth of cut per revolution characterize rapid cooling of HDR. The complete paper analyzes drilling-performance variations in HDR associated with a combination of rotary drilling and rapid cooling in front of the drill bit. Laboratory Experiments Equipment and Materials. The vertical-drilling-test simulator consists of a drill shaft with a swivel for drilling-fluid injection at one end and a screw-in drill bit at the other. A direct-current electric motor rotates the drillstring, and two hydraulic cylinders apply weight on bit (WOB). Hydraulic pressure controls confining pressure, and drilling-fluid pressure is exerted by the circulating fluid in the active mud system. The full-scale drilling system accommodates a wide range of parameters: WOB up to 20 tons, rotational speed up to 1,000 rev/min, and flow rates up to 610 L/min. Standard tests involve constant WOB or constant rate of penetration (ROP) with a full-size drill bit, up to 216 mm in diameter. Data for each test are collected and recorded at a sampling rate of 200 Hz.

Hydraulic fracturing optimization method for fractured reservoir based on phase-field modeling

Hydraulic fracturing technology is commonly used in unconventional oil and gas reservoirs, geothermal resources, and coal seam fracturing. Interactions between hydraulic fractures (HFs) and natural fractures (NFs) can affect fracture morphology and productivity. However, the influence of NFs on HF propagation has often been overlooked or underestimated. In this study, we investigated the influence of sequential fracturing, staged fracturing, and modified zipper fracturing methods on fracture morphology and complexity. We employed a phase-field modeling (PFM) that accounts for reservoir heterogeneity, including Young's modulus, Poisson's ratio, and porosity. The aim was to understand how these fracturing techniques can effectively stimulate reservoirs and enhance hydrocarbon production. The study found that the modified zipper fracturing method could achieve the optimal reservoir stimulation effect, but fracture interconnection was not conducive to resource exploitation. We further discuss the influence of fracturing fluid viscosity, in situ stress difference, and natural fracture angle on fracture propagation and interaction patterns between HFs and NFs. The results show that when the stress difference exceeds 4 MPa and the natural fracture angle is greater than 45°, HFs tend to open and cross NFs. When the fracturing fluid viscosity ranges from 6 to 9.74 mPa·s, it promotes the formation of independent, disconnected, and more complex fracture morphologies. These findings provide a theoretical basis for optimizing oil and gas exploitation in fractured reservoirs.

On the Role and Mechanism of Anomalous Heat Generation From Low Energy Nuclear Reaction (LENR) During Earthquakes

After going over the empirical study made by seismologists Jiwen Teng, Zuoxun Zeng, Jianguo Du, and Earth scientists Dewei Li, Guanghe Liang certain characteristics other than stress building up and rock slipping, of major earthquakes can be seen. And a reasonable heat producing mechanism is required. Based on pioneering research conducted by Song-Sheng Jiang, Wei-Yin Chen, Tadahiko Mizuno, Edmund Storms and other researchers, we believe that source cavities of these earthquakes may indicate a few possible scenarios initiating energy surge or energy increase, while depicting profiles of active environment that sustains thermal energy accumulation confined in a source cavity. In particular, the work of S.-S. Jiang, E. Storms and F. J. Mayer gave rise to the postulate that deep in Earth, nuclear reaction may take place due to the formation of a nuclear active environment (NAE) resulting in anomalous heat generation. Conditions for such reactions may foster similar processes to occur at shallower depth in source cav- ities of earthquakes: the deep fractures can serve as conduits for the transportation of species from deep Earth. An enclosed source cavity receives heat-producing substances, forming nuclear active sites generating excess heat on the fluid-solid interface within the media, leading to temperature and pressure accumulation, and subsequent melting of surrounding rocks. Accordingly, static electricity replenished from the atmosphere and formation of electron-proton composite (tresinos) and electron clusters thus formed within the source zone in the crust, may become contributors to the initiation of low energy nuclear reaction (LENR). Elements of H(D) may play a role in prolonged thermal energy generation responsible for energy surge in source zone, and electromag- netic/thermal energy anomaly close by an epicenter. Active lava flow on the Moon 2 billion years ago may indicate a similar energy generation mechanism. Finally, based on the field study in Fujian Province, southeast China, a twin relation between seismic events and geothermal energy release was proposed: Geothermal energy resource may bear great potential in understanding, diagnosing earthquake occurrence and even tempering hazardous seismic events by its conversion into a new paradigm of renewable energy.

Geothermal Networks Can Aid Decarbonization Through Repurposed Hydrocarbon Wells

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 220014, “Decarbonizing the Residential Sector With Geothermal District-Heating Networks: The Contribution of Hydrocarbon Wells,” by Claudio Alimonti, SPE, Sapienza University of Rome and Istituto di Geologia Ambientale e Geoingegneria, and Davide Scrocca, Istituto di Geologia Ambientale e Geoingegneria. The paper has not been peer reviewed. _ This study highlights how the recovery and reuse of existing hydrocarbon infrastructure can contribute to the diffusion of district-heating (DH) projects that implement principles of circular economy. The complete paper presents two examples of reusing hydrocarbon wells to satisfy the energy demand for heating residential buildings through locally available geothermal renewable energy sources. Background The mature phase of oil and gas reservoirs usually is characterized by the production of formation waters together with hydrocarbons. The volume of the produced water generally increases as fields mature until hydrocarbon production becomes uneconomical and wells are cemented and closed. Reservoir fluids could have temperatures high enough to support geothermal exploitation depending on the geothermal gradient. Therefore, when hydrocarbon wells are approaching the end of their productive life, and where geothermal potential exists, conversion to geothermal wells could be a reasonable alternative to closure. The authors’ results show how the repurposing of hydrocarbon wells into geothermal wells constitutes an excellent opportunity to access geothermal resources, reducing investment and mining risks and improving project economics. Considering that the temperature of reservoir fluids accessible through existing active wells generally is lower than 100–110°C, one of the more suitable applications for the harvested heat is to power new-generation DH systems that can operate with delivery temperatures even lower than 60°C. Data and Results Geothermal Potential of Using Hydrocarbon Wells in Italy. Data regarding hydrocarbon production concessions and active hydrocarbon wells are made available by the Italian Ministry of Environment and Energy Security. Further data are provided by the Visibility of Petroleum Exploration Data in Italy project. In Italy, 1,561 active wells are distributed in 183 hydrocarbon concessions. In 111 onshore hydrocarbon production concessions, 847 active wells have different operational statuses, including 436 productive wells and 399 potentially productive wells. A first selection of onshore fields hosting the most-promising productive or potentially productive wells was performed through comparison of the well location and total depth with the known subsurface temperature field. In that study, the reference thermal data were temperature maps at depths of 1000, 2000, and 3000 m below ground level. In one approach proposed in the literature, given that the focus was on space-heating applications, the minimum production temperature was set to 70°C. On this basis, 42 fields have been identified with depths greater than 2000–3000 m and with temperatures greater than 60–70 °C. However, heat recoverable from even-lower-temperature reservoir fluids could have potential uses with the most-recent generations of DH systems and with direct heat.

Analysis of geothermal resources in the northeast margin of the Pamir plateau

Analysis of geothermal resources in the northeast margin of the Pamir plateau

Prospects of using organic Rankine cycle for geothermal power generation

The relevance of this study stems from the desire to develop efficient and sustainable methods of energy extraction from low-temperature geothermal resources, which is of key importance in the context of finding alternative energy sources and reducing dependence on conventional, often non-renewable sources. The purpose of this study was to analyze the organic Rankine cycle (ORC) to improve the efficiency of energy recovery from low-temperature geothermal sources. The present study employed the analytical method, the deduction method, the induction method, the functional method, the classification method, the synthesis method. ORC applications for geothermal energy were comprehensively analyzed, with a focus on the investigation of low-temperature resources. The best cycle performance parameters were determined, considering diverse operating conditions. Concrete technical recommendations were developed for the selection of organic working media to improve system efficiency. The summarized findings highlight the potential of the ORC in enhancing the sustainability and efficiency of geothermal systems.

Assessment of geothermal resources for power generation on La Palma Island, Canary Islands

Assessment of geothermal resources for power generation on La Palma Island, Canary Islands

Geothermal resources of Réunion Island, Indian Ocean, studied by noble gas systematics in thermal springs

Geothermal resources of Réunion Island, Indian Ocean, studied by noble gas systematics in thermal springs

Numerical assessment of the geothermal resource potential of the Charlevoix meteorite impact crater, Canada

Numerical assessment of the geothermal resource potential of the Charlevoix meteorite impact crater, Canada

Zoning of development and utilization and evaluation of deep geothermal resources in Xiong'an New Area

Zoning of development and utilization and evaluation of deep geothermal resources in Xiong'an New Area

A Preliminary Geothermal Prospect Investigation in Lemeu, Northeast Lebong, Indonesia, Using Magnetotelluric Method

The magnetotelluric (MT) field method is an excellent way to generate 2D resistivity cross-sections for mapping geothermal potential. One way to use magnetotellurics is to study how deep the Earth's crust is. This study uses single-point magnetotelluric (MT) measurements to look at the potential for geothermal energy. We used MT magnetotelluric measurements to look at the potential for geothermal energy in the Lemeu area in northeast Lebong in Bengkulu, Indonesia. The magnetotelluric (MT) measurements we selected pass through areas identified as potential sites for hydrothermal activity. This area includes faults and hot springs, which we felt were worthy of investigation. This study collected data from seven magnetotelluric (MT) stations along the profile, which passes through the Lemeu hot springs. Data were collected in the frequency range of 4096 to 128 Hz. This study used a station spacing of approximately ±1 km for the best resolution. We used Non-Linear Conjugate Gradient (NLCG) for inversion modeling with ZONDMT1D and ZONDMT2D software. ZONDMT1D and ZONDMT2D software. Geothermal resources are located at a depth of 7 km, while geothermal fluid reserves are between 2 and 6 km below.