Search Results (263)

The Moxi area in the Sichuan Basin hosts abundant deep geothermal resources, but their thermal regime and accumulation mechanisms remain poorly understood. Using 2D/3D seismic data, drilling records, and temperature measurements (DST), we analyze deep thermal fields, reservoir–caprock systems, and structural features. The following are our key findings: (1) Heat transfer is conduction-dominated, with thermal anomalies in Late Permian–Early Cambrian strata. Four mudstone/shale caprocks and three carbonate reservoirs occur, with the Longtan Formation as the key seal. Reservoir geothermal gradients (25.05–32.55 °C/km) exceed basin averages. (2) Transtensional strike-slip faults form E-W/NE/NW networks; most terminate at the Permian Longtan Formation, with few extending into the Lower Triassic while penetrating the Archean–Lower Proterozoic basement. (3) Structural highs positively correlate with higher geothermal gradients. (4) The deep geothermal reservoirs and thermal accumulation mechanisms in the Moxi area are jointly controlled by crustal thinning, basement uplift, and structural architecture. Mantle-derived heat converges at basement uplift cores, generating localized thermal anomalies. Fault networks connect these deep heat sources, facilitating upward fluid migration. Thick Longtan Formation shale seals these rising thermal fluids, causing anomalous heating in underlying strata and concentrated thermal accumulation in reservoirs—enhanced by thermal focusing effects from uplift structures. This study establishes a theoretical framework for target selection and industrial-scale geothermal exploitation in sedimentary basins, highlighting the potential for repurposing oil/gas infrastructure. Full article

The Jurassic Tamulangou Formation in the Hongqi Depression has favorable hydrocarbon generation conditions and great resource potential. This study systematically analyzes the geochemical characteristics and thermal evolution history of the source rocks using data from multiple key wells. The dark mudstone of the Tamulangou Formation has a thickness ranging from 50 to 200 m, with an average total organic carbon (TOC) content of 0.14–2.91%, an average chloroform bitumen “A” content of 0.168%, and an average hydrocarbon generation potential of 0.13–3.71 mg/g. The organic matter is primarily Type II and Type III kerogen, with an average vitrinite reflectance of 0.71–1.36%, indicating that the source rocks have generally reached the mature hydrocarbon generation stage and are classified as medium-quality source rocks. Thermal history simulation results show that the source rocks have undergone two major thermal evolution stages: a rapid heating phase from the Late Jurassic to Early Cretaceous and a slow cooling phase from the Late Cretaceous to the present. There are differences in the thermal evolution history of different parts of the Hongqi Depression. In the southern part, the Tamulangou Formation entered the hydrocarbon generation threshold at 138 Ma, reached the hydrocarbon generation peak at approximately 119 Ma, and is currently in a highly mature hydrocarbon generation stage. In contrast, the central part entered the hydrocarbon generation threshold at 128 Ma, reached a moderately mature stage around 74 Ma, and has remained at this stage to the present. Thermal history simulations indicate that the Hongqi Depression reached its maximum paleotemperature at 100 Ma in the Late Early Cretaceous. The temperature evolution pattern is characterized by an initial increase followed by a gradual decrease. During the Late Jurassic to Early Cretaceous, the Hongqi Depression experienced significant fault-controlled subsidence and sedimentation, with a maximum sedimentation rate of 340 m/Ma, accompanied by intense volcanic activity that created a high-temperature geothermal gradient of 40–65 °C/km, with paleotemperatures exceeding 140 °C and a heating rate of 1.38–2.02 °C/Ma. This thermal background is consistent with the relatively high thermal regime observed in northern Chinese basins during the Late Early Cretaceous. Subsequently, the basin underwent uplift and cooling, reducing subsidence and gradually lowering formation temperatures. Full article

Bioactive glasses are known for their surface reactivity and ability to bond with bone tissue through the formation of hydroxyapatite. This study investigates the effects of substituting ultrapure water with natural geothermal waters from the Azores in the sol–gel synthesis of 45S5 and MgO-modified bioglasses. Using high-resolution X-ray photoelectron spectroscopy (XPS), we examined how the mineral composition of the waters influenced the chemical environment and network connectivity of the glass surface. The presence of trace ions, such as Mg²⁺, Sr²⁺, Zn²⁺, and B³⁺, altered the silicate structure, as evidenced by binding energy shifts and peak deconvolution in O 1s, Si 2p, P 2p, Ca 2p, and Na 1s spectra. Thermal treatment further promoted polymerization and reduced hydroxylation. Our findings suggest that mineral-rich waters act as functional agents, modulating the reactivity and structure of bioactive glass surfaces in eco-sustainable synthesis routes. Full article

The utilization of geothermal resources as renewable energy is a subject of interest for the regions that possess these resources. The exploitation of geothermal energy must consider local geological conditions and an integrated approach, which should include practical studies on the chemistry of geothermal waters and their effect on thermal installations. Geothermal waters from Bihor County, Romania, have a variable composition, depending on the crossed geological layers, but also on pressure and temperature. Obviously, water transport and heat transfer are involved in all applications of geothermal waters. This article aims to characterize certain geothermal waters from the point of view of composition and corrosion if used as a thermal agent. Atomic absorption spectroscopy (AAS) and UV–Vis spectroscopy were employed to analyze water specimens. Chemical composition includes calcite (CaCO₃), chalcedony (SiO₂), goethite (FeO(OH)), and magnetite (Fe₃O₄), which confirms the corrosion and scale potential of these waters. Corrosion resistance of mild carbon steel, commonly used as pipe material, was studied by the gravimetric method and through electrochemical methodologies, including chronoamperometry, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization method, and open circuit potential measurement (OCP). Statistical analysis shows that the medium corrosion rate of S235 steel, expressed as penetration rate, is between 0.136 mm/year to 0.615 mm/year. The OCP, EIS, and chronoamperometry experiments explain corrosion resistance through the formation of a passive layer on the surface of the metal. This study proposes an innovative methodology and a systematic algorithm for analyzing chemical processes and corrosion phenomena in geothermal installations, emphasizing the necessity of individualized assessments for each aquifer to optimize operational parameters and ensure sustainable resource utilization. Full article

The southeastern Hainan Island boasts abundant hydrothermal resources, most of which are exposed as thermal springs. Analyzing the hydrochemical characteristics, hydrochemical evolutionary mechanisms, and material transition of these resources is significant for their exploitation and utilization. This study investigated the Nanping geothermal field in southeastern Hainan Island, using five groups of geothermal water samples collected in 2022, as well as seven groups of geothermal water samples, one group of shallow groundwater samples, and one group of surface water samples taken in 2023. Specifically, this study examined water–rock interactions in the geothermal field using the Gibbs model, ion ratios, chloro-alkaline indices (CAIs), and the sodium adsorption ratio (SAR). Moreover, the mineral transfer process in groundwater was analyzed using inverse hydrogeochemical simulation. The results indicate that in the study area the geothermal water temperatures range from 64 °C to 80 °C, pH values from 8.32 to 8.64, and TDS concentrations from 431 mg/L to 623 mg/L. The primary hydrochemical types of geothermal water in the study area include Cl-Na and Cl·HCO₃-Na, suggesting low-temperature, slightly alkaline geothermal water. The hydrochemical components of geothermal water in the study area are primarily affected by water–rock interactions. Besides the dissolution of silicate minerals and halite, cation exchange reactions contribute greatly to the formation of Na⁺ and K⁺ in geothermal water. Geothermal water receives recharge from the atmospheric precipitation of the Diaoluo Shan area in the northwest of the study area, with the recharge elevation ranging from 967 to 1115 m. The inverse hydrogeochemical simulation results reveal that during the water–rock interactions, silicate minerals, clay minerals, gypsum, and halite dissolve, while quartz and carbonate minerals precipitate. Additionally, these processes are accompanied by cation exchange reactions dominated by the replacement of Na⁺ in surrounding rocks by Ca²⁺ in geothermal water. This study can provide a geological basis for the exploitation, utilization, and management of the Nanping geothermal field. Full article

Elevated thermal conditions, rock formations exhibit distinct mechanical behaviors that significantly deviate from their characteristics under ambient temperature environments. This phenomenon raises critical questions regarding the applicability of conventional failure criteria in accurately assessing wellbore stability and maintaining the structural integrity of subsurface infrastructure within geothermal environments. Based on the least absolute deviation method, this paper studies the response characteristics of rock strength at different temperatures and evaluates the prediction performance of six commonly used strength criteria under various temperature and stress environments. The experimental findings reveal a pronounced nonlinear dependence of rock strength on confining pressure elevation. A comparative analysis of failure criteria demonstrates hierarchical predictive performance: the Hoek–Brown (HB) criterion achieves superior temperature-dependent strength prediction fidelity, outperforming the modified Griffith (MGC), Mohr–Lade (ML), and modified Wiebols–Cook (MWC) criteria by 12–18% in accuracy metrics. Notably, the Zhao–Zheng (ZZ) and conventional Mohr–Coulomb (MC) criteria exhibit statistically significant deviations across the tested thermal range. The HB criterion’s exceptional performance in high-temperature regimes is attributed to its dual incorporation of nonlinear confinement effects and thermally activated microcrack propagation mechanisms. The implementation of this optimized model in Well X’s borehole stability analysis yielded 89% alignment between predictions and field observations, with principal stress variations remaining within 7% of critical failure thresholds. These mechanistic insights offer critical theoretical and practical references for thermo-hydro-mechanical coupling analysis in enhanced geothermal systems and deep subsurface containment structures. Full article

Thermal infrared (TIR) ground observations are a well-established method for investigating surface temperature variations in thermally anomalous areas. However, commercially available technical solutions are currently limited, often offering proprietary products with minimal customization options for establishing a permanent TIR monitoring network. This work presents the comprehensive development of a thermal infrared monitoring network, detailing everything from the hardware schematics of the remote monitoring station (RMS) to the code for the final data processing software. The procedures implemented in the RMS for managing TIR sensor operations, acquiring environmental data, and transmitting data remotely are thoroughly discussed, along with the technical solutions adopted. The processing of TIR imagery is carried out using ASIRA (Automated System of InfraRed Analysis), a free software package, now developed for GNU Octave. ASIRA performs quality filtering and co-registration, and applies various seasonal correction methodologies to extract time series of deseasoned surface temperatures, estimate heat fluxes, and track variations in thermally anomalous areas. Processed outputs include binary, Excel, and CSV formats, with interactive HTML plots for visualization. The system’s effectiveness has been validated in active volcanic areas of southern Italy, demonstrating high reliability in detecting anomalous thermal behavior and distinguishing endogenous geophysical processes. The aim of this work is to enable readers to easily replicate and deploy this open-source, low-cost system for the continuous, automated thermal monitoring of active volcanic and geothermal areas and environmental pollution, thereby supporting hazard assessment and scientific research. Full article

Groundwater sustains ecosystems, agriculture, and human consumption; therefore, its interaction with hydrocarbons is an important area of research under the umbrella of environmental science and resource exploration. Naturally occurring or anthropogenically introduced hydrocarbons can significantly impact groundwater through complex geochemical processes such as dissolution, adsorption, biodegradation, and redox reactions and can also affect groundwater chemistry in terms of pH, redox potential, dissolved organic carbon, and trace element concentrations. Accurate determination and identification of hydrocarbon contaminants requires advanced analytical methods like gas chromatography, GC–MS, and fluorescence spectroscopy, complemented with isotopic analysis and microbial tracers, which provide insights into sources of contamination and biodegradation pathways. The presence of hydrocarbons in groundwater is a matter of environmental concern but can also valuable data for petroleum exploration, tracing subsurface reservoirs and seepage pathways. This paper refers to the basic need for geochemical investigations combined with advanced detection techniques for successful regulation of thermal–mineral groundwater quality. This contributes towards successful sustainable hydrocarbon resource exploration and water resource conservation, with emphasis on the relationship between groundwater quality and hydrocarbon exploration. The study points out the significance of continuous observation of thermal mineral waters to identify their connection with the specific hydrocarbons of each study area. Full article

Pulsed Power Plasma Stimulation (3PS) represents a promising and environmentally favorable alternative to conventional well stimulation techniques for enhancing subsurface permeability. This comprehensive review tracks the evolution of plasma-based rock stimulation, offering insights from key laboratory, numerical, and field-scale studies. The review begins with foundational electrohydraulic discharge concepts and progresses through the evolution of Pulsed Arc Electrohydraulic Discharge (PAED) and the more advanced 3PS systems. High-voltage, ultrafast plasma discharges generate mechanical shockwaves and localized thermal effects that result in complex fracture networks, particularly in tight and crystalline formations. Compared to conventional well stimulation techniques, 3PS reduces water use, avoids chemical additives, and minimizes induced seismicity. Laboratory studies demonstrate significant improvements in permeability, porosity, and fracture intensity, while field trials show an increase in production from oil, gas, and geothermal wells. However, 3PS faces some limitations such as short stimulation radii and logistical constraints in wireline-based delivery systems. Emerging technologies like plasma-assisted drilling and hybrid PDC–plasma tools offer promising integration pathways. Overall, 3PS provides a practical, scalable, low-impact stimulation approach with broad applicability across energy sectors, especially in environmentally sensitive or water-scarce regions. Full article

Geothermal systems play a crucial role in understanding Earth’s heat dynamics. The Yunkai Uplift in southern China exemplifies a geothermally rich region characterized by ancient lithologies and high heat flow. This study investigates the geochemical characteristics of geothermal waters in the Yunkai Uplift. Both geothermal and non-thermal water samples were collected along the Xinyi–Lianjiang (XL) Fault Zone and the Cenxi–Luchuan (CL) Fault Zone flanking the core of the Yunkai Mountains. Analytical techniques were applied to examine major ions, trace elements, and dissolved CO₂ and H₂, as well as isotopic characteristics of O, H, Sr, C, and He in water samples, allowing for an investigation of geothermal reservoir temperatures, circulation depths, and mixing processes. The findings indicate that most geothermal waters are influenced by water–rock interactions primarily dominated by granites. The region’s diverse lithologies, change from ancient Caledonian granites and medium–high-grade metamorphic rocks in the central hinterland (XL Fault Zone) to low-grade metamorphic rocks and sedimentary rocks in the western margin (CL Fault Zone). The chemical compositions of geothermal waters are influenced through mixing contacts between diverse rocks of varying ages, leading to distinct geochemical characteristics. Notably, δ¹³C_CO2 values reveal that while some samples exhibit significant contributions from metamorphic CO₂ sources, others are characterized by organic CO₂ origins. Regional heat flow results from the upwelling of mantle magma, supplemented by radioactive heat generated from crustal granites. Isotopic evidence from δ²H and δ¹⁸O indicates that the geothermal waters originate from atmospheric sources, recharged by precipitation in the northern Yunkai Mountains. After infiltrating to specific depths, meteoric waters are heated to temperatures ranging from about 76.4 °C to 178.5 °C before ascending through the XL and CL Fault Zones under buoyancy forces. During their upward migration, geothermal waters undergo significant mixing with cold groundwater (54–92%) in shallow strata. As part of the western boundary of the Yunkai Uplift, the CL Fault Zone may extend deeper into the crust or even interact with the upper mantle but exhibits weaker hydrothermal activities than the XL Fault Zone. The XL Fault Zone, however, is enriched with highly heat-generating granites, is subjected more to both the thermal and mechanical influences of upwelling mantle magma, resulting in a higher heat flow and tension effect, and is more conducive to the formation of geothermal waters. Our findings underscore the role of geotectonic processes, lithological variation, and fault zone activity in shaping the genesis and evolution of geothermal waters in the Yunkai Uplift. Full article

This study systematically analyzes reservoir formation mechanisms under deep burial conditions, integrating macroscopic observations from representative ultra-deep clastic reservoirs in four major sedimentary basins in central and western China. Developing effective clastic reservoirs in ultra-deep strata (6000–8000 m) remains a critical yet debated topic in petroleum geology. Recent advances in exploration techniques and geological understanding have challenged conventional views, confirming the presence of viable clastic reservoirs at such depths. Findings reveal that reservoir quality in ultra-deep strata is preserved and enhanced through the interplay of sedimentary, diagenetic, and tectonic processes. Key controlling factors include (1) high-energy depositional environments promoting primary porosity development, (2) proximity to hydrocarbon source rocks enabling multi-phase hydrocarbon charging, (3) overpressure and low geothermal gradients reducing cementation and compaction, and (4) late-stage tectonic fracturing that significantly improves permeability. Additionally, dissolution porosity and fracture networks formed during diagenetic and tectonic evolution collectively enhance reservoir potential. The identification of favorable reservoir zones under the sedimentation–diagenesis-tectonics model provides critical insights for future hydrocarbon exploration in ultra-deep clastic sequences. Full article

Enhanced or engineered geothermal systems (EGSs), or non-hydrothermal resources, are highly notable among sustainable energy resources because of their abundance and cleanness. The EGS concept has received worldwide attention and undergone intensive studies in the last decade in the US and around the world. In comparison, hydrothermal reservoir resources, the ‘low-hanging fruit’ of geothermal energy, are very limited in amount or availability, while EGSs are extensive and have great potential to supply the entire world with the needed energy almost permanently. The EGS, in essence, is an engineered subsurface heat mining concept, where water or another suitable heat exchange fluid is injected into hot formations to extract heat from the hot dry rock (HDR). Specifically, the EGS relies on the principle that injected water, or another working fluid, penetrates deep into reservoirs through fractures or high-permeability channels to absorb large quantities of thermal energy by contact with the host hot rock. Finally, the heated fluid is produced through production wells for electricity generation or other usages. Heat mining from fractured EGS reservoirs is subject to complex interactions within the reservoir rock, involving high-temperature heat exchange, multi-phase flow, rock deformation, and chemical reactions under thermal-hydrological-mechanical (THM) processes or thermal-hydrological-mechanical-chemical (THMC) interactions. In this paper, we will present a THM model and reservoir simulator and its application for simulation of hydrothermal geothermal systems and EGS reservoirs as well as a methodology of coupling thermal, hydrological, and mechanical processes. A numerical approach, based on discretizing the thermo-poro-elastic Navier equation using an integral finite difference method, is discussed. This method provides a rigorous, accurate, and efficient fully coupled methodology for the three (THM) strongly interacted processes. Several programs based on this methodology are demonstrated in the simulation cases of geothermal reservoirs, including fracture aperture enhancement, thermal stress impact, and tracer transport in a field-scale reservoir. Results are displayed to show geomechanics’ impact on fluid and heat flow in geothermal reservoirs. Full article

The Tankou area is a vital production capacity replacement area in the Jianghan oilfield. The recovery of the amount of erosion in Qianjiang Formation and Jinghezhen Formation is significant for studying this area’s tectonic evolution and geothermal history. The target layer, characterised by well-developed plastic materials, intense tectonic deformation, and insufficient well data, fails to meet the applicability criteria of the conventional denudation estimation methods. This study proposes a novel approach based on the structural strain characteristics. The method estimates the stratigraphic denudation by analysing residual formation features and fault characteristics. First, a stress analysis is performed using the fault characteristics, and the change law for the thickness of the target layer is summarised based on the characteristics of the residual strata to recover the amount of erosion in the profile. Second, a grid of the stratigraphic lines in the profiles of the main line and the tie line is used to complete the recovery of the amount of erosion in the plane through interpolation, and the results of the profile recovery are corrected again. Finally, the evolution results of the geological equilibrium method and the stress–strain analysis are compared to analyse the reasonableness of their differences and verify the accuracy of the erosion recovery results. The area of erosion in each layer increases from bottom to top. The amount of denudation in each layer gradually increases from the denudation area near the southern slope to the surrounding area. It converges to 0 at the boundary of the denudation area. The maximum amount of erosion is distributed in the erosion area close to the side of the residual layer with a low dip angle. The specific denudation results are as follows: Qian1 Member + Jinghezhen Formation has a denudation area of 6.3 km² with a maximum denudation thickness of 551 m; Qian2 Member has a denudation area of 2.6 km² with a maximum denudation thickness of 164 m; Qian3 Member has a denudation area of 2.3 km² with a maximum denudation thickness of 215 m; Upper Qian4 Submember has a denudation area of 1.54 km² with a maximum denudation thickness of 191 m; and Lower Qian4 Submember has a denudation area of 1.2 km² with a maximum denudation thickness of 286 m. This method overcomes the conventional denudation restoration approaches’ reliance on well logging and geochemical parameters. Using only seismic interpretation results, it achieves relatively accurate denudation restoration in the study area, thereby providing reliable data for timely analyses of the tectonic evolution, sedimentary facies, and hydrocarbon distribution patterns. In particular, the fault displacement characteristics can be employed to promptly examine how reasonable the results on the amount of denudation between faults are during the denudation restoration process. Full article

In hot dry rocks (HDRs), hydraulic fracturing is necessary to create enhanced geothermal systems (EGSs) and optimize flow rates between injection and production wells. The geometry of the induced fracture is related to numerous factors, including rock mechanical properties, especially Young’s modulus and Poisson’s ratio. In this paper, we show the influence of Young’s and Poisson’s parameters on fracture geometry in selected HDR-type prospective areas in Poland. Parameters were determined in the laboratory based on drill core samples from granite and sandstone formations using both dynamic and static methods. The results obtained reveal strong differences between dynamic and static values in granite and less diverse results in sandstone. Based on these data, numerical simulations of fracture geometry were carried out, taking into account the variability in the rocks’ elastic parameters. Sensitivity analysis showed that relatively high diversity in the elastic parameters led to a relatively slight impact on the fracture geometry of the tested formations. The influence of Young’s modulus did not exceed 6.5% of the reference half-length and width values for sandstone and 7.3% of the half-length for granite. Variability in the fracture width was significant in granite formation and amounted to 46.4%. The influence of Poisson’s ratio was marginal in both tested types of rocks. The research results, which have not been reported previously, can be considered for the design of hydraulic fracturing operations in enhanced geothermal systems in Poland. Full article

This study analyzes the effects of varying H₂S and CO₂ concentrations and temperature on the pH of geothermal fluids flowing through superduplex S32750 stainless-steel pipelines, classified as corrosion-resistant alloys (CRAs). Corrosive decay is evaluated by comparing OLI Studio software simulations with experimental data from the literature. The results indicate that an increase in the partial pressure of either gas lowers pH levels, with temperature exerting a more pronounced exponential effect on corrosion than gas partial pressure. When both gases are present, the dominant gas dictates the corrosion behavior. In cases where CO₂ and H₂S are in equal proportions, FeS₂ forms as the primary corrosive product due to the higher potential corrosivity of H₂S. The H₂S/CO₂ ratio influences the formation of passive films containing chromium oxides or hydroxides (Cr₂O₃, Cr(OH)₃), iron oxides (Fe₂O₃, Fe₃O₄), or iron sulfides (FeS). Full article