Search Results (162)

Pistachio nuts are among the 50 best foods with the highest antioxidant potential. They have a balanced content of mono- (~70%) and polyunsaturated (~20%) fatty acids, minerals, and bioactive compounds such as tocopherols, phytosterols, and phenolic compounds, which have shown rapid accessibility in the stomach. Pistachio consumption provides several health benefits, primarily due to its antioxidant properties and high content of essential nutrients. In this study, we analyzed the mineral composition, total phenolic content (TP), antioxidant activity (AA), and UHPLC/MS-MS polyphenolic profile of three Argentinian pistachio crops. Additionally, the physicochemical parameters and the elemental profiles of the growing soils were determined, as they influence mineral uptake and the synthesis of bioactive compounds in pistachio kernels. The TP was not significantly modified by the growing soils, with Crop3 presenting the highest TP content (276 ± 14 mg GA/100 g DW). Crop3 exhibited 18% higher TP content compared to Crop2. Similarly, FRAP values ranged from 28.0 to 36.5 mmol TE/100 g DW, with Crop1 showing a 30% increase compared to Crop2. DPPH values varied from 19.0 to 24.3 mmol TE/100 g DW, with Crop1 displaying 28% higher activity than Crop2. However, the polyphenolic profile was similar for all crops analyzed. Thirty compounds were identified; only Crop 1 contained the flavanone eriodyctiol and the isoflavone genistein, while the flavanone naringenin and the flavone luteolin were identified in Crop1 and Crop3. Regarding mineral content, the pistachio kernels mainly contained K, Ca, and Mg. Multivariate analyses revealed distinct elemental and antioxidant profiles among crops. LDA achieved classification accuracies of 77.7% for soils and 74.4% for kernels, with Pb, Zn, Cu, Rb, Sr, and Mn as key discriminants. CCA confirmed strong soil–kernel mineral correlations (r = 1), while GPA showed higher congruence between antioxidant traits and kernel composition than with soil geochemistry. These findings underscore the importance of soil composition in determining the nutritional quality of pistachio kernels, thereby supporting the beneficial health effects associated with pistachio consumption. Full article

The pathways and mechanisms of primary hydrocarbon migration, which are still not well understood, are of great significance for evaluating both conventional and unconventional oil and gas resources, understanding the mechanisms of shale oil retention, and predicting sweet spots. To investigate the petrography, geochemistry, and pore systems of organic-rich mudstones and organic-lean sand-silt intervals in core samples from the Yanchang shale in the Ordos Basin, China, we conducted thin-section observation, X-ray diffraction, Rock-Eval pyrolysis, field emission scanning electron microscopy (FE-SEM), and porosity analysis. Sand-silt intervals are heterogeneously developed within the Yanchang shale. The petrology, mineral composition, geochemistry, type, and content of solid organic matter as well as the pore type, pore size, and porosity of these intervals differ significantly from those of mudstones. Compared with mudstones, sand-silt intervals typically have coarser detrital grain sizes, higher contents of quartz, feldspar, and migrated solid bitumen (MSB), larger pore sizes, higher porosity, and higher oil saturation index (OSI). In contrast, they have lower contents of clay minerals, total organic carbon (TOC), free liquid hydrocarbons (S₁), and total residual hydrocarbons (S₂). The sand-silt intervals in the Yanchang shale serve as both pathways for hydrocarbon primary migration and “micro reservoirs” for hydrocarbon storage. The interconnected inorganic and organic pore systems, organic matter networks, fractures, and sand-silt intervals form the hydrocarbons’ primary migration pathways within the Yanchang shale. A model for the primary migration of hydrocarbons within the Yanchang shale is proposed. Full article

The production of gas and condensate from liquid-rich shale reservoirs, particularly within heterogeneous lacustrine systems, remains a critical challenge in unconventional hydrocarbon exploration due to intricate multiphase hydrocarbon partitioning, including gases (C₁–C₂), volatile liquids (C₃–C₇), and heavier liquids (C₇₊). This study investigates a 120-meter-thick interval dominated by lacustrine deposits from the Lower Cretaceous Shahezi Formation (K₁sh) in the Songliao Basin. This interval, characterized by high clay mineral content and silicate–pyrite laminations, was examined to identify the factors controlling hybrid shale gas condensate systems. We proposed the Hybrid Shale Condensate Index (HSCI), defined as the molar ratios of (C₁–C₇)/C₇₊, to categorize fluid phases and address shortcomings in traditional GOR/API ratios. Over 1000 samples were treated by geochemical pyrolysis logging, X-ray fluorescence (XRF) spectrum element logging, SEM-based automated mineralogy, and in situ gas desorption, revealing four primary controls: (1) Thermal maturity thresholds. Mature to highly mature shales exhibit peak condensate production and the highest total gas content (TGC), with maximum gaseous and liquid hydrocarbons at T_max = 490 °C. (2) Lithofacies assemblage. Argillaceous shales rich in mixed carbonate and clay minerals exhibit an intergranular porosity of 4.8 ± 1.2% and store 83 ± 7% of gas in intercrystalline pore spaces. (3) Paleoenvironmental settings. Conditions such as humid climate, saline water geochemistry, anoxic bottom waters, and significant input of volcanic materials promoted organic carbon accumulation (TOC reaching up to 5.2 wt%) and the preservation of organic-rich lamination. (4) Laminae and fracture systems. Silicate laminae account for 78% of total pore space, and pyrite laminations form interconnected pore networks conducive to gas storage. These findings delineate the “sweet spots” for unconventional hydrocarbon reservoirs, thereby enhancing exploration for gas condensate in lacustrine shale systems. Full article

High-enthalpy geothermal resources in volcanic settings often lack clear surface manifestations, requiring integrated, data-driven approaches to identify hidden reservoirs. In this study, we apply a multivariate clustering technique—genetic K-Means clustering (GKMC)—to a comprehensive soil gas dataset collected from 1050 sampling sites across the ~100 km² Garehagua mining license, located in the southern rift zone of Tenerife (Canary Islands). The survey included diffuse CO₂ flux measurements and concentrations of key soil gases (He, H₂, CH₄, O₂, N₂, Ar isotopes, and ²²²Rn, among others). Statistical-graphical analysis using the Sinclair method allowed for an objective classification of geochemical anomalies relative to background populations. The GKMC algorithm segmented the dataset into geochemically coherent clusters. One cluster, defined by elevated CO₂, helium, and ²²²Rn levels, showed a clear spatial correlation with inferred tectonic lineaments in the southern rift zone. These anomalies are interpreted as structurally controlled conduits for the ascent of deep magmatic-hydrothermal fluids. The findings support the presence of a concealed geothermal system structurally constrained in the southern region of Tenerife. This study demonstrates that integrating GKMC clustering with soil gas geochemistry offers a robust methodology for detecting hidden geothermal anomalies. By enhancing anomaly detection in areas with subtle or absent surface expression, this approach contributes to reducing exploration risk and provides a valuable decision-support tool for targeting future drilling operations in volcanic terrains. Full article

The Dehbid region, located in the southern part of the Sanandaj–Sirjan Zone (SSZ), is a significant iron oxide mining district with over 20 iron oxide deposits (IODs) and reserves of up to 50 million tons of iron oxide ores. The region features a NW–SE oriented ductile shear zone, parallel to the Zagros thrust zone, experienced significant deformation. Detailed structural studies indicate that the iron mineralization is primarily stratiform to stratabound and hosted in late Triassic to early Jurassic silicified dolomites and schists. These ore deposits consist of lenticular iron oxide orebodies and exhibit various structures and textures, including banded, laminated, folded, disseminated, and massive forms of magnetite and hematite. The Fe₂O₃ content in the mineralized layers varies from 30 to 91 wt%, whereas MnO has an average of 3.9 wt%. The trace elements are generally low, except for elevated concentrations of Cu (up to 4350 ppm) and Zn (up to 3270 ppm). Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) analysis of magnetite reveals high concentrations of Mg, Al, Si, Mn, Ti, Cu, and Zn, with significant depletion of elements such as Ga, Ge, As, and Nb. This study refutes the hypothesis of vein-like or hydrothermal genesis, providing evidence for a sedimentary origin based on the trace element geochemistry of magnetite and LA-ICP-MS geochemical data. The Dehbid banded iron ores (BIOs) are thought to have formed under geodynamic conditions similar to those of BIOs in back-arc tectonic settings. The combination of anoxic conditions, submarine hydrothermal iron fluxes, and redox fluctuations is essential for the formation of these deposits, suggesting that similar iron–manganese deposits can form during the Phanerozoic under specific geodynamic and oceanographic conditions, particularly in tectonically active back-arc environments. Full article

The use of a conceptual model of reference and modelling of relevant processes is mandatory to correctly interpret chemical and isotopic data. Adopting these basic guidelines, we have interpretated the unprecedented increase in the H₂S_(g) concentration and the concurrent unexpected decrease in the δ³⁴S value of H₂S_(g) recorded since 2018 in the fumarolic effluents of the Bocca Grande fumarolic vent at Solfatara, Campi Flegrei caldera, in the framework of our conceptual model of the Solfatara magmatic–hydrothermal system. Assuming that the magma chamber situated at depths ≥ 8 km was filled at the end of the 1982–1984 bradyseismic crisis and no refilling episodes took place afterwards, as suggested by gas geochemistry, the concentration and the δ³⁴S value of H₂S_(g) of the Bocca Grande fumarolic effluents are controlled by closed-system degassing of the melt at depths ≥ 8 km and disproportionation of SO₂ in the deep hydrothermal reservoir (6.5–7.5 km depth) hosted in carbonate rocks where H₂S equilibrates. These processes have been active during the last 40 years, but 41.1% (±6.4%) of the sulfur initially stored in the melt (2200 mg/kg) was lost in the 4-year period of April 2018–April 2022. This marked loss of S from the melt in 2018–2022 might be due to the high solubility of sulfur in the melt, which caused its preferential separation during the late degassing stages. These findings are of utmost importance for the surveillance of the Solfatara magmatic–hydrothermal system during the ongoing bradyseismic crisis. Full article

The Pliensbachian–Toarcian boundary and early Toarcian events indicate significant environmental and oceanographic instabilities attributed to the emplacement of the Karoo–Ferrar large igneous province and subsequent greenhouse gas emissions. These geologic processes influenced carbon cycle perturbations and global warming, consistent with phases of a sea level rise. This study presents a high-resolution dataset of total organic carbon (TOC) and bulk rock geochemistry and mineralogy from a complete upper Pliensbachian–Toarcian interval of the Quse Formation at the Qixiangcuo section in the Southern Qiangtang Basin. The Qixiangcuo section consists of carbonate and siliciclastic organic carbon-poor sediments deposited in a shallow-shelf setting in the eastern Tethys Ocean. Chemostratigraphic data, including Ti, Zr, U, Ca, Mn, and Sr and their ratios normalized to Al, record characteristic changes linked to sea level evolution and resulting depositional sequences. Trends in these geochemical data allow for the subdivision of the Quse Formation into nine complete third-order transgressive–regressive sequences, referred to as Pliensbachian sequences PSQ1 and PSQ2, Toarcian sequences TSQ1 to TSQ7, and one incomplete sequence. Elemental proxies indicative of terrigenous detrital input and sediment grain size along with a mineralogical composition of quartz, plagioclase, and clay minerals exhibit similar trends. Increased values of these proxies suggest a sea level fall and the deposition of regressive systems tract (RST) sediments, with peak values indicating a maximum regressive surface (MRS), and vice versa for transgressive systems tract (TST) sediments and the maximum flooding surface (MFS). On the contrary, rising trends in calcite content and carbonate-bound elements indicate phases of a relative sea level transgression, reaching maximum values at the MFS, while declining trends mark a sea level regression. The Sr/Ca ratio exhibited inverse patterns to the carbonate proxies, in part, with rising values indicating a sea level fall and vice versa. Full article

The Beishan Orogenic Belt, situated along the southern margin of the Central Asian Orogenic Belt, represents a critical tectonic domain that archives the prolonged subduction–accretion processes and Paleo-Asian Ocean closure from the Early Paleozoic to the Mesozoic. Early Permian magmatism, exhibiting the most extensive spatial-temporal distribution in this belt, remains controversial in its geodynamic context: whether it formed in a persistent subduction regime or was associated with mantle plume activity or post-collisional extension within a rift setting. This study presents an integrated analysis of petrology, zircon U-Pb geochronology, in situ Hf isotopes, and whole-rock geochemistry of Early Permian granites from the Tiancang area in the southern Beishan Orogenic Belt, complemented by regional comparative studies. Tiancang granites comprise biotite monzogranite, monzogranite, and syenogranite. Zircon U-Pb dating of four samples yields crystallization ages of 279.3–274.1 Ma. These granites are classified as high-K calc-alkaline to calc-alkaline, metaluminous to weakly peraluminous I-type granites. Geochemical signatures reveal the following: (1) low total rare earth element (REE) concentrations with light REE enrichment ((La/Yb)_N = 3.26–11.39); (2) pronounced negative Eu anomalies (Eu/Eu* = 0.47–0.71) and subordinate Ce anomalies; (3) enrichment in large-ion lithophile elements (LILEs: Rb, Th, U, K) coupled with depletion in high-field-strength elements (HFSEs: Nb, Ta, P, Zr, Ti); (4) zircon ε_Hf(t) values ranging from −10.5 to −0.1, corresponding to Hf crustal model ages (T_DMC) of 1.96–1.30 Ga. These features collectively indicate that the Tiancang granites originated predominantly from partial melting of Paleoproterozoic–Mesoproterozoic crustal sources with variable mantle contributions, followed by extensive fractional crystallization. Regional correlations demonstrate near-synchronous magmatic activity across the southern/northern Beishan and eastern Tianshan Orogenic belts. The widespread Permian granitoids, combined with post-collisional magmatic suites and rift-related stratigraphic sequences, provide compelling evidence for a continental rift setting in the southern Beishan during the Early Permian. This tectonic regime transition likely began with lithospheric delamination after the Late Carboniferous–Early Permian collisional orogeny, which triggered asthenospheric upwelling and crustal thinning. These processes ultimately led to the terminal closure of the Paleo-Asian Ocean’s southern branch, followed by intracontinental evolution. Full article

In recent years, substantial hydrocarbon discoveries have been documented in Member 4 of the Yingcheng Formation (Ying IV) in the northern Songliao Basin. To fully understand the developmental characteristics of the Yingcheng Formation source rocks and clarify the main controlling factors of their formation, this study focuses on typical wells in the Xujiaweizi Fault Depression. By integrating core data, organic geochemistry, elemental geochemistry, and paleoenvironmental parameter reconstruction, we determined the paleoenvironment, key controls, and organic matter enrichment model during the deposition of Ying IV. The results show that the total organic carbon (TOC) content of the source rocks ranges from 1.46% to 4.34% (average 2.65%). The paleoclimate during deposition was predominantly warm and humid, with low oxygen, reduced water conditions, freshwater-to-brackish salinity, and a deep-lake environment. Paleoproductivity was moderate to high. Relationship analysis indicates that TOC content was jointly controlled by paleoclimate (warm and humid conditions promoting biological proliferation) and paleoproductivity (nutrient supply from volcanic activity and terrigenous clastics). The positive feedback between elevated productivity under warm-humid conditions and deep-lake reducing environments led to organic matter enrichment in the source rocks of Ying IV, following a productivity-controlled model. This study provides critical geological insights for deep natural gas exploration in the Songliao Basin. Full article

Permian black shale, as a potential target for marine shale gas exploration in South China, is characterized by its great thickness and organic matter (OM) content. To understand the constraints on the heterogeneous accumulation of OM in Permian black shale, high-resolution geochemical data related to paleoenvironment variations are collected on the Gufeng and Dalong Formations of the Putaoling area, the Anhui province, and the Lower Yangtze area. The OM was heterogeneously enriched in the Permian shales, as shown by the highly organic-matter-rich Gufeng Formation and the moderately organic-matter-rich Dalong Formation. The distribution patterns of rare earth elements (REEs) indicate a stably high sedimentary rate throughout the shale deposition. Redox indexes, including Mo_EF, U_EF, V/Sc, and U/Th, indicate anoxic conditions for the deposition of the Gufeng and Dalong Formations, and that seawater oxygenation has occurred. The stratigraphic decreases in the (Fe+Mn)/Ti ratios, the index of chemical alteration (CIA), and the content of nutrient elements demonstrate the upward weakening patterns of hydrothermal activity and chemical weathering, which result in a reduction in the primary production. The redox state combined with the primary production jointly control the heterogeneous accumulation of OM in the Permian shales. Our paleoenvironmental evolution model for OM accumulation in the black shales indicates that the Gufeng Formation might be the priority object for the exploration of shale gases in the Permian strata within the Lower Yangtze area. Full article

This study investigates the combined effects of impurities in CO₂ stream, geochemistry, water salinity, and wettability alteration on oil recovery and CO₂ storage in carbonate reservoirs and optimizes injection strategy to maximize oil recovery and CO₂ storage ratio. Specifically, it compares the performance of pure CO₂ water-alternating gas (WAG), impure CO₂-WAG, pure CO₂ low-salinity water-alternating gas (LSWAG), and impure CO₂-LSWAG injection methods from perspectives of enhanced oil recovery (EOR) and CO₂ sequestration. CO₂-enhanced oil recovery (CO₂-EOR) is an effective way to extract residual oil. CO₂ injection and WAG methods can improve displacement efficiency and sweep efficiency. However, CO₂-EOR has less impact on the carbonate reservoir because of the complex pore structure and oil-wet surface. Low-salinity water injection (LSWI) and CO₂ injection can affect the complex pore structure by geochemical reaction and wettability by a relative permeability curve shift from oil-wet to water-wet. The results from extensive compositional simulations show that CO₂ injection into carbonate reservoirs increases the recovery factor compared with waterflooding, with pure CO₂-WAG injection yielding higher recovery factor than impure CO₂-WAG injection. Impurities in CO₂ gas decrease the efficiency of CO₂-EOR, reducing oil viscosity less and increasing interfacial tension (IFT) compared to pure CO₂ injection, leading to gas channeling and reduced sweep efficiency. This results in lower oil recovery and lower storage efficiency compared to pure CO₂. CO₂-LSWAG results in the highest oil-recovery factor as surface changes. Geochemical reactions during CO₂ injection also increase CO₂ storage capacity and alter trapping mechanisms. This study demonstrates that the use of impure CO₂-LSWAG injection leads to improved oil recovery and CO₂ storage compared to pure CO₂-WAG injection. It reveals that wettability alteration plays a more significant role for oil recovery and geochemical reaction plays crucial role in CO₂ storage than CO₂ purity. According to optimization, the greater the injection of gas and water, the higher the oil recovery, while the less gas and water injected, the higher the storage ratio, leading to improved storage efficiency. This research provides valuable insights into parameters and injection scenarios affecting enhanced oil recovery and CO₂ storage in carbonate reservoirs. Full article

Critical metals in coal-bearing strata have recently emerged as a frontier hotspot in both coal geology and ore deposit research. In the Upper Carboniferous coal-bearing “Si–Al–Fe” strata (Benxi Formation) of the North China Craton (NCC), several critical metals, including Li, Ga, Sc, V, and rare earth elements and Y (REY or REE + Y), have been discovered, with notable mineralization anomalies observed across northern, central, and southern Shanxi Province. However, despite the widespread occurrence of outcrops of the “Si–Al–Fe” strata in the northeastern Qinshui Basin of eastern Shanxi, there has been no prior report on the critical metal content in this region. Traditionally, the “Si–Al–Fe” strata have been regarded as a primary source of clastic material for the surrounding coal seams of the Carboniferous–Permian Taiyuan and Shanxi Formations, which are known to display critical metal anomalies (e.g., Li and Ga). Given these observations, it is hypothesized that the “Si–Al–Fe” strata in the northeastern Qinshui Basin may also contain critical metal mineralization. To evaluate this hypothesis, new outcrop samples from the “Si–Al–Fe” strata of the Benxi Formation in the Yangquan area of the northeastern Qinshui Basin were collected. Detailed studies on critical metal enrichment were assessed using petrographic observations, mineralogy (XRD, X-ray diffractometer), and geochemistry (XRF, X-ray fluorescence spectrometer, and ICP-MS, inductively coupled plasma mass spectrometer). The results indicate that the siliceous, ferruginous, and aluminous rocks within the study strata exhibit varying degrees of critical metal mineralization, mainly consisting of Li and REY, with minor associated Nb, Zr, and Ga. The Al₂O₃/TiO₂, Nb/Y vs. Zr/TiO₂, and Nb/Yb vs. Al₂O₃/TiO₂ diagrams suggest that these critical metal-enriched layers likely have a mixed origin, comprising both intermediate–felsic magmatic rocks and metamorphic rocks derived from the NCC, as well as alkaline volcaniclastics associated with the Tarim Large Igneous Province (TLIP). Furthermore, combined geochemical parameters, such as the CIA (chemical index of alteration), Sr/Cu vs. Ga/Rb, Th/U, and Ni/Co vs. V/(V + Ni), indicate that the “Si–Al–Fe” strata in the northeastern Qinshui Basin were deposited under warm-to-hot, humid climate conditions, likely in suboxic-to-anoxic environments. Additionally, an economic evaluation suggests that the “Si–Al–Fe” strata in the northeastern Qinshui Basin hold considerable potential as a resource for the industrial extraction of Li, REY, Nb, Zr, and Ga. Full article

The Dibei Gas Field, located in the northern Kuqa Foreland Basin, Tarim Basin, western China, is one of the most important condensate gas-producing areas in China, with over one trillion cubic feet of gas reserves discovered in the Jurassic terrestrial reservoirs. However, further hydrocarbon exploration and development in the area is hampered by uncertainties on the petroleum sources. A robust oil–source and gas-source correlation analysis was carried out in the Dibei area to enhance our understanding of the gas accumulation potential. An integrated molecular geochemical analysis, multivariate analysis, and basin modeling were conducted to investigate source rocks, inclusion oils, reservoir oils, and gas from the Dibei area. Two types of source rocks have been identified in the Dibei area: a Jurassic coaly source rock and a Triassic lacustrine source rock based on multivariate analysis. The compositions of the n-alkanes, steranes, and terpanes and the carbon isotope ratios of individual n-alkanes in the inclusion oil extracts and reservoir oils from Jurassic Yangxia and Ahe reservoirs show distinct differences when compared with the two types of source extracts. Multiple oil sources are revealed in the Dibei area, with various degrees of mixing between reservoir oil (present) and inclusion oil (paleo), reflecting evolving oil sources. Basin modeling shows that during the late Himalayan orogeny, the Jurassic strata in the Dibei area experienced a rapid burial within ~20 Ma, with the oil generation window of the source rocks expanding greatly. This caused the shallowly buried Jurassic source rocks to enter the oil generation window, resulting in the occurrence of two oil sources for the inclusion oils and reservoir oils, and an increasing degree of mixing over time. Our finding confirms that the accumulated condensate gas in the Dibei area is mainly derived from the Jurassic source rocks. This allows the extent of prospective exploration to be better defined. Full article

Organic matter (OM) is the primary carrier for the generation and occurrence of shale oil and gas. The combination of sequence stratigraphy and elemental geochemistry plays a crucial role in the study of organic matter enrichment mechanisms in marine shale, but it is rarely applied to terrestrial lacustrine basins. As a product of the last large-scale lake transgression in the Sichuan Basin, the Early Jurassic Lianggaoshan Formation (LGS Fm.) developed multiple organic-rich shale intervals, which is a good example for studying the OM enrichment in lacustrine basins. Based on a high-resolution sequence stratigraphic framework, the evolutionary process of terrestrial debris input, redox conditions, and paleo-productivity during the sedimentary period of the Lianggaoshan Formation lacustrine shale at different stages of lake-level variations has been revealed. The main controlling factors for OM enrichment and the establishment of their enrichment patterns have been determined. Sequence stratigraphy studies have shown that there are three third-order lake transgression-lake regression (T-R) cycles in the LGS Formation. The total organic carbon content (TOC) is higher in the TST cycle, especially in the T-R3 cycle, and lower in the RST cycle. There are differences in the redox conditions, paleo-productivity, terrestrial detrital transport, and OM accumulation under the influence of lacustrine shale deposition in different system tracts. The results indicate that changes in lake level have a significant impact on the reducibility of bottom water and paleo-productivity of surface seawater, but have a relatively small impact on the input of terrestrial debris. In the TST cycle, the reducibility of bottom water gradually increases, and the paleo-productivity gradually increases, while in the RST cycle, the opposite is true. Within the TST cycle, the OM accumulation is mainly influenced by paleo-productivity and redox condition of bottom water, with moderate input of terrestrial debris playing a positive role. In the RST cycle, the redox condition of bottom water is the main inducing factor for OM enrichment, followed by paleo-productivity, while terrestrial input flux plays a diluting role, which is generally not conducive to OM accumulation. Full article

As the global economy moves toward net-zero carbon emissions, large-scale energy storage becomes essential to tackle the seasonal nature of renewable sources. Underground hydrogen storage (UHS) offers a feasible solution by allowing surplus renewable energy to be transformed into hydrogen and stored in deep geological formations such as aquifers, salt caverns, or depleted reservoirs, making it available for use on demand. This study thoroughly evaluates UHS concepts, procedures, and challenges. This paper analyzes the most recent breakthroughs in UHS technology and identifies special conditions needed for its successful application, including site selection guidelines, technical and geological factors, and the significance of storage characteristics. The integrity of wells and caprock, which is important for safe and efficient storage, can be affected by the operating dynamics of the hydrogen cycle, notably the fluctuations in pressure and stress within storage formations. To evaluate its potential for broader adoption, we also examined economic elements such as cost-effectiveness and the technical practicality of large-scale storage. We also reviewed current UHS efforts and identified key knowledge gaps, primarily in the areas of hydrogen–rock interactions, geochemistry, gas migration control, microbial activities, and geomechanical stability. Resolving these technological challenges, regulatory frameworks, and environmental sustainability are essential to UHS’s long-term and extensive integration into the energy industry. This article provides a roadmap for UHS research and development, emphasizing the need for further research to fully realize the technology’s promise as a pillar of the hydrogen economy. Full article