Search Results (44)

The Chang 7 member of the Ordos Basin hosts abundant shale oil and gas resources and plays a vital role in the development of unconventional energy. This study investigates differences in damage evolution and underlying mechanisms between representative shale oil and shale gas reservoir cores from the Chang 7 member under fracturing fluid hydration. A combination of high-temperature expansion tests, nuclear magnetic resonance (NMR), and micro-computed tomography (Micro-CT) was used to systematically characterize macroscopic expansion behavior and microscopic pore structure evolution. Results indicate that shale gas cores undergo faster expansion and higher imbibition rates during hydration (reaching stability in 10 h vs. 23 h for shale oil cores), making them more vulnerable to water-lock damage, while shale oil cores exhibit slower hydration but more pronounced pore structure reconstruction. After 72 h of immersion in fracturing fluid, both core types experienced reduced pore volumes and structural reorganization; however, shale oil cores demonstrated greater capacity for pore reconstruction, with a newly formed pore volume fraction of 34.5% compared to 24.6% for shale gas cores. NMR and Micro-CT analyses reveal that hydration is not merely a destructive process but a dynamic “damage–reconstruction” evolution. Furthermore, the addition of clay stabilizers effectively mitigates water sensitivity and preserves pore structure, with 0.7% identified as the optimal concentration. The research results not only reveal the differential response law of fracturing fluid damage in the Chang 7 shale reservoir but also provide a theoretical basis and technical support for optimizing fracturing fluid systems and achieving differential production increases. Full article

As global demand for energy-efficient cooling technologies grows, optimizing window air conditioners (WACs) is crucial. This study integrates computational fluid dynamics (CFD) and experimental fluid dynamics (EFD) to analyze condensate transport induced by the slinger ring in a WAC system. To investigate condensate behavior, the WAC domain is divided into six regions based on the slinger ring’s rotational direction and impact. In the initial impact zone, large liquid structures adhere to the slinger ring before breaking into ligaments. In the upward transport region, condensate films rise along the wall due to centrifugal forces, forming short ligaments. In the rebound region, condensate impacts the top surface and transitions into droplets. In the accumulation zone, droplet coalescence occurs in a confined space, leading to localized mass buildup. In the dispersion region, condensate spreads widely due to increased rotational speed. In the splash zone, splashing and wave-like structures form near the reservoir surface. A newly identified mechanism of condensate mass discharge shows that mass ejection is concentrated in four key regions near the condenser coils. These findings offer insights into optimizing a slinger ring design for improved condensate dispersion. Future research should explore airflow variations and alternative slinger ring configurations to enhance WAC performance. Full article

The Luhai uranium deposit is a large-scale uranium deposit newly discovered in recent years through comprehensive prospecting methods. It is located in the Basaiqi Paleochannel Uranium metallogenic belt of the Erlian Basin and is characterized by its shallow burial and large scale. This paper provides new data on the genetic processes of sandstone-type uranium mineralization through sedimentological and geochemical environmental indicators (such as Fe³⁺/Fe²⁺, organic carbon, total sulfur, etc.), analysis of C-O isotopes of carbonate cements and H-O isotopes of groundwater, and geochemical and mineralogical studies of uranium minerals, iron–titanium oxides (involving backscatter analysis, micro-area chemical composition determination, and elemental surface scanning), and organic matter. Sedimentological analysis shows that the ore- bearing layer in the upper member of the Saihan Formation developed a braided channel within floodplain subfacies, which control the distribution of uranium ore bodies. Uranium mineralogical observations, geochemical environmental indicators, and organic geochemical data indicate that the main reducing agents related to mineralization are pyrite, terrestrial plants, and deep-sourced oil and gas. The δD values of groundwater in the ore-bearing layer range from −95.34‰ to −90.68‰, and the δ¹⁸O values range from −12.24‰ to −11.87‰. For calcite cements, the δ¹⁸O_V-PDB values range from −24‰ to −11.5‰, and the δ¹⁸_OV-SMOW values range from 6.2‰ to 19‰. It was determined that the ore-forming fluid is mainly surface fresh water that entered the strata during the tectonic uplift stage, with local mixing of deep-sourced brine. Based on these data, the main modes of uranium mineralization in the paleochannel were obtained as follows: (1) Redox mineralization occurs due to the reducing medium within the sand body itself and the reduction caused by deep- sourced oil and gas generated from the Tengge’er and Arshan Formations. (2) Mineralization is achieved through the mixing of fluids from different sources. Furthermore, a genetic model related to uranium mineralization in the paleochannels of the Luhai area has been established: favorable uranium reservoirs were formed during the sedimentary period, and during the post-sedimentary stage, reverse structures promoted redox reactions and fluid-mixing-induced mineralization. The research findings can provide guidance for the exploration of paleochannel sandstone-type uranium deposits in other areas of the Erlian Basin. Full article

The rapid proliferation of water hyacinth (Eichhornia crassipes) in newly formed reservoirs poses a significant threat to aquatic ecosystems and hydroelectric operations. The objective of this study was to map and monitor the spatio-temporal distribution of water hyacinth in the Hidroituango reservoir in Colombia from 2018 to 2023, using Sentinel-2 satellite imagery and machine learning algorithms. The Random Forest (RF) and Support Vector Machine (SVM) algorithms were employed for image classification, and their performance was evaluated using various accuracy metrics. The results revealed that both algorithms effectively detected and mapped water hyacinth infestations, with RF demonstrating greater stability in capturing long-term trends and SVM exhibiting higher sensitivity to rapid changes in coverage. The study also highlighted the impact of the COVID-19 pandemic on control efforts, leading to a temporary increase in infestation. The findings underscore the importance of continuous monitoring and adaptive management strategies to mitigate the ecological and economic impacts of water hyacinth in the Hidroituango reservoir and similar environments. Full article

The sand–gravel brine deposit in the Mahai Basin is a newly discovered large-scale potassium–bearing brine deposit. The potassium–bearing brine is primarily found at depths exceeding 150 m within the porous alluvial and fluvial sand–gravel reservoir of the Middle to Lower Pleistocene. This deposit is characterized by a relatively shallow water table, moderate–to–strong aquifer productivity, high salinity, and a KCl content that meets the conditions for exploitation, with the advantage of reduced salt crystallization during well mining, making it a potential reserve base for potash development. A geochemical analysis of the sand–gravel brine revealed consistent trends for the major ions K⁺, Na⁺, Mg²⁺, Cl⁻, and SO₄²⁻ along the east–west axis of the alluvial fan, while Ca²⁺ showed an opposite trend compared to Mg²⁺. Along the exploration lines from north to south, the concentrations of the main ions gradually increase. The brine is enriched in Na⁺ and Cl⁻ ions, while SO₄²⁻ and HCO₃⁻ are depleted. In the K⁺-Na⁺-Mg²⁺/Cl⁻-H₂O (25 °C) quaternary phase diagram, the brine falls within the halite stability field, with the hydrochemical type classified as chloride type. The brine coefficient characteristics indicate a multi-source origin involving residual evaporation, salt rock leaching, and metamorphic sedimentary brine. Comparison studies of the ionic composition and isotopic signatures (δD, δ¹⁸O, δ³⁷Cl, and δ⁷Li) of deep sand–gravel brines in the study area with interstitial and confined brines in the southern depression suggest similar geochemical characteristics between them. The genetic analysis of the deposit proposes that during the basin tectonic evolution, the potassium-rich interstitial and confined brines originally located in the southern depression of the Mahai Basin were displaced under compressional forces and migrated northward as the depositional center shifted, eventually backfilling into the loose alluvial and fluvial sand and gravel reservoirs at the front of the Saishiteng Mountains, forming the deep sand–gravel brine deposits in the foreland. Full article

The origin of volatile elements, the timing of their accretion and their distribution during Earth’s differentiation are fundamental aspects of Earth’s early evolution. Here, we present the result of a newly developed accretion and core formation model, which features the results of high P–T metal–silicate partitioning experiments. The model includes well-studied reference elements (Fe, Ni, Ca, Al, Mg, Si) as well as trace elements (V, Ga, Ag, Au, S) covering a wide range from refractory to volatile behavior. The accretion model simulates the different steps of planet formation, such as the effects of continuous, heterogenous core formation at high P–T, the effect of the Moon-forming giant impact and the addition of matter after the core formation was completed, the so-called “late veneer”. To explore the “core formation signature” of the volatile depletion patterns and the quantitative influence of a late veneer, we modeled planets that would have formed from known materials, such as CI, CM, CV, CO, EH and EL meteorites, and from a hypothetical volatile depleted material, CI*. Some of the resulting planets are Earth-like in key properties, such as overall core size, major element composition, oxygen fugacity and trace element composition. The model predicts the chemical signatures of the main planetary reservoirs, the metallic core and bulk silicate planet (BSP) of the modeled planets, which we compare with the chemical signature of Earth derived previously from core formation models and mass balance-based approaches. We show that planets accreted from volatile depleted carbonaceous chondrites (CM, CV, CO and CI*) are closest in terms of major element (Si, Mg, Fe, Ca, Al, Ni) and also siderophile volatile element (Ge, Ga, Au) concentrations to the components from which Earth accreted. Chalcophile volatile elements (S, Ag), instead, require an additional process to lower their concentrations in the BSP to Earth-like concentrations, perhaps the late segregation of a sulfide melt. Full article

A case of spontaneous chirality generation was observed during a synthetic project studying the allylboration of 1,2,3-triazolic aldehydes. Here, we present computational studies supported by experimental findings targeting the elucidation of border conditions required for the observation of spontaneous chirality generation in the reaction of 1-Ar-1H-1,2,3-triazole-4-carbaldehydes 1a,b with triallylborane. Three possible sources of symmetry breaking were found computationally. Thus, dimerization of the initial reaction products, alcoholates 4a,b, gives dimers 5a,b (homochiral) and 6a,b (heterochiral). The latter were computed to be more stable thermodynamically, which can lead to amplification of the initial stochastic imbalance of the enantiomers of 4a,b via the reservoir mechanism. Furthermore, enantiomeric excess can be increased during the transfer of the second allylic group in the reaction of optically active boronates 4a,b with 1a,b, which was computed to be enantioselective due to the strong activating and stereoregulating properties of the 1,2,3-triazole group. In addition, reactions of borinic esters 8a,b, products of the previous reaction with triallylborane, recovered in each case two molecules of 4a,b of the same handedness, which can lead to additional chirality amplification. Experimentally, reactions of optically active alcohols (+)-R-2a,b with triallylborane provided chiral alcoholates 4a,b, which were reacted with equivalent amounts of corresponding aldehydes 1a,b. Unexpectedly, in two series of 10 experiments each, preferential formation of both enantiomers of the newly formed product was observed: seven times S and three times R in the case of 1a and six times S and four times R in the case of 1b. Full article

Defining the structure and evolution of multi-trend faults is critical for analyzing the accumulation of hydrocarbons in buried hills. Based on high-resolution seismic and drilling data, the structural characteristics and evolutionary mechanism of multi-trend faults were investigated in detail through the structural analysis theory and quantitative calculations of fault activity, allowing us to determine the implication that fault evolution exerts on hydrocarbon accumulation in the BZ19-6 buried hill. There are four kinds of strike faults developed on the buried hill: SN-, NNE-, NE–ENE-, and nearly EW-trending, which experienced the Mesozoic Indosinian, Yanshan, and Cenozoic Himalayan tectonic movements. During the Indosinian, the BZ19-6 was in a SN-oriented compressional setting, with active faults composed of SN-trending strike-slip faults (west branch of the Tanlu fault zone) and near EW-trending thrust faults (Zhang-peng fault zone). During the Yanshanian, the NNE-trending normal faults were formed under the WNW–ESE tensile stress field. Since the Himalayan period, the BZ19-6 buried hill has evolved into the rifting stage. In rifting stage Ⅰ, all of the multi-trend pre-existing faults were reactivated, and the EW-trending thrust faults became normal faults due to negative inversion. In rifting stage II, a large number of NE–ENE-trending normal faults were newly formed in the NW–SE-oriented extensional setting, which made the structure pattern more complicated. In rifting stage III, the buried hill entered the post-rift stage, with only part of the NNE- and NE–ENE-trending faults continuously active. Multi-trend faults are the result of the combination of various multi-phase stress fields and pre-existing structures, which have great influence on the formation of tectonic fractures and then control the distribution of high-quality reservoirs in buried hills. The fractures controlled by the NNE- and EW-trending faults have higher density and scale, and fractures controlled by NE–ENE trending faults have stronger connectivity and effectiveness. The superposition of multi-trend faults is the favorable distribution of high-quality reservoirs and the favorable accumulation area of hydrocarbon. Full article

The viscoelastic behavior of shale reservoirs indeed impacts permeability evolution and further gas flow characteristics, which have been experimentally and numerically investigated. However, its impact on the gas depletion profile at the field scale has seldom been addressed. To compensate for this deficiency, we propose a multiscaled viscoelasticity constitutive model, and furthermore, a full reservoir deformation–fluid flow coupled model is formed under the frame of the classical triple-porosity approach. In the proposed approach, a novel friction-based creep model comprising two distinct series of parameters is developed to generate the strain–time profiles for hydraulic fracture and natural fracture systems. Specifically, an equation considering the long-term deformation of hydraulic fracture, represented by the softness of Young’s modulus, is proposed to describe the conductivity evolution of hydraulic fractures. In addition, an effective strain permeability model is employed to replicate the permeability evolution of a natural fracture system considering viscoelasticity. The coupled model was implemented and solved within the framework of COMSOL Multiphysics (Version 5.4). The proposed model was first verified using a series of gas production data collected from the Barnett shale, resulting in good fitting results. Subsequently, a numerical analysis was conducted to investigate the impacts of the newly proposed parameters on the production process. The transient creep stage significantly affects the initial permeability, and its contribution to the permeability evolution remains invariable. Conversely, the second stage controls the long-term permeability evolution, with its dominant role increasing over time. Creep deformation lowers the gas flow rate, and hydraulic fracturing plays a predominant role in the early term, as the viscoelastic behavior of the natural fracture system substantially impacts the long-term gas flow rate. A higher in situ stress and greater formation depth result in significant creep deformation and, therefore, a lower gas flow rate. This work provides a new tool for estimating long-term gas flow rates at the field scale. Full article

The reservoir water level fluctuation zones (RWLFZs) and the natural riparian zones (NRZs) are two riparian ecosystems with dramatically opposite hydrological rhythms that notably influence the plant guilds. However, little is known about the discrepancies of the functional traits and niche characteristics of plant guilds in the RWLFZs and NRZs under different flooding rhythms. The aims of this study were to assess the divergent influence of natural and non-seasonal hydrological fluctuations on functional traits and niche characteristics of plant guilds. The results showed that 78 vascular plant species were identified in the riparian zones of the Xiangxi River basin. The dominant species were annuals in the two riparian ecosystems and their percentage increased temporally from 65.79% in the NRZs to 67.34% in the RWLFZs. Compared with the NRZs, the specific leaf area, vegetation coverage and the aboveground biomass in the RWLFZs significantly increased by 74%, 27% and 19.6%, respectively, while the water-use efficiency of the RWLFZ decreased by 59.6% and there was no significant difference in the net photosynthetic rate between them, which showed that annuals in the RWLFZs adopted the R adaptation strategy of being fast-growing with a short lifespan and quickly acquiring and investing resources by altering leaf morphology, including expanding the leaf area. The Simpson dominance index of RWLFZs was significantly higher than that of NRZ. Thus, counter-seasonally hydrological alterations had significant effects on functional traits of dominant species in the RWFLZs. Moreover, the highly adaptable and widely distributed species with larger niche breadths and high important values usually had a higher niche overlap value in the RWLFZs than in the NRZs, which showed that the competition in the plant communities after experiencing anti-seasonal flooding was much more intraspecific than interspecific and would facilitate the expansion of species niches. Our findings imply that the species with large niche breadths and high important values should be prioritized in ecological restoration efforts in the newly formed hydro-fluctuation zones of the TGR. Full article

The intricate geological conditions of reservoir banks render them highly susceptible to destabilization and damage from fluctuations in water levels. The study area, the Cheyipin section of the Huangdeng Hydroelectric Station, is characterized by numerous ancient landslides of varying scales and ages. In June 2019, during the reservoir filling process of the Huangdeng Hydroelectric Station, a large-scale reactivation of ancient landslides occurred in this area, posing severe threats to riverside infrastructure and human safety, including ground cracking, house cracking, foundation settlement, and road collapse. The reactivation mechanism of ancient landslides at reservoir banks is highly complex due to fluid dynamics. This study conducted field investigations in the Cheyipin landslide area, monitored surface and subsurface deformations using GNSS and inclinometers, and analyzed the distribution characteristics, destruction features, and reactivation mechanisms of the landslides through correlation analysis and numerical calculations. The results indicate that the instability pattern of the slopes manifests as traction-type sliding failure. The slopes do not slide along the ancient sliding surface but along a newly formed arcuate sliding surface, with the direct impact area mainly concentrated near the waterline. The stability of the slopes in this project is closely related to the reservoir water level. It can be assumed that the lowering of the reservoir water level triggered the reactivation of the ancient landslides in the Cheyipin section, while the influence of rainfall can be ignored. To prevent the reactivation of ancient landslides, attention should be focused on the changes in reservoir water level, avoiding rapid adjustments in water level during the initial lowering and final raising of the water level. Full article

Whether from the near-surface or at great depths, geothermal energy aims to harness the heat of the Earth to produce energy. Herein, emphasis is put on geothermal reservoirs and their cap rock in crystalline rocks, in particular, the basements of sedimentary basins and volcanic islands in the context of subduction. This study is based on a case study of three examples from around the world. The aim of this paper is to show how the study of newly formed minerals can help the exploration of geothermal reservoirs. The key parameters to define are the temperature (maximum temperature reached formerly), fluid pathways, and the duration of geothermal events. To define these parameters, numerous methods are used, including optical and electronic microscopy, X-ray diffraction, microthermometry on fluid inclusions, chlorite geothermometry, and geochemistry analysis, including that of isotopes. The key minerals that are studied herein are phyllosilicates and, in particular, clay minerals, quartz, and carbonates. They are formed because of hydrothermal alterations in fracture networks. These minerals can have temperatures of up to 300 °C (and they can cool down to 50 °C), and sometimes, they allow for one to estimate the cooling rate (e.g., 150 °C/200 ka). The duration of a hydrothermal event (e.g., at least 63 Ma or 650 ka, depending on the site) can also be established based on phyllosilicates. Full article

Due to various historical events, in the Russian Federation, in addition to the radioactive waste storage facilities used in world practice, there are various nuclear and radiation hazardous facilities that require special procedures for monitoring and decommissioning. One of these facilities is the disposal site for LRW on the territory of the JSC Siberian Chemical Plant, where specially prepared waste is injected into sand reservoirs lying at depths of 300–350 m between clayey strata. This study examines in detail the features of the lithological and mineral composition of reservoir sands and aquitards. The processes of environmental transformation in reservoir sands, which lead to changes in the composition and structure of rocks, were characterized. These processes manifest themselves in the form of the development of leaching zones and their “healing” with newly formed smectite, the destruction of terrigenous grains, including the development of cracks, and the growth of newly formed smectite in the pore space of reservoirs. The forms of occurrence and localization of authigenic smectite formed as a result of technogenic impact are described. It has been shown that, despite the obvious impact of highly reactive solutions accompanying liquid radioactive waste, the insulating properties of the geological environment are maintained and even improved to some extent. Full article

The reservoir coastal zone is the transitional zone between the terrestrial ecosystem and the aquatic ecosystem. Soil is an essential part of the terrestrial ecosystem and vital for life on Earth. To understand the composition and diversity of the soil eukaryotic microbial community under the background of artificial planting of Chrysopogon zizanioides in various habitats after reservoir construction, including the original habitat (OH), the hydro-fluctuation belt (HB), and the road slope (RS), and to analyze the interaction between the main groups of eukaryotic microorganisms, this study conducted 18S rDNA amplification high-throughput sequencing of the soil eukaryotic microbial community. The study found that the dominant phylum of eukaryotic microorganisms in the three habitats was consistent, but there were significant differences in the community and diversity of eukaryotic microorganisms in the three habitats. The differences in fungal communities between sample sites were greater than those of soil microfauna. Correlation analysis showed that nitrogen, phosphorus, and organic matter were significantly correlated with eukaryotic microbial diversity, with alkaline-hydrolyzed nitrogen and total phosphorus significantly correlated with fungal communities and pH and water content correlated with soil microfauna. Co-occurrence network analysis found that the interactions between fungi and the correlation between fungi and soil microfauna dominated the eukaryotic microbial community, and the interactions between eukaryotic microbes in different habitats were dominated by positive correlations. After the construction of the reservoir, the newly formed hydro-fluctuation belt reduced the types of interrelationships between fungi and microfauna compared to the original habitat. The road slope provided protection of the supporting project for the reservoir construction, although there was also planted vegetation. Eukaryotic microbes declined significantly due to the damage to and loss of the organic layer, and the decline in microfauna was the most significant, resulting in a simple structure of the soil food web, which affects the function and stability of the soil ecosystem. Full article

Flow-mediated skin fluorescence (FMSF) at 460 nm is a non-invasive method for assessing dynamic changes in the reduced form of nicotinamide adenine dinucleotide (NADH) and microcirculation in forearm skin under varying conditions of tissue perfusion. Typically, fluorescence increases during ischaemia, but atypical cases show a temporary signal decrease instead of a constant increase. This study aimed to explore the clinical implications of atypical FMSF patterns in patients with newly diagnosed untreated hypertension. NADH fluorescence and pulse wave analysis were performed on 65 patients. Differences in peripheral and arterial pulse pressure profiles were examined based on FMSF curve courses. Patients with atypical curve courses had significantly (p < 0.05 or lower for all) higher heart rate, peripheral and central diastolic pressure, tension time index, central rate pressure product, shorter diastole duration, and reservoir pressure–time integral. Hypertensive patients with atypical FMSF signals had less advantageous blood pressure profiles. Although the underlying factors causing these symptoms are unknown, the atypical FMSF pattern may reflect increased sympathetic stimulation and vascular resistance. The visual assessment of the FMSF curve may have important clinical implications that deserve further investigation. Full article