Search Results (183)

In the global energy sector, water-bearing reservoir-typed gas storage accounts for about 30% of underground gas storage (UGS) reservoirs and is vital for natural gas storage, balancing gas consumption, and ensuring energy supply stability. However, when constructing the UGS in the M gas reservoir, selecting suitable areas poses a challenge due to the complicated gas–water distribution in the multi-layered water-bearing gas reservoir with a long production history. To address this issue and enhance energy storage efficiency, this study presents an integrated geomechanical-hydraulic assessment framework for choosing optimal UGS construction horizons in multi-layered water-bearing gas reservoirs. The horizons and sub-layers of the gas reservoir have been quantitatively assessed to filter out the favorable areas, considering both aspects of geological characteristics and production dynamics. Geologically, caprock-sealing capacity was assessed via rock properties, Shale Gouge Ratio (SGR), and transect breakthrough pressure. Dynamically, water invasion characteristics and the water–gas distribution pattern were analyzed. Based on both geological and dynamic assessment results, the favorable layers for UGS construction were selected. Then, a compositional numerical model was established to digitally simulate and validate the feasibility of constructing and operating the M UGS in the target layers. The results indicated the following: (1) The selected area has an SGR greater than 50%, and the caprock has a continuous lateral distribution with a thickness range from 53 to 78 m and a permeability of less than 0.05 mD. Within the operational pressure ranging from 8 MPa to 12.8 MPa, the mechanical properties of the caprock shale had no obvious changes after 1000 fatigue cycles, which demonstrated the good sealing capacity of the caprock. (2) The main water-producing formations were identified, and the sub-layers with inactive edge water and low levels of water intrusion were selected. After the comprehensive analysis, the I-2 and I-6 sub-layer in the M 8 block and M 14 block were selected as the target layers. The numerical simulation results indicated an effective working gas volume of 263 million cubic meters, demonstrating the significant potential of these layers for UGS construction and their positive impact on energy storage capacity and supply stability. Full article

To alleviate environmental pressures, manufactured sand (MS) are increasingly being used in the production of ultra-high-performance concrete (UHPC) due to their consistent supply and environmental benefits. However, manufactured sand properties are critically influenced by processing and production techniques, resulting in substantial variations in fundamental characteristics that directly impact UHPC matrix pore structure and ultimately compromise performance. Traditional testing methods inadequately characterize UHPC’s pore structure, necessitating multifractal theory implementation to enhance pore structural interpretation capabilities. In this study, UHPC specimens were fabricated with five types of MS exhibiting distinct properties and at varying water to binder (w/b) ratios. The flowability, mechanical strength, and pore structure of the specimens were systematically evaluated. Additionally, multifractal analysis was conducted on each specimen group using mercury intrusion porosimetry (MIP) data to characterize pore complexity. SM-type sands have a more uniform distribution of pores of different scales, better pore structure and matrix homogeneity due to their finer particles, moderate stone powder content, and better cleanliness. Both excessively high and low stone powder content, as well as low cleanliness, will lead to pore aggregation and poor closure, degrading the pore structure. Full article

This study presents a comprehensive material characterization, including physical, hygric, and mechanical properties, of historical ceramic bricks to enhance the understanding of heritage masonry structures and support the effective planning of conservation interventions. The primary objective is to systematize the knowledge of constituent materials in brick walls from different historical periods and to evaluate the compatibility of modern repair materials with the original fabric. To this end, a comprehensive experimental protocol was employed, which included the determination of fundamental physical properties such as density, water absorption, and sorptivity. Additionally, chemical and thermogravimetric analyses were performed, followed by freeze–thaw resistance testing and compressive strength measurements. Microstructural analysis was conducted using mercury intrusion porosimetry. The results identified the pore size ranges most susceptible to frost-induced degradation and revealed correlations between the physical, hygric, and mechanical properties of the tested ceramic materials. These findings provide essential data on the physico-mechanical characteristics of historical bricks, establishing a basis for the informed selection of compatible materials in conservation practice. Full article

Morocco’s Témara Plain relies heavily on its aquifer system as a critical resource for drinking water, irrigation, and industrial activities. However, this essential groundwater reserve is increasingly threatened by over-extraction, seawater intrusion, and complex hydrogeochemical processes driven by the region’s geological characteristics and anthropogenic pressures. This study aims to assess groundwater quality and its vulnerability to pollution risks and map the spatial distribution of key hydrochemical processes through an integrated approach combining Geographic Information System (GIS) techniques and multivariate statistical analysis, as well as applying the DRASTIC model to evaluate water vulnerability. A total of fifty-eight groundwater samples were collected across the plain and analyzed for major ions to identify dominant hydrochemical facies. Spatial interpolation using Inverse Distance Weighting (IDW) within GIS revealed distinct patterns of sodium chloride (Na-Cl) facies near the coastal areas with chloride concentrations exceeding the World Health Organization (WHO) drinking water guideline of 250 mg/L—indicative of seawater intrusion. In addition to marine intrusion, agricultural pollution constitutes a major diffuse pressure across the aquifer. Shallow groundwater zones in agricultural areas show heightened vulnerability to salinization and nitrate contamination, with nitrate concentrations reaching up to 152.3 mg/L, far surpassing the WHO limit of 45 mg/L. Furthermore, other anthropogenic pollution sources—such as wastewater discharges from septic tanks in peri-urban zones lacking proper sanitation infrastructure and potential leachate infiltration from informal waste disposal sites—intensify stress on the aquifer. Principal Component Analysis (PCA) identified three key factors influencing groundwater quality: natural mineralization due to carbonate rock dissolution, agricultural inputs, and salinization driven by seawater intrusion. Additionally, The DRASTIC model was used within the GIS environment to create a vulnerability map based on seven key parameters. The map revealed that low-lying coastal areas are most vulnerable to contamination. Full article

Elucidating the compositions, sources and mixing processes of dissolved organic matter (DOM) is crucial for a gaining deeper understanding of the coastal carbon cycle and global carbon budget. Hangzhou Bay (HZB), a vital estuary in China, receives freshwater inputs in the upper bay, borders the Changjiang River Estuary (CRE) to the north and is adjacent to Zhoushan Islands Region (ZIR) to the east. In HZB, the DOM sources and their compositions in estuaries remain unclear due to the complexity of this dynamic environment. In this study, we aimed to explore the chemical composition and sources of the DOM in the HZB and its adjacent coastal waters based on chromophoric DOM, fluorescent DOM indices and other hydrochemical parameters in the winter. The results showed that the DOM compositions in HZB have significant differences in the upper bay, middle bay and lower bay. The highest concentration of DOC was found in the CRE, close to the northern lower HZB, with high humification index (HIX), low biological index (BIX) and high proportion of humic-like fluorescent component (C1), indicating terrestrial inputs. In contrast, the DOM in the upper bay had high BIX and low HIX, being dominated by protein-like fluorescent components (C2 and C3), indicating an autochthonous source. The DOM in the middle bay showed mixed composition characteristics indicated by the chromophoric DOM (CDOM) and fluorescent DOM (FDOM) indices. Moreover, the terrestrial DOM transported via CDW intrusion accounted for a large proportion of the DOM in Northern HZB. Our study shows that, even in coastal estuaries with very strong hydrodynamics, the DOM composition can still retain its unique source signal, which, in turn, affects its migration and transformation processes. The results of this study provide supplement insights into the global carbon cycle and carbon budget estimation. Full article

Although Mercury Intrusion Porosimetry (MIP) and Nuclear Magnetic Resonance (NMR) are widely used for pore characterization, their effectiveness is fundamentally constrained by theoretical limitations. This study investigated the pore structure characteristics of coal-bearing sandstones from the northeastern Ordos Basin using an integrated approach combining experimental measurements and model-based inversion. The experimental measurements comprised a stress-dependent acoustic velocity test (P- and S-wave velocities), X-ray diffraction (XRD) mineralogical analysis, and NMR relaxation T₂ spectra characterization. For model-based inversion, we developed an improved Mori-Tanaka (M-T) theoretical framework incorporating stress-sensitive pore geometry parameters and dual-porosity (stiff/soft) microstructure representation. Systematic analysis revealed four key findings: (1) excellent agreement between model-inverted and NMR-derived total porosity, with a maximum absolute error of 1.09%; (2) strong correlation between soft porosity and the third peak of T₂ relaxation spectra; (3) stiff porosity governed by brittle mineral content (quartz and calcite), while soft porosity showing significant correlation with clay mineral abundance and Poisson’s ratio; and (4) markedly lower elastic moduli (28.78%–51.85%) in Zhiluo Formation sandstone compared to Yan’an Formation equivalents, resulting from differential diagenetic alteration despite comparable depositional settings. The proposed methodology advances conventional NMR analysis by simultaneously quantifying both pore geometry parameters (e.g., aspect ratios) and the stiff-to-soft pore distribution spectra. This established framework provides a robust characterization of the pore architecture in Jurassic sandstones, yielding deeper insights into sandstone pore evolution within the Ordos Basin. These findings provide actionable insights for water hazard mitigation and geological CO₂ storage practices. Full article

Managed Aquifer Recharge (MAR) is increasingly being adopted across Europe to enhance water security in semiarid regions, with over 230 operational sites. The Akrotiri MAR system in Limassol, Cyprus, comprises 17 recharge ponds operating since 2016 to counteract saltwater intrusion. This study evaluates MAR effectiveness by analyzing spatial and temporal variations in water quality from 2016 to 2020. Parameters analyzed include nutrients, metals, pesticides, pharmaceuticals, fecal indicators, physicochemical characteristics, recharge and pumping volumes, and groundwater levels. The results show that soil aquifer treatment (SAT) generally improves groundwater quality but certain boreholes exhibited elevated nitrate (range 12.70–31 mg/L), electrical conductivity (range 936–10,420 μs/cm), and chloride concentrations (range 117–1631 mg/L), attributed to recharge water quality, seawater intrusion, and nearby agricultural activities. Tertiary treated wastewater used for recharge occasionally exceeds permissible limits, particularly in E. coli (up to 2420/100 mL), chloride (up to 385 mg/L), and nitrogen (up to 41 mg/L). Supplementing recharge with dam-supplied freshwater improves groundwater quality and raises water levels. These findings underline the importance of continuous monitoring and effective management, adopting sustainable farming practices, and the strict control of recharge water quality. The study offers valuable insights for optimizing MAR systems and supports integrating MAR into circular water management frameworks to mitigate pollution and seawater intrusion, enhancing long-term aquifer sustainability. Full article

Concrete porosity is one of the fundamental properties for the structural characterization of cementitious materials. This study compares porosity data obtained with dynamic water vapor sorption (DWVS) with the more commonly used mercury intrusion porosimetry (MIP) method for a wide range of concrete samples made with basaltic aggregates, typical of the Canary Islands, which are porous. The objective was to propose an alternative method for routine concrete monitoring that avoids the use of a hazardous substance such as mercury. The results reveal fundamental differences between the MIP and water-accessible porosimetry (WAP) data, although a correlation between the methods was revealed where MIP = 1.18 × WAP. The study was completed by an analysis of the relationships between the porosity and the characteristics and properties of concrete (water/cement ratio and strength), as well as the calculation of the tortuosity factor and a frost durability factor. Full article

The water absorption behavior of concrete is a critical indicator of its durability, and a comprehensive understanding of water transport characteristics can significantly enhance concrete performance. This study investigates the capillary water absorption properties of steel fiber-reinforced concrete across various strength grades by combining mercury intrusion porosimetry (MIP) and ¹H low-field nuclear magnetic resonance (¹H low-field NMR) techniques. Key findings reveal that the capillary water absorption of steel fiber-reinforced concretes occurs in the following two distinct stages: an initial rapid absorption phase (0 min to 6 h) and a subsequent slow absorption phase (1 day to 12 days). Modifications to the concrete matrix composition substantially reduce capillary water absorption rates, with ultra-high-performance concrete (UHPC) exhibiting exceptionally low absorption levels (the cumulative capillary water absorption of UHPC accounts for only 4.5–5.7% of that of C30 concrete). Additionally, for higher-strength concrete and extended absorption durations, the capillary water absorption rate deviates from the linear relationship with the square root of time. This deviation is attributed to the interaction of gel pore water with unhydrated cement particles, generating more hydration products, which refine the pore structure, reduce capillary pore connectivity, and increase pore tortuosity. Furthermore, steel fibers influence water transport through the following two primary mechanisms: interfacial interactions between the fibers and the matrix and a physical blocking effect that impedes water movement. Full article

Deep coalbed methane (CBM) reservoirs have the characteristics of low permeability, low porosity, and low water saturation, which easily experience wellbore instability due to drilling fluid, severely affecting drilling safety. Based on the physical property analysis of coal samples, the wellbore instability mechanism of the deep CBM reservoir was investigated by multiple methods. It was found that the wellbore instability is mainly caused by drilling fluid intrusion and the interaction between drilling fluid and coal formation; the fracture pressure of coal after immersion decreased from 27.4 MPa to 25.0 MPa because of the imbibition of drilling fluid. A novel nano-plugging agent with a size of 460 nm was prepared that can cement coal particles to form disc-shaped briquettes with a tensile strength of 2.27 MPa. Based on that, an effective anti-collapse drilling fluid for deep coal rock reservoirs was constructed, the invasion depth of the optimized drilling fluid was only 6 mm. The CT result shows that the number of fractures and pores in coal rock significantly reduced after treatment with the wellbore-stabilizing drilling fluid; nano-plugging anti-collapse agent in drilling fluid can form a dense layer on the coal surface, and then the hydration swelling of clay in the wellbore region can be effectively suppressed. Finally, the drilling fluid in this work can achieve the purpose of sealing and wettability alternation to prevent the collapse of the wellbore in the deep coal reservoir. Full article

The intricate gas–water distribution patterns in tight sandstone gas reservoirs significantly impede effective exploration and development, particularly challenging sweet spot prediction. In the Upper Paleozoic Shanxi Formation of the Ordos Basin, the complex and variable gas–water distribution characteristics remain poorly understood regarding their spatial patterns and controlling mechanisms. This study employs an integrated analytical approach combining casting thin sections, conventional porosity–permeability measurements, and mercury intrusion porosimetry to systematically investigate the petrological characteristics, pore structure, and physical properties of the Shan 2 member reservoirs in southern Yulin. Through the comprehensive analysis of production data coupled with structural and sand body distribution patterns, we identify three predominant formation water types: edge/bottom water, isolated lens-shaped water bodies, and residual water in tight sandstone gas layers. Our findings reveal that three primary factors govern water distribution in the Shan 2 member reservoirs: sand body architecture controlling fluid migration pathways; reservoir quality determining fluid storage capacity; and structural configuration influencing fluid accumulation patterns. This multi-scale characterization provides critical insights for optimizing development strategies in similar tight sandstone reservoirs. Full article

Owing to its superior mechanical properties and recyclability, the carbon fabric/polyetheretherketone (CFF/PEEK) composite has seen increasing application in engineering domains. However, studies examining the impact of hygrothermal aging on its performance remain relatively limited in the existing literature. To investigate its durability in hygrothermal environments, this study fabricated CFF/PEEK composites with a fiber volume fraction of 55 vol% and subjected them to equilibrium hygroscopic treatment at 70 °C. The hygroscopic behavior of polyetheretherketone (PEEK) resin and CFF/PEEK composites, along with their tensile and compressive properties under dry conditions at room temperature (RTD) and wet conditions at 70 °C (ETW), were systematically evaluated. The results indicated that both PEEK resin and CFF/PEEK composites exhibited Fickian diffusion behavior during the initial stages of aging but diverged in later stages. The equilibrium moisture absorption rates were approximately 0.32% for PEEK resin and 0.19% for CFF/PEEK composites. After aging at 70 °C, the strength of both materials decreased significantly, while the modulus showed only minor changes. Under ETW conditions, the tensile strength retention rate of PEEK resin was 74.92%, and the compressive strength retention rate was 81.85%. For the CFF/PEEK composites, the tensile strength retention rate was approximately 85%, and the compressive strength retention rate was about 95%. The typical failure modes of CFF/PEEK composites did not exhibit notable differences between tensile and compressive specimens after hygrothermal aging. Resin debonding was observed in the moisture-absorbed composite specimens, while no microcracks or delamination were detected. The degradation of mechanical properties is predominantly attributed to the deterioration of the resin matrix and interface characteristics, which are caused by water molecule intrusion and the adverse effects of wet strain mismatch between the resin and fibers. Full article

The hydrogeological study of the Rharb coastal basin, located in the semi-arid northwest region of Morocco, focuses on its two aquifers: the Plio-Quaternary aquifer characterized by high-quality water with salt concentrations ranging from 0.4 to 2 g/L, and the Upper Quaternary aquifer, with lower water quality (2 to 6 g/L). The deep aquifer is overexploited for agricultural purposes. This overexploitation has led to declining piezometric levels and the worsening of the oceanic intrusion phenomenon. The study aims to develop a numerical model for a period of 15 years, from 1992/93 to 2006/07 for monitoring groundwater quantity and quality, considering recharge, exploitation, and basin characteristics. A hydrodynamic model based on storage coefficient calibration identifies overexploitation for irrigation, increasing from 93 Mm³ in 1993 to 170 Mm³ in 2007, as the primary driver of declining water levels. A hydrodispersive model highlights higher salt concentrations in the shallow aquifer (up to 6 g/L), high nitrate concentrations due to human activity, and pinpoints areas of seawater intrusion approximately 500 m from the shoreline. Although the deeper aquifer remains relatively preserved, negative hydraulic balances from −15.4 Mm³ in 1993 to −36.6 Mm³ in 2007 indicate an impending critical period. Full article

The pore solution in expansive soil contains numerous chemical components that can significantly affect the soil’s water-retention properties, strength, and deformation. This study focuses on Ningming expansive soil and investigates the effects of varying concentrations of NaCl solutions on its water-retention characteristics. The soil–water characteristic curve of expansive soil over the full suction range was obtained using the pressure plate method. The microstructure of expansive soil was analyzed using mercury intrusion porosimetry and scanning electron microscopy. The results indicate that the water-retention capacity of expansive soil increases with higher concentrations of NaCl at equivalent suction levels. MIP tests demonstrated that, regardless of changes in pore solution concentration, the interparticle pores in pre-consolidated samples consistently dominate the pore structure, while agglomeration pores play a secondary role. Importantly, variations in the pore solution concentration primarily alter the characteristics of interparticle pores without significantly affecting their overall structure. SEM analysis revealed that the microstructure of pre-consolidated samples exposed to different pore solution concentrations exhibited less development than that of compactable samples, with a notable reduction in macropores. Furthermore, the arrangement of soil particles became increasingly uniform, and the stratification within the soil matrix was more pronounced. In addition, the Brooks–Corey (BC) model and van Genuchten (VG) model were employed to fit the measured data. It was found that the air entry values predicted by the two models were closely aligned with the measured data; therefore, it is recommended to utilize the average value as the air entry value corresponding to the changes in pore solution concentration of pre-consolidated Ningming expansive soil. Full article

This study aimed to reduce the environmental impact of rapeseed straw accumulation and explore its engineering potential by examining how straw affects the mechanical properties of cement–sand composites. Experiments were conducted using varying straw dosages and curing ages to assess water consumption, setting time, flexural and compressive strengths, pore characteristics (via mercury intrusion), hydration products, and microstructures (via thermogravimetry and X-ray diffraction). Results showed that flexural and compressive strengths decreased with higher straw content, most notably up to 2%, but increased with age due to straw’s water absorption, which altered cement hydration and porosity. Over time, enhanced hydration and pore filling improved strength. This research supports straw’s use in civil engineering and advances eco-friendly concrete material development. Full article