Search Results (4,569)

Stabilization/solidification (S/S) is a crucial technology for the engineering reuse of oil-contaminated soil. A key challenge, however, is preventing the migration of residual oil under varying hydraulic conditions. This study investigates the efficacy of a lime and fly ash binder in treating oil-contaminated soil. We systematically compared the performance of untreated (UOCS) and treated (TOCS) soils under different aqueous environments (humidity injection, water injection, and permeation). We evaluated oil migration, water-holding capacity, and permeability characteristics. The results demonstrate that the lime–fly ash treatment effectively adsorbed and immobilized oil contaminants, restricting their mobility to a remarkably low range of 0.54% to 4.90%. Furthermore, the S/S treatment significantly improved the soil’s hydraulic properties: it enhanced the water-holding capacity, reduced the soil-water characteristic curve hysteresis, and counteracted the oil-induced hydrophobicity. Consequently, the effective permeation channels were restored, leading to a higher permeability coefficient in TOCS compared to UOCS. Crucially, the hydro-mechanical performance of the treated soil met the criteria of the Solidification/Stabilization Resource Guide, confirming its suitability for engineering applications. Full article

The widely applied empirical Darcy’s law in geotechnical engineering faces significant challenges in describing low-velocity flow processes in low-permeability porous media such as tight sandstones containing irreducible water. A deep understanding of low-velocity non-Darcy two-phase flow behavior in low-permeability porous media is essential for evaluating the development of ultra-low-permeability reservoirs. In this study, seven low-permeability three-dimensional digital cores with distinct pore structures were constructed based on realistic ultra-low-permeability sandstones. Using the lattice Boltzmann method, pore-scale investigations of water displacing oil were conducted. Low-velocity two-phase flow behavior under varying wettability conditions, pore structures, and fluid viscosities was simulated. The underlying mechanisms of low-velocity non-Darcy flow in ultra-low-permeability sandstones were examined, leading to a modified low-velocity non-Darcy flow equation. This improved model was subsequently applied to numerical simulations of ultra-low-permeability reservoirs. The results demonstrate that non-Darcy effects manifest primarily as nonlinearities in seepage curves, representing a marked departure from conventional Darcy’s law. Low-velocity non-Darcy (LVND) flow is predominantly constrained by the influence of complex pore-throat structures and capillary forces on fluid distribution. The dynamic equilibrium among capillary forces arising from residual water saturation, viscous forces, and pressure gradients constitutes the fundamental mechanism governing the onset of LVND flow. Enhanced nonlinear behavior is observed with increasing viscosity of the invading phase and elevated capillary forces. Substantial discrepancies in reservoir production dynamics are identified between LVND and classical Darcian regimes. Through pore-scale numerical simulations, this study systematically elucidates LVND behavior during bi-phasic flow in low-permeability porous media, while identifying critical controlling factors. These findings provide scientific rationale and technical support for addressing geological engineering challenges in tight sandstone formations. Full article

To investigate the mitigation of high-pressure CO₂-induced degradation of wellbore cement sheath in Carbon Capture, Utilization, and Storage–Enhanced Oil Recovery applications (CCUS-EOR), conventional Class G oil well cement and modified cement systems incorporating graphene, waterborne epoxy resin, and a composite of waterborne epoxy resin with graphene were formulated. This study presents the original comparative investigation on the long-term carbonation resistance of graphene-modified, waterborne-epoxy-modified, and their composite-modified oil well cements under 130 °C and 7 MPa CO₂ partial pressure, filling the research gap of unclear synergistic effects of the two modifiers in high-temperature CCUS environments. The specimens were subjected to simulated downhole conditions, and key properties, including compressive strength and permeability, were evaluated. The underlying mechanisms were elucidated through material characterization techniques such as X-ray diffraction, X-ray computed tomography, and scanning electron microscopy. Results indicated that the waterborne epoxy resin–modified cement system exhibited superior long-term carbonation resistance, achieving a 90 d compressive strength retention rate of 84%. The graphene-modified cement showed a 90 d compressive strength retention rate of 65%, while the waterborne epoxy–graphene composite system only retained 39.7% of its compressive strength at 90 d due to negative synergistic effects. The enhanced durability of the waterborne-epoxy-modified cement is attributed to the formation of a continuous polymeric film, which acts as a protective barrier against CO₂ penetration. This study provides valuable insights for the design of CO₂-resistant cement systems in CCUS-EOR environments. Full article

The multi-cycle high-rate injection and production operations in Underground Gas Storage (UGS) facilities converted from depleted fracture-pore carbonate gas reservoirs induce complex rock–fluid interactions that threaten long-term integrity and performance. This study experimentally investigates the petrophysical responses of the Xiangguosi (XGS) UGS carbonate reservoirs in China using multi-cycle stress sensitivity tests, fines migration experiments, and water evaporation–salt precipitation analyses. SEM observations distinguish the contributions of crack closure and matrix compression to permeability evolution. Results show a sharp contrast in mechanical damage: high-quality rocks present negligible permanent deformation (<8% Young’s modulus reduction), whereas poor-quality rocks suffer catastrophic deterioration (>60%). Fines migration exhibits a three-stage behavior under cyclic flow, with water saturation significantly aggravating permeability impairment. A critical salinity threshold (220,000 ppm) is identified for the transition between drying-enhanced storage and salt plugging. Permeability declines sharply despite a slight porosity increase due to selective salt clogging of key pore throats, revealing a clear porosity–permeability decoupling. Salt deposition under movable water conditions can reduce UGS capacity by up to 1.45%. Reservoir heterogeneity, microfractures, karst structures, and initial petrophysical properties dominate the storage and flow space evolution. This work provides a predictive framework for optimizing injection–production strategies and improving the performance of complex carbonate UGS. Full article

The growing demand for improved operational efficiency of cast components used in various types of equipment necessitates the development of advanced casting technologies. One of the key challenges currently faced by the foundry industry is enhancing the surface quality of castings and reducing rejection rates caused by casting defects. These requirements can be effectively met by castings produced using shell mold casting technology. Sand–resin mixtures are used for their production. Foundry molds made from such mixtures make it possible to obtain high-quality castings from various alloys. However, their widespread industrial application is limited by the relatively high cost of the binder, namely pulverbakelite. The influence of pulverbakelite content on the properties of sand–resin mixtures during shell mold formation under variational static pressure was investigated. It was established that pressure variation during the molding process increases mold strength and improves surface quality while maintaining the required level of gas permeability. The optimal binder content was determined to be 4–6%, which makes it possible to reduce binder consumption without deteriorating the mechanical and technological characteristics of the mold. With respect to novelty, it should be noted that previous studies addressed individual aspects of variable pressure application. In the present article: a wider range of pulverized bakelite content (3–9%) was investigated; the relationship between binder content, strength, and gas permeability was established; the optimal binder content range (4–6%) was determined; and microstructural analysis was extended to include composition and pressure regimes. Thus, the present work significantly extends previous findings and provides a more comprehensive investigation. Full article

The emergence of membrane boundaries represents a decisive transition in the origin of life, yet the molecular nature of the earliest abiotic membranes remains uncertain. Existing models based on simple fatty acids, while experimentally tractable, often lack the environmental robustness required under fluctuating prebiotic conditions. Furthermore, the absence of clear pathways linking primitive amphiphiles to later phospholipid systems highlights the need for chemically continuous intermediate frameworks. Here, we explore borate-bridged amphiphile–carbohydrate conjugates as plausible intermediates between simple prebiotic surfactants and modern lipid bilayers. These conjugates arise from low-molecular-weight polyols—including glycerol, butane-1,2,3,4-tetraol, pentane-1,2,3,4,5-pentaol, and hexane-1,2,3,4,5,6-hexitol—reacting with long-chain alkyl ethers and borate species under alkaline conditions, enabling reversible coupling to ribose and other vicinal diol-containing sugars. This chemistry integrates three essential properties for early compartmentalization: hydrolytically robust ether-linked hydrophobic domains, multivalent and highly hydrated headgroups, and environmentally responsive borate coordination. Comparative physicochemical analysis suggests that single-tail alkylglycerol derivatives preferentially form micelles and interfacial films, while di- and tri-tail tetritol and pentitol conjugates favor lamellar assemblies and vesicle formation across realistic prebiotic pH and salinity ranges. Hexitol-based systems, particularly those bearing three hydrophobic chains, may act as membrane-stabilizing components that enhance rigidity and reduce permeability under extreme conditions. We propose that heterogeneous mixtures dominated by two-tail polyol diethers, supplemented by tri-tail stabilizers and surface-active alkylglycerols, could provide mechanically robust, pH-tunable, and sugar-decorated abiotic membranes. Such borate-mediated amphiphiles offer a chemically coherent framework linking carbohydrate stabilization, ether lipid persistence, and dynamic self-assembly, potentially representing a transitional stage in the evolutionary pathway from primitive amphiphilic films to biologically encoded membranes. Full article

Adobe is a sustainable yet highly porous construction material, inherently vulnerable to moisture and environmental pollution, which poses challenges for both contemporary construction and heritage conservation. This study presents multifunctional coatings that combine hydrophobic/oleophobic and photocatalytic properties to enhance adobe durability. The coatings incorporate nano-heterostructured LaFeO₃ photocatalysts into water-repellent and hydro-oleo-repellent formulations, selected to preserve the characteristic dark brown color of adobe. Microstructural analyses revealed the formation of non-uniform protective layers, particularly in hydro-oleo-repellent systems, which influenced performance. The treated surfaces exhibited significant water and oil repellency, while maintaining adequate vapor permeability. Durability tests confirmed improved resistance to water ingress, reduced capillary absorption, and enhanced erosion resistance compared to untreated adobe. Sustainability assessments highlighted the environmental and economic benefits of the proposed approach, especially when using locally sourced materials. Overall, this work proposes a scalable and multifunctional strategy that integrates protective and photocatalytic functionalities to extend the service life of both historical and modern adobe structures. Full article

Natural gas reservoirs characterized by high heterogeneity and containing bottom-bound water often face the problem of water intrusion, making it difficult to recover the recoverable gas. This paper addresses the issue of enhanced gas recovery in water-flooded reservoirs and, through high-temperature, high-pressure long-core displacement experiments, investigates the displacement effects of different reservoir properties and injection media (dry gas, N₂, CO₂) under simulated water-flooding conditions. The experiment utilized two sets of sandstone cores—one with moderate permeability (304.8 mD) and one with high permeability (1004.6 mD). Three cores from each set were spliced together to form a 0.9 m long core, simulating the gas injection and displacement process following water infiltration. The results indicate that while water intrusion occurs more rapidly in high-permeability reservoirs, gas injection yields better recovery results than in medium-permeability reservoirs. Among the three injection media, dry gas demonstrated the best displacement efficiency, followed by N₂, with CO₂ performing the worst. CO₂ tends to react with highly mineralized formation water under high-temperature and high-pressure conditions, forming precipitates and causing energy to be absorbed by the water, which reduces displacement efficiency. It is recommended that dry gas injection be used for enhanced recovery in the moderate-permeability reservoirs of the Y gas field, while N₂ injection may be considered for the high-permeability reservoirs to balance effectiveness and cost. The research results provide experimental support for subsequent gas injection to enhance gas recovery in this gas field. Full article

The growing volume of construction and demolition waste has made discarded concrete a major source of urban solid waste, placing increasing pressure on land resources and the environment. Recycling waste concrete into recycled aggregate concrete (RAC) offers an effective solution for resource conservation and carbon reduction, aligning with the goals of sustainable development. However, due to the residual mortar, high porosity, and microcracks of recycled aggregates, RAC generally exhibits lower compactness, strength, and durability than conventional concrete, particularly under freeze–thaw conditions where degradation accelerates and service life decreases. To address these challenges, this study investigates the optimization of RAC mix design and its frost resistance performance for pavement base applications. An orthogonal experimental design was employed, with the water-to-binder ratio, recycled aggregate replacement ratio, and air-entraining agent dosage as key variables, while 7-day compressive strength, permeability coefficient, and rebound modulus served as evaluation indices. The influence and interaction of these factors were analyzed to determine an optimal mix meeting both mechanical and durability requirements. Rapid freeze–thaw cycling tests were then conducted to examine the variations in mass loss, relative dynamic modulus, and compressive strength retention, followed by exponential and damage variable modeling to characterize the degradation process. Results show that the water-to-binder ratio primarily governs strength, the replacement ratio affects stiffness and permeability, and the air-entraining agent significantly enhances frost resistance by improving pore structure. The optimized mix retained over 70% of its relative dynamic modulus after 300 freeze–thaw cycles, exhibiting superior durability. This work establishes a systematic framework for multi-factor optimization and durability evaluation of RAC, providing theoretical and practical guidance for its application in cold-region pavement bases. Full article

The Xiangshan ore field is characterized by extensive alkali metasomatism, which represents the early-stage hydrothermal event before the acidic metasomatism during major U mineralization. However, the mineralogical and geochemical characteristics of alkali metasomatism, as well as its association with uranium mineralization, remain poorly understood. This study evaluates these scientific problems by conducting petrographic and geochemical analyses on feldspar, together with thermodynamic modeling. Hydrothermal feldspars are present as veinlets, differing from the magmatic ones with granular and subhedral structures. Hydrothermal albites have lower Na but higher K content than magmatic ones, while hydrothermal K-feldspars have lower K but higher Na content than magmatic ones. In addition, hydrothermal feldspars are significantly depleted in Ca and Sr, likely associated with the consumption of Ca in fluids by fluorite and calcite precipitation. Furthermore, alkali metasomatism is accompanied by intense hematitization, indicating the oxidized properties of ore fluids that are favorable for uranium transport. Thermodynamic modeling further demonstrates that continuous K⁺ consumption during fluid–rock interaction leads to a pH increase in the fluid, which is buffered by quartz–muscovite–K-feldspar (QMF). Given that quartz solubility is positively correlated with pH, this process induces extensive quartz dissolution in the host rocks. Such dissolution significantly enhances the porosity and permeability of the host rocks, creating ideal physical traps for the subsequent accumulation of uranium-bearing fluids. Consequently, alkali-metasomatized rocks associated with quartz dissolution and hematitization serve as critical indicators for regional uranium exploration. Full article

A sustainable polymer-based filtration control system was developed for high-temperature, high-density water-based drilling fluids. The system’s rheological stability, filtration performance, and filter cake properties were evaluated under varying conditions of temperature, salinity, and density. The drilling fluid density ranged from 1.80 to 2.20 g/cm³, the temperature from 25 to 150 °C, and the NaCl mass fraction w(NaCl) = 5–20%. The results indicated that increasing fluid density resulted in a progressive increase in apparent and plastic viscosities (from 42.6/28.4 mPa·s to 65.1/47.9 mPa·s), while the yield point remained relatively stable (14.2–17.2 Pa), suggesting that high solid loading enhanced viscous dissipation without inducing structural stiffening. Filtration loss increased moderately with temperature (6.8–12.3 mL at 25–150 °C) and salinity (6.8–10.7 mL at w(NaCl) = 5–20%), whereas it decreased significantly with increasing density (13.1–9.4 mL at 1.80–2.20 g/cm³), indicating a density-dominated filtration regime. At 120 °C, w(NaCl) = 12%, and 2.00 g/cm³, the developed system achieved a low filtration loss of 8.4 mL, outperforming three representative conventional filtration-control systems, including starch-based, sulfonated asphalt-based, and polymer-based technologies. Filter cake analysis revealed that increasing density facilitated the packing of multi-scale solids, reducing filter cake thickness from 1.62 mm to 0.98 mm and permeability from 1.34 × 10⁻¹⁵–4.05 × 10⁻¹⁶ m², while significantly improving resistance to erosion and compression. These findings demonstrate that the combination of interfacial stabilization and filter cake densification offers a robust and controllable filtration solution for high-temperature, high-density drilling environments, presenting a promising approach for drilling fluid systems in challenging conditions. Full article

Liquid nitrogen (LN₂) fracturing is a highly promising stimulation technology for unconventional reservoirs. Understanding its in situ fracture network formation mechanism is essential for engineering practice. This study investigates coal rock fracturing driven by the synergistic effect of thermal stress and fluid pressure during LN₂ injection. A coupled thermal–hydraulic–mechanical–damage (THMD) numerical model is developed, incorporating in situ stress conditions and LN₂ phase change behavior. Through true triaxial LN₂ fracturing simulations validated against physical experiments, the multi-field dynamic coupling behavior is systematically analyzed, revealing the synergistic mechanism of fracture propagation and permeability enhancement under cryogenic conditions. The results show the following: (1) The proposed model effectively reproduces the true triaxial LN₂ fracturing process, with simulation results in good agreement with physical experiments. (2) LN₂ fracturing exhibits distinct stage-wise characteristics: cryogenic temperatures induce thermal stress that triggers micro-crack initiation; the self-enhancing effects of damage and permeability significantly promote fracture propagation; fluid pressure then becomes the dominant driving force. (3) Coal rock damage follows a four-stage evolution—wellbore crack initiation, stable propagation, unstable propagation, and through-going failure—ultimately forming a complex spatial fracture network. (4) The horizontal stress ratio is a key factor controlling fracture morphology: a single dominant fracture forms under a high stress difference, whereas a multi-directional complex network develops under equal confining pressure. Fractal analysis reveals significant anisotropy and a non-monotonic stress response in the fracture complexity, reflecting structural evolution from multi-directional propagation to main channel connection. This study provides theoretical support for understanding LN₂ fracturing mechanisms and optimizing field treatment parameters. Full article

To reduce food waste and mitigate health risks from accidentally consuming spoiled food, freshness-indicating technologies are increasingly demanded. However, conventional colorimetric-based freshness-indicating packaging is limited by instability, subtle color changes, and complex production processes. This study presents a curcumin-based ink suitable for eco-friendly polylactic acid (PLA) food packaging films enabling real-time shrimp freshness monitoring via integrated intelligent packaging. The ink comprised curcumin as the indicator, ethyl cellulose (EC) and polyvinyl butyral (PVB) as binders, and polyethylene glycol 400 (PEG 400) to regulate permeability. Excellent printability was demonstrated by fineness, initial dryness and fluidity tests. It also demonstrated good thixotropic, viscosity, and flow curve properties. Printing minimally affected the PLA films’ mechanical and barrier properties. The indicator label showed high sensitivity, rapid response, and excellent reversibility to ammonia vapor. Practical application in monitoring shrimp spoilage at 25 °C and 4 °C revealed a strong correlation between the distinct color transition of the label and the increase in total volatile basic nitrogen (TVB-N) content and pH value, providing a reliable visual warning before obvious spoilage signs appeared. This work provides a viable integrated indicator packaging strategy for developing intelligent packaging, offering significant potential to reduce food waste and enhance supply chain transparency for perishable goods. Full article

Alkaline water electrolysis (AWE) is a pivotal technology for sustainable hydrogen production. However, hydrogen permeation through its membranes remains a critical concern, as excessive gas crossover can lead to the formation of explosive mixtures and pose severe safety hazards. While conventional measurement techniques, such as pressure drop and electrochemical methods, are suitable for porous membranes, they exhibit inherent limitations when applied to dense membranes such as anion exchange membranes. This study proposes a cross-flow measurement methodology applicable to all types of AWE membranes. Unlike traditional dead-end configurations, the cross-flow approach effectively mitigates impurity accumulation and maintains a continuous electrolyte flow parallel to the membrane surface. This configuration ensures uniform electrolyte distribution, minimizes local concentration and pressure fluctuations, and enhances measurement reliability and reproducibility relative to the conventional dead-end flow. Furthermore, the methodology ensures accurate and reproducible measurements, demonstrating enhanced detection capability for dense membranes with intrinsically low permeability by mitigating fouling and concentration polarization effects. These findings provide a robust framework for the development of high-performance membranes designed to suppress dissolved hydrogen permeability. Full article

Plastic manufacturing depends heavily on petroleum-derived monomers like terephthalic acid, the main component of polyethylene terephthalate (PET). However, the depletion of fossil resources and increasing environmental concerns have heightened the need for sustainable alternatives. Lignocellulosic biomass has emerged as a promising resource due to its renewable, abundant, and eco-friendly nature. Understanding its chemical composition enables conversion of this biomass into platform chemicals, such as 2,5-furandicarboxylic acid (FDCA) and lactic acid, derived from cellulose and hemicellulose. These can be polymerized into bio-based plastics such as polyethylene furanoate (PEF), polylactic acid (PLA), and polyhydroxyalkanoates (PHAs), offering greener alternatives to fossil-based plastics. PEF features rigid furan rings that enhance thermal stability, mechanical strength, and barrier properties, and reduce gas permeability compared to PET. PLA is a renewable, biodegradable plastic widely used in packaging and medical applications. This review covers the chemical composition of lignocellulosic biomass cellulose, hemicellulose, and lignin, and various pretreatment strategies, chemical, physicochemical, and physical, to overcome biomass recalcitrance and improve conversion efficiency. It also highlights recent catalytic advances in transforming cellulosic carbohydrates into bio-based plastic precursors such as FDCA and lactic acid. Lastly, this review discusses polymerization pathways for producing PEF and PLA, emphasizing their role in reducing the environmental impact of polymer manufacturing and promoting green chemistry principles. Full article