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Quaternary mudstone biogas reservoirs in the Qaidam Basin have shown great potential. However, complex pore structures with high clay contents and high heterogeneity limit the understanding of the storage and migration principles of these reservoirs. In this paper, HPMI and nitrogen adsorption experiments, in combination with NMR experiments under water saturation, centrifugation, various drying temperatures and other conditions, were adopted to determine the pore structure characteristics. Specifically, the reservoir space types and pore radius distribution characteristics were clarified. The cutoff values for different types of pores were identified based on the water-saturated mudstone NMR T2 spectra for full aperture distribution scales jointly characterized by mercury injection and nitrogen adsorption experiments. Furthermore, the three pore components and the saturation of different fluids were obtained. The research results indicate that the mudstone biogas reservoir has developed various reservoir spaces, and the pore size is primarily in the micronanometer range. The average total porosity reaches 27.28%, but the proportion of movable water pores is only 9.23% with poor fluid mobility, and the fluids in the pores are mostly capillary-bound water and clay-bound water. Among the different lithologies, argillaceous sand is more likely to become a good production layer. [ABSTRACT FROM AUTHOR]

ABSTRACT Rock masses in alpine regions inevitably undergo freeze–thaw (F–T) cycles, which affects the safety of infrastructure such as slopes, with shear failure being a significant concern. This study investigates the Mode II fracture behavior of F–T treated granite via the short core in compression (SCC) test, analyzing the related physical properties and mechanical properties while also discussing F–T damage mechanism at a microscopic level. Results reveal that as F–T cycles increase, the dynamic elastic modulus and P‐wave velocity decrease, whereas porosity and backbone fractal dimension of pore scale increase, indicating a transition towards a large‐scale pore. Mode II fracture toughness decreased by 31.19% and fracture process zone width increased by 248.49% with F–T cycles rising from 0 to 80, and related fractal dimension of surface morphology also increased by 11.17%. Microscopic observation reveals the microstructure deterioration induced by F–T treatment, indicating the correlation between microscopic damage and macroscopic fracture properties. [ABSTRACT FROM AUTHOR]

In order to tackle the issue of excessive coal dust and hydrogen sulfide (H2S) concurrently in underground coal mines, an alkaline dust suppressant was formulated by combining surfactant sodium sec-alkyl sulfonate (SAS60) and sodium carbonate (Na2CO3) at a certain mass ratio, meant for injection into coal seams. This study principally targeted long-flame coal extracted from Hequ County, located in Shanxi Province, China. The objective was to investigate and analyze the underlying process of how alkaline dust suppressants affect the wettability of coal. A comprehensive strategy including contact angle determination, Fourier transform infrared absorption spectrometer(FTIR) analysis, low-temperature nitrogen adsorption tests, scanning electron microscope(SEM) experimental studies, and molecular dynamics simulations was employed for this examination. The results revealed that merging Na2CO3 with SAS60 could reduce the coal's contact angle. Despite the core structure of the coal surface staying unchanged after alkaline dust suppressant treatment, a rise in the number of hydrophilic functional groups was observed. This count notably surpassed the amount of hydrophobic functional groups, consequently boosting the coal's hydrophilicity. The permeability of the examined coal specimens was chiefly affected by the existence of macropores and mesopores. Processing with 0.05 wt% SAS60 and 1.0 wt% Na2CO3, the coal acquired additional pores and cracks, causing an upswing of average pore size by 25.79% and a 30.64% increase in the maximum gas adsorption. This facilitated more straightforward infiltration of water into the coal dust. Molecular dynamics simulation outcomes indicated a closer affiliation between coal and water following the incorporation of Na2CO3. It led to a heightened activity in water molecule movement, fortifying intermolecular electrostatic interactions, and fostering the creation of hydrogen bonds. Consequently, this improved the coal's wettability. The increase in the mass fraction of Na2CO3 directly corresponds to a more considerable enhancement in the solution's ability to wet the coal. The outcomes of the molecular dynamics simulation validated the experimental results' precision. [ABSTRACT FROM AUTHOR]

Alkali dissolution is an effective method to regulate the pore structure of porous mineral material. The main chemical composition of diatomite is amorphous SiO 2 , which can be dissolved in alkali dissolution. The diatomite samples with alkali dissolution treatment were systematacially characterized by the particle size analysis, low temperature nitrogen adsorption, MIP, fractal theory, SEM, TEM, XRD, FTIR and surface hydroxyl density to analyze the pore structure and surface properties. And the humidity control performance of diatomite was tested under different temperatures and relative humidities. The relationship among pore structure, surface properties and humidity control performance were analyzed. The results show that alkali dissolution can regulate the mesoporous and macroporous of diatomite, and some new microporous can generate at high alkali dosage. The specific surface area, mesoporous pore volume, proportion of macroporous volume, surface roughness, heterogeneity of pore structure and number of hydroxyl groups on the surface of diatomite are important factors which determining the humidity control performance. The humidity control performance of diatomite is positively correlated with the specific surface area, mesoporous volume, surface roughness, heterogeneity of pore structure and number of hydroxyl groups on the surface, while is negatively correlated with the proportion of macroporous volume. [ABSTRACT FROM AUTHOR]

Rock pore structure coupled with fluid pressure plays an important role in controlling fault slip behavior. Observation of fluid-induced seismicity in geoenergy extraction has raised fundamental questions about the physics of fault rock structure and fault frictional stability in the presence of fluid. Here, we change the pore structure of faults by thermal treatment and report on the frictional stability of granite faults with pore evolution and pore fluid pressure in velocity stepping experiments under the rate-and-state framework, where the variation of pore fluid is monitored. The experiments under constant fluid pressure show that pore structure propagation leads to an increase in friction coefficient from 0.71 to 0.78. As the degree of pore propagation increases, the drained fault exhibits a transition from velocity strengthening to weakening behavior. The decrease in frictional stability could be caused by the coupling between the pore fluid and the well-connected pores, namely “fluid oscillation”. Pore pressure overpressurization could develop and cause non-uniform stress distribution along the fault surface due to pore fluid oscillation at velocity steps. The time required to equilibrate fluid pressure could be prolonged by fluid oscillation, leading to intrinsic velocity strengthening behavior appearing as velocity weakening. The decrease in rate-and-state parameter with elevating pore fluid pressure on high-porosity fault corroborates the fluid-induced fault destabilization. The fluid oscillation at the greater pore pressure could be responsible for fault reactivation. Therefore, the coupling effect of rock pore structure with pore fluid could be a potential mechanism governing fault frictional stability. [ABSTRACT FROM AUTHOR]

Radon release rate is one of the most important indicators to assess the environmental radon hazard. In the loess-covered area of northern China, the decay of uranium ore associated with the coal seams has caused elevated radon concentrations in overlying soil layers, significantly increasing the risk of various respiratory diseases to residents. In this paper, the effects of burial depth and soil type on radon release rate were investigated by X-ray diffraction (XRD) analysis, low-temperature nitrogen adsorption (LTNA) experiments, and measurement of radon concentrations in the soil based on the pore structure characteristics of soil layers. The results showed that all N2 adsorption isotherms in the soil were inverse-S shaped with well-developed mesopores. The number of mesoporous materials was positively correlated with the radon release rate of the soil. The overall tendency of the radon release rate was to firstly increase and then decrease with increasing depth. The relative degree of variation in radon exhalation rate between adjacent soil layers was in the order as follows: red clay > paleosoil > loess > pedocal. The results of this study can help to understand the release pattern of radon in different soils and provide valuable references in reflecting the characteristics of radon release in regional soils. [ABSTRACT FROM AUTHOR]

Honeycomb mullite ceramics with controllable pore geometries were prepared using stereolithography 3D printing. The influence of sintering temperature on the phase evolution, microstructure and compressive strength of honeycomb mullite ceramics was explored. The results showed that the mullite phases were basically completely transformed for the sample sintered at 1600 °C. As the sintering temperature increased, a huge number of rod-like mullite grains were generated through the dissolution-precipitation mechanism. As a result, the apparent porosity was reduced, while the densification and compressive strength were improved. Furthermore, the impact of the pore geometry on the mechanical properties of the sample was also investigated. Among all the honeycomb mullite ceramics, the compressive strength of the sample with square pores reached a maximum value of approximately 206.71 MPa. In addition, the compressive strength of honeycomb mullite was simulated using SolidWorks software. The results were in good agreement with the experimental data. The fracture behavior of honeycomb mullite ceramics exhibited three stages, including the linear elastic, plateau, and densification regions and the fracture mechanism was mainly layer-by-layer fracture of the pore structure. [ABSTRACT FROM AUTHOR]

The potential benefits of biochar, a carbon-rich substance derived from biomass, for enhancing agricultural yield and soil health have drawn increasing interest. Nevertheless, owing to the lack of specialized studies, the role of its poly-spatial structure in the success of fostering plant growth remains unclear. This study aimed to assess the effects of various biochar pore shapes on tobacco growth and the underlying microbiological processes. Three pyrolysis temperatures (250 °C, 400 °C, and 550 °C) were used to produce biochar from tobacco stems, resulting in different pore structures (T3 > T2 > T1). We then used BET-specific surface area (BET), t.Plot micropore specific surface area (t.Plot), mesopore specific surface area (MSSA), specific pore volume (SPV), average pore size (AP), and mesopore pore volume (MPV) measurements to evaluate the effects of these biochars on tobacco growth and biomass accumulation, and microbial analyses were performed to investigate the underlying mechanisms. When applied to plants, biochar increased their growth compared to untreated controls. The most notable improvement in tobacco growth was observed in the biochar produced at 400 °C (T3), which possessed the largest and most advantageous pore structure among all treatments. Further studies demonstrated that biochars with greater specific surface areas (BET, t.Plot, and MSSA) positively altered the abundance of key microbial taxa (e.g., Stenotrophobacter, Ensifer, Claroideoglomus) and community composition, thereby encouraging plant development and biomass accumulation. Conversely, greater pore volumes (SPV, AP, and MPV) inhibited microbial activity and significantly affected growth and biomass accumulation. Structural equation modeling further demonstrated that the pore structure of biochar greatly affected plant growth by changing the relative abundance and community composition of soil microbes. Maximizing the benefits of biochar in stimulating plant growth and improving soil microbial communities depends on optimizing the material's pore structure, particularly by increasing the specific surface area. These findings will help expand the use of biochar in sustainable agriculture. [ABSTRACT FROM AUTHOR]

Using a mixture of TiH 2 , Al, B 4 C, and graphite powders with a molar ratio of 3+2 m/1.2/m/2-m (where m ranges from 0 to 0.25, with increments of 0.05), porous Ti 3 AlC 2 -TiB 2 composite ceramics were successfully synthesized through activated reaction sintering. The effect of B 4 C content on the phase composition, volumetric expansion, microstructure, and pore structure parameters (including pore size, porosity, and permeability) was systematically studied. When the molar ratio of B 4 C was less than 0.1, the volumetric expansion rate, average pore size, and permeability increased with the addition of B 4 C, reaching maximum values of −5.46 %, 2.23 μm, and 92.4 m3 m−2·10 kPa−1 h−1, respectively. Conversely, when the B 4 C molar ratio exceeded 0.1, the parameters related to the pore structure of the porous Ti 3 AlC 2 -TiB 2 composite ceramics decreased, with minimum values of −10.40 %, 1.46 μm, and 68 m3 m−2·10 kPa−1 h−1, respectively. In addition, the pore formation mechanism of the porous Ti 3 AlC 2 -TiB 2 composite ceramics was systematically explored. The revolution tendency of pores is related to the decomposition of TiH 2 , Kirkendall partial diffusion, diffusion between B and C, and the transition process of the final phase Ti 3 AlC 2 -TiB 2. This research work could provide a reference for the preparation of the MAX phase composite porous materials. [ABSTRACT FROM AUTHOR]

Liquid manipulation using tubular actuators finds diverse applications ranging from microfluidics, printing, liquid transfer to micro‐reactors. Achieving flexible and simple regulation of manipulated liquid droplets during transport is crucial for the tubular liquid actuators to perform complex and multiple functions, yet it remains challenging. Here, a facile tubular actuator for directional transport of various liquid droplets under the control of an externally applied magnetic field is presented. The surfaces of the actuator can be engineered with submillimeter‐sized through‐hole pores, which enables the liquid droplet to be easily modulated in the transport process. Furthermore, the liquid actuator with featured through‐hole pores is expanded to function as a switch in an integrated external electric circuit by magnetically controlling the motion of a conductive liquid droplet. This work develops a strategy for regulating liquid droplets in the tubular actuation systems, which may inspire ideas for designing functional liquid actuators with potential applications in microfluidics, microchemical reaction, liquid switch, and liquid robotics. [ABSTRACT FROM AUTHOR]

Lotus-type porous copper was fabricated using a continuous casting method in pressurized hydrogen and nitrogen gas atmospheres. This study evaluates the effects of process parameters, such as the hydrogen ratio, total pressure, and transference velocity, on the resulting pore structure. A continuous casting process was developed to facilitate the mass production of lotus-type porous copper. To achieve the desired porosity and pore diameter for large-scale manufacturing, a systematic evaluation of the influence of each process parameter was conducted. Lotus-type porous copper was produced within a hydrogen ratio range of 25–50%, a transference velocity range of 30–90 mm∙min−1, and a total pressure range of 0.2–0.4 MPa. As a result, the porosity ranged from 36% to 55% and the pore size varied from 300 to 1500 µm, demonstrating a wide range of porosities and pore sizes. Through process optimization, it is possible to control the porosity and pore size. The hydrogen ratio and total pressure were found to primarily affect porosity, whereas the hydrogen ratio, transference velocity, and total pressure significantly influenced pore diameter. When considering these parameters together, porosity was most influenced by the hydrogen ratio, whereas the total pressure and transference velocity had a greater influence on pore diameter. Reducing the hydrogen ratio and increasing the transference velocity and total pressure reduced the pore diameter and porosity. This optimization of the continuous casting process enables the control of porosity and pore diameter, facilitating the production of lotus-type porous copper with the desired pore structures. [ABSTRACT FROM AUTHOR]

This study compared the physical properties and mechanical strength development of PCBAs with water, sealed, standard, and open ambient air curing over 28 days to find a suitable curing method for the production of phosphogypsum-based cold-bonded aggregates. The types and relative amounts of hydration products, microstructural morphology and pore structure parameters were characterized utilizing XRD, TGA, FTIR, SEM and nitrogen adsorption methods. According to the results, water curing leads to rapid increases in single aggregate strength, reaching 5.26 MPa at 7 d. The standard curing condition improved the 28 d mechanical strength of the aggregates by 19.3% over others by promoting the generation of hydration products and the transformation of the C-S-H gel to a higher degree of polymerization and by optimizing the pore structure. Further, PCBAs achieved an excellent solidification of phosphorus impurities under all four curing conditions. This work provides significant guidance for selecting an optimized PCBA curing method for industrial production. [ABSTRACT FROM AUTHOR]

To explore the influence of surfactant concentration on the pore structure and permeability of coal samples during the chemical enhancement of coalbed methane production, different kinds and different concentrations of surfactants were added to the chemical solution, and the coal samples were soaked. Methods such as low-field nuclear magnetic resonance testing (NMR), fractal theory, permeability testing, surface tension testing, and contact angle testing were employed to analyze the variation patterns of coal sample pore structure, fractal characteristics, and permeability, and to explore the correlation between surface tension, contact angle, and the degree of pore structure development. The results show that the increase in total porosity of coal samples, the increase in the seepage pore porosity, the decrease in Dt, and the growth rate of permeability increase with the increase in surfactant concentration, and are negatively correlated with the surface tension of the solution and the contact angle of the coal-solution interface, while the decrease in Ds is not significantly correlated with surfactant concentration, surface tension, or contact angle. In terms of the erosion effect of a chemical solution on coal samples, the influence of contact angle is greater than that of surface tension, while surface tension has the greatest impact on the development of adsorption pores. By adding different surfactants, the surface tension of the chemical solution and the contact angle of the coal-solution interface can be controlled, further promoting the erosion of coal samples, which is of positive significance for the chemical enhancement of coalbed methane production. [ABSTRACT FROM AUTHOR]

In-situ thermal upgrading is used to tune the pore system in low-maturity oil shales. We introduce fractal dimension (D), form factor (ff) and stochastic entropy (H) to quantify the heating-induced evolution of pore morphological complexity and azimuthal disorder and develop a model to estimate the impact on seepage capacity via permeability. Experiments are conducted under recreated in-situ temperatures and consider anisotropic properties-both parallel and perpendicular to bedding. Results indicate that azimuthal distribution of pores in the bedding-parallel direction are dispersed, while those in the bedding-perpendicular direction are concentrated. D values indicate that higher temperatures reduce the uniformity of the pore size distribution (PSD) in the bedding-parallel direction but narrow the PSD in the bedding-perpendicular direction. The greater ff (> 0.7) values in the bedding-parallel direction account for a large proportion, while the dominated in the bedding-perpendicular direction locates within 0.2e0.7, for all temperatures. The H value of the bedding-parallel sample remains stable at ~0.925 during heating, but gradually increases from 0.808 at 25 ℃ to 0.879 at 500 ℃ for the beddingperpendicular sample. Congruent with a mechanistic model, the permeability at 500 ℃ is elevated ~1.83 times (bedding-parallel) and ~6.08 times (bedding-perpendicular) relative to that at 25 -Cdconfirming the effectiveness of thermal treatment in potentially enhancing production from lowmaturity oil shales. [ABSTRACT FROM AUTHOR]

The cyclic hydraulic stimulation (CHS) has proven as a prospective technology for enhancing the permeability of unconventional formations such as coalbeds. However, the effects of CHS on the microstructure and gas sorption behavior of coal remain unclear. In this study, laboratory tests including the nuclear magnetic resonance (NMR), low-temperature nitrogen sorption (LTNS), and methane sorption isotherm measurement were conducted to explore changes in the pore structure and methane sorption characteristics caused by CHS on an anthracite coal from Qinshui Basin, China. The NMR and LTNS tests show that after CHS treatment, meso- and macro-pores tend to be enlarged, whereas micropores with larger sizes and transition-pores may be converted into smaller-sized micro-pores. After the coal samples treated with 1, 3, 5 and 7 hydraulic stimulation cycles, the total specific surface area (TSSA) decreased from 0.636 to 0.538, 0.516, 0.505, and 0.491 m²/g, respectively. Fractal analysis based on the NMR and LTNS results show that the surface fractal dimensions increase with the increase in the number of hydraulic stimulation cycles, while the volume fractal dimensions exhibit an opposite trend to the surface fractal dimensions, indicating that the pore surface roughness and pore structure connectivity are both increased after CHS treatment. Methane sorption isothermal measurements show that both the Langmuir volume and Langmuir pressure decrease significantly with the increase in the number of hydraulic stimulation cycles. The Langmuir volume and the Langmuir pressure decrease from 33.47 cm³/g and 0.205 MPa to 24.18 cm³/g and 0.176 MPa after the coal samples treated with 7 hydraulic stimulation cycles, respectively. The increments of Langmuir volume and Langmuir pressure are positively correlated with the increment of TSSA and negatively correlated with the increments of surface fractal dimensions. [ABSTRACT FROM AUTHOR]

Quantitative prediction of reservoir properties (e.g., gas saturation, porosity, and shale content) of tight reservoirs is of great significance for resource evaluation and well placements. However, the complex pore structures, poor pore connectivity, and uneven fluid distribution of tight sandstone reservoirs make the correlation between reservoir parameters and elastic properties more complicated and thus pose a major challenge in seismic reservoir characterization. We have developed a partially connected double porosity model to calculate elastic properties by considering the pore structure and connectivity, and to analyze these factors' influences on the elastic behaviors of tight sandstone reservoirs. The modeling results suggest that the bulk modulus is likely to be affected by the pore connectivity coefficient, while the shear modulus is sensitive to the volumetric fraction of stiff pores. By comparing the model predictions with the acoustic measurements of the dry and saturated quartz sandstone samples, the volumetric fraction of stiff pores and the pore connectivity coefficient can be determined. Based on the calibrated model, we have constructed a 3D rock physics template that accounts for the reservoir properties' impacts on the P-wave impedance, S-wave impedance, and density. The template combined with Bayesian inverse theory is used to quantify gas saturation, porosity, clay content, and their corresponding uncertainties from elastic parameters. The application of well-log and seismic data demonstrates that our 3D rock physics template-based probabilistic inversion approach performs well in predicting the spatial distribution of high-quality tight sandstone reservoirs in southwestern China. [ABSTRACT FROM AUTHOR]

The pore structure and mineral characteristics affect the accumulation and migration of hydrocarbons in shale, which determines the production capacity of shale oil. In this study, shale samples from the Chang 7 member of the Ordos Basin in China were selected to investigate the pore space characteristics, the effect of hydrocarbon accumulation on pore heterogeneity, and the hydrocarbon migration changes based on fractal theory, and a series of experiments were conducted involving X-ray diffraction (XRD), total organic carbon (TOC), Soxhlet extraction, and low-temperature nitrogen (N2) and carbon dioxide (CO2) adsorption. Then, the factors affecting extraction efficiency in shale pores were discussed. The interparticle pores contributed most to the accumulation of shale oil, and the organic matter (OM) pores contributed positively to the adsorption of hydrocarbons. The accumulation of hydrocarbons in the pore space did not increase the heterogeneity of the shale pore structure. The contents, states, and positions of hydrocarbons changed during the extraction process. Hydrocarbons were redistributed on the pore surface after Soxhlet extraction, and the heterogeneity of hydrocarbon adsorption and pore surface roughness were improved. Some heavy hydrocarbons and adsorbed components were pyrolyzed, resulting in the gradual escape of the adsorbed layer in the large pores. However, the free oil in the small pores diffused to the large pores and reaggregated on the surface, restoring a stable adsorption layer. The extraction rate was closely related to the pore throat structure and the wettability of mineral surfaces. The configuration between pores and throats had a crucial influence on the extraction rate. A high proportion of meso-pores, which effectively connect micro- and macro-pores, had a higher diffusion efficiency and a higher extraction rate. The OM pores with high energy adsorption were located in the micro-pores, and the shale oil existed in a dissolved state with high mobile capacity. The wettability of mineral surfaces affected the adsorption behavior during extraction, and strong oil wetting promoted hydrocarbon re-adsorption in clay minerals, so that the volume of micro-pores was smaller after extraction. [ABSTRACT FROM AUTHOR]

Shale gas is a prospective cleaner energy resource and the exploration and development of shale gas has made breakthroughs in many countries. Structure deformation is one of the main controlling factors of shale gas accumulation and enrichment in complex tectonic areas in southern China. In order to estimate the shale gas capacity of structurally deformed shale reservoirs, it is necessary to understand the systematic evolution of organic pores in the process of structural deformation. In particular, as the main storage space of high-over-mature marine shale reservoirs, the organic matter pore system directly affects the occurrence and migration of shale gas; however, there is a lack of systematic research on the fractal characteristics and deformation mechanism of organic pores under the background of different tectonic stresses. Therefore, to clarify the above issues, modular automated processing system (MAPS) scanning, low-pressure gas adsorption, quantitative evaluation of minerals by scanning (QEMSCAN), and focused ion beam scanning electron microscopy (FIB-SEM) were performed and interpreted with fractal and morphology analyses to investigate the deformation mechanisms and structure of organic pores from different tectonic units in Silurian Longmaxi shale. Results showed that in stress concentration areas such as around veins or high-angle fractures, the organic pore length-width ratio and the fractal dimension are higher, indicating that the pore is more obviously modified by stress. Under different tectonic backgrounds, the shale reservoir in Weiyuan suffered severe denudation and stronger tectonic compression during burial, which means that the organic pores are dominated by long strip pores and slit-shaped pores with high fractal dimension, while the pressure coefficient in Luzhou is high and the structural compression is weak, resulting in suborbicular pores and ink bottle pores with low fractal dimension. The porosity and permeability of different forms of organic pores are also obviously different; the connectivity of honeycomb pores with the smallest fractal dimension is the worst, that of suborbicular organic pores is medium, and that of long strip organic pores with the highest fractal dimension is the best. This study provides more mechanism discussion and case analysis for the microscopic heterogeneity of organic pores in shale reservoirs and also provides a new analysis perspective for the mechanism of shale gas productivity differences in different stress–strain environments. [ABSTRACT FROM AUTHOR]

Due to the influence of terrigenous debris, the internal pore structure of continental shale is highly heterogeneous, and the controlling factors are complex. This paper studies the structure and controlling factors of shale reservoirs in the first member of the Qingshankou Formation in the Southern Songliao Basin using core data and various analytical test data. The results show that the original deposition and subsequent diagenesis comprehensively determine the shale reservoirs' pore structure characteristics and evolution law. According to the severity of terrigenous debris, the shale reservoirs in the study area are divided into four categories and six subcategories of lithofacies. By comparing the characteristics of different shale lithofacies reservoirs, the results show that the lithofacies with a high brittle mineral content have more substantial anti-compaction effects, more primary pores to promote retention and a relatively high proportion of mesopores/macropores. Controlling the organic matter content when forming high-quality reservoirs leads to two possibilities. An excessive organic matter content will fill pores and reduce the pore pressure resistance. A moderate organic matter content will make the inorganic diagenesis and organic hydrocarbon generation processes interact, and the development of organic matter mainly affects the development of dissolution pores. The comprehensive results show that A3 (silty laminated felsic shale) reservoirs underwent the pore evolution process of "two drops and two rises" of compaction, cementation and pore reduction, dissolution and pore increase, and organic matter cracking and pore increase, and they are the most favourable lithofacies of the shale reservoirs in the study area. [ABSTRACT FROM AUTHOR]

Rock pores crack and expand subjected to freeze-thaw cycles, resulting in the reduction of their physical and mechanical properties, it is necessary to study its evolution and deterioration mechanism. However, the majority of existing studies employ a singular pore testing methodology, and neglecting the impact of the thawing process on frost heave damage in rocks. To address this, this study employs a combination of non-destructive testing techniques, including nuclear magnetic resonance (NMR) and computed tomography (CT) scanning, to comprehensively analyze the evolution of pores during freeze-thaw cycles. Investigating the migration and redistribution of pore water and its effect on frost heave damage in sandstone during the freeze-thaw process. Finally, the study examines the mechanisms of pores frost heave initiation and propagation in sandstone during freeze-thaw cycles. The results demonstrate that freeze-thaw cycles result in an expansion of pore volume at all scales within the samples. However, the degree of expansion varies, with macropores, mesopores, and micropores exhibiting a less pronounced increase in sequence. During the freeze-thaw process, water in sandstone pores redistributes, moving from larger to smaller pores. The saturation of water increases in micropores, but decreases in mesopores and macropores, thereby rendering micropores more susceptible to frost heave initiation in subsequent freeze-thaw cycles. With repeated freeze-thaw, the expansion of rock pores will continue in the direction of the lowest tensile strength, eventually forming macroscopic cracks. This study provides valuable insights into the mechanisms of freeze-thaw disaster genesis in rock masses. [ABSTRACT FROM AUTHOR]

The injection of CO2 into deep, unmineable coal seams is an effective strategy for reducing greenhouse gas emissions. At depths greater than 800 m, the carbon dioxide transitions to the supercritical state (Sc-CO2). This study investigated the complex interactions between Sc-CO2 and coal, which substantially affected the pore structure, mineralogy, and permeability of the coal. We used low-pressure nitrogen gas adsorption (LP-N2GA) to assess the impact of Sc-CO2 on the pore characteristics of the coal. X-ray diffraction (XRD) was also used to determine the causal factors. We performed comparative triaxial permeability tests before and after Sc-CO2 exposure to evaluate the changes in permeability for various coal types. Our findings suggested that Sc-CO2 exposure markedly increased the complexity of the coal pore structure, which in turn affects coal-rock permeability. Specifically, a 10-day exposure period resulted in considerable increases of 43.5% and 50.9% in the pore volume and the specific surface area, respectively, along with a slight increase of 0.01 nm in the average pore diameter. Furthermore, there were notable decreases in the contents of minerals such as kaolinite, calcite, and pyrite, with decreases of 1.5%, 2.8%, and 2.2%, respectively, whereas the quartz content increased by 3%, indicating that significant mineral dissolution influenced the pore structure. A significant positive correlation was observed between the loss of coal mass and the increase in permeability. The effects of Sc-CO2 were most pronounced in coals with low permeabilities, particularly during the initial phase of saturation. Subsequent saturation cycles and prolonged exposure resulted in a reduced rate for permeability enhancement, which eventually reached a plateau. This study underscores the critical role of Sc-CO2 in long-term geological CO2 storage and improved efficiency for coalbed methane production. [ABSTRACT FROM AUTHOR]

Utilizing recycled concrete aggregate (RCA) is a countermeasure to address the scarcity of landfills and the depletion of natural aggregates. Surface modification techniques have been proposed and implemented to improve the properties of RCA; however, to our best knowledge, few investigations on improving RCA under various pozzolanic slurry concentrations and extended soaking durations have been done. This study comprehensively assessed the properties and microstructure of low-strength RCA treated with cement–fly ash slurry with different concentrations and soaking durations. The purposes of this study were not only to provide the optimal slurry concentration and treatment duration but also to explore the enhancement mechanism of RCA under various treatment conditions. The RCA from concrete with a low-strength grade of 20 MPa was soaked in cement–fly ash slurry at low and high concentrations (i.e., 30% and 70% by mass of RCA, respectively) for 24 and 72 h. The physical and mechanical properties of RCA before and after treatment were evaluated through water absorption and crushing value measurements, respectively. Additionally, the pore structure, Ca(OH)2 contents, surface morphology, and phase compositions of RCAs were evaluated through a mercury intrusion porosimetry test, thermal gravimetric differential thermal analysis (TG-DTA), scanning electron microscopy, and X-ray diffraction (XRD) analyses, respectively. The water absorption of treated RCA reduced by 9.2%–37.9%, whereas the crushing value decreased by 8.6%–26.9% compared with the untreated RCA. The TG-DTA results indicated a 22.3%–43.8% increase in the Ca(OH)2 content of treated RCA. The XRD analysis depicted a higher ettringite (AFt) peak in all treated RCA samples compared with the untreated sample. For both concentrations, with a 24 h treatment, the slurry infiltration effect was clearly observable, whereas the 72 h treatment resulted in the formation of a pozzolanic coating layer on the RCA surface. In conclusion, the optimal slurry concentration and soaking duration were 70% and 72 h, respectively. [ABSTRACT FROM AUTHOR]

The mechanism of steel corrosion in recycled brick powder (RBP)–incorporated concrete remains unclear considering the potential utilization of active RBP for low-carbon design in engineering structures. This study aimed to point the influence of RBP on the corrosion behavior of reinforced concrete under the action of chloride or carbonation. Mortar containing RBP (RBPM) was used in this study to concentrate on the effect of RBP and limit the effect of coarse aggregate. The mechanical, chloride penetration, and carbonation properties of RBPM were first investigated. Then the steel corrosion in reinforced RBPM under the action of chloride or carbonation was evaluated by different electrochemical tests. The underlying mechanisms were elucidated by the chemical composition, pH value, and pore structures of RBPM. The results showed that the compressive strength of mortar decreased 21.7% when 30% RBP was used. The addition of RBP reduced the chloride ion permeability but increased the carbonation depth of RBPM. The corrosion caused by chloride penetration in reinforced RBPM was reduced with a higher corrosion potential and lower corrosion current density, which resulted in an approximately 20% lower mass loss with 30% RBP. However, compared with normal concrete, RBPM suffered an increase in corrosion after carbonation. The corrosion current density and mass loss were greatly increased with increasing the RBP content. When the replacement ratio of RBP was 20%, the mortar was in low corrosion state after carbonation curing for 56 days. This was because a combination of the pozzolanic, filling, and nucleation effect of RBP contributed to a 16.28% lower cumulative pore volume and lower pH of RBPM. Considering the effect of RBP on the mechanical properties and corrosion of reinforce mortar, this study suggested a utilization ratio of 20% for RBP in the practical project. [ABSTRACT FROM AUTHOR]

Influenced by the cyclic fluctuation of reservoir water levels and rainfall, the rocks of reservoir bank slopes have been subjected to alternating wet and dry environments for a long time. This leads to their deterioration and damage, posing a great threat to the stability of the bank slopes. This study investigates the red sandstone of the Baihetan hydropower station as the research object, and the structural deterioration of the red sandstone under wetting-drying cycles of sodium sulfate salt solution were investigated by carrying out wetting-drying cycles test, CT scanning test, digital core modeling and seepage simulation. The results show that the mass loss rate (a) and permeability (k) of the red sandstone increase exponentially with the number of cycles (N). The total porosity, effective porosity, and effective porosity ratio initially decrease and then increase with N. The study suggests that the structural deterioration of the red sandstone under wetting-drying cycles in the salt solution results from the combined effect of dissolution and salt crystallization. In the early stages, structural damage is mainly due to calcite, plagioclase feldspar and other minerals in solution dissolution. In the middle stages, the rocks undergoes damage from both salt crystallization and dissolution. In the later stages, the effect of salt crystallization is gradually weakened and rock dissolution becomes the dominant factor causing rock damage again. The results of the study provide an important theoretical basis for the long-term stability evaluation of reservoir slopes at the Baihetan hydropower station. [ABSTRACT FROM AUTHOR]

Activated carbon paper is a type of porous carbon material with a highly developed pore structure and a large specific surface area. It finds extensive applications in adsorption, complexation, and catalyst support. To prepare high-performance activated carbon paper, this study investigates the changes in performance and structure of Poly(p-phenylene terephthalamide) (PPTA) paper under CO2 activation, ZnCl2 activation, H3PO4 activation, and NaOH activation conditions. The research reveals that carbon paper after CO2 activation has a certain tensile strength (0.36 MPa), while chemically activated carbon paper lacks tensile strength. Incorporating 15% carbon fiber (CF) into PPTA paper increases the tensile stress (1.26 MPa) and tensile strain (4.18%) of the activated carbon paper. NaOH-activated carbon paper has the highest specific surface area (1321.6 m2/g), the most disordered carbon structure (ID/IG = 1.22), the lowest carbon yield (23.9%), and a pore rate 4.16% higher than that of CO2-activated samples. The activated carbon paper prepared by ZnCl2 activation has the highest content of C = N bonds, with the nitrogen content of pyridine increasing by 31.8% compared to CO2 activation. This indicates that ZnCl2 protects the N elements in PPTA paper during the activation process, preventing their decomposition during carbonization. The activated carbon paper prepared by H3PO4 activation has the lowest electrical conductivity (1.62 S/cm). [ABSTRACT FROM AUTHOR]

This research systematically investigates the influence of raw material particle size and calcium content on the geopolymerization process to gain insight into the physical and mechanical properties of geopolymer gels, including setting time, fluidity, pore structure, compressive strength, and leaching characteristics of encapsulated Cr3+ heavy metal ions. Utilizing a diverse range of particle sizes of metakaolin (MK; 3.75, 7.5, and 12 µm) and fly ash (FA; 18, 45, and 75 µm), along with varied calcium levels, this study assesses the dual impact of these factors on the final properties of both metakaolin- and fly-ash-based geopolymers. Employing sophisticated analytical techniques such as Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and Nuclear Magnetic Resonance (NMR), the research meticulously documents alterations in chemical bonding, micro-morphology, and pore structures. Key findings reveal that reducing the size of MK and FA particles to 3.75 and 18 µm, respectively, enhances the compressive strength of their matrices by 128.37 and 297.58%, respectively, compared to their original values (63.59 and 33.87 MPa, respectively) at larger particle sizes. While smaller particle sizes significantly bolster compressive strength, they adversely affect slurry flow and reduce the leaching rates of Cr3+ from MK- and FA-based matrices, reaching 0.42 and 0.75 mg/L at 3.75 and 18 µm, respectively. Conversely, increased calcium content markedly enhances setting times and contributes to the formation of dense microstructures through the production of calcium aluminate silicate hydrate (C-A-S-H) gels, thus improving the overall curing performance and durability of the materials. These insights underline the importance of fine-tuning particle size and calcium content to optimize geopolymer formulations, offering substantial benefits for varied engineering applications and promoting more sustainable construction practices. [ABSTRACT FROM AUTHOR]

Solid waste recycling plays a crucial role in environmental protection and energy conservation. This study explores the impact of the modulus of the alkaline activator on the dry density, water absorption rate, thermal conductivity, electromagnetic wave absorption, and compressive and flexural strength of rice husk ash (RHA)‐foamed composites. Additionally, the foamed composite's micropore structure and hydration characteristics were characterized. For the first time, the study reveals the correlation between the pore structure, hydration products, and hardening properties of alkali‐activated RHA‐foamed composites. The study found that decreasing the modulus of the alkaline activator increased the amount of OH− ions available in the gel, and the number of micropores (r ≤ .1 µm) in the foamed composites increased from 7.1903% to 21.3156%. This resulted in the refinement of pore sizes and optimization of heat transfer paths. Meanwhile, increasing the C–S–H gel composition in the hydrated products improved its compressive and flexural strength. When the alkali modulus reaches 1, 28 days foamed composites display compressive strength of 8.33 MPa and thermal conductivity of .1404 W/(m·K). Furthermore, the superior pore structure improved the electromagnetic wave absorption of the foamed composites, yielding a reflection loss value of −12.02 dB. [ABSTRACT FROM AUTHOR]

In this paper, the effect of basalt fiber (BF) on the frost resistance of concrete under different curing conditions was investigated, and its frost resistance mechanism was analyzed. Three different curing conditions (normal curing, short-term curing, and seawater curing) were adopted, and concrete with different BF volume contents was designed. Freeze-thaw (FT) tests were carried out using the rapid freezing method to test the frost resistance of basalt fiber reinforced concrete (BFRC). Additionally, the mass loss rate (MLR), relative dynamic modulus of elasticity (RDME) change, and compressive strength reduction of specimens during the freeze-thaw cycles (FTCs) were evaluated. The results show that when the BF content is 0.15%, under normal curing, short-term curing, and seawater curing conditions, the residual compressive strength of BFRC after FTCs was increased by 5.4%, 28.1%, and 30.9%, respectively, compared to plain concrete. By incorporating BF into concrete, the development of microcracks can be effectively retarded, and damage generation during FTCs can be reduced. In addition, the microscopic morphological characteristics and pore structure characteristics of concrete further elucidate the frost resistance mechanism of BFRC from a microscopic perspective. [ABSTRACT FROM AUTHOR]

The pore structure of coal plays a key role in the effectiveness of gas extraction. Conventional hydraulic fracturing techniques have limited success in modifying the pore structure using clean fracturing fluid (CFF), and the stimulating effects of ultrasonic can enhance the effectiveness of CFF in modifying coal pore structures. To research the effects of ultrasonic stimulation on the pore structure of medium to high-rank coal when using CFF, this study employed mercury intrusion porosimetry (MIP) and low-temperature nitrogen adsorption (LT-N2A) methods to analyze the changes in pore structures after cooperative modification. The results indicate that the pore volume and surface area of medium to high rank coal exhibit an increase and followed by a decrease with increasing Ro,max values, while the average pore diameter and permeability demonstrate a decrease and followed by an increase with Ro,max. Although there are some variations in the results of MIP and LT-N2A analysis for different pore size ranges, the overall findings suggest that ultrasonic stimulation in conjunction with CFF effectively alters the coal pore structure. The most significant improvement was observed in coking coal, where pore volume increased by 22%, pore area decreased by 11% and tortuosity decreased by 47%. The improvement of lean coal is the smallest, the pore volume increases by about 7%, and the surface area decreases by about 14%. It is found that the modification of coal pore volume is mainly concentrated in transition pores and macropores. These research outcomes provide valuable insights into the application of ultrasonic technology in coalbed gas extraction. [ABSTRACT FROM AUTHOR]

The Permian Fengcheng Formation (P1f.) in the Hashan area, situated on the southwestern margin of the Junggar Basin, has witnessed a remarkable breakthrough in shale oil exploration in recent years with nearly 789 million tons of shale oil resources. As a unique set of mixed sedimentary shales, the Fengcheng Formation in the Hashan area is characterized by mixed sedimentation of terrigenous siliciclastic sediments, authigenic minerals, and tuffaceous materials. However, the understanding of pore characteristics in the mixed sedimentary reservoir still remains limited, prohibiting accurate estimation of the oil content and insights into oil mobility. Scanning electron microscopy (SEM), X-ray diffraction (XRD), mercury injection capillary pressure (MICP), nuclear magnetic resonance (NMR), X-Ray Computer Tomography (X-CT), and geochemical analysis were performed to investigate the pore size distribution and main controlling factors of the mixed sedimentary reservoir. Results showed that the main pore types in the mixed sedimentary reservoir are intergranular pores and dissolution pores. The pores of the P1f. mixed shales in the Hashan area were classified into II-micropores (< 25 nm), I-micropores (25–100 nm), mesopores (100–1000 nm) and macropores (> 1000 nm). In general, the mixed sedimentary rocks of P1f. formation feature few macropores but a large number of micropores and mesopores. The CS exhibits the most favourable physical properties among all lithofacies. It is concluded that the abundance and maturity of organic matter, mineral composition, sedimentary structure, and diagenesis of reservoir together impact the pore structure in the mixed sedimentary reservoirs. The maturity of organic matter and the content of tuffaceous minerals are the most significant in influencing the pore structure of P1f. shales. Overall, the pore structure of complex lithologic reservoir formed by mixed deposition and its influence on physical properties are studied, and the characteristics of the microscopic pore-throat system of the dominant lithofacies in the Hashan area are clarified, which is of great significance as a guide for the exploration and development of mixed sedimentary reservoirs in continental shale oil in China. [ABSTRACT FROM AUTHOR]

Nowadays, some fracking fluids can enable resourceful extraction of coalbed methane and reduce greenhouse gas emissions. However, their toxicity or corrosiveness will cause harm to downhole workers and pollute groundwater resources. Thus, five kinds of clean composite fracturing fluids were developed in this paper by using starch solution as the matrix and adding various preparations. The change rule of methane adsorption capacity by microstructure changes of coal samples was investigated systematically, and the optimal composite fracturing fluid was determined. The results showed that the new fracturing fluid increased the degree of aromatic ring condensation by 43.3% and the average pore size by 52.1%. Also, the adsorption constants of a value decreased by 11.6% and b value decreased by 23.9%, which can remarkably reduce the methane adsorption. The experimental results provide theoretical support for the clean production of coalbed methane. [ABSTRACT FROM AUTHOR]

Inorganic membranes are used to effectively capture particulate matter in dust without causing secondary pollution. However, fine dust particles accumulate on the surface and penetrate the structure of inorganic membranes, thereby degrading their performance. This study investigated the influence of the precoating of inorganic membranes with needle‐shaped wollastonite particles on their regeneration efficiency. The filter‐cake‐curing technique was employed, and the results were obtained by characterization methods, including scanning electron microscopy and energy‐dispersive spectroscopy. The mechanism for controlling membrane fouling was examined based on the quantity and depth of particle penetration to the filtration medium and pore structure of the filter cake. The results demonstrated that precoating can prevent fine particles from penetrating the membrane pores, thereby alleviating pore blocking in inorganic membranes. Furthermore, this increased the porosity and decreased the fractal dimension of the pore in the cake, thereby reducing the structural complexity and resistance during cake removal. The regeneration efficiency of the inorganic membrane increased from 59.4% without a precoating to 94.1% when wollastonite particles with an aspect ratio of 10 were used for precoating. [ABSTRACT FROM AUTHOR]

The global increase in water consumption has led to significant domestic wastewater (DW), with only 55.5% being treated properly. Discharging untreated DW has serious environmental consequences and wastes a valuable resource. Therefore, this study proposed replacing 25%–100% potable water with DW in preparing alkali-activated slag (AAS) mortars. The results indicated that the use of DW promoted the hydration of AAS. Pore structure analysis revealed that DW enhanced the formation of gel pores while reducing mesopores, resulting in a higher elastic modulus and a denser microstructure of AAS mortars. Consequently, the compressive strength of AAS mortars increased by 9.0%–20.3%, and the autogenous shrinkage decreased by 7.5%–34.5%. Moreover, replacing 100% of potable water with DW maximizes its utilization and improves the cost–benefit and eco-efficiency of AAS mortars by 9.4% and 10.0%. These findings demonstrate the feasibility of using DW as mixing water for AAS mortars, offering a sustainable approach to the utilization of DW. [ABSTRACT FROM AUTHOR]

Based on investigated mechanical properties of alkali residue-based foamed concrete (A-FC), this paper presents a comprehensive examination of the microstructural features of A-FC and their impact on compressive properties. A detailed investigation of the compressive performance and pore structure characteristics was conducted through compression tests and low-field nuclear magnetic resonance (NMR) tests. The results demonstrate that the primary pore size in A-FC falls within the microscale, and the pores can be categorized into three types—gel pores, capillary pores, and air voids. In addition, the T2 spectrum of A-FC exhibits three distinct relaxation peaks, each of which is attributed to different water components, i.e., adsorbed water, pore water, and free water. As the pore size, air void ratio, and porosity increase, the compressive strength of A-FC decreases. The main reasons for the increased in strain in low-strength A-FC include compression at the bottom, internal stress dissipation through the pore structure, and changes in the failure mode. [ABSTRACT FROM AUTHOR]

In this study, we investigate the water and chloride ion (Cl−) transport properties of aeolian sand mortar (ASM) in an unsaturated state. Capillary absorption tests were conducted on ASM with varying water-to-binder ratios and different concentrations of chloride salts in clear water solutions. The Cl− content at different depths in ASM was determined using layered drilling, powder extraction, and chemical titration. The relationship between water and Cl− transport properties under capillary absorption was examined. The results indicate that moisture serves as a transport medium for Cl− in mortar, but its transport depth is significantly smaller than that of water, revealing a non-synchronization between the two transports. The transmission depth and capillary absorption ratio of water in the mortar decrease with increasing initial saturation. A linear relationship between water and Cl− transport depths is observed within the first 7 days of capillary absorption. Beyond 7 days, the water transport rate gradually slows down, while Cl− continues to be transported due to the presence of an ion concentration gradient. As the initial saturation increases, the percentage of gel pores decreases, and the percentage of transition pores and capillary pores in the matrix increases. Finally, incorporating the theory of unsaturated capillary water absorption, we introduce Boltzmann variables and develop a predictive model for the relative water content distribution under capillary water absorption in ASM. This study provides a theoretical foundation for the widespread application of ASM, and the proposed research model offers new insights into the underground environment and the durability of concrete structures affected by moisture transport. [ABSTRACT FROM AUTHOR]

The hydration reaction mechanism of geopolymers is intimately linked to their composition and structure. Additionally, pore structure characteristics play a vital role in the properties of hardened geopolymer pastes, significantly influencing the material's strength, impermeability, and thermal conductivity. In this study, fly ash geopolymer (FAG) was synthesized by utilizing NaOH, Na2SiO3 , and low-calcium fly ash. The pore structure characteristics of FAGs were analyzed using mercury intrusion porosimetry (MIP), and the fractal dimension of FAGs was calculated using the Menger sponge model (Df) and a fractal model based on thermodynamic relationships (Ds). Fourier infrared spectroscopy (FTIR), thermogravimetric differential thermal (TG/DTA), and scanning electron microscopy secondary electron phase (SEM-SE) were used to test the composition of the hydration products of FAGs and their microscopic morphology. The results showed that after 90 days of maintaining ambient temperature, the porosity of FAG is between 20% and 30%, and the most available pore size is 10–50 nm. The fractal dimension calculated using the analytical model based on thermodynamic relations can more comprehensively determine the pore structure characteristics of FAG. The geopolymerization reaction process of fly ash particles can be categorized into four primary processes, forming an amorphous aluminosilicate gel as the hydration product. [ABSTRACT FROM AUTHOR]

[Display omitted] • Sub-nanopores are verified to be capable of promoting the desolvation of [Zn(H2O)6]2 + to optimize the ion storage performance of the carbon cathodes in ZHSs. • A new strategy is proposed to study the dehydration behaviors of [Zn(H2O)6]2 + in carbon cathodes. • Superior electrochemical performance especially exceptional fast charge/discharge ability is realized for carbon cathodes of ZHSs. Aqueous Zn-ion hybrid supercapacitors (ZHSs) are attracting significant attention as a promising electrochemical energy storage system. However, carbon cathodes of ZHSs exhibit unsatisfactory ion storage performance due to the large size of hydrated Zn-ions (e.g. , [Zn(H 2 O) 6 ]2+), which encumbers compact ion arrangement and rapid ion transport at the carbon-electrolyte interfaces. Herein, a porous carbon material (HMFC) with abundant sub-nanopores is synthesized to optimize the ion storage performance of the carbon cathode in ZHSs, in which the sub-nanopores effectively promote the dehydration of hydrated Zn-ions and thus optimize the ion storage performance of the carbon cathode in ZHSs. A novel strategy is proposed to study the dehydration behaviors of hydrated Zn-ions in carbon cathodes, including quantitatively determining the desolvation activation energy of hydrated Zn-ions and in-situ monitoring active water content at the carbon-electrolyte interface. The sub-nanopores-induced desolvation effect is verified, and its coupling with large specific surface area and hierarchically porous structure endows the HMFC cathode with improved electrochemical performance, including a 53 % capacity increase compared to the carbon cathode counterpart without sub-nanopores, fast charge/discharge ability that can output 46.0 Wh/kg energy within only 4.4 s, and 98.2 % capacity retention over 20,000 charge/discharge cycles. This work provides new insights into the rational design of porous carbon cathode materials toward high-performance ZHSs. [ABSTRACT FROM AUTHOR]

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To mitigate the exploration and development risks, it is necessary to have a deeper understanding of the formation mechanism and gas-bearing control factors of low-resistance shale reservoirs. This study focuses on typical shale gas wells (including low-resistivity wells) in Luzhou area, and identification criteria for low-resistance shale reservoirs are redefined as resistivity less than 10 Ω·m and continuous formation thickness greater than 6 m. At the macro scale, low-resistivity shale reservoirs are characterized by high clay mineral content and high water saturation with low gas content. At the micro scale, the main pore size is less than 10 nm, with a small total pore volume but a large specific surface area. Shale reservoirs close to the Class II fault have high water saturation and strong compaction, which hinders the mutual transformation between minerals, resulting in low-resistivity shale with high clay mineral content, small pore volume, and pore size, which promotes the enhancement of reservoir conductivity. The gas content of low-resistivity shale reservoirs is lower, because the distance from the Class II fault is closer, resulting in high water saturation and strong diagenesis, which is not conducive to pore development and shale gas accumulation. When the water saturation exceeds 40%, the pore volume of shale reservoirs rapidly decreases to as low as 0.0074 cm3/g. In order to reduce the risk of exploration and development of the area, the well location deployment needs to be more than 2.8 km away from the Class II fault. [ABSTRACT FROM AUTHOR]

The exploration and development of conventional oil and gas resources are becoming more difficult, and the proportion of low-permeability reservoirs in newly discovered reservoir resources has expanded to 45%. As the main focus of the oil industry, the global average recovery rate of low-permeability reservoir resources is only 20%, and most crude oil is still unavailable, so our understanding of such reservoirs needs to be deepened. The microscopic pore structure of low-permeability reservoir rocks exhibits significant complexity and variability; reservoir evaluation is more difficult. For elucidating the internal distribution of storage space and the mechanisms influencing seepage, we focus on the low-permeability sandstone reservoir of the Shahejie Formation, located on the northern slope of the Chenjiazhuang uplift, Bohai Bay. Employing a suite of advanced analytical techniques, including helium expansion, pressure pulse, high-pressure mercury intrusion (HPMI), and micro-computed tomography (micro-CT) scanning, we examined the main pore–throat size affecting reservoir storage and seepage in the reservoir at both the micrometer and nanometer scales. The results reveal that pores with diameters exceeding 40 μm are sparsely developed within the low-permeability reservoir rocks of the study area. However, pores ranging from 0 to 20 μm predominate, exhibiting an uneven distribution and a clustered structure in the three-dimensional pore structure model. The pore volume showed a unimodal and bimodal distribution, thus significantly contributing to the storage space. The main sizes of the reservoir in this study area are 40–80 μm and 200–400 μm. Micron-sized pores, while present, are not the primary determinants of the reservoir's seepage capacity. Instead, coarser submicron and nano-pores exert a more substantial influence on the permeability of the rock. Additionally, the presence of micro-fractures is found to enhance the reservoir's seepage capacity markedly. The critical pore–throat size range impacting the permeability of the reservoir in the study area is identified to be between 0.025 and 0.4 μm. [ABSTRACT FROM AUTHOR]

This study primarily investigates the effect of fly ash (FA) content on the mechanical properties and hydration performance of alkali-activated ground granulated blast furnace slag cement (AAGC) and compares the related properties with ordinary Portland cement (OPC). Additionally, we examined the hydration products; performed thermal analysis, MIP, and SEM; and determined chemically bound water and pH values of AAGC. The compressive strength of AAGC showed a retrogression phenomenon from 3 to 28 days, with the 14-day and 28-day compressive strengths of AAGC being higher than those of OPC. The AAGC with 20% FA content exhibited the highest 28-day compressive strength (75 MPa). The hydration heat release rate curve of OPC and AAGC was divided into the initial induction period, induction period, acceleration period, deceleration period, and steady period. As FA content increased, the 28-day pore volume of AAGC increased, while pH values and chemically bound water decreased. SEM images of AAGC with low FA content showed more microcracks. [ABSTRACT FROM AUTHOR]

Water reducer and water-repellent admixture are very important in improving the workability and durability of cement-based materials. However, the synergistic effect of the two types of admixtures has not been well investigated. In this study, polycarboxylate ether-based superplasticizer (PCE) and octyltriethoxysilane (OTS) were adopted as water reducer and water-repellent admixture, respectively. Their synergistic effect on the fluidity, compressive strength, and water absorption rate of cement-based materials was investigated. Particularly, the pore structure and hydration state of cement paste were analyzed using 1H Low-Field Nuclear Magnetic Resonance (1H LF NMR). The result showed that the fluidity of cement paste containing different dosages of PCE was reduced by 5–10 mm by incorporating 1% OTS, and the compressive strength at the early age of 3 d of mortar containing high PCE dosage of 0.25% decreased up to 15% by using 1% OTS. In contrast, the compressive strength of mortar containing 0.20% PCE was slightly enhanced by the addition of 1% OTS. 1H LF NMR analysis revealed that the combination of PCE and OTS would increase the pore size and total pore volume of cement paste, and more bleeding water would be generated at high PCE dosage. The intensity-weighted T2 values of the main peak ( T 2 ¯ ) implied that both PCE and OTS produced a retardation effect on cement hydration. However, the water absorption rate decreased by 46.6% despite the increase in pore size and total pore volume. The conflict phenomenon powerfully revealed that the internal hydrophobic treatment by OTS has been successfully achieved. Overall, the combination of 0.20% PCE and 1% OTS exerted a positive synergistic effect in improving the compressive strength and water-repelling ability of cement-based materials, which is meaningful for improving their durability and service life. [ABSTRACT FROM AUTHOR]

In this study, the adsorption of phenoxyacetic acid (PAA) and its chlorinated derivatives, including 4-chlorophenoxyacetic acid (4CPA) and 2,4-dichlorophenoxyacetic acid (2,4-D), on activated carbons (ACs) from corn kernels (AC-K), corn leaves (AC-L), and corn silk (AC-S) were investigated. The adsorption kinetics followed the pseudo-second-order model, and the film diffusion was the rate-limiting step. The adsorption rate increased in the order PAA < 4CPA < 2,4-D and was correlated with the porous structure (mesopore volume) of these ACs. The Langmuir isotherm models best fit the experimental data; PAA was adsorbed least and 2,4-D most preferentially. The observed trend (PAA < 4CPA < 2,4-D) was positively correlated with the molecular weight of the adsorbates and their hydrophobicity while being inversely correlated with their solubility in water. The adsorption for 2,4-D, according to the Langmuir equation, is equal to 2.078, 2.135, and 2.467 mmol/g and SBET 1600, 1720, and 1965 m2/g, respectively. The results for other herbicides showed a similar correlation. The adsorption of phenoxy herbicides was strongly pH-dependent. The ACs produced from corn biomass can be an eco-friendly choice, offering sustainable products that could be used as efficient adsorbents for removing phenoxyacetic herbicides from water. [ABSTRACT FROM AUTHOR]

Abstract In order to tackle the issue of excessive coal dust and hydrogen sulfide (H2S) concurrently in underground coal mines, an alkaline dust suppressant was formulated by combining surfactant sodium sec-alkyl sulfonate (SAS60) and sodium carbonate (Na2CO3) at a certain mass ratio, meant for injection into coal seams. This study principally targeted long-flame coal extracted from Hequ County, located in Shanxi Province, China. The objective was to investigate and analyze the underlying process of how alkaline dust suppressants affect the wettability of coal. A comprehensive strategy including contact angle determination, Fourier transform infrared absorption spectrometer(FTIR) analysis, low-temperature nitrogen adsorption tests, scanning electron microscope(SEM) experimental studies, and molecular dynamics simulations was employed for this examination. The results revealed that merging Na2CO3 with SAS60 could reduce the coal’s contact angle. Despite the core structure of the coal surface staying unchanged after alkaline dust suppressant treatment, a rise in the number of hydrophilic functional groups was observed. This count notably surpassed the amount of hydrophobic functional groups, consequently boosting the coal’s hydrophilicity. The permeability of the examined coal specimens was chiefly affected by the existence of macropores and mesopores. Processing with 0.05 wt% SAS60 and 1.0 wt% Na2CO3, the coal acquired additional pores and cracks, causing an upswing of average pore size by 25.79% and a 30.64% increase in the maximum gas adsorption. This facilitated more straightforward infiltration of water into the coal dust. Molecular dynamics simulation outcomes indicated a closer affiliation between coal and water following the incorporation of Na2CO3. It led to a heightened activity in water molecule movement, fortifying intermolecular electrostatic interactions, and fostering the creation of hydrogen bonds. Consequently, this improved the coal’s wettability. The increase in the mass fraction of Na2CO3 directly corresponds to a more considerable enhancement in the solution’s ability to wet the coal. The outcomes of the molecular dynamics simulation validated the experimental results’ precision.

Abstract Quaternary mudstone biogas reservoirs in the Qaidam Basin have shown great potential. However, complex pore structures with high clay contents and high heterogeneity limit the understanding of the storage and migration principles of these reservoirs. In this paper, HPMI and nitrogen adsorption experiments, in combination with NMR experiments under water saturation, centrifugation, various drying temperatures and other conditions, were adopted to determine the pore structure characteristics. Specifically, the reservoir space types and pore radius distribution characteristics were clarified. The cutoff values for different types of pores were identified based on the water-saturated mudstone NMR T2 spectra for full aperture distribution scales jointly characterized by mercury injection and nitrogen adsorption experiments. Furthermore, the three pore components and the saturation of different fluids were obtained. The research results indicate that the mudstone biogas reservoir has developed various reservoir spaces, and the pore size is primarily in the micronanometer range. The average total porosity reaches 27.28%, but the proportion of movable water pores is only 9.23% with poor fluid mobility, and the fluids in the pores are mostly capillary-bound water and clay-bound water. Among the different lithologies, argillaceous sand is more likely to become a good production layer.

The supercritical CO2 fracturing technology has significant potential for developing coal fracture and increasing gas permeability. Understanding its influence mechanism on coal is crucial for advancing research and practical engineering applications of this technology. In order to accurately characterize the changes of pore-fracture structures and mechanical properties of the high-rank coal under the action of supercritical CO2, taking high-rank coal from Zhongmacun Mine of Coking Coal Group as the experimental object, the changes of pore and fracture structure of the high-rank coal before and after supercritical CO2 treatment were analyzed by Brunauer-Emmet-Teller (BET) and Mercury intrusion porosimetry (MIP), and the mechanical and acoustic emission characteristics of the high-rank coal before and after supercritical CO2 treatment were tested by combining with uniaxial compression and acoustic emission experimental system. The results show that supercritical CO2 had a good effect on pore expansion and permeability enhancement of the high-rank coal. After supercritical CO2 treatment, the percentage of micro-small pore volume of the high-rank coal decreased, the percentage of medium and large pore volume increased, and the total pore volume of the high-rank coal increased after supercritical CO2 treatment. Supercritical CO2 had an obvious deteriorating effect on the mechanical properties of the high-rank coal. The uniaxial compressive strength and modulus of elasticity of the high-rank coal after supercritical CO2 treatment were significantly decreased by 70.06% and 55.56%, respectively. The acoustic emission signal activity of the high-rank coal after supercritical CO2 treatment decreased significantly, and the uniaxial compressive time, cumulative ring counts and cumulative energy of the high-rank coal were reduced by 98.68 s, 95.14×103, and 200.30 V·ms, with the decreases of 46.65%, 37.65%, and 50.03%, respectively. The proportion of accumulated ringing count and accumulated energy in the quiet period of high rank coal increased significantly, while the proportion in the slow period decreased. The proportion in the surge period of accumulated ringing count decreased, while the proportion of accumulated energy increased slightly. The research results will be conducive to promoting the mechanism research, and have certain guiding significance for the coalbed methane extraction of deep high-rank coal and CO2 underground storage.

To produce carbon materials with superior performance for supercapacitors, the study was conducted to prepare activated carbon based on penicillin waste bacterial residue with superior hardness and electrical properties by KOH activation method. During the production process, it was considered that the pore structure and electrical properties of activated carbon were greatly related to the activation temperature and impregnation ratio. Therefore, the study was conducted to experimentally analyze the optimum activation temperature and the optimum impregnation ratio in this production process, so as to further optimize the performance of this bacterial residue-based activated carbon. The results showed that the activated carbon samples with an activation temperature of 700 ◦C and an impregnation ratio of 3.0:1 had a maximum surface area and microporous area of 956 m^2/g and 794 m^2/g, respectively, and total pore volume and total microporous volume of 0.786 cm^3/g and 0.624 cm^3/g, which had a stable and rich pore structure. The charging and discharging times of the activated carbon electrodes were about 792 s and 54 s at current densities of 0.5 A/g and 10 A/g. In addition, the capacitance retention of the activated carbon was 86.1% and it had a shorter impedance curve. It indicates that the penicillin waste bacterial residue prepared in the study is suitable as an electrode material for supercapacitors and can have better performance in industrial applications.

This is an article in the field of ceramics and composites. The mix proportion of limestone powder cement is designed based on the mixture design principle, and the effects of limestone powder content and particle size on the mechanical properties of limestone powder Portland cement system are studied. The hydrate phase and microporous structure of portland cement paste mixed with 0.44 mm and 0.025 mm limestone powder were analyzed by X-ray diffraction (XRD) and low field nuclear magnetic resonance (NMR). The results show that the two limestone powders have a negative effect on the early compressive strength. However, with the progress of hydration, limestone powder within a certain dosage range can enhance the later strength of cement. When the dosage exceeds this range, the compressive strength decreases gradually with the increase of dosage. Although the addition of limestone powder produces hydrated calcium carboaluminate in the hydration products which is conducive to the mechanical properties of cement stone, its coarsening of microporous structure greatly reduces the compressive strength of limestone powder cement specimens when the content of limestone powder exceeds a certain value.

Abstract To further raise the gas extraction efficiency of the tight sandstone, the liquid nitrogen (LN2) freezing-thawing cycles method can be employed to improve the permeability of the low-permeability reservoirs. Permeability is generally regarded as a macroscopic description of the pore structure and usually has functional relationship to pore structure properties. The permeability of the rock is closely related to the change of microscopic pore structure. The permeability of rock depends on how the subzero temperatures changed the microscopic pore structure of rock, but it has not yet been confirmed obviously. In this study, the nuclear magnetic resonance (NMR) technique was adopted to investigate the pore structure evolution law and permeability of the tight sandstone with different LN2 freezing-thawing cycles. The results demonstrate that the LN2 freezing-thawing cycles promotes pore development and micro-fracture connection, and enhances the pore connectivity. The proportion of meso-pores, macro-pores and micro-fractures in the sandstone samples increases significantly, which provides a channel for the sandstone gas flow and extraction. Total porosity and effective porosity of the samples present a trend of rapid increase as the number of LN2 freezing-thawing cycles increasing, while the residual porosity decreases as the number of LN2 freezing-thawing cycles increasing. Coates model, SDR model (mean T2 model) and PP model were used to calculate and evaluate the permeability of the samples subjected to different LN2 freezing-thawing cycles. Furthermore, PP model can provide a better permeability estimate than the classical Coates and SDR model.