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Taking the tight sandstone reservoir of the Sulige gas field in Ordos Basin as an example, the pore size distribution, pore morphology and pore type of the reservoir are revealed by a variety of comprehensive experimental analysis methods. The pore throat was distinguished by nuclear magnetic resonance, and the radius distribution of the pore throat was determined. A tight reservoir pore structure classification model is used to accurately classify pore structure types and evaluate reservoir seepage characteristics. The experimental results show that the pores in the study area are mainly secondary solution pores, hetero-basic pores, intergranular pores and micro-fractures. From the three-dimensional pore network, it is observed that the pore shape is mainly columnar and spherical, the distribution is not uniform, and there are many isolated pores in tight sandstone. The NMR T2 spectrum has bimodal characteristics, indicating that the aperture is mainly distributed in two ranges. A new pore structure classification parameter PSCI is determined by using the improved K-C equation. Using this classification model, the tight sandstone samples in the Sulige gas field are divided into four categories, and the pore relationships of various pore structures are obtained by fitting the pore relationship curves according to the categories, which is helpful to predict the permeability more accurately through the porosity.

Confinement of fluorescent dyes is known to enhance fluorescence properties by reducing aggregation and restricting molecular motion, but few studies have attempted to modulate the extent of confinement. In this work, we explored extreme confinement by exploiting the rigid structure of metal–organic frameworks (MOFs). Other than the commonly known restriction of peripheral substituents in fluorescent molecules for aggregation‐induced emission (AIE)‐like effects, the more powerful confinement surprisingly led to buckling of the chromophore core, leading to reduced fluorescence lifetime. We name these effects buckling‐induced quenching (BIQ). By studying 14 dyes in zeolitic‐imidazolate framework 8 (ZIF8), we systematically analyzed their confined behaviors, establishing strong correlations: The reduction of chromophore planarity always leads to a decrease of fluorescence lifetimes, whereas reduction in the longest dimension of the confined molecule, while maintaining chromophore planarity, always leads to an increased lifetime. Confinement in the larger cavities of ZIF71 leads to signs of alleviation, in good agreement with our hypotheses. The BIQ effects provide an important complement for the well‐known confinement effects, and the extreme confinement serves also as an important reference for more subtle effects in various applications. This study investigates the behavior of 14 fluorescent dyes under extreme confinement in metal–organic frameworks. A dragonfly illustration analogizes three states: free flight for unconfined dyes, folded wings for AIE‐like effects, and buckled bodies for BIQ effects. The visual metaphor highlights how extreme spatial restriction alters molecular conformation and fluorescence.

Superabsorbent polymers (SAPs) are used as internal curing agents in cementitious materials, which reduce autogenous shrinkage in concrete as they have a low water-to-cement ratios and improve the freeze–thaw resistance. However, the compressive strength of concrete may also be reduced due to additional voids in the hydrated cement matrix. In this study, we fabricated a delayed absorption type of SAP (I-SAP) composed of cross-linked modified acrylate and studied its absorption characteristics and effect on compressive strength after 28 days. Furthermore, the effect of curing conditions on the strength of concrete and hydrated cement paste with SAP were investigated. The absorption capacity of I-SAP in the synthetic pore solution and deionised water was examined and compared with that of a conventional SAP, and the former was absorbed more by I-SAP. The results revealed that the compressive strength of concrete increased with the addition of I-SAP, particularly with the curing condition of 60% RH. Although the compressive strength of hydrated cement paste with I-SAP reduced in water or sealed curing conditions, no loss of strength in the paste cured at 60% RH was seen. The cement matrix densification due to hydration of belite around the SAP surface is the main mechanism for strength development in concrete cured at sealed and 60% RH. However, the voids formed by SAP control the compressive strength of hydrated paste.

Nanoscale pore structure characteristics and their main controlling factors are key elements affecting the gas storage capacity, permeability, and the accumulation mechanism of shale. A multidisciplinary analytical program was applied to quantify the pore structure of all sizes of Xiamaling shale from Zhangjiakou, Hebei. The result implies that Mercury injection porosimetry (MIP) and low-pressure N2 curves of the samples can be divided into three and four types, respectively, reflecting different connectivity performances. The maximum CO2 adsorbing capacity increases with increasing total organic carbon (TOC) content, pore volume (PV), and surface area (SA) of the micropores are distributed in a three-peak type. The full-scale pore structure distribution characteristics reveal the coexistence of multiple peaks with multiple dominant scales and bi-peak forms with mesopores and micropores. The porosity positively correlates with the TOC and quartz content, but negatively correlates with clay mineral content. Organic matter (OM) is the main contributor to micropore and mesopore development. Smectite and illite/smectite (I/S) assist the development of the PV and SA of pores with different size. Illite promotes the development of the nanoscale PV, but is detrimental to the development of the SA. Thermal maturity controls the evolution of pores with different size, and the evolution model for the TOC-normalized PVs of different diameter scales is established. Residual hydrocarbon is mainly accumulated in micropores sized 0.3 to 1.0 nm and mesopores sized 40 nm, 2 nm and less than 10 nm. Since the samples were extracted, the pore space occupied by residual hydrocarbon was released, resulting in a remarkable increase in PV and SA.

Carbonate rock is a critical reservoir for China’s onshore oil and gas exploration. Carbonate reservoirs in different regions significantly differ in sedimentary and diagenesis processes and factors affecting their petrophysical and seismic rock physics properties. Therefore, it is critical to analyze the corresponding properties of carbonate rocks in different regions. Based on systematic petrological, rock microstructure, physical property, and seismic elastic characteristic measurements of deep carbonate reservoir samples in the Tarim Basin, the variation laws and influencing factors of the samples’ physical and seismic elastic properties are analyzed. Based on these measurements, the variation patterns and influencing factors of petrophysical and seismic rock properties of rock samples are analyzed. The results show that the carbonate pore structure controls the overall variations of petrophysical and seismic rock physical properties of carbonate samples, and it is challenging to build a simple statistical model of porosity—permeability, porosity—velocity, and density—velocity. P- and S-velocities correlate well, and the P-and S-velocity ratio is a good index for rock typing. For tight carbonate samples, apparent velocity dispersion at a seismic exploration frequency band (5–200 Hz) can be observed, and the pore structure controls the velocity dispersion and attenuation features. Carbonate samples with crack-dissolution pores show moderately stronger velocity dispersion than samples with dissolution and microcrack pores. The pore aspect ratio and the frame flexibility factor (γ) calculated from the seismic rock physics model correlate well with pore structure parameters, such as the characteristic ratio surface. The pore aspect ratio and frame flexibility factor can be used to quantitatively characterize the changes in the pore structure of tight carbonate samples, reflecting the pore structure effects on the elastic wave velocity. This study’s results can provide a basis for rock-typing carbonate reservoirs, lithology, and hydrocarbon detection of relevant reservoirs.

Plastics is a group of materials commonly encountered on a daily basis by many people. They have enabled rapid, low-cost manufacturing of products with complicated geometries and have contributed to the weight reduction of heavy components, especially when produced into a foamed structure. Despite the many advantages of plastics, some drawbacks such as the often fossil-based raw-material and the extensive littering of the material in nature, where it is not degraded for a very long time, needs to be dealt with. One way to address at least one of the issues could be to use polymers from nature instead of fossil-based ones. Here, a β-glucan concentrate originating from barley was investigated. The concentrate was processed into a foam by hot-melt extrusion, and the processing window was established. The effect of different blowing agents was also investigated. Water or a combination of water and sodium bicarbonate were used as blowing agents, the latter apparently giving a more uniform pore structure. The porous structure of the foamed materials was characterized mainly by using a combination of confocal laser scanning microscope and image analysis. The density of the samples was estimated and found to be in a similar range as some polyurethane foams. A set of 3D parameters were also quantified on two selected samples using X-ray microtomography in combination with image analysis, where it was indicated that the porous structure had a pre-determined direction, which followed the direction of the extrusion process.

Pressure mercury intrusion test is (MIP) one of the most commonly used methods to characterize pore-fracture structure. Here, we use the fractal dimension of the mercury intrusion curve to analyze the heterogeneity of pore and fracture distribution. Differing from the intrusive mercury curve, the extrusive curve provides a better representation of the seepage capacity of a reservoir. In this paper, the division method of sample types using both mercury invasive parameters (pore volume, pore volume percentage, porosity, permeability) and extrusive parameters (mercury removal efficiency) is discussed. The fractal dimension values of mercury intrusive and extrusive curves are calculated for all samples using the Menger, Thermodynamics, and Multifractal fractal models. Moreover, the fractal significance of the mercury withdrawal curve is examined. The results are as follows. 1) The samples can be divided into three types based on the mercury removal efficiency and total pore volume. Type A is characterized by lower total pore volume (< 0.08 cm 3·g −1) and removal efficiency (< 30%), type B has lower total pore volume (< 0.08 cm 3·g −1) and higher removal efficiency (> 30%), and type C has larger total pore volume (> 0.08 cm 3·g −1) and higher removal efficiency(> 30%). 2) Mercury removal efficiency does not correlate with the mineral composition or total pore volume, but it does show a clear positive correlation with pore volume in the range of 100 to 1000 nm. Unlike the Menger model, the mercury removal curve analyzed using the thermodynamics and multifractal model shows good fractal characteristics. 3) In contrast to the injective curves, the fractal dimension of mercury removal curves exhibits an obvious linear negative correlation with pore structure parameters and mercury removal efficiency. Moreover, the multifractal dimensions D 0- D 10 obtained from the mercury removal curves show a negative correlation with porosity and permeability. This indicates that fractal dimension based on the mercury extrusion curve can be used as a new parameter for characterizing pore-fracture structure heterogeneity.

Bentonite pellets are recognized as good buffer/backfill materials for sealing technological voids in high-level radioactive waste (HLW) repository. Compared to that of a traditional compacted bentonite block, one of the most important particularities of this material is the initially discrete pellets and the inevitable heterogeneous porosity formed, leading to a distinctive water retention behaviour. In this paper, water retention and mercury intrusion porosimetry (MIP) tests were conducted on pellet mixture (constant volume), single pellet (free swelling) and compacted block (constant volume) of GMZ bentonite, water retention properties and pore structure evolutions of the specimens were comparatively investigated. Results show that the water retention properties of the three specimens are almost similar to each other in the high suction range (> 10 MPa), while the water retention capacity of pellet mixture is lower than those of the compacted block and single pellet in the low suction range (< 10 MPa). Based on the capillary water retention theory (the Young–Laplace equation), a new concept ‘saturated void ratio’ that was positively related to water content and dependent on pore size distribution of the specimen was defined. Then, according to the product of saturated void ratio and water density in saturated void, differences of water retention properties for the three specimens at low suctions were explained. Meanwhile, MIP tests indicate that as suction decreases, the micro- and macrovoid ratios of pellet mixture and compacted block decrease as the mesovoid ratio increases, while all the void ratios of single pellets increase. This could be explained that upon wetting, water is successively adsorbed into the inter-layer, inter-particle and inter-pellet voids, leading to the subdivision of particles and swelling of aggregates and pellets. Under constant volume condition, aggregates and pellets tend to swell and fill into the inter-aggregates or inter-pellets voids. While under free swelling condition, the particles and aggregates in a single pellet tend to swell outward rather than squeezing into the inter-aggregate voids, leading to the expansion of the pores and even formation of cracks. Results including the effects of initial conditions (initial dry density and fabric) and constraint conditions (constant volume or free swelling) on the water retention capacity and pore structure evolution reached in this work are of great importance in designing of engineering barrier systems for the HLW repository.

Recently, to further improve the performance of aluminum foam, functionally graded (FG) aluminum foams, whose pore structure varies with their position, have been developed. In this study, three types of FG aluminum foam of aluminum alloy die casting ADC12 with combinations of two different amounts of added blowing agent titanium(II) hydride (TiH2) powder were fabricated by a friction stir welding (FSW) route precursor foaming method. The combinations of 1.0–0 mass %, 0.4–0 mass %, and 0.2–0 mass % TiH2 were selected as the amounts of TiH2 relative to the mass of the volume stirred by FSW. The static compression tests of the fabricated FG aluminum foams were carried out. The deformation and fracture of FG aluminum foams fundamentally started in the high-porosity (with TiH2 addition) layer and shifted to the low-porosity (without TiH2 addition) layer. The first and second plateau regions in the relationship between compressive stress and strain independently appeared with the occurrence of deformations and fractures in the high- and low-porosity layers. It was shown that FG aluminum foams, whose plateau region varies in steps by the combination of amounts of added TiH2 (i.e., the combination of pore structures), can be fabricated.

Nowadays, in the after-treatment of diesel exhaust gas, a diesel particulate filter (DPF) has been used to trap nano-particles of the diesel soot. However, as there are more particles inside the filter, the pressure which corresponds to the filter backpressure increases, which worsens the fuel consumption rate, together with the abatement of the available torque. Thus, a filter with lower backpressure would be needed. To achieve this, it is necessary to utilize the information on the phenomena including both the soot transport and its removal inside the DPF, and optimize the filter substrate structure. In this paper, to obtain useful information for optimization of the filter structure, we tested seven filters with different porosities and pore sizes. The porosity and pore size were changed systematically. To consider the soot filtration, the particle-laden flow was simulated by a lattice Boltzmann method (LBM). Then, the flow field and the pressure change were discussed during the filtration process.