Search Results (132)

Shale pores and throats are key factors controlling the enrichment and development efficiency of shale oil and gas. However, the characteristics and formation mechanisms of shale pores and throats remain unclear. Taking the Permian continental shales in the Mahu Sag of the Junggar Basin as an example, this paper studies the formation mechanisms of pores and throats in shales of different lithofacies through a series of experiments, such as high-pressure mercury injection and scanning electron microscopy. The results show that the Permian continental shales in the Junggar Basin are mainly composed of five lithofacies: rich siliceous shale (RSS), calcareous–siliceous shale (CSS), argillaceous–siliceous shale (ASS), siliceous–calcareous shale (SCS), and mixed-composition shale (MCS). The pores in shale are dominated by intergranular and intragranular pores. The intergranular pores are mainly primary pores and secondary dissolution pores. The primary pores are mainly slit-like and polygonal, with diameters between 40 and 1000 nm. The secondary dissolution pores formed by dissolution are irregular with serrated edges, and their diameters range from 0.1 to 10 μm. The throats are mainly pore-constriction throats and knot-like throats, with few vessel-like throats, overall exhibiting characteristics of nanometer-scale width. The mineral composition has a significant influence on the development of pores and throats. Siliceous minerals promote the development of macropores, and carbonate minerals promote the development of mesopores. Clay minerals inhibit pore development. Diagenesis regulates the development of pores and throats through mechanical compaction, cementation, and dissolution. Compaction leads to a reduction in porosity, and cementation has varying effects on the preservation of pores and throats. Dissolution is the main factor for increased pores and throats. These findings provide a lithofacies-based geological framework for evaluating effective porosity, seepage capacity, and shale oil development potential in continental shale reservoirs. Full article

The characteristics of shale oil reservoirs, such as low porosity, ultra-low permeability, and complex pore structure, are key factors affecting effective pore space and fluid migration. This study focuses on medium-to-high maturity mud shale in the Qing-1 Member of the Qingshankou Formation in the Gulong Sag. Using methods such as XRD, organic geochemical testing, and multi-scale pore characterization (FE-SEM, low-temperature CO₂–N₂ adsorption, high-pressure mercury intrusion, and CT scanning), the lithofacies and pore structure were comprehensively characterized, and their controlling factors were analyzed. The results indicate: (1) The mineral composition is dominated by felsic and clay minerals. Based on a three-level classification standard of “mineral composition–sedimentary structure–organic matter abundance”, seven subfacies were identified, with the dominant lithofacies being Felsic–Clayey Mixed Shale and Felsic-bearing Clay Shale. (2) The reservoir space consists of inorganic pores, organic pores, microfractures, and a small amount of other auxiliary pores, exhibiting “bimodal” pore size characteristics. Micro–mesopores dominate adsorption, while macropores/microfractures control free oil seepage; mesopores contribute the most to pore volume. (3) In terms of oil-bearing potential, Felsic–Clayey Mixed Shale shows prominent movable oil potential (average OSI: 133.08 mg/g; S₁ > 2 mg/g, OSI > 100 mg/g). (4) CT-based 3D stick-and-ball models indicate that Felsic–Clayey Mixed Shale has the best connectivity (connectivity rate: 30.63%), with throat radii mostly ranging from 1–15 μm and pore radii from 2–20 μm. (5) Pore development is synergistically controlled by total organic carbon (TOC, with an optimal range of approximately 1–2.5%), clay/felsic mineral ratio, and bedding/structural fractures. The formation of the pore system is the result of dynamic coupling of organic–inorganic interactions during diagenetic evolution: intergranular pores of clay minerals and microfractures jointly contribute to specific surface area and pore volume, while bedding fractures connect nanopore clusters to enhance seepage capacity. This study improves the integrated understanding of dominant lithofacies, pore structure, and oil-bearing potential in the Qing-1 Member of the Gulong Sag, providing a basis for sweet spot evaluation and development optimization. Full article

In shale oil accumulation, the sealing capacity of roof strata is a key factor controlling hydrocarbon retention, primarily governed by pore–throat structures. This study examines the Chang 7₃ sub-member roof in the Ordos Basin using core and drilling samples, combined with SEM, mercury intrusion porosimetry, nitrogen adsorption, and breakthrough pressure tests. The roof rocks are dense and mainly composed of mudstone, silty mudstone, and argillaceous siltstone, which can be further classified into clay-rich and felsic-rich types. The pore system includes organic matter pores, dissolution pores, intergranular pores, clay interlayer pores, intercrystalline pores, and microfractures. Pores are dominated by mesopores (4–10 nm), with few macropores, and display slit-like, plate-, and wedge-shaped morphologies. Breakthrough pressure averages above 20 MPa, reflecting strong sealing capacity. Although dissolution of felsic minerals generates secondary porosity that may weaken sealing, the overall complex pore–throat system, reinforced by compaction and cementation of clay minerals, forms a dense fabric and favorable sealing conditions. These features restrict hydrocarbon migration and enhance the sealing performance of the Chang 7₃ shale oil roof. Full article

Tectonic deformation can substantially change the pore characteristics and the resulting methane adsorption capacity of shales; thus, it strongly influences shale gas exploration and development in structurally complex areas of southern China. Two sets of shales with identical lithofacies that were derived from either structurally stable or deformed regions were collected at Fuling Field to evaluate the response of their pore properties and methane adsorption behavior to tectonic deformation through field emission scanning electron microscopy (FE-SEM), low-pressure gas (CO₂/N₂) adsorption, and high-pressure methane adsorption experiments. Three primary shale lithofacies were identified in each set of shales: organic-lean (OL) siliceous-rich argillaceous (CM-1) shale lithofacies, organic-moderate (OM) argillaceous/siliceous mixed (M-2) shale lithofacies, and organic-rich (OR) argillaceous-rich siliceous (S-3) shale lithofacies. In the stable region, organic matter (OM) pores dominated the pore types of OR S-3 shales, whereas the primary pore types of OL CM-1 shales were clay cleavage micro-fractures. OM M-2 shales exhibited a composite type of OM pores and clay cleavage micro-fractures. Compared with structurally stable shales, the original OM-hosted and clay-related pores in structurally deformed shales were extensively compacted or even closed due to tectonic compression during structural deformation. Despite pore collapse, two new types of tectonic micro-fractures were generated and found to be well developed in deformed shales through the rupture of brittle minerals in OR S-3 shales and the deformation of clay minerals in OL CM-1 shales. Simultaneously, organic matter–clay aggregates that formed during tectonic compression constituted a distinctive structure in deformed OM M-2 shales. As a result, the deformed shales displayed a decrease in their micropore and mesopore volumes, as well as a decrease in their pore surface areas, because of strong tectonic compression accompanied by an increase in the macropore volume due to the development of tectonic micro-fractures. Furthermore, the large pore surface areas in structurally stable shales could supply abundant adsorption sites and facilitate the enrichment of adsorbed gas. The expanded macropore volumes in structurally deformed shales could provide more storage spaces that are favorable for the accumulation of free gas. Full article

Pore–throat structure and gas distribution are critical factors in evaluating the quality of tight sandstone reservoirs and hydrocarbon resource potential. Twelve tight sandstone samples from the Lower Permian Shihezi Formation in Hangjin Banner, Ordos Basin, were selected for CTS, X-ray diffraction, HPMI, and gas displacement NMR analyses. By converting the T₂ spectra into pore–throat distributions and applying fractal methods, we quantitatively analyzed the influences of multiple factors on gas distribution characteristics across different pore–throat sizes. The main results are as follows: All samples exhibit a three-stage pore–throat distribution, defining mesopores, micropores, and nanopores; quartz content mainly influences the fractal dimension of mesopores by enhancing structural stability and gas storage capacity, whereas clay minerals control the fractal characteristics of nanopores by increasing pore–throat complexity. An increase in clay mineral content increases the fractal dimension, indicating stronger reservoir heterogeneity and consequently poorer gas-bearing capacity. Larger pore–throat parameters (R_m, S_k, and S_max) correspond to lower fractal dimensions, indicating better connectivity and greater gas storage capacity. Among these factors, pore–throat parameters exert the most significant influence on the fractal dimensions of mesopores and micropores, jointly determining the overall connectivity and the upper limit of the reservoir’s gas-bearing capacity. The results demonstrate that larger pore–throat parameters and higher quartz content help reduce the fractal dimension and enhance the gas-bearing capacity of tight reservoirs. This research enhances understanding of pore–throat structures and gas-bearing capacity in low-permeability reservoirs and provides a theoretical basis for exploration, development, and enhanced recovery in the study area. Full article

Low-pressure N₂ adsorption experiments were conducted on 20 samples from the Doushantuo Formation in the Yichang area to quantitatively characterize their pore structures and fractal properties. The samples are mainly composed of quartz, dolomite, and clay minerals, with minor amounts of feldspar, calcite, and pyrite. The N₂ adsorption–desorption isotherms display typical type IV characteristics with a pronounced hysteresis loop, indicating that mesopores are dominant. The specific surface areas range from 3.78 to 11.49 m²/g, and the total pore volumes range from 0.0039 to 0.0169 mL/g, with mesopores contributing most of the total pore volume. Fractal analysis based on the FHH model reveals two distinct fractal dimensions (D_f): D_f1 = 2.5–2.9 for small pores and D_f2 = 2.0–2.3 for large pores. The fractal dimensions are negatively correlated with TOC, quartz, and carbonate contents but positively correlated with clay and pyrite contents. Higher organic matter content tends to produce relatively smooth organic pores, reducing pore heterogeneity, whereas higher clay content increases surface roughness and structural complexity. Overall, the heterogeneity of pore structures in the Doushantuo Formation shales is primarily controlled by mineral composition and organic matter content. These results provide new insights into the pore characteristics and storage potential of Ediacaran marine shales. Full article

Heavy-textured soils in monsoon-affected regions face challenges related to waterlogging and structural degradation, yet the long-term efficacy of biochar as a physical soil amendment under such conditions remains inadequately understood. This two-year field study (2018–2019) therefore evaluated the transient impacts of birch-derived biochar (360–380 °C pyrolysis; 0, 1, 3 kg/m²), subsurface drainage systems, and fertilizer regimes on key physical properties of Endoargic Anthrosols (clay loam) in coastal Primorsky Krai, Russia. Granulometric composition remained stable (silt loam: sand 42–48%, silt 38–44%, clay 12–16%), though drainage significantly increased the silt fraction by >7.5% (p < 0.05). Biochar induced short-term reductions in bulk density (ρ_b; max −12% at 3 kg/m², 2018) and aggregate density (ρ_a; max −9.3%, 2018), but these effects dissipated by 2019 due to tillage redistribution and monsoonal fragmentation, as verified by SEM. Total porosity fluctuated seasonally (0.50–0.65 cm³/cm³), peaking post-tillage but declining under monsoon saturation, with no significant sustained biochar contribution. Crucially, intra-aggregate pore architecture (2–50 nm) resisted amendment-induced changes; N₂ adsorption showed treatment-invariant mesopore dominance (65–75% volume; mean pore diameter 17–21 nm), attributable to biochar’s physical exclusion (>1 µm particles from sub-0.5 µm pores) and inert fragmentation. Drainage dominated structural dynamics, modulating pore volume seasonally (−15% in 2018; +18% in 2019), while organic fertilizer enhanced porosity through polysaccharide-stabilized microaggregation (+22%, 2019). We conclude that biochar’s physical benefits in clay loams under monsoon climates are transient and dose-dependent, operating primarily through inter-aggregate macroporosity rather than intra-aggregate modification, necessitating reapplication for sustained improvements. Full article

The significant heterogeneity of continental shale reservoirs within the Permian Lucaogou Formation of the Jimsar Sag presents a major challenge for shale oil exploration. This study aims to quantitatively characterize the pore structure complexity of different lithofacies to identify favorable “sweet spots.” By integrating geochemical, petrological, and high-resolution pore characterization data with fractal theory, we introduce a comprehensive fractal dimension (D_c) for evaluation. Five distinct lithofacies are identified: massive felsic siltstone (MFS), bedded dolostone (BD), bedded felsic dolostone (BFD), laminated dolomitic felsic shale (LDFS), and laminated mud felsic shale (LMFS). Pore structures vary significantly: MFS is dominated by mesopores (100–2000 nm), BD and BFD exhibit a bimodal distribution (<30 nm and >10 μm), while LDFS and LMFS are characterized by nanopores (<50 nm). D_c analysis reveals a descending order of pore structure complexity: BFD > LMFS > LDFS > MFS > BD. Furthermore, D_c shows positive correlations with clay mineral and feldspar contents but a negative correlation with carbonate minerals. A significant negative correlation between D_c and measured permeability confirms its effectiveness in characterizing reservoir heterogeneity. We propose that MFS and LDFS, with higher pore volumes and relatively lower D_c values, represent the most favorable targets due to their superior storage and seepage capacities. This study provides a theoretical foundation for the efficient development of continental shale oil reservoirs. Full article

Adsorption studies of ciprofloxacine (CPX) and lidocaine (LID) emerging contaminants were performed on two fibrous Mg clays from the Madrid basin and Senegal. The samples were characterized by X-ray diffraction, ICP major element analysis, infrared spectroscopy, thermal analysis, optical petrography, scanning and transmission electron microscopy, cation exchange capacity (CEC), and N₂-BET analysis. Two mineral assemblages were established. Assemblage 1 mainly consists of sepiolite and minor trioctahedral smectite, while assemblage 2 is mostly composed of palygorskite, which is associated with dioctahedral smectite. The sorption was fast and reached equilibrium in 2 h. Fibrous Mg clays showed a higher adsorption capacity for CPX than for LID in the conditions studied. CPX adsorption on sepiolite and palygorskite can be the result of the combination of various mechanisms: ion exchange with permanently charged sites, electrostatic attractions with external surfaces, and an inner sphere complex with broken edges. LID adsorption mainly occurs by ion exchange and electrostatic interaction with the external surfaces of the clays. Dioctahedral smectite, as an associated phase, contributed to a higher removal percentage in palygorskite samples. By contrast, the trioctahedral smectite did not play a significant role in the adsorption of the samples with sepiolite. The mesoporous structure, high surface area, and moderate cation exchange of fibrous clays play a key role in the sorption process of CPX and LID. Full article

The low aqueous solubility of many new drug candidates, a key challenge in oral drug development, has been effectively addressed by liquid self-emulsifying drug delivery systems (SEDDS). However, the inherent instability and manufacturing limitations of liquid formulations have prompted significant research into solid SEDDS. This review provides a comprehensive analysis of the recent advancements in solid SEDDS, focusing on the pivotal roles of solid carriers and solidification techniques. We examine a wide range of carrier materials, including mesoporous silica, polymers, mesoporous carbon, porous carbonate salts, and clay-based materials, highlighting how their physicochemical properties can be leveraged to control drug loading, release kinetics, and in vivo performance. We also detail the various solidification methods, such as spray drying, hot melt extrusion, adsorption, and 3D printing, and their impact on the final product’s quality and scalability. Furthermore, this review explores applications of solid SEDDS, including controlled release, mucoadhesive technology, and targeted drug delivery, as well as the key commercial challenges and future perspectives. By synthesizing these diverse aspects, this paper serves as a valuable resource for designing high-performance solid SEDDS with enhanced stability, bioavailability, and functional versatility. Full article

To overcome the limitations imposed by the anisotropy and heterogeneity of natural loess, this study establishes a novel quantitative macro–micro correlation framework for investigating the deformation mechanisms of artificial structural loess (ASL). ASL samples were prepared by mixing remolded loess with cement (0–4%) and NaCl (0–16%), followed by static compaction (95% degree) and 28-day curing (20 ± 2 °C, >90% RH) to replicate the structural properties of natural loess under controlled conditions. An integrated experimental methodology was employed, incorporating consolidation/collapsibility tests, particle size analysis, X-ray diffraction (XRD), and mercury intrusion porosimetry (MIP). A three-dimensional nonlinear model was proposed. The findings show that intergranular cementation, particle size distribution, and pore architecture are the main factors influencing loess’s compressibility and collapsibility. A critical transition from medium to low compressibility was observed at cement content ≥1% and moisture content ≤16%. A strong correlation (Pearson |r| > 0.96) was identified between the mesopore volume ratio and the collapsibility coefficient. The innovation of this study lies in the establishment of a three-dimensional nonlinear model that quantitatively correlates key microstructural parameters (fractal dimension value (D), clay mineral ratio (C), and large and medium porosity (n)) with macroscopic deformation indicators (porosity ratio (e) and collapsibility coefficient (δ_s)). The measured data and the model’s output agree quite well, with a determination coefficient (R²) of 0.893 for porosity and 0.746 for collapsibility, verifying the reliability of the model. This study provides a novel quantitative tool for loess deformation prediction, offering significant value for engineering settlement assessment in controlled cementation and moisture conditions, though its application to natural loess requires further validation. Full article

The laminae of lacustrine shale in China have been systematically identified and characterized by a combination of core/slice observations, mineral compositions, geochemical analysis, pore structure characterization, and oil-bearing evaluation. The shale of the Chang 7 Member, Yanchang Formation, Ordos Basin was examined as an example in the study. Four types of laminae are developed in the Chang 7 Member, including felsic laminae (FQL), clay laminae (CLL), organic matter laminae (OML), and tuff laminae (TUL). The shale reservoirs exhibit significant heterogeneity. Of these, FQL and TUL have superior reservoir characteristics. The pore diameter of TUL is primarily composed of micrometer-sized secondary pores that are generated during the diagenesis process, while mesopore and macropore development are dominant in FQL. The main source laminae in the Chang 7 Member of the Ordos Basin are the OML and CLL, while the main reservoir laminae are the FQL and TUL. Some of the hydrocarbons produced by hydrocarbon generation are stored in the pore space inside the laminae, while the majority migrate to the inorganic pores of the adjacent FQL and TUL. It confirms that OML and CLL afford abundant shale oil, the combination of organic pores and inorganic pores in FQL and TUL serve as reservoir space, and the “clay generation-siliceous reservoir” shale oil enrichment model is established in the Chang 7 Member of Ordos Basin. Full article

Ultra-deep tight sandstone gas reservoirs are key targets for natural gas exploration, yet their pore structures under high temperature, pressure, and stress greatly affect gas occurrence and flow. This study investigates representative reservoirs in the Kelasu structural belt, Tarim Basin. Porosity–permeability were measured under in situ conditions, and multi-scale pore structures were analyzed using thin sections, a SEM, mercury intrusion, and nitrogen adsorption. The results show that (1) the median permeability of cores at an ambient temperature and a confining stress of 3 MPa is 13.33–29.63 times that under the in situ temperature and pressure conditions. When the core permeability is lower than 0.1 mD, the stress sensitivity effect is significantly enhanced; (2) nanopores and micron-fractures are well developed yet exhibit poor connectivity. The majority of a core’s porosity is derived from the intergranular pores in clay minerals; (3) the volume of nano-sized pores within the 100 nm diameter range is mainly composed of mesopores, with an average proportion of 73.37%, while the average proportions of macropores and micropores are 22.29% and 4.34%, respectively; (4) full-scale pore sizes show bimodal peaks at 100–1000 nm and >100 μm, which are poorly connected; (5) the pore structure exhibits distinct fractal characteristics. The fractal dimension D_f1 (2.65 on average) corresponds to the larger pore diameters of the primary intergranular pores, residual intergranular pores, and intragranular dissolution pores. The fractal dimension D_f2 (2.10 on average) corresponds to the grain margin fractures, micron-fractures and partial throats. The pore types corresponding to the fractal dimensions D_f3 (2.36 on average) and D_f4 (2.58 on average) are mainly intercrystalline pores of clay minerals and a small number of intraparticle dissolution pores. These findings clarify the pore structure of ultra-deep tight sandstones and provide insights into their gas occurrence and flow mechanisms. Full article

Shale pore architecture governs gas storage capacity, permeability, and production potential in reservoirs. Therefore, this study systematically investigates the pore structure features and influencing factors of the Niutitang Formation shale from the QX1 well in northern Guizhou using field emission scanning electron microscopy (FE-SEM), high-pressure mercury intrusion (HPMI), low-temperature nitrogen adsorption (LTNA), and nuclear magnetic resonance (NMR) experiments. The results show that ① The pore size of the QX1 well’s Niutitang Formation shale is primarily in the nanometer range, with pore types including intragranular pores, intergranular pores, organic matter pores, and microfractures, with the former two types constituting the primary pore network. ② Pore shapes are plate-shaped intersecting conical microfractures or plate-shaped intersecting ink bottles, ellipsoidal, and beaded pores. ③ The pore size distribution showed a multi-peak distribution, predominantly mesopores, followed by micropores, with the fewest macropores. ④ The fractal dimension D₁ > D₂ indicates that the shale pore system is characterized by a rough surface and some connectivity of the pore network. ⑤ Carbonate mineral abundances are the main controlling factors affecting the pore structure of shales in the study area, and total organic carbon (TOC) content also has some influence, while clay mineral content shows negligible statistical correlation. Full article

Persistent reactive azo dyes released from textile finishing are a serious threat to water systems, but effective methods using sunlight to break them down are still limited. Everzol Yellow 3RS (EY-3RS) is particularly recalcitrant: past studies have relied almost exclusively on physical adsorption onto natural or modified clays and zeolites, and no photocatalytic pathway employing engineered nanomaterials has been documented to date. This study reports the synthesis, characterization, and performance of a visible-active ternary nanocomposite, Cu₄O₃/ZrO₂/TiO₂, prepared hydrothermally alongside its binary (Cu₄O₃/ZrO₂) and rutile TiO₂ counterparts. XRD, FT-IR, SEM-EDX, UV-Vis, and PL analyses confirm a heterostructured architecture with a narrowed optical bandgap of 2.91 eV, efficient charge separation, and a mesoporous nanosphere-in-matrix morphology. Photocatalytic tests conducted under midsummer sunlight reveal that the ternary catalyst removes 91.41% of 40 ppm EY-3RS within 100 min, markedly surpassing the binary catalyst (86.65%) and TiO₂ (81.48%). Activity trends persist across a wide range of operational variables, including dye concentrations (20–100 ppm), catalyst dosages (10–40 mg), pH levels (3–11), and irradiation times (up to 100 min). The material retains ≈ 93% of its initial efficiency after four consecutive cycles, evidencing good reusability. This work introduces the first nanophotocatalytic strategy for EY-3RS degradation and underscores the promise of multi-oxide heterojunctions for solar-driven remediation of colored effluents. Full article