Search Results (2,414)

The application of multi-branch pinnate drilling has great prospects in gas control. Although there are many studies on the parameters of multi-branch plume drilling, the mathematical model used in the study is still not sufficient for the addition of the slippage effect and thermodynamic changes. In this paper, a thermal–fluid–solid coupling model is used to study the influence of branch angle and branch length on the extraction effect in high-gas and extra-thick coal seams. The reliability of the model is verified by simulating an onsite extraction environment to fit the onsite gas production rate. Under identical simulation conditions, the experiment investigated the gas extraction performance of boreholes with varying branch angles (30°, 40°, 50°, and 60°) and branch lengths (50 m, 75 m, 100 m, and 125 m). The results show that temperature affects the dynamic viscosity of gas, which in turn affects the flow rate. The slippage effect affects permeability. When the branch angle is less than 50°, the increase in the branch angle can expand the control range of drilling. By continuing to increase the angle, the improvement in the extraction effect is weakened. As the branch angle exceeds 50° and continues to increase, the branch borehole progressively approaches the edge of the coal seam. At this time, the overall control range of the borehole is greatly increased, and the gas extraction effect is improved. The increase in the branch length leads to a considerable improvement in the extraction effect. When the branch length is below 100 m, the improvement in extraction efficiency diminishes progressively with increasing branch length. This is because the effect of increasing the branch length on improving the overall control range of the borehole is weakened. When the branch length exceeds 100 m and continues to increase, the branch borehole approaches the edge of the coal seam. The overall control effect of drilling has been greatly improved. The extraction effect of boreholes has increased significantly compared with before. Full article

Conventional thermal recovery techniques face challenges in low-permeability heavy oil reservoirs due to low recovery factors and poor economic viability. To address these challenges, low-temperature oxidation (LTO) during oxygen-reduced air flooding was employed to achieve in situ oil upgrading and enhance oil recovery. Static oxidation tests at oxygen concentrations of 5%, 10%, 15%, and 21% were designed to analyze the produced gas composition and the physical properties of the oil following oxidation. We further employed Differential Scanning Calorimetry (DSC) and Thermogravimetric (TG) analysis to evaluate the oxidation behavior of crude oil under the same oxygen concentration conditions. Finally, long-core displacement experiments were performed to assess how the oxygen concentration influences the recovery efficiency. The results showed that under the tested conditions, oxygen consumption exceeded CO₂ generation, indicating that low-temperature oxygen addition reactions (formation of oxygenated species) dominated over complete oxidation. As the oxygen concentration increased, the oxidized crude oil exhibited a higher viscosity. At higher oxygen concentrations (15% and 21%), the asphaltene content increased significantly, resulting in poorer fluidity. The activation energy in the LTO stage decreased with increasing oxygen concentration, as revealed by kinetic analysis over the range of 5% to 21%. The LTO stage dominated the crude oil oxidation process. However, the heat release during this stage was less affected by the oxygen concentration. Consequently, increasing the oxygen concentration contributed only marginally to elevating the reservoir temperature. For the studied reservoir, oxygen-reduced air flooding with a 5% oxygen concentration achieved a final recovery factor of 34.82%. This represented a 1.76% improvement over conventional air flooding, thereby enabling economically efficient reservoir development. Full article

Due to the strong heterogeneity of the reservoir, early gas breakthrough and low CO₂ displacement efficiency are common issues in the CO₂ flooding process of domestic gravel reservoirs. This study focuses on a gravel reservoir in Xinjiang, proposing a quantitative evaluation method that combines early gas breakthrough identification and the inversion of gas channel characteristic parameters. The aim is to provide theoretical support and technical guidance for gas breakthrough risk warning, injection-production system optimization, and control measures during the CO₂ flooding process. The research method includes the following several key steps: first, clarifying the criteria for determining the time of gas breakthrough and proposing a classification method for early gas breakthrough types based on CO₂ concentration levels; second, adopting a “matrix-dominant gas channel” dual-medium model, considering the geometric and physical characteristics of inter-well gas channels, and deriving a theoretical calculation formula with gas breakthrough time and CO₂ concentration in the produced gas as the target; third, using actual gas breakthrough time and CO₂ concentration as constraints, constructing a method to invert the characteristic parameters of gas channels, quantitatively representing key parameters such as gas channel thickness ratio, permeability variation, and equivalent permeability; finally, through the combined analysis of CO₂ concentration and gas channel characteristic parameters, establishing a method for identifying gas channel types suitable for domestic gravel reservoirs. The practical application results show that the test area has formed localized dominant gas channels, but the overall stage is still in the early phase of weak gas breakthrough. Most gas breakthrough phenomena are weak, with only a few well groups experiencing severe gas breakthrough issues. The gas channel thickness ratio is generally less than 0.05, and the permeability variation mainly ranges from 2 to 20. The gas channels are primarily of the fracture type, with some areas also containing ordinary fractures and main control fractures. The method proposed in this study, which combines early gas breakthrough identification with the inversion of gas channel characteristic parameters, not only provides a new approach to revealing the characteristics of gas breakthrough during CO₂ flooding but also offers solid theoretical and technical support for optimizing CO₂ flooding technology and controlling gas breakthrough risks. Full article

The long-term operational reliability of underground gas storage (UGS) facilities in depleted reservoirs is significantly challenged by reservoir damage during multi-cycle injection and production (I&P). While the impact of cycle numbers has been extensively studied, the influence of variable pressure depletion rates remains insufficiently quantified. This study investigates the reservoir damage mechanisms of sandstone cores from the Sichuan Basin under different depletion rates (0.5 and 2.5 MPa/min) over 20 I&P cycles. Experimental results indicate that the pressure depletion rate is a decisive factor in permeability impairment. For the sample subjected to a fast depletion rate (2.5 MPa/min), the total permeability loss reached 18.2%, which is 2.16 times higher than that of the slow-rate sample (8.4% at 0.5 MPa/min). Notably, the high-rate sample sustained nearly 60% of its total damage within the initial three cycles, highlighting a critical window of vulnerability during early UGS operations. Theoretical hydrodynamic analysis suggests that at 2.5 MPa/min, the instantaneous shear force (6.42 nN) exceeds the representative adhesion force of clay minerals (~5.0 nN), which may increase the likelihood of clay mobilization under the present experimental conditions. Combined with the XRD-identified clay content and the observed permeability evolution, the damage is interpreted as being likely associated with fines migration and pore-throat plugging. Based on these findings, a “Slow-Start” operational protocol—maintaining depletion rates below 1.0 MPa/min during the initial cycles—is preliminarily recommended under the present experimental conditions to help preserve reservoir conductivity and extend facility longevity. Full article

High-temperature gaseous deuterium charging was used to investigate hydrogen isotope permeation, retention, microstructural stability, and fracture response in 310S austenitic stainless steel. Gas-driven permeation, thermal desorption spectroscopy, two-dimensional diffusion simulation, XRD/EBSD characterization, tensile testing, and fractographic analysis were combined to correlate isotope transport with mechanical and fracture behavior. The deuterium permeability and diffusion coefficient followed an Arrhenius relationship, and the diffusion coefficient extrapolated at 673 K was 1.11 × 10⁻¹¹ m²/s. With increasing charging time, the deuterium distribution evolved from a surface-enriched unsaturated state to an overall near-saturated state with higher retention. Although deuterium charging had little influence on yield strength, ultimate tensile strength, and elongation under the present room-temperature tensile condition, local quasi-cleavage-like facets, secondary cracks, and serrated fracture edges became more evident after charging. These results indicate that the embrittlement response of 310S stainless steel was mainly characterized by localized hydrogen-assisted damage rather than dominant brittle fracture. Full article

This article examines the interaction of clay minerals with iron ore concentrate in the context of the efficient use of composite mineral resources. The role of the adsorption properties of mineral additives in the formation of interparticle bonds in green pellets is analyzed. Using X-ray diffraction (XRD) and infrared spectroscopy, the dehydration processes of Na- and Ca-montmorillonite were investigated, and the influence of the cation type on the minerals’ ability to retain water was established. The high thermal stability of the structural OH groups of montmorillonite from the IV-layer clay of the Cherkasy deposit was confirmed, which is an important factor during high-temperature processing of mineral raw materials. Electron microscopy results showed that the fourth-layer clay forms an optimal porous composite microstructure, which contributes to increased water-holding capacity and gas permeability of the pellets. A direct correlation between the adsorption capacity of mineral additives and the strength of raw and dried pellets was experimentally confirmed. Montmorillonite with palygorskite from Layer IV, characterized by high adsorption capacity and prolonged dehydration processes, was identified as the most effective composite binding additive. The results obtained deepen scientific understanding of the mechanisms underlying pellet strength formation and have practical significance for the rational and resource-efficient use of mineral resources in the production of iron ore pellets. The results also demonstrate the potential for improving resource efficiency in pellet production through reduced consumption of traditional binder materials. Full article

The aim of this study was to use lemon balm extract (Melissa officinalis L.), prepared via microwave-assisted extraction, for the development of novel formulations of functional edible films based on chitosan, gum arabic, and gelatine (simple and blended formulations). This study focused on changes in the antioxidant properties of enriched films, in addition to their physicochemical and barrier performance for potential applications. Thickness, colour, transparency, water solubility, gas and water vapour permeability, total polyphenol content, and antioxidant capacity were evaluated. The addition of lemon balm extract resulted in an increased polyphenol content (of about 30%) and enhanced antioxidant properties (approximately three-fold), without influencing hydration-related properties (solubility, moisture content and water absorption). These parameters were significantly influenced by the matrix structure (neat chitosan vs. blends with gelatine and gum arabic). Significant increases in the oxygen (three-fold for neat chitosan and five-fold for blends) and carbon dioxide (21-fold for blends) permeability coefficients were also observed in all films with extracts. However, all values remained below 30 × 10⁻⁵ cm³ m⁻¹ d⁻¹ bar⁻¹, indicating that all films retained good gas barrier properties. The results indicate the potential of the developed material for applications in active food packaging as a sustainable alternative to traditional packaging materials, which should be further validated through studies on real food systems and shelf-life evaluation. Full article

The Quemocuo area in the Qiangtang Basin is a key prospect for permafrost gas hydrate exploration in China. This study investigates source-reservoir-caprock characteristics and their control on gas hydrate accumulation based on drilling results from wells QK-8 and QK-9, integrated with multiple analytical methods. Two high-quality marine source rocks with cumulative thickness ~1000 m exhibit TOC values of 0.74–2.5%, Type II₂ kerogen, and vitrinite reflectance (Ro) of 1.37–2.94%, indicating high to over-mature thermal evolution primarily generating dry thermogenic methane. Gas logging shows hydrocarbon anomalies with a maximum desorbed gas content of 90 mL, confirming strong gas generation capacity. Although reservoir matrix properties are poor (porosity mostly <5%, permeability < 0.2 × 10⁻³ μm²), multi-phase tectonics and dissolution formed a secondary fracture-vug system. Permafrost conditions are favorable (thickness 100–120 m; geothermal gradient 4.5–4.7 °C/100 m), with extremely low permeability at high ice saturations, forming an effective multi-level seal together with thick mudstones. A key novel finding is the significant mixing of biogenic and thermogenic gases, with the biogenic component interpreted to originate from overlying Jurassic-Quaternary low-maturity strata, facilitated by late tectonic uplift and fault conduits. NW-trending faults connect deep thermogenic reservoirs and provide pathways for shallow biogenic gas migration. For the first time, this study establishes a region-specific composite accumulation model for the Qiangtang Basin, characterized by “lower generation and upper storage, fault-fracture conduit and permafrost sealing”, which reveals fault-controlled migration, fracture-vug-controlled storage, permafrost-controlled sealing, and mixed gas enrichment under a high geothermal gradient. Full article

Efficient gas drainage in deep coal seams is critical for safe mining, yet the coupling between plastic damage evolution in borehole surrounding rock and seepage characteristics remains a key barrier to improving drainage efficiency. This study established a dual-porosity model that couples gas diffusion–seepage with elastoplastic coal deformation and conducted numerical simulations under various stress states. Triaxial tests were conducted to support the stress–deformation–permeability trends used in the numerical analysis. The simulation results showed a strongly nonlinear positive correlation between plastic damage and in situ stress, and the damage scale under uniform stress was well described by an empirical quadratic fit. The lowest and most symmetric damage occurred at a lateral pressure coefficient of 1.0, whereas deviations from this value changed the damage morphology, produced uneven gas pressure distributions, and formed high-velocity seepage zones favorable for directional drainage. Plastic damage exerted dual effects on drainage, with moderate damage enhancing permeability and high stress suppressing far-field seepage. Experiments revealed that confining pressure was the dominant factor affecting permeability and that it suppressed both deformation and seepage, whereas gas pressure was kept constant and was not treated as an independent variable in the experimental design. These findings provide support for optimizing gas drainage parameters in deep coal seams. Full article

Along with the growth in the production of metallurgical grade silicon and high-silicon ferrous alloys, there is a significant increase in the formation of microsilica, which is an ultra-fine technogenic waste. The direct application of microsilica in ore-thermal furnaces is hindered by low bulk density, poor gas permeability, and high dusting. This paper explores the thermophysical and microstructure properties of briquettes based on microsilica, which includes various types of carbonaceous reducing agents such as semi-coke and coal. For manufacturing, the liquid glass was used as the inorganic binder for the preparation of microsilica briquettes. The best variants were chosen based on strength tests carried out during preliminary studies. In the laboratory tests, the stability of the briquettes at elevated temperatures was evaluated. Samples were heated to 1000–1500 °C and subjected to impact testing. Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM/EDS) was used to investigate the microstructure and local elemental distribution. It was revealed that the calcinated briquettes of the microsilica–semi-coke mixture have better thermal stability compared to the samples with coal and withstand the temperature range up to 1500 °C. The microstructure of the briquette from the microsilica-semi-coke mixture is characterized by the formation of a more uniform silicate matrix with the presence of a homogeneously distributed carbonaceous component. Coal-based samples show higher heterogeneity and porosity. Therefore, it can be stated that the selection of carbonaceous reductants is one of the key factors influencing the thermal stability of microsilica briquettes. Full article

In this study, the task of integrating capture and conversion of CO₂ into a single material platform is realized by developing bifunctional membranes based on polymer ionic liquids (PILs). The novelty of this work lies in the fabrication and comprehensive evaluation of PIL-based membrane materials that combine catalytic activity toward CO₂ conversion with gas separation performance within one material system. In contrast to most previously reported imidazolium-based PILs, which have mainly been considered either as catalysts or as membrane materials, the present approach focuses on their dual functionality under both catalytic and gas transport conditions. A series of imidazolium-based PILs, including homopolymers and block copolymers with polystyrene, were synthesized. The materials were characterized to determine their catalytic activity during the cycloaddition of CO₂ to epichlorohydrin and to determine their gas transport properties using pure gases (N₂, O₂, CO₂) and a simulated dry flue gas mixture; membrane morphology was studied by scanning electron microscopy. Block copolymers exhibited higher catalytic conversions (up to 82.7%) than homopolymers, with selectivities above 93%. Chloride-containing block copolymers gave the best combination of CO₂ permeability (up to 7.5 Barrer) and CO₂/N₂ selectivity (18–22) under mixed-gas conditions. Iodide-containing analogs demonstrated higher selectivity (up to 30) but lower CO₂ permeability. Morphological analysis confirmed the presence of dense, defect-free structures in materials with the chloride anion, while materials with the iodide anion showed increased free volume and microheterogeneity. These results indicate that by altering the polymer and anion architecture, PIL-based membranes can effectively combine catalytic activity with selective CO₂ transport, providing a promising avenue for enhancing carbon capture and utilization processes. Full article

This study investigates the development of mixed matrix membranes based on polyethersulfone incorporated with attapulgite for gas separation applications, addressing the existing gap regarding the use of this mineral in dense membranes obtained exclusively by solvent evaporation and its combined effects on microstructure and transport. The membranes were prepared by phase inversion via solvent evaporation, using solvent/polymer ratios of 75/25 and 80/20 and a thickness of 0.25 mm. The solutions were evaluated in terms of viscosity, and the membranes were characterized by structural techniques such as X-ray diffraction (XRD), atomic force microscope (AFM), contact angle, mechanical properties (tensile testing), and water vapor permeation. The results showed that attapulgite incorporation promoted a reduction in surface roughness (up to ~40%) and a decrease in contact angle (from ~89° to ~68°), indicating increased hydrophilicity. In addition, water vapor permeability was influenced in a non-linear manner, with optimized performance observed at 3 wt% filler loading. Solution viscosities remained within ranges suitable for processing. Structural analyses indicated compatibility between the phases, while morphology changes dependent on filler content were decisive for transport behavior. It is concluded that attapulgite is a promising additive for fine-tuning membrane properties, enabling optimization of the sorption–diffusion balance and improvement of membrane performance in separation applications. Full article

Accurate quantification of mineralogical composition in carbonate rocks is essential for reservoir characterization in the oil industry, directly influencing petrophysical properties such as porosity and permeability. However, traditional methods such as X-ray diffraction (XRD) are destructive and provide limited spatial sampling. The aim of this study was to develop and validate a workflow for the continuous quantification of calcite and dolomite in drill cores from the Brazilian pre-salt oil province by integrating short-wave infrared (SWIR) hyperspectral imaging (HSI) and Machine-Learning algorithms. A total of 80 m of cores were evaluated using 170 XRD-validated samples to calibrate linear, nonlinear, and ensemble models. The results showed that the combination of Multiplicative Scatter Correction (MSC) preprocessing with Multilayer Perceptron (MLP) and Support Vector Regression (SVR) achieved the best performance, reaching an $R^2$ of 0.84. Explainable Artificial Intelligence (SHAP) confirmed the relevance of diagnostic bands between 2330 and 2360 nm, improving geological interpretability of the predictions. The proposed methodology provides a non-destructive and high-resolution alternative for mineralogical profiling, supporting the evaluation of complex reservoirs and decision-making in the oil and gas industry. Although the workflow was validated using a specific pre-salt dataset, future studies should assess its transferability to other carbonate reservoirs and broader geological settings. Full article

This study investigates methane leakage and diffusion from a buried high-pressure natural gas pipeline (8 MPa, 1000 mm diameter) using CFD simulations with the DES turbulence model. Based on homogeneous and layered soil models, the influences of soil porosity (0.46 to 0.54), particle size (10 μm to 100 μm), and soil stratification on the spatial and temporal characteristics of methane diffusion are systematically explored. The simulation results show that (1) methane diffuses from the leak hole to the surrounding soil in an ellipsoidal pattern, with the fastest diffusion speed along the pipeline’s axial direction. (2) In homogeneous soil, within the range of soil parameter values considered in this study, the absolute changes in risk assessment indices (FDR, GDR) caused by soil particle size were more significant; whereas the relative percentage changes in risk assessment indicators caused by soil porosity were more pronounced. (3) In layered soil, the permeability contrast between adjacent layers creates the permeability discontinuity interface effect. When a fine-grained or low-porosity layer overlies a coarse-grained layer, the upper layer acts as a hydraulic barrier, prolonging FDT from 130 s to 354 s while promoting significant horizontal spread at the interface. Conversely, a coarse-grained or high-porosity upper layer accelerates vertical breakthrough. These findings provide a scientific basis for risk assessment, monitoring site optimization, and emergency response planning, particularly in regions with heterogeneous stratified soils. Full article

Perovskite mixed proton–electron hydrogen-permeable membranes have been widely applied in the field of membrane separation due to their 100% selectivity for hydrogen separation. La_5.5WO_11.25-δ-La_0.87Sr_0.13CrO_3-δ (LWO-LSF) four-channel hollow fiber membranes were prepared by the phase inversion and sintering technique using a one-step thermal processing (OSTP) approach. The effects of temperature, feed gas concentration, sweep gas flow, permeation mode, and water vapor on hydrogen flux were systematically investigated. At 900 °C, the hydrogen permeation flux of 50% H₂/N₂ feed from the shell side to the lumen side was 0.613 mL·min⁻¹·cm⁻², which was 62.59% higher than that from the lumen side to the shell side. The enhanced hydrogen permeation performance is attributed to the lower gas mass transfer resistance under shell-side feeding. Under humidified conditions on the sweep side, the hydrogen flux increased by an additional 3.42%. The presence of water vapor increased the number of proton carriers, effectively enhancing proton–electron-coupled transport and thereby increasing the hydrogen permeation flux. Full article