Search Results (840)

This study investigates the combined effects of impurities in CO₂ stream, geochemistry, water salinity, and wettability alteration on oil recovery and CO₂ storage in carbonate reservoirs and optimizes injection strategy to maximize oil recovery and CO₂ storage ratio. Specifically, it compares the performance of pure CO₂ water-alternating gas (WAG), impure CO₂-WAG, pure CO₂ low-salinity water-alternating gas (LSWAG), and impure CO₂-LSWAG injection methods from perspectives of enhanced oil recovery (EOR) and CO₂ sequestration. CO₂-enhanced oil recovery (CO₂-EOR) is an effective way to extract residual oil. CO₂ injection and WAG methods can improve displacement efficiency and sweep efficiency. However, CO₂-EOR has less impact on the carbonate reservoir because of the complex pore structure and oil-wet surface. Low-salinity water injection (LSWI) and CO₂ injection can affect the complex pore structure by geochemical reaction and wettability by a relative permeability curve shift from oil-wet to water-wet. The results from extensive compositional simulations show that CO₂ injection into carbonate reservoirs increases the recovery factor compared with waterflooding, with pure CO₂-WAG injection yielding higher recovery factor than impure CO₂-WAG injection. Impurities in CO₂ gas decrease the efficiency of CO₂-EOR, reducing oil viscosity less and increasing interfacial tension (IFT) compared to pure CO₂ injection, leading to gas channeling and reduced sweep efficiency. This results in lower oil recovery and lower storage efficiency compared to pure CO₂. CO₂-LSWAG results in the highest oil-recovery factor as surface changes. Geochemical reactions during CO₂ injection also increase CO₂ storage capacity and alter trapping mechanisms. This study demonstrates that the use of impure CO₂-LSWAG injection leads to improved oil recovery and CO₂ storage compared to pure CO₂-WAG injection. It reveals that wettability alteration plays a more significant role for oil recovery and geochemical reaction plays crucial role in CO₂ storage than CO₂ purity. According to optimization, the greater the injection of gas and water, the higher the oil recovery, while the less gas and water injected, the higher the storage ratio, leading to improved storage efficiency. This research provides valuable insights into parameters and injection scenarios affecting enhanced oil recovery and CO₂ storage in carbonate reservoirs. Full article

This study investigates groundwater flow patterns in a landslide area above the settlement of Koroška Bela in NW Slovenia using a series of tracer tests with sodium chloride (NaCl) and fluorescein (uranine). The tracer experiments, using a combination of pumping tests and continuous groundwater observations, reveal two distinct groundwater flow horizons within the landslide body: a prevailing shallower flow within highly permeable gravel layers and a slower deep flow in the weathered low-permeability clastic layers. Uranine injections suggest longer retentions, indicating complex hydrogeological conditions. Groundwater is recharged by the infiltration of precipitation and subsurface inflow from the upper-lying carbonate rocks. In the upper landslide, highly permeable gravel layers accelerate flow, especially during heavy rainfall, while downstream interactions between permeable gravel and less permeable clastic materials create local aquifers and springs. These groundwater dynamics significantly influence landslide stability, as rapid infiltration during intense precipitation events can lead to transient increases in pore water pressure, reducing shear strength and potentially triggering slope movement. Meanwhile, slow deep flows contribute to prolonged saturation of critical failure surfaces, which may weaken the landslide structure over time. The study emphasizes the region’s geological heterogeneity and landslide stability, providing valuable insights into the groundwater dynamics of this challenging environment. By integrating hydrogeological assessments with engineering measures, the study provides supportive information for mitigating landslide risks and improving groundwater management strategies. Full article

Carbonate reservoirs have various types of reservoir spaces and complex pore structures, so the evaluation of microscopic pore structures is of great significance to favorable reservoir identification. In order to accurately characterize the micro-pore structure of carbonate reservoir, this paper uses the NMR experiment, high-pressure mercury injection, and NMR logging data to establish a conversion model between the NMR T₂ spectrum and the capillary pressure curve by piecewise power function method. The nuclear magnetic T₂ spectrum of the reservoir is mainly bimodal, with small pore T₂ ranging from 0.1 to 6 ms, the peak value being about 2 ms, and the large pore throat T₂ ranging from 100 to 6000 ms. The throat radius of small pores is 0.04–0.1 μm, the peak value is 0.08 μm, and the throat of large pores is 0.1–10 μm. The Bash layer has the smallest pore throat radius and median radius, higher median pressure, and poorer pore structure. By converting the T2 spectrum of nuclear magnetic logging into a pseudo-capillary pressure curve, the continuous and quantitative characterization of reservoir pore structure parameters was achieved vertically. The secondary method has important reference significance for the quantitative characterization of pore structure in reservoirs of the same type. Full article

The present study aims to create porous materials through the acid activation of bentonites using 0.5 M oxalic acid at different pH values. Two types of bentonites (containing aluminum montmorillonite and ferruginous montmorillonite) were treated with oxalate solutions at pH 1 to 5. During acid activation at the three pH values, Al, Fe, Mg and Si kinetics were monitored; the porosity of the samples was modified; and the specific surface area increased, while the crystal structure did not completely collapse. The optimum conditions occurred at pH 1, where the highest metal leaching was obtained for both samples. For the sample with aluminum smectite, the specific surface increased from 28.1 m²/g to 149 m²/g and the pore volume quadrupled. In the case of samples with ferruginous smectite, the specific surface area rose from 63. 2 m²/g to 372 m²/g and the pore volume increased sixfold. The mechanism of smectite activation was investigated, revealing that at the optimum experimental conditions, which is ferruginous bentonite activation at pH 1, the products have the highest concentration of small 30 to 50 Å pores, which is attributed to the creation of an adequate number of active sites and the formation of aluminum complexes with the oxalate anions. The modified bentonites have elevated porosity; therefore, they could be used as adsorbents in industry. Full article

With the advancement of industrial production and urban modernization, pollution from heavy metal ions and the accumulation of solid waste have become critical global environmental challenges. Establishing an effective recycling system for solid waste and removing heavy metals from wastewater is essential. Coal gangue was used in this study as the primary material for the synthesis of a fully coal gangue-based phosphorus-silicon-aluminum (SAPO-5) molecular sieve through a hydrothermal process. The SAPO-5 molecular sieve was characterized through several methods, including X-ray diffraction (XRD), scanning electron microscopy (SEM), BET surface analysis, Fourier-transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS), to examine its mineral phases, microstructure, pore characteristics, and material structure. Adsorption performance towards wastewater with Cd²⁺ and Pb²⁺ ions was investigated. It was found that the adsorption processes of these ions are well described by both the pseudo-second-order model and the Langmuir isotherm. According to the Langmuir model, the coal gangue-based SAPO-5 molecular sieve exhibited maximum adsorption capacities of 93.63 mg·g⁻¹ for Cd²⁺ and 157.73 mg·g⁻¹ for Pb²⁺. After five cycles, the SAPO-5 molecular sieve retained strong stability in adsorbing Cd²⁺ and Pb²⁺, with residual adsorption capacities of 77.03 mg·g⁻¹ for Cd²⁺ and 138.21 mg·g⁻¹ for Pb²⁺. The excellent adsorption performance of the fully solid waste coal gangue-based SAPO-5 molecular sieve is mainly attributed to its mesoporous channel effects, the complexation of -OH functional groups, and electrostatic attraction. Full article

The evolution of coal’s pore structure is crucial to the efficient capture of carbon dioxide (CO₂) within coalbeds, as it provides both adsorption sites and seepage space for the adsorbed- and free-phase CO₂, respectively. However, the conventional single fractal method for characterizing pore structure fails to depict the intricacies and variations in coal pores. This study innovatively applies the low-temperature N₂/CO₂ sorption measurement and multifractal theory to investigate the evolution of the microporous structure of coals (e.g., from the Huainan coalfield) during the supercritical CO₂(ScCO₂)–water–rock interaction process. Firstly, we observed that the ScCO2–water–rock interaction does not significantly alter the coal’s pore morphology. Notably, taking the ZJ-8# sample as an example, low-temperature N₂ sorption testing displayed a stable pore volume following the reaction, accompanied by an increase in specific surface area. Within the CO₂ sorption testing range, the ZJ-8# sample’s pore volume remained unchanged, while the specific surface and pore width performed displayed a slight decrease. Secondly, by introducing key parameters from multifractal theory (such as D_q, α(q), τ(q), and f(α)), we assessed the heterogeneity characteristics of the coal’s pore structure before and after the ScCO2–water–rock reaction. The N₂ sorption analysis reveals an increase in pore heterogeneity for the ZJ-8# sample and a decrease for the GQ-13# sample within the sorption testing range. In the context of low-temperature CO₂ sorption analysis, the pore distribution complexity and heterogeneity of the GQ-11# and GQ-13# samples’ pores were escalated after ScCO2–water–rock interaction. The experimental and analysis results elucidated the dual roles of precipitation and dissolution exerted by the ScCO2–water–rock interaction on the micropores of coal reservoirs, underscoring the heterogeneous nature of the reaction’s influence on pore structures. The application of fractal theory offers a novel perspective compared to traditional pore characterization methods, significantly improving the precision and comprehensiveness of pore structure change descriptions. Full article

The electroreduction of CO₂ (CO₂RR) is a promising and environmentally sustainable approach to closing the carbon cycle. However, achieving high activity and selectivity for multicarbon (C₂₊) products remains a significant challenge due to the complexity of reaction pathways. In this study, porous carbon-supported copper catalysts (CuHCS) with pore sizes of 120 nm (CuHCS120) and 500 nm (CuHCS500) were synthesized to tailor the microenvironment at the electrode–electrolyte interface and enhance product selectivity. CuHCS120 achieved a maximum faradaic efficiency (FE) for C₂₊ products of 46%, double that of CuHCS500 (23%). In contrast, CuHCS500 showed a higher FE for CO (36%) compared to CuHCS120 (14%) at the same potential. In-depth ex situ and in situ investigations revealed that smaller pores promote the enrichment and adsorption of *CO intermediates, thereby enhancing C–C coupling and the formation of C₂₊ products. These findings underscore the critical role of structural confinement in modulating the catalytic microenvironment and provide valuable insights for the rational design of advanced catalysts for CO₂RR. Full article

The blockage of a tunnel drainage system has a significant impact on the stability and operation safety of a tunnel lining structure. In this paper, changes in the pore water pressure, stress and displacement of a tunnel lining under different blocking conditions are studied by means of indoor test and numerical simulation. The results show that the calcium carbonate crystallization phenomenon in the tunnel’s initial support concrete gradually appears with the passage of time, which leads to a decline in concrete quality and has a negative impact on its compressive strength and elastic modulus. The pore water pressure, stress and displacement increase with the precipitation of calcium carbonate crystals and the intensification of drainage system blockage. However, the influence of calcium carbonate crystallization on pore water pressure, stress and displacement is relatively limited within 40 days. The study provides a reference for tunnel construction in complex geological environments. Full article

Complex pore structures with multiple inclusions challenge the predictive accuracy of rock physics models. This study introduces a novel method for estimating a single equivalent pore aspect ratio that optimizes rock physics model predictions by minimizing discrepancies with experimental measurements in porous rocks with multiple inclusions with variable aspect ratios and proportions. The proposed methodology uses digital rock physics numerical simulations for validation. A comparative analysis is conducted between the equivalent aspect ratio derived from optimized rock physics models, numerical simulations, and the aspect ratio distribution estimated from digital rock samples. The approach is tested on both synthetic and real core samples, demonstrating its robustness and applicability to field data, including core samples and well log data. The validation results confirm that the method enhances predictive accuracy and offers a versatile framework for addressing pore complexity in subsurface rock formations. Full article

Gle1 functions as a regulator of Dbp5, a DEAD-box-containing RNA helicase that is a component of the nuclear pore complex. In association with Gle1 and inositol hexakisphosphate (IP6), ADP-bound Dbp5 facilitates the release of RNA. The RNA-bound Dbp5 undergoes ATP hydrolysis and is activated by Gle1 in the presence of IP6. The formation of a ternary complex involving Dbp5, Gle1, and the nucleoporin Nup159 promotes ADP secretion and prevents RNA recombination. To date, several complex structures of Gle1 with its binding partners have been described; however, the structure of unbound Gle1 remains elusive. To investigate the structural features associated with complex formation, the crystal structure of N-terminally truncated Gle1 from Debaryomyces hansenii (DhGle1ΔN) was determined at a resolution of 1.5 Å. The DhGle1ΔN protein comprises 13 α-helices. Structural comparisons with homologs, all of which have been characterized in various complexes, revealed no significant conformational changes. However, several distinct secondary structural elements were identified in α1, α3, α4, and α8. This study may provide valuable insights into the architecture of yeast Gle1 proteins and their interactions with Dbp5, which is crucial for understanding the regulation of mRNA export. Full article

On-chip microfluidics are advanced in vitro models that simulate lung tissue’s native 3D environment more closely than static 2D models to investigate the complex lung architecture and multifactorial processes that lead to pulmonary disease. Current microfluidic systems can be restrictive in the quantities of biological sample that can be retrieved from a single micro-channel, such as RNA, protein, and supernatant. Here, we describe a newly developed large-scale airway-on-chip model that employs a surface area for a cell culture wider than that in currently available systems. This enables the collection of samples comparable in volume to traditional cell culture systems, making the device applicable to any workflow utilizing these static systems (RNA isolation, ELISA, etc.). With our construction method, this larger culture area allows for easier handling, the potential for a wide range of exposures, as well as the collection of low-quantity samples (e.g., volatiles or mitochondrial RNA). The model consists of two large polydimethylsiloxane (PDMS) cell culture chambers under an independent flow of medium or air, separated by a semi-permeable polyethylene (PET) cell culture membrane (23 μm thick, 0.4 μm pore size). Each chamber carries a 5 × 18 mm, 90 mm² (92 mm² with tapered chamber inlets) surface area that can contain up to 1–2 × 10⁴ adherent structural lung cells and can be utilized for close contact co-culture studies of different lung cell types, including airway epithelial cells, fibroblasts, smooth muscle cells, and endothelial cells. The parallel bi-chambered design of the chip allows for epithelial cells to be cultured at the air–liquid interface (ALI) and differentiation into a dense, multi-layered, pseudostratified epithelium under biological flow rates. This millifluidic airway-on-chip advances the field by providing a readily reproducible, easily adjustable, and cost-effective large-scale fluidic 3D airway cell culture platform. Full article

Laminated shale oil reservoirs feature well-developed microcracks, with significant differences in wettability on either side of these fractures. The complex pore structure of laminated shale oil reservoirs makes capillary imbibition prevalent during both water injection and well shut-in periods. Therefore, based on the phase field method, this study investigates the imbibition behavior and the influencing factors during the injection and shut-in stage. This research shows that the imbibition mode determines the recovery rate: co-current imbibition > co-current imbibition + counter-current imbibition > counter-current imbibition. Co-current imbibition predominantly occurs in the dominant seepage channels, while counter-current imbibition mainly takes place in pore boundary regions. During the water injection stage, a low injection rate is beneficial for synergistic oil recovery through imbibition and displacement. As the injection rate increases, the capillary imbibition effect diminishes. Increased water saturation strengthens the co-current imbibition effect. Compared to injecting for 5 ms, injecting for 10 ms resulted in a 4.53% increase in imbibition recovery during the shut-in stage. The water sweep efficiency increases with the tortuosity of fractures. The wettability differences on either side of the fractures have a certain impact on imbibition. Around the fracture, the recovery in the strongly wetted area is 35% higher than that in the weakly water-wetted area. The wettability difference across fractures causes water to penetrate along the strongly water-wet pores, while only the inlet end and the pores near the fracture in the weakly water-wet zone are affected. Therefore, it is crucial to monitor the injection pressure to maximize the synergistic effects of displacement and imbibition during the development of laminated shale oil reservoirs. Additionally, surfactants should be used judiciously to prevent fingering due to wettability differences. Full article

Red sandstone is widely distributed in southern China. Due to the significant difference in mechanical properties before and after hydration and its poor water stability, red sandstone often triggers landslide accidents. In this paper, red sandstone from an open pit slope in Jiangxi Province was taken as the research object. Two variables, namely the initial saturation degree (25%, 50%, 75%, and 100%) and the number of wetting–drying cycles (0, 10, 20, 30, and 40), were set. With the help of nuclear magnetic resonance, the Brazilian disc test, and fractal theory, the relationships among its meso-structure, macroscopic fracture mechanics characteristics, and deterioration mechanism were analyzed. The research results are as follows: (1) Wetting–drying cycles have a significant impact on the pore structure and fracture mechanics characteristics of red sandstone. Moreover, the higher the initial saturation degree, the more obvious the deterioration effect of the wetting–drying cycles on the rock mass. (2) After further subdividing the pores according to their size for research, it was found that sandstone is mainly composed of mesopores, and the deterioration laws of different types of pores after the wetting–drying cycles are different. The porosities of total pores and macropores increase, while the proportions of mesopores and micropores decrease. The fractal dimensions of macropores and total pores of each group of rock samples are all within the range of 2–3, and the fractal dimension value increases with the increase in the number of wetting–drying cycles, showing significant and regular fractal characteristics. Micropores and some mesopores do not possess fractal characteristics. The fractal dimension of rock samples basically satisfies the rule that the larger the pore diameter, the larger the fractal dimension and the more complex the pore structure. (3) Both the type I and type II fracture toughness of rock samples decrease with the increase in the number of cycles, and the decrease is the most significant when the initial saturation degree is 100%. After 40 cycles, the decreases in type I and type II fracture toughness reach 23.578% and 30.642%, respectively. The fracture toughness is closely related to the pore structure. The porosity and fractal dimension of rock samples and their internal macropores are linearly negatively correlated with the type II fracture toughness. The development of the macropore structure is the key factor affecting its fracture mechanics performance. (4) After the wetting–drying cycles, the internal pores of red sandstone continue to develop. The number of pores increases, the pore diameter enlarges, and the proportion of macropores rises, resulting in internal damage to the rock mass. When bearing loads, the expansion and connection of internal cracks intensify, ultimately leading to the failure of the rock mass. The research results can provide important reference for the stability analysis of sandstone slope engineering. Full article

Deep-sea Fe-Mn polymetallic nodules formed nowadays at the deep-sea ocean floor were evaluated as promising critical raw materials (CRMs). Here, we report results of polymetallic nodules from the H22_NE block of the Interoceanmetal (IOM) exploration area in the eastern part of the Clarion–Clipperton Zone (CCZ), NE Pacific Ocean. The polymetallic nodules were studied with X-ray Diffraction, Raman spectroscopy, SEM-EDS, and LA-ICP-MS (bulk nodules and in situ nodule layers). Additionally, we combine geochemical data of polymetallic nodules with the previously reported data of pore waters and sediments from six stations. Our study aims to define the mineral composition and determine the content of CRMs in the polymetallic nodules and to assess the main factors controlling metal deposition and nodule enrichment in some CRMs. Mn content and the Mn/Fe ratio of the nodules classify them mostly as mixed hydrogenetic–diagenetic type. They are also enriched in Ni, Cu, Co, Zn, Mo, W, Li, Tl, and REE. The in situ REE patterns exhibit MREE and HREE enrichment and a variable Ce anomaly that argues for a changing oxic/suboxic environment and periodically changing of diagenetic and hydrogenetic nodule growth. The results of the joint study of the bottom sediments, pore waters, and polymetallic nodules show a complexity of processes that influence the formation of these deposits. The changing oxic and anoxic conditions are well documented in the chemistry of the nodule layers. Probably the most important controlling factors are sedimentation rate, bioturbation, adsorption, desorption, and oxidation. In addition, growth rates, water depth variations, electro-chemical speciation, phosphatization, and the structures of the Fe-Mn adsorbents are also considered. The polymetallic nodule deposits in the IOM contract area are estimated for future mining for Ni, Cu, Co, and Mn resources. They, however, contain additional metals of economic importance, such as REE and other trace elements (referred to as CRMs) that are potential by-products for metal mining. They can significantly increase the economic importance of exploited polymetallic nodules. Full article

The extensive release of water contaminated with lead (Pb(II)) and antimony (Sb(V)) constitutes a serious threat to the human living environment and public health, necessitating immediate attention. In this study, a novel MnFe@SBA composite was synthesized using the hydrothermal method through the in situ growth of MnFe₂O₄ on SBA-15. The MnFe@SBA exhibits an amorphous structure with a high specific surface area of 405.9 m²/g and pore sizes ranging from 2 to 10 nm. Adsorption experiments demonstrated that MnFe@SBA removed over 99% of Pb(II) and 80% of Sb(V) within 120 min at initial concentrations of 10 mg/L, whereas both MnFe₂O₄ and SBA-15 exhibited poor adsorption capacities. Additionally, the MnFe@SBA displayed excellent tolerance towards coexisting cations, including Na⁺, K⁺, Mg²⁺, Ca²⁺, Zn²⁺, Ni²⁺, and Cd²⁺, as well as anions such as Cl⁻, NO₃⁻, CO₃²⁻, and PO₄³⁻. The adsorption behavior of Pb(II) onto MnFe@SBA was satisfactorily described by the pseudo-second-order kinetic model and the Freundlich isotherm, while the adsorption of Sb(V) was well-fitted by the pseudo-second-order kinetic model and the Langmuir isotherm. At 318 K, the maximum adsorption capacities of MnFe@SBA for Pb(II) and Sb(V) were determined to be 329.86 mg/g and 260.40 mg/g, respectively. Mechanistic studies indicated that the adsorption of Pb(II) and Sb(V) onto MnFe@SBA involved two primary steps: electrostatic attraction and complexation. In conclusion, the MnFe@SBA is anticipated to serve as an ideal candidate for efficient removal of Pb(II) and Sb(V) from contaminated water. Full article