Porous Research Articles

Insight into the Imbibition Behavior of Low-Frequency Artificial Vibration Stimulation in Tight Sandstone.

Spontaneous imbibition is the primary mechanism responsible for the enhanced oil production in a tight reservoir after hydraulic fracturing. In this article, a low-frequency artificial vibration physics stimulation method was employed to evaluate the effect of low-frequency vibration on imbibition recovery in tight sandstones. Furthermore, a high-precision in situ computed tomography (CT) scan was employed to investigate the effect of low-frequency vibration on the distribution of remaining oil micro-occurrence dynamic alterations in pore space. The findings of the study show that (1) low-frequency artificial physical vibration stimulation has been found to be highly effective in enhancing imbibition recovery in tight sandstone. The sensitivity of the vibration parameters on imbibition recovery from highest to lowest is vibration frequency, vibration intensity, and vibration time. The optimum vibration parameters for this process are a vibration frequency of 30 Hz, a vibration intensity of 2.0 m/s2, and a vibration time of 30 h. (2) Under the optimum low-frequency vibration, the imbibition recovery of tight sandstone with various physical properties can reach between 13.6 and 28.3%. This is remarkably higher than the spontaneous imbibition recovery, which ranges from 9.4 to 17.1%. Additionally, core samples with higher permeability and better pore structure show a more significant increase in imbibition recovery under the vibration treatment. Furthermore, low-frequency vibration stimulation effectively shortens the imbibition completion time, reducing the completion time from 81 h to approximately 55 h. (3) After the spontaneous imbibition process, the initial continuous oil phase present in the pore space is dispersed by the water phase imbibition process. The remaining oil is dominant in the form of a network type, which is concentrated in the central pore space area of the core. Low-frequency vibration treatment can effectively promote a positive imbibition process. The network remaining oil saturation in the core can be further dispersed, especially closer to the surface of the core area after frequency vibration treatment. Then, the cluster remaining oil type with a more dispersed and simpler individual structure has become the new dominant remaining oil micro-occurrence form in the pore space. The findings of this research investigate a novel technological approach to enhance the imbibition efficiency of a tight sandstone reservoir.

Reverse Separation of Carbon Dioxide and Acetylene in Two Isostructural Copper Pyridine‐Carboxylate Frameworks

AbstractSeparating acetylene from carbon dioxide is important but highly challenging due to their similar molecular shapes and physical properties. Adsorptive separation of carbon dioxide from acetylene can directly produce pure acetylene but is hardly realized because of relatively polarizable acetylene binds more strongly. Here, we reverse the CO2 and C2H2 separation by adjusting the pore structures in two isoreticular ultramicroporous metal–organic frameworks (MOFs). Under ambient conditions, copper isonicotinate (Cu(ina)2), with relatively large pore channels shows C2H2‐selective adsorption with a C2H2/CO2 selectivity of 3.4, whereas its smaller‐pore analogue, copper quinoline‐5‐carboxylate (Cu(Qc)2) shows an inverse CO2/C2H2 selectivity of 5.6. Cu(Qc)2 shows compact pore space that well matches the optimal orientation of CO2 but is not compatible for C2H2. Neutron powder diffraction experiments confirmed that CO2 molecules adopt preferential orientation along the pore channels during adsorption binding, whereas C2H2 molecules bind in an opposite fashion with distorted configurations due to their opposite quadrupole moments. Dynamic breakthrough experiments have validated the separation performance of Cu(Qc)2 for CO2/C2H2 separation.

Understorey Plant Functional Traits of Platycladus orientalis Depends on Crown Closure and Soil Properties in the Loess Plateau, China

The crown closure of Platycladus orientalis forests has a wide-ranging impact on vegetation and soil, thereby affecting the overall functioning of the ecosystem. There is limited research on the effects of the Platycladus orientalis forest crown closure on changes in community plant functional traits, and their interactions are not yet clear. Therefore, we investigated 50 plots of different types of Platycladus orientalis crown closure, and we measured the functional traits of nine shrub species and 68 herb species in 50 plots under five different densities of Platycladus orientalis forests in the Loess Plateau. The consequence of Pearson’s correlation analysis showed significant positive correlations between LC and LTD, LN and LP, LN and LNP, LN and LV, LN and H, LP and LV, LP and H, and SLA and LV (p < 0.05). LC was significantly negatively correlated with LP, LC with SLA, LC with LV, LN with LTD, LP with LNP, LP with LTD, and LTD with H (p < 0.05). Only the soil phosphorus content (SP) and soil water content (SWC) showed a significant positive correlation with multiple plant functional traits. The crown closure of Platycladus orientalis forests increased significantly, as did the plant functional features. Changes in the Platycladus orientalis forest crown closure significantly increased the LC, LV, LN, LP, and SLA in plant functional traits. An increase in Platycladus orientalis forest crown closure significantly increased the soil organic carbon (SC), soil phosphorus content (SP), soil nitrogen content (SN), soil water content (SWC), field capacity (FC), and soil porosity (PO). Based on a structural equation model, we found that, while changes in the Platycladus orientalis forest crown closure did not directly affect plant functional traits, they could indirectly influence these traits through soil factors, primarily the soil water content (SWC) and soil phosphorus content (SP) (p < 0.05). Additionally, the mechanisms of the Platycladus orientalis forest crown closure’s impact on different functional traits vary. The research results provide scientific elements for the ecological restoration of Platycladus orientalis forests on the Loess Plateau.

Impedance Characteristics of Berea Sandstone Cores in the Process of CO<sub>2</sub> Injection Displacement with Saturated Brine

As an important means of CO<sub>2</sub> geological storage leakage monitoring, resistivity monitoring technology is of great significance to the safety and stability of CCUS project. In order to study the electrical signal response rule of the evolution of CO<sub>2</sub> saturation in the reservoir, a joint core displacement experiment system of electrochemical impedance analysis and microfocus X-ray CT was designed and constructed to simulate the process of CO<sub>2</sub> displacement of brine in Berea sandstone cores under stratigraphic temperature and pressure conditions. The electrochemical impedance characteristics of the core-fluid system are analyzed by electrochemical impedance spectroscopy. The experimental results show that at lower temperature and pressure, it is more difficult for CO<sub>2</sub> to invade the pore space occupied by the brine in situ, resulting in drastic changes in CO<sub>2</sub> plane saturation along the displacement direction. With the increase of temperature and pressure, the CO<sub>2</sub> saturation curve becomes smoother and the migration and displacement front becomes even. The Cole equivalent circuit model is used to describe the conduction mode of AC electrical signals inside the core, and the electrochemical impedance characteristic analysis focusing on the high frequency region shows that the system impedance increases with the increase of CO<sub>2</sub> saturation, and decreases with the increase of scanning frequency. In addition, the changes of impedance characteristics in the electrochemical impedance spectroscopy not only reflect the pore structure characteristics of the core, but also reveal the evolution law of CO<sub>2</sub> saturation in the porous medium. With the increase of CO<sub>2</sub> saturation, the low pore space is gradually occupied by CO<sub>2</sub>, and the residual brine connectivity of the pore space as a conductive component decreases. The decrease of the internal conductive circuit leads to the rapid increase of the impedance, which is consistent with the change of resistance and capacitance when fitting the Cole equivalent circuit model.

Facile and economic preparation of graphene hydrothermal nanocomposite from sunflower waste: Kinetics, isotherms and thermodynamics for Cd(II) and Pb(II) removal from water

Keeping the need for good water quality and the demand of climatic issues, the sunflower waste was converted into graphene hydrothermal nanocomposite absorbents for the removal of toxic Cd(II) and Pb(II) metal ions from water. The graphene composite materials were studied by scanning (SEM) and transmission electron microscopy (TEM), XRD analysis, TG and DSC, Raman and IR spectroscopy. According to SEM and TEM analysis, the decarbonized materials had a disordered structure with amorphous carbon with a small pore content. During the carbonization process, the pores space was opened due to the removal of amorphous organic matter and the formation of defects; providing a significant number of meso- and micropores. The prepared graphene composite showed 133.33 and 222.22 mg/g Langmuir adsorption of Cd(II) and Pb(II) at pH 6.0, dose 0.33 g/30 mL, initial concentration 300 mg/L, time 30 min and at 45 °C temperature using hydrothermal nanocomposite HTC/graphene oxide absorbent. The obtained results followed the sorption of heavy metal ions in a mixed-diffusion mode with the contribution of a second-order reaction between the active center of the sorbent and the metal ions. The Temkin and Dubinin-Radushkevich model’s parameters and thermodynamic results confirmed endothermic physical interactions among adsorbent and metal ions. This paper is highly useful for managing sunflower waste and purifying water; leading to the present demand for clean water and climatic issues. The production of the effective low-cost nanocomposite using green synthesis technologies (hydrothermal carbonization of raw materials) is highly useful for the removal of Cd(II) and Pb(II) toxic metal ions from water.

Multi-scale pore model construction and damage behavior analysis of SiCf/SiC composite tubes

SiCf/SiC composite materials are essential for spacecraft thermal protection, determining the safety of spacecraft. However, their complex structures and intricate fabrication processes have led to an unclear understanding of their failure mechanisms, limiting their application. In this study, circumferential compression experiments were conducted, and X-ray computed tomography (X-CT) was used to analyze the distribution characteristics of pore spaces. The experimental results indicate that damage manifests as secondary fracture phenomena based on temporal evolution characteristics. Specifically, after experiencing performance degradation of 24.73–60.96%, the material still maintained basic stability, exhibiting a performance recovery of 31.55–36.1% under the applied load until failure. To predict the dynamic damage behavior of materials at multiple scales, a multi-scale method combining statistical and microscopic approaches was proposed. A micro representative volume element (RVE) random fiber pore distribution model was established based on random processes and random medium theory. Finally, considering the CT data and the principle of minimum potential energy, a macroscopic finite element model of the micro-pores' structural characteristics in a three-dimensional wound tube was reconstructed. The results indicate that cracks initiate around pore defects and gradually propagate to form crack bands. The model closely matches the macroscopic damage and microscopic characteristics of the material. This work provides a new approach for the numerical simulation of pore defects in such materials.

Coupling of porosity and diffusive transport in highly reactive systems: Open issues of reactive transport modelling

Mineral precipitation at interfaces between contrasting materials and porewaters decreases the local porosity and consequently reduces transport across the interface. The near-field of waste repositories usually contains reactive interfaces, and the long-term evolution of diffusive transport away from the waste across the near-field is of special interest in this context. Diffusion as well as further mineral reactions significantly slow down when complete porosity clogging is approached, such that any further development is difficult to detect in experiments. But ongoing diffusion, even if very limited, might be significant for relevant times of up to 1 million years. If clogging occurs in clay materials, experimental studies report a much stronger decrease in anion diffusion compared to that of cations or neutral species. Continuum-scale reactive transport codes can predict experimentally observed clogging, but rely on specific implementations based on conceptual assumptions. Typically, the codes calculate porewater-mineral reactions only within a single cell, and they neglect the physical contact of the clogging mineral in one cell with the porewater in an adjacent cell (no inter-cell reactions considered). This can lead to unrealistic model predictions if porosity approaches zero. For instance, neutral pH porewater is permitted to be in contact with clogging cement hydrates in the adjacent cell, and the implied dissolution of the high-pH minerals is not considered anymore. Thus, intrinsically reactive minerals can be converted erroneously into inert, relict phases by such models. We present a new approach that mimics inter-cell reactions. In doing so, clogging is substantially delayed, and no real steady state with the boundary conditions can be attained, in contrast to conventional approaches. Furthermore, we use a dual-porosity reactive transport approach that takes into account the electrostatic effects of charged clay surfaces on diffusion and precipitation, and apply it to concrete-clay interaction. No complete clogging of the pore space occurs, and the predictions well fit experimental data. Modelling studies that predict the separation of a reactive system into two domains by localised full porosity clogging, followed by separate internal equilibration of the domains, are widespread in the literature. This prediction is interpreted as a conceptual artefact of continuum-scale modelling, which should be avoided by allowing for reactions of completely clogged cells with adjacent porewater. For clays, the dual-porosity model may be a viable option in this respect.

Investigating snap-off behavior during spontaneous imbibition in 3D pore-throat model by pseudopotential lattice Boltzmann method

As a result of complex pore-throat geometry and precursor corner flow, the snap-off of the non-wetting phase occurs during the spontaneous imbibition (SI) of wetting phase. However, accurate modeling of such pore-scale flow behavior remains a big challenge, and its influencing factors remain unclear. In this study, an improved pseudopotential lattice Boltzmann method (LBM) is used to analyze the snap-off behavior during the SI process in three-dimensional (3D) pore-throat models with rough surfaces. The influence of the pore-to-throat size ratio (λ), contact angles (θ), and Ohnesorge number (Oh) on the occurrence of the snap-off are investigated and based on which a 3D phase diagram is established. The snap-off is more likely to occur with the increase in λ and Oh and decrease in θ, respectively. Only when the λ is ≥2 and the θ is <13°, the snap-off may occur. With the increase in θ from 0° to 13°, the snap-off is suppressed due to the relatively small advancing difference between the corner flow and the bulk meniscus. Volume fraction of the entrapped gas bubble in the pore increases with the increase in λ and Oh and the decrease in θ. The time when snap-off occurred increases with the increase in λ and θ, and decrease in Oh. These results are fundamental for investigating snap-off phenomena in real 3D pore space and guide how to avoid or facilitate the occurrence of snap-off and to control the degree of snap-off.

Impact of nanopore confinement on phase behavior and enriched gas minimum miscibility pressure in asphaltenic tight oil reservoirs

Miscible gas injection in tight/shale oil reservoirs presents a complex problem due to various factors, including the presence of a large number of nanopores in the rock structure and asphaltene and heavy components in crude oil. This method performs best when the gas injection pressure exceeds the minimum miscibility pressure (MMP). Accordingly, accurate calculation of the MMP is of special importance. A critical issue that needs to be considered is that the phase behavior of the fluid in confined nanopores is substantially different from that of conventional reservoirs. The confinement effect may significantly affect fluid properties, flow, and transport phenomena characteristics in pore space, e.g., considerably changing the critical properties and enhancing fluid adsorption on the pore wall. In this study, we have investigated the MMP between an asphaltenic crude oil and enriched natural gas using Peng-Robinson (PR) and cubic-plus-association (CPA) equations of state (EoSs) by considering the effect of confinement, adsorption, the shift of critical properties, and the presence of asphaltene. According to the best of our knowledge, this is the first time a model has been developed considering all these factors for use in porous media. We used the vanishing interfacial tension (VIT) method and slim tube test data to calculate the MMP and examined the effects of pore radius, type/composition of injected gas, and asphaltene type on the computed MMP. The results showed that the MMP increased with an increasing radius of up to 100 nm and then remained almost constant. This is while the gas enrichment reduced the MMP. Asphaltene presence changed the trend of IFT reduction and delayed the miscibility achievement so that it was about 61% different from the model without the asphaltene precipitation effect. However, the type of asphaltene had little impact on the MMP, and the controlling factor was the amount of asphaltene in the oil. Moreover, although cubic EoSs are particularly popular for their simplicity and accuracy in predicting the behavior of hydrocarbon fluids, the CPA EoS is more accurate for asphaltenic oils, especially when the operating pressure is within the asphaltene precipitation range.

Generation of pore-space images using improved pyramid Wasserstein generative adversarial networks

High-resolution three-dimensional X-ray microscopy can be used to image the pore space of materials. Machine learning algorithms can generate a statistical ensemble of representative images of arbitrary sizes for rock characterization, modeling, and analysis. However, current methods struggle to capture features at different spatial scales observed in many complex rocks which have a wide range of pore size. We use the Improved Pyramid Wasserstein Generative Adversarial Network (IPWGAN) to automatically reproduce multi-scale features in segmented three-dimensional images of porous materials, enabling the reliable generation of large-scale representations of complex porous media. A Laplacian pyramid generator is introduced, which creates pore-space features across a hierarchy of spatial scales. Feature statistics mixing regularization enhances the discriminator’s ability to distinguish between real and generated images by mixing their feature statistics, thereby indirectly enhancing the generator’s ability to capture and reproduce multi-scale pore-space features, leading to increased diversity and realism in the generated images. The method has been tested on five sandstone and carbonate samples. The generated images, which can be of any size – including cm-scale ten-billion-cell images – demonstrate the power of the approach. These images have two-point correlation functions, porosity, permeability, Euler characteristic, curvature, and specific surface area closer to those of the training datasets than existing machine learning techniques. The generated images accurately capture geometric and flow properties, demonstrating a considerable improvement over previously published studies using generative adversarial networks. For instance, the mean relative error in the calculated absolute permeability between the Berea sandstone images generated by IPWGAN and the corresponding real rock images can be reduced by 79%. The work allows representative models of a wide range of porous media to be generated, offering potential benefits in carbon dioxide sequestration, underground hydrogen storage, and enhanced oil recovery.

Pore Space Partitioning by Using Two C3 Ligands as a Route toward a Quaternary Metal–Organic Framework

Pore Space Partitioning by Using Two <i>C</i>₃ Ligands as a Route toward a Quaternary Metal–Organic Framework

Nitrous Oxide Emissions and Ammonia Volatilization from Pasture after Cattle Dung and Urine Applications in the Dry and Rainy Seasons of the Brazilian Cerrado

An important source of greenhouse gases in Brazil is the nitrous oxide (N2O) emission from pasture, and microorganisms play an important role in nitrogen transformations in the soil. This study aimed to evaluate N2O emission and NH3 volatilization from bovine excreta in pasture in an integrated crop–livestock system (ICL) in the Brazilian Cerrado. Three treatments (urine, dung and control) were performed in two pastures (Area 1—three-year pasture of Urochloa ruziziensis and Area 2—one-year pasture of Urochloa brizantha cv. Piatã), with two application times of the excreta (dry and rainy season), during two successive years of application. Compared to the control, the excreta deposition on ICL increased soil N2O and NH3 fluxes. In the dry season, N2O fluxes were associated with higher ammonium (NH4+) availability. In the rainy season, these fluxes were related to NO3− availability and water-filled pore space (WFPS). In both areas, NH3 volatilization was higher after urine than dung application, especially in the dry season. The highest N2O emission factors were obtained for urine (0.32%), the rainy season (0.36%), and older pasture (Area 1: 0.24%). All these values were below the mean IPCC default values (0.77%). These results indicate that N2O emissions in pasture should be evaluated in regional conditions.

Changes in the enamel surface in patients with polymorphism of the &lt;i&gt;VDR&lt;/i&gt; gene under the action of remineralizing composition and vitamin D

BACKGROUND: The leading role in the pathogenetic mechanism of caries development is the imbalance between the de and remineralization of hard tooth tissues. The combination of VDR alleles affects calcium-phosphate metabolism. In 65% of the human population, the structure of the VDR gene has a genetic polymorphism. AIM: To study the effect of vitamin D and a remineralizing paste on the enamel surface structure in patients with genetic polymorphism of VDR gene receptors. MATERIALS AND METHODS: In 18 individuals with a polymorphism index of the VDR A/A gene, a laboratory indicator of 25 (OH) vitamin D in the blood of 18.20±1.84 ng/ml, according to orthodontic indications, the retinated third molars in the lower jaw were removed. Then, the samples were lowered into three flasks of six pieces with 100 ml of artificial saliva. Containers with teeth were divided into groups: group 1, with a solution of artificial saliva only; group 2, an additional 1,000 IU of an aqueous solution of vitamin D; and group 3, tooth enamel was treated for 2 minutes with an electric toothbrush with a paste containing a remineralizing composition, immersed in artificial saliva with cholecalciferol 1,000 IU. The flasks were in the thermostat at a temperature of 37.4 C per day. In all samples, electron microscopy of the enamel contact surface at the level of the crown equator was performed using a Tescan Mira 3 LMU microscope (TESCAN, Czech Republic) with an Oxford X-MAX 5 energy dispersive X-ray detector (Oxford Instruments, United Kingdom) with analysis of local mineral composition. RESULTS: In group 1, with electron microscopy of enamel, areas of increased mineralization alternated with areas of reduced density. The coefficient of the molar ratio Ca/P was 1.32±0.13, indicating the destruction of hydroxyapatites. In group 2 the intercrystalline pore space was filled with calcium and phosphate ions. In group 3, the enamel surface acquired a smooth homogeneous relief. An increase in the weight percentage of trace elements was observed, and the Ca/P ratio was 2.20±0.02, which indicated a phase of remineralization. CONCLUSION: Patients with VDR gene polymorphism have a vitamin D deficiency in the blood serum. The trace element composition of the enamel surface is characterized by a phase of demineralization. Treatment with remineralizing paste and addition of cholecalciferol solution to artificial saliva changes the structure of hydroxyapatite and increases the caries-resistant properties of enamel.

A Novel Method to Calculate Water Influx Parameters and Geologic Reserves for Fractured-Vuggy Reservoirs with Bottom/Edge Water

In practical oilfield production, the phenomenon of water influx typically shortens the water-free recovery period of wells, leading to water flooding and causing a sharp decline in the production well yields, bringing great harm to production. Water invasion usually occurs as a result of the elastic expansion of the water as well as the compaction of the aquifer pore space. However, it can be due to the special characteristics of fractured-vuggy reservoirs such as non-homogeneity and the discrete distribution of the pore spaces. It is challenging to use traditional seepage flow theories to analyze the characteristics of water influx. Also, reservoir numerical simulation methods require numerous parameters which are difficult to obtain, which significantly reduces the accuracy of the results. In this study, considering the driving energy for water influx, a water influx characteristic model was obtained by fitting a graph plate. Subsequently, an iterative calculation method was used to simultaneously obtain water influx volume and OOIP. The aquifer to hydrocarbon ratio was determined by fitting the water influx curve with the graphic plate. Results show that the calculation method is sensitive to the values of reservoir pressure and the crude oil formation volume factor. After applying the method to one field case, it was discovered that water influx performance can be characterized into two types, i.e., linear water influx and logarithmic water influx. In the early stages, the water influx rate of logarithmic water influx is greater compared to linear water influx. However, the volume and energy of waterbody are limited, and the water invasion phenomenon occurs almost exclusively within a short period after the invasion. On the other hand, the volume of waterbody invaded by linear water influx is larger, and it can maintain a stable rate of water influx. The results of the study can provide theoretical support for the waterbody energy evaluation and dynamic analysis of water influx, as well as the control and management of water in these types of reservoirs.

Influence of N, P, K, Rhizobium and Vermicompost on Soil Health Parameters and Yield of Green Gram (Vigna radiata L.) var. Samrat

An experiment was conducted on “Influence of N, P, K, Rhizobium and Vermicompost on Soil Health Parameters and Yield of Green Gram (Vigna radiata L.) var. Samrat”. during zaid season 2023-2024 at the central research farm, department research farm of Soil Science and Agricultural Chemistry, The design applied was 3x3 RBD having three levels each of vermicompost and N.P.K i.e., 0, 50, and 100% respectively and three levels of rhizobium treated seed @ 0, 50, 100%. The result obtained in treatment T9 (N25P50K25 kg ha-1 + vermicompost @ 5 t ha-1 and rhizobium @ 200g 10 kg-1) has showed a slight change in soil pH i.e., 6.79 and EC i.e., 0.208 dS m-1. The post-harvest soil samples have showed significant increase in pore space, water holding capacity and organic carbon i.e., about 49.20 %, 47.59 % and 0.49 % respectively. Whereas available N, P and K found to be 334.12 kg ha-1, 34.36 kg ha-1, and 204.28 kg ha-1 respectively. The increase in NPK (kg ha-1) was found to be significant among all treatments in green gram cultivation and soil quality improvement. The best results among all treatment combination with respect to plant height (65.76 cm), number of leaves plant-1 (44.34), number of branches plant-1 (14.58), number of grain pod-1 (14.28), number of pod plant-1 (42.11) and seed yield q ha-1 (16.67) were found in treatment combination T9 (N25P50K25 kg ha-1 + vermicompost @ 5 t ha-1 and Rhizobium @ 200g 10 kg-1. T9 gave the highest gross return with ₹ 1,49,030 and the benefit of ₹ 29,849.13 with highest cost benefit ratio i.e., 1:1.38. vermicompost along with other combinations has showed improvement in soil health as well as in crop development and yield. Study has also revealed that the application of N, P, and K with vermicompost was an excellent source for fertilization than sole fertilizers.

Vulnerability of firn to hydrofracture: poromechanics modeling

Abstract On the Greenland Ice Sheet, hydrofracture connects the supraglacial and subglacial hydrologic systems, coupling surface runoff dynamics and ice velocity. In recent decades, the growth of low-permeability ice slabs in the wet snow zone has expanded Greenland's runoff zone, but observations suggest that surface-to-bed connections are rare, because meltwater drains through crevasses into the porous firn beneath ice slabs. However, there is little quantitative evidence confirming the absence of surface-to-bed fracture propagation. Here, we use poromechanics to investigate whether water-filled crevasses in ice slabs can propagate vertically through an underlying porous firn layer. Based on numerical simulations, we develop an analytical estimate of the water injection-induced effective stress in the firn given the water level in the crevasse, ice slab thickness, and firn properties. We find that the firn layer substantially reduces the system's vulnerability to hydrofracture because much of the hydrostatic stress is accommodated by a change in pore pressure, rather than being transmitted to the solid skeleton. This result suggests that surface-to-bed hydrofracture will not occur in ice slab regions until all pore space proximal to the initial flaw has been filled with solid ice.

Elucidating the failure of the Ideal Adsorbed Solution Theory for CO2/H2O mixture adsorption in CALF-20

The use of CALF-20 for CO2 capture from humid flue gases has attracted a vast amount of attention from both academia and industry. The focus of this article is on CO2/H2O mixture adsorption for which published experimental data demonstrate the severe limitations of the Ideal Adsorbed Solution Theory (IAST) in providing a quantitative estimation of the component loadings. We use Configurational-Bias Monte Carlo (CBMC) simulations for elucidating the origins of thermodynamic non-idealities. The CBMC simulations reveal that two distinct regimes prevail during mixture adsorption. For low relative humidities less than say 20 %, the CO2 loadings in the adsorbed phase is significantly higher than anticipated by the IAST. CBMC simulations of intermolecular distances for guest pairs reveal that failure of the IAST can be traced to the phenomenon of segregated adsorption. The H2O-H2O pairs are close together at typical distances of about 3 Å. The CO2-H2O pairs are typically 8 Å apart, occupying adjacent adsorption sites corresponding to the O atoms of the oxalate group. This implies that the CO2 molecules face a less severe competitive adsorption with H2O than is anticipated by the IAST, whose applicability mandates a uniform and homogeneous distribution of adsorbates in pore space. The situation changes dramatically at high values of relative humidities, typically larger than about 50 %; in this scenario, the adsorbed phase is significantly richer in H2O. The CO2 molecules are compelled to share same adsorption site with pairs of H2O molecules that are hydrogen-bonded with each other. Consequently, the competition faced by CO2 is significantly higher than anticipated by the IAST, resulting in significantly lower CO2 uptakes.The important message that emerges from this investigation is the need to incorporate the Real Adsorbed Solution Theory (RAST) for quantitative modelling of fixed-bed adsorbers in CO2 capture with CALF-20.

Conservation tillage: a way to improve yield and soil properties and decrease global warming potential in spring wheat agroecosystems.

Climate change is one of the main challenges, and it poses a tough challenge to the agriculture industry globally. Additionally, greenhouse gas (GHG) emissions are the main contributor to climate change; however, croplands are a prominent source of GHG emissions. Yet this complex challenge can be mitigated through climate-smart agricultural practices. Conservation tillage is commonly known to preserve soil and mitigate environmental change by reducing GHG emissions. Nonetheless, there is still a paucity of information on the influences of conservation tillage on wheat yield, soil properties, and GHG flux, particularly in the semi-arid Dingxi belt. Hence, in order to fill this gap, different tillage systems, namely conventional tillage (CT) control, straw incorporation with conventional tillage (CTS), no-tillage (NT), and stubble return with no-tillage (NTS), were laid at Dingxi, Gansu province of China, under a randomized complete block design with three replications to examine their impacts on yield, soil properties, and GHG fluxes. Results depicted that different conservative tillage systems (CTS, NTS, and NT) significantly (p < 0.05) increased the plant height, number of spikes per plant, seed number per meter square, root yield, aboveground biomass yield, thousand-grain weight, grain yield, and dry matter yield compared with CT. Moreover, these conservation tillage systems notably improved the soil properties (soil gravimetric water content, water-filled pore space, water storage, porosity, aggregates, saturated hydraulic conductivity, organic carbon, light fraction organic carbon, carbon storage, microbial biomass carbon, total nitrogen, available nitrogen storage, microbial biomass nitrogen, total phosphorous, available phosphorous, total potassium, available potassium, microbial counts, urease, alkaline phosphatase, invertase, cellulase, and catalase) while decreasing the soil temperature and bulk density over CT. However, CTS, NTS, and NT had non-significant effects on ECe, pH, and stoichiometric properties (C:N ratio, C:P ratio, and N:P ratio). Additionally, conservation-based tillage regimes NTS, NT, and CTS significantly (p < 0.05) reduced the emission and net global warming potential of greenhouse gases (carbon dioxide, methane, and nitrous oxide) by 23.44, 19.57, and 16.54%, respectively, and decreased the greenhouse gas intensity by 23.20, 29.96, and 18.72%, respectively, over CT. We conclude that NTS is the best approach to increasing yield, soil and water conservation, resilience, and mitigation of agroecosystem capacity.

Petrography and Diagenesis of Thin-Bed Reservoirs from the Eastern Folded Belt of Bangladesh

The main purpose of the study is to identify the thin-bed reservoirs of the Eastern Folded Belt (Sylhet and Bandarban) and characterize them with diligence. A detailed qualitative and quantitative analysis has been carried out. It is based on thin-section petrographic analyses of sandstone samples. These samples are from the reservoir horizons of the Sylhet region and Bandarban region fields. The purpose of this analysis is to characterize the textural and mineralogical properties. Additionally, it aims to evaluate the post-depositional diagenetic changes. The results obtained from the field and laboratory analysis are studied extensively to characterize the thin-bed reservoirs. Samples from the Sylhet area are medium-coarse-grained, fairly sorted, tight packing, submature-mature sublithic characteristics. Contrarily, samples from the Bandarban region are mature-submature sublithic arenites, which are fine-medium-grained, moderately well-sorted, and moderately loosely packed. Despite the similarity of the detrital elements (quartz, feldspar, lithic grains, mica, etc.) in the two areas, silica cementation is more frequent in Sylhet region samples than early carbonate cementation in Bandarban region samples. Comparatively speaking, the sediments in the Sylhet region are more compact than those in the Bandarban region. The most important outcome of this study is that the thin bed of the unconventional reservoir and the conventional reservoir are in close proximity. The Thin-bed reservoir units of the Eastern Folded Belt are found to be medium to fine-grained and well sorted, with frequent alteration of sand-shale with the prevalence of parallel bedded sandstone. Average porosity is 4% to 12%, and pore spaces are interconnected. So, the permeability rate is good enough to flow the hydrocarbon through these pore spaces. Most importantly, the thin bed and tight reservoir (average porosity 4% to 12%, but pore spaces are not interconnected) are not more prominent than 1 meter or 2 meters. Subsequently, though the vertical thickness is not so high, they keep up a momentous tirelessness of horizontal progression. On the contrary, at whatever point it comes to a conventional reservoir, the vertical thickness is higher than that of the unconventional reservoir. But their lateral persistence is not as long as unconventional ones.

Competitive adsorption of CH4/CO2 in shale nanopores during static and displacement process

During the development of shale gas, various issues such as low individual well production, rapid decline, limited reservoir control, and low recovery rates have arisen. Enhancing shale gas reservoir recovery rates has consistently been a focal point and challenge within the industry. Therefore, this paper employs molecular dynamic (MD) simulation methods to study the adsorption and diffusion characteristics of CH4/CO2 at different temperatures and mixing ratios. It compares the effects of temperature and CH4/CO2 molar ratio changes on the selectivity coefficient, adsorption capacity, and diffusion coefficient of CH4/CO2. The paper also plots the displacement interface and the function of CH4/CO2 injection/residual amounts over time. Furthermore, it analyzes the adsorption capacity of molecules on the graphene surface, the migration capacity of molecules in the slit, and the displacement process of CH4 by CO2 on the nanoscale, revealing the microscopic mechanism of CH4/CO2 competitive adsorption and displacement. The research results indicate that the influence of temperature on the selectivity coefficient is not significant, with an average decrease of 3% for every 20 K rise in temperature. Pressure has a more pronounced effect on the selectivity coefficient, with values around 1.4 at low pressures and around 1.2 at high pressures. Elevating the mole fraction of CO2 in the binary gas mixture results in an increase in the total adsorption amount and an accelerated variation of adsorption amount with pressure. As the CH4 mole fraction rises, the diffusion coefficient of CH4 increases, while the diffusion coefficient of CO2 diminishes with an increasing CO2 mole fraction. Under identical conditions, CO2 exhibits a stronger adsorption capacity over CH4 in shale organic nanopores, resulting in a concave moon-shaped displacement interface in the model. The larger the pre-adsorption pressure of CO2, the more intense the movement of CO2 along the graphene surface, and the faster the diffusion speed of CO2 along the wall. In a displacement pore (the pore space used to provide the displacement location or site) with a diameter of 3 nm, at smaller pressure differentials (≤10 MPa), the residual amount of CH4 remains relatively stable without substantial alteration. However, at a pressure differential of 20 MPa, the residual amount of CH4 decreases rapidly, and the displacement efficiency significantly improves.