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A series of sulfosuccinate esters of cyclic alcohols was synthesized and we studied their effect on the kinetics of methane hydrate formation in high-pressure autoclaves. The effects of the structure of these compounds on foaming, induction time, and water-to-hydrate conversion were considered in comparison with sodium dodecyl sulfate. The preparation of these compounds was presented in detail. An increase in size of the cyclic fragment from C5 to C7 leads to some increase in the rates of nucleation and growth of the methane hydrate, while going to an eight-membered carbon ring leads to a decrease in the promotion effect. The effect of the synthesized compounds on the increase in rate of gas hydrates is comparable to the effect for sodium dodecyl sulfate. At the same time, the proposed reagents possess better performance characteristics (do not contribute to foaming). [ABSTRACT FROM AUTHOR]

Experimental data on dissociation of propane hydrate samples obtained from bulk samples of ice and frozen aqueous polyvinylpyrrolidone solutions are presented. It was observed that propane hydrate exhibits self-preservation effect (with very low dissociation rate) when subjected to a sudden pressure drop in the presence of polyvinylpyrrolidone. This phenomenon occurs at temperatures below 271 K. The results of the experiments made it possible to establish the range of polyvinylpyrrolidone concentration in frozen aqueous solutions and to estimate the thickness of the ice crust formed on the gas hydrate surface during dissociation, at which the self-preservation effect of propane hydrate is realized. It has been established experimentally that the shielding effect of the ice crust of preserved propane hydrate is retained up to 272 K and disappears completely near 273 K. [ABSTRACT FROM AUTHOR]

Results are given for a study of the formation and decomposition of natural gas hydrates in quartz sand in the presence of fresh water as well as 0.25 and 2 mass % aqueous sodium bicarbonate and 5 mass % aqueous sodium chloride. These solutions are models of stratum water of subpermafrost aquifers of the Vilyui syneclise. We studied the effect of the porous medium and salinity on hydrate formation using differential thermal analysis with initial pressure from 4 to 7 MPa. Equilibrium conditions and kinetic parameters for hydrate formation were determined. The hydrate formation kinetic parameters in porous media decrease for each initial pressure depending on the salinity in the following order: 0.25 mass % NaHCO3 ≈ H2O > 2 mass % NaHCO3 > 5 mass % NaCl. We studied the stability of the hydrates obtained in porous media with different salinity. The stability of the hydrates in the porous media decreases with increasing salt concentration in the solution. [ABSTRACT FROM AUTHOR]

This article presents the results of experimental studies of the kinetics of methane hydrate formation from frozen ground soy lecithin (particle size 80-140 μm) solutions with lecithin concentrations from 0.1 to 1 wt. % at 273.2 K temperature and initial pressure of about 5 MPa without stirring. It was observed that the presence of soy lecithin additive in frozen powdered solutions enhances the water-to-methane hydrate conversion ratio roughly twofold compared to ground ice. The proposed mechanisms of promotion of methane hydrate formation in frozen powdered soy lecithin solutions are described by use of nuclear magnetic resonance (NMR) spectroscopy, viscometry, and optical microscopy. [ABSTRACT FROM AUTHOR]

This work is devoted to the synthesis and optimization of methods for obtaining low‑dose hydrate formation inhibitors derived from waterborne polyurethanes. Some monomers were replaced by less expensive reagents that need not be imported to Russia in order to optimize the synthesis of such inhibitors. Two polymerization procedures were tested. One method was carried out in a batch reactor, while the other continuous method was carried out in a flow reactor. A laboratory flow unit was designed to simulate the conditions of the continuous synthesis. [ABSTRACT FROM AUTHOR]

The study investigated the kinetics of methane hydrate nucleation and growth in aqueous methanol solutions with concentrations of 0, 1, 2.5, 5, 10, and 20 mass%. It was established that the reduction of the supercooling at the onset of methane hydrate formation ΔTo by adding methanol is statistically significant, even at low concentrations. The value of ΔTo decreases by a factor of five in the transition from water to 20 mass% alcohol solution. It was found that a correlation involving an increase in the amount of hydrate at the end of the cooling stage is observed with an increase in the alcohol content. Further, adding methanol to the water also increases the growth rate of the methane hydrate. The experimental data shows that methanol plays a role as a promoter of nucleation and growth of methane hydrate, and also indicates the dual nature of methanol, which is simultaneously a thermodynamic inhibitor of gas hydrates. [ABSTRACT FROM AUTHOR]

Heavy metal pollution is an urgent challenge worldwide due to the acceleration of industrialization. While adsorption desalination is regarded as an innovative method for wastewater treatment, the current technologies have been impeded by high costs and intensive energy consumption. In this work, a novel low-temperature evaporation wastewater treatment apparatus based on hydrate adsorption was proposed. The water vapor from wastewater evaporation reacted with CO2 to form hydrate under the pressure of 3.3 MPa, constantly promoting wastewater evaporation due to the consumption of water vapor. The effect of feeding concentration on treatment effect was analyzed in terms of removal efficiency, water yield, and enrichment factor. Remarkably, a maximum removal efficiency of 97.4% can be achieved by treating an artificial solution with a Cu2+ concentration of 500 mg/L. Furthermore, compared with the control group that only depended on evaporation and condensation without forming hydrate, the maximum water yield of purified water in the experimental group increased to 310%. This innovative design concept for a low-temperature wastewater treatment apparatus based on hydrate adsorption presents a promising solution for the green and energy-efficient treatment of heavy metal wastewater. [ABSTRACT FROM AUTHOR]

However, some gases (mainly methane) are buried in bottom sediments and become sequestered in gas hydrates forming large gas reservoirs. Meanwhile, heat insulation of tubing will keep the permafrost frozen over the whole well lifespan and prevent its degradation, as well as the ensuing dissociation of intrapermafrost gas hydrates and methane emission. Explosive gas emission is modeled for the case of the Yamal Peninsula, with regard to high gas contents in shallow permafrost which encloses ground ice, unfrozen intra-permafrost and sub-permafrost saline lenses (cryopegs), and hydrocarbon accumulations with related ascending gas-water fluids. [Extracted from the article]

On Earth, natural hydrates are mostly encountered in clay‐rich sediments. Yet their formation processes in such matrices remain poorly understood. Achieving an in‐depth understanding of how methane hydrates accumulate on continental margins is key to accurately assess (a) their role in sustaining the development of some chemosynthetic communities at cold seeps, (b) their potential in terms of energy resources and geohazards, and (c) the fate of the methane releases, a powerful greenhouse gas, in this changing climate. This study investigated the formation of methane hydrates and their gas storage capacity (GSC) in clay‐rich sediments. A set of hydrate experiments were performed in matrices composed of sand, illite‐rich clay, and montmorillonite‐rich clay at different proportions aiming to determine the role of mineralogy on hydrate formation processes. The experiments demonstrate that a clay content of 10% in a partially water saturated sand/clay mixture increases the induction time by ∼60%, irrespective of the nature of the clay used. The increase in water saturation in the two matrices promotes hydrate formation. Micro‐Raman spectroscopic analyses reveal that increasing the clay content leads to a decrease in the hydrate small‐cage occupancy, with an impact on the storage capacity. Finally, the analyses of collected natural samples from the Black Sea (off Romania) enable us to estimate the GSC of the deposit. Our estimates is different from previous ones, and supports the importance of coupling multiscale properties, from the microscale to the geological scale, to accurately assess the total amount of methane hosts in hydrate deposits worldwide. Plain Language Summary: Natural gas hydrates are amongst the largest methane reservoirs on Earth. They are sensitive to temperature increase. Societal and environmental concerns surrounding natural gas hydrates pertain to their decomposition, and in particular to the amount of gas they may release and its fate: can it trigger geohazards, or jeopardize the development of unique chemosynthetic communities encountered on continental margins? In‐depth knowledge of hydrate formation processes and properties are essential to provide reliable answers to these questions. The majority of hydrate deposits are characterized by clay‐rich sediments. We led a comprehensive study coupling fine microstructural analyses of both natural and synthetic hydrate samples with macroscale laboratory experiments within different matrices to show how clays can affect their formation kinetics and storage capacity. We found that even a small amount of clay can significantly change the formation kinetics of hydrates, and the matrix mineralogy affects their storage capacity. This study is crucial with a view to accurately assessing the amount of methane trapped in hydrate deposits, and for improved prediction of the consequences of their decomposition on the environment in a changing climate. Key Points: Clay content and clay mineralogy significantly affect the induction time of methane hydrate formation as well as the hydrate morphologyIllite‐rich clays reduce the cage occupancy of hydrates and thus the resulting gas storage capacity (GSC)Microscale analyses underpins the need to characterize microscopic properties of hydrates to estimate GSC [ABSTRACT FROM AUTHOR]

Methane hydrates in natural geological settings are commonly distributed within sediments, with a variety of minerals (such as silica sand, talc, and montmorillonite). The mechanisms that control the influence of sediments on methane hydrate formation remain poorly understood. In this study, we performed experiments on methane hydrate formation in pure H2O with the addition of 3% sediments (montmorillonite, talc, and silica sand). A large-volume stirred reactor (80 mL) and a small-volume unstirred reactor (20 mL) were used. The results show that montmorillonite and talc severely inhibit methane hydrate formation. For experiments in the stirred reactor with pure H2O, normalized gas consumption is 30 (mmol/mol) after 1000 min. In contrast, normalized gas consumption in experiments with the addition of 3% montmorillonite and talc decreases greatly to <5 (mmol/mol) over the same period. The inhibiting effect of montmorillonite and talc is closely associated with the release of cations (Mg2+, Ca2+, K+, and Na+) into fluids, with higher concentrations of cations for slower rates of methane hydrate formation. The interaction of montmorillonite and talc with H2O consumes hydrogen ions (H+), resulting in alkaline solutions. It was found that alkaline solutions may not be favorable for methane hydrate formation. In contrast, silica sand slightly promotes methane hydrate formation in the unstirred reactor, which may be related to acidic solutions formed during the interaction of silica sand with H2O. The phase equilibrium temperatures and pressures of methane hydrate in the presence of 3% montmorillonite, talc, and silica sand are essentially the same as those in pure H2O, excluding the thermodynamic effect of minerals. The experiments of this study are important for understanding the formation of massive methane hydrates with low amounts of sediment (e.g., ≤3%). They suggest that methane hydrates may not be highly concentrated in sediments with abundant talc and montmorillonite. The experiments of this study may explain the close association of methane hydrates with silica sand. [ABSTRACT FROM AUTHOR]

The construction of a dam for the Irkutsk hydroelectric power plant caused the water level in Lake Baikal to increase by 80 cm between 1958 and 1961. This led to a downward migration of the base of the gas hydrate stability zone (BGHSZ) in the sediments of the lake, which was followed by a long transition process to a new state of equilibrium. In the first stage of the transition, new gas hydrates formed at the BGHSZ, which was accompanied and followed by a decrease in pore pressure, a decrease in methane transfer from the BGHSZ to the lake floor (via fast transfer pathways, such as faults or mud volcanoes), a decrease in the intensity of methane release from the lake floor into the water column, and a decrease in the methane concentrations in the water. In the second stage, which covers the last 10–15 years, methane concentrations in the water column have started to increase again, possibly in response to an uptick in methane flux from the lake floor. In this paper, we look at possible explanations. Mathematical modeling of the migration of the BGHSZ allowed us to estimate how long the transition process takes. The modeled transition times are different for different locations in the lake, depending mainly on the sedimentation rate and the gas hydrate content of the sediments. In the near future, Lake Baikal may reach a quasi-stationary state again similar to that before the construction of the dam. This stationary state likely involves much higher methane concentrations in the water column than what is observed today, as well as adverse effects on biota of pulsed expulsions of methane, sourced from the BGHSZ, into the water column by means of e.g. mud-volcano eruptions. Such effects may include events of mass deaths of the endemic deep-water fish, golomyanka, similar to what was reported to have occurred in the 19th and first half of the twentieth century, prior to the construction of the dam. This study also reemphasizes how variations in the dynamics of a natural gas hydrate system may have a profound impact on the water bodies in which they occur and on the ecosystems within these water bodies. It also highlights which effects can be expected in other hydrate-bearing marine basins where climate-induced sea-level rise will impact the dynamics of the hydrate reservoirs. [ABSTRACT FROM AUTHOR]

The rate of resorption of calcium phosphate self-hardening materials for bone regeneration can be changed by changing the phase composition. The Ca3(PO4)2/CaCO3/Ca(H2PO4)2·H2O/Na2HPO4·12H2O system is important for the synthesis of self-curing bioactive materials with variable resorption rates by changing the ratios of the initial components. Cement compositions in twelve figurative points of a four-component composition diagram at a fixed content in the α-Ca3(PO4)2 system were studied with XRD, FTIR, SEM, calorimetric, and volumetric methods to obtain an idea of the effect of composition on solubility in vitro and resorption in vivo. It was found that the presence of the highly resorbable phase of dicalcium phosphate dihydrate in cement and the substitution of phosphate ions with the carbonate ions of hydroxyapatite increased solubility in vitro and resorption in vivo. The obtained results confirm the possibility of changing the solubility of a final product in the Ca3(PO4)2/CaCO3/Ca(H2PO4)2·H2O/Na2HPO4·12H2O system by changing the ratio of the initial components. [ABSTRACT FROM AUTHOR]

In natural gas exploitation, foam drainage, corrosion inhibition and hydrate inhibition of wellbore fluid are conventional operations. However, there is often a problem where multiple chemical agents cannot be effectively used together and can only be used separately, resulting in complex production processes. In this study, the final integrated formulation was determined: 0.1% sodium alpha-olefin sulfonate (AOST) + 0.3% dodecyl dimethyl betaine (BS-12) + 0.3% sodium lignosulfonate + 0.5% hydrazine hydrate. The minimum tension of the integrated agent could be reduced to 23.5 mN/m. The initial foaming height of the integrated agent was 21.5 cm at 65 °C, the liquid-carrying capacity was 143 mL, and the liquid-carrying rate reached 71.5%. The maximum corrosion depth also decreased from 11.52 µm without the addition of hydrazine hydrate, gradually decreasing to 5.24 µm as the concentration of hydrazine hydrate increased. After adding an integrated agent, the growth rate of hydrates was slow and aggregation did not easily occur, and the formation temperature was also more demanding. Therefore, the integrated agent has a inhibitory effect on the formation of hydrates and has a good anti-aggregation effect. From the observation of the microstructure, the emulsion is an oil-in-water type, and the integrated agent adsorbs at the oil–water interface, preventing the dispersed water droplets in the oil phase from coalescing in one place. The oil-in-water type emulsion is more likely to improve the performance of the natural gas hydrate anti-aggregation agent. [ABSTRACT FROM AUTHOR]

Methane (CH4) hydrate dissociation and CH4 release are potential geohazards currently investigated using X-ray computed tomography (XCT). Image segmentation is an important data processing step for this type of research. However, it is often time consuming, computing resource-intensive, operator-dependent, and tailored for each XCT dataset due to differences in greyscale contrast. In this paper, an investigation is carried out using U-Nets, a class of Convolutional Neural Network, to segment synchrotron XCT images of CH4-bearing sand during hydrate formation, and extract porosity and CH4 gas saturation. Three U-Net deployments previously untried for this task are assessed: (1) a bespoke 3D hierarchical method, (2) a 2D multi-label, multi-axis method and (3) RootPainter, a 2D U-Net application with interactive corrections. U-Nets are trained using small, targeted hand-annotated datasets to reduce operator time. It was found that the segmentation accuracy of all three methods surpass mainstream watershed and thresholding techniques. Accuracy slightly reduces in low-contrast data, which affects volume fraction measurements, but errors are small compared with gravimetric methods. Moreover, U-Net models trained on low-contrast images can be used to segment higher-contrast datasets, without further training. This demonstrates model portability, which can expedite the segmentation of large datasets over short timespans.

The accurate prediction of wellbore temperature and pressure is important for safe drilling. However, annulus temperature and pressure changes are more complicated due to phase transition. To study this problem, a prediction model of temperature and pressure in deep water riserless drilling is established by considering hydrate cuttings decomposition, interphase mass transfer, and phase transition heat. Based on this model, the effects of hydrate cuttings decomposition on the temperature and pressure of drilling in a hydrate reservoir are explored. The results show that the influence of hydrate cuttings decomposition increases significantly with an increase in the inlet temperature. The influence of hydrate cuttings decomposition on temperature and pressure decreases with an increase in displacement. A small range in the variation of density and penetration rates has little impact on the annulus pressure but mainly affects the temperature. The influence of hydrate cuttings decomposition increases with an increase in the penetration rate. In normal drilling conditions, hydrate cuttings decomposition has little impact on annulus temperature and pressure, but under the conditions of a high inlet temperature, high hydrate saturation, low displacement, and high penetration rate, it is necessary to consider the impact of hydrate cuttings decomposition. This study can provide reference for the prediction of temperature and pressure in deep water hydrate reservoir riserless drilling. [ABSTRACT FROM AUTHOR]

Past intensity of methane release from deep-ocean methane hydrates continues to be challenging to reconstruct reliably. Here, we used fossil ostracode fauna paired with foraminiferal δ13C values in a marine sediment core from Vestnesa Ridge, western Svalbard margin, to reconstruct methane seepage activity during the late Quaternary and to examine faunal response to deglacial climatic changes. Benthic foraminiferal δ13C values indicate methane seepage activity was relatively strong during marine isotope stage 2, corresponding to a high percentage of the ostracode Rosaliella svalbardensis in the assemblage. In contrast, this species was absent under conditions of no or very strong seepage of methane. Faunal changes in other taxa were more related to global climate changes regardless of the seepage activity. This result indicates that Rosaliella svalbardensis is a potential new useful proxy for past methane release. [ABSTRACT FROM AUTHOR]

Objective During the exploitation process of high-sulfur gas reservoirs, natural gas hydrates are easily formed in the wellbore and pipeline, causing ice blockage and affecting normal production. Methods Under the conditions of constant temperature and volume, the effects of the mineralization ions on the growth rate of high-sulfur gas hydrates are experimentally studied in an Hastelloy reactor. The effects of pressure, mineral ions of gas field water and solution morphology on the growth process morphology, growth characteristics and extension pattern of high-sulfur gas hydrate at the gas-liquid interface were also studied by direct top-view observation. Results It is shown that the salts can decrease the growth rate of hydrates and change the morphology of the hydrate crystal. At the gas-liquid interface, the hydrate grows from the nucleation point in a two-dimensional expansion pattern. When elevating the pressure, it has little effects on the morphology of hydrate crystal, but it can increase the growth rate of hydrate. Conclusions The analysis shows that ionization effects of the salts decrease the activities of water and affect the growth process of hydrate. The experimental results of this work have great significance for hydrate prevention and the normal exploitation of high-sulfur gas reservoir. [ABSTRACT FROM AUTHOR]

• New norfloxacin cocrystals synthesized by a mechanochemical method. • The apparent aqueous solubility in the cocrystals is higher compared to pure drug. • Establishment of scale-up conditions from solution crystallization. Cocrystals are recognized as one of the most efficient approaches to improve aqueous solubility of Biopharmaceutical Classification System, BCS, classes II and IV drugs. Cocrystal discovery and the establishment of experimental conditions suitable for scale-up purposes are some of the main challenges in cocrystal investigation. In this work, the investigation of mechanochemical synthesis of norfloxacin cocrystals with picolinic and isonicotinic acids is performed, leading to the discovery of two new cocrystals of this important BCS class IV antibiotic, which were characterized through thermal, spectral and diffractometric analysis. Norfloxacin apparent aqueous solubility using the cocrystals is also presented, with higher values being obtained for all the investigated systems when compared to the pure drug. Norfloxacin has 3 polymorphs and several solvents/hydrates, which represents a challenge for obtaining pure cocrystal forms from solvent crystallization. This challenge was successfully overcome in this work, as experimental conditions to obtain the pure cocrystals (the new ones and also norfloxacin-nicotinic acid and norfloxacin-saccharin) were established using Crystal16 equipment. This is a crucial step to envisage future scale-up procedures and therefore a valuable information for the pharmaceutical industry. [Display omitted] [ABSTRACT FROM AUTHOR]

The resazurin reduction test is one of the basic tests for bacterial culture viability and drug resistance endorsed by the World Health Organisation. At the same time, conventional spectrophotometric and spectrofluorimetric methods demand rather bulky and expensive equipment. This induces a challenge for developing simpler approaches to sensor systems that are portable and applicable in resource-limited settings. In this work, we address two such alternative approaches, based on the colour processing of the microbiological plate's photographic images and single-channel photometry with a recently developed portable microbiological analyser. The key results consist of establishing a sequential linear correspondence between the concentration of resorufin produced due to the reduction of resazurin by viable bacteria as determined by the UV-Vis studies, the intensity of the a* channel of the CIE L*a*b* colour space and the transmitted light intensity registered by a luxmeter under the LED illumination with a yellow colour filter. This route is illustrated with the chemical system "Hydrazine hydrate – resazurin", isolating the target colour change-inducing reaction and the test of determining the minimal inhibition concentration of the antibacterial first-line drug isoniazid acting on the culture of the H37Rv strain of M. tuberculosis. [ABSTRACT FROM AUTHOR]

The process of combustion of a liquid fuel layer (diesel, kerosene, gasoline, separated petroleum, and oil) in the presence of CO2 hydrate has been studied. These fuels are widely used in engineering, which explains the great interest in effective methods of extinguishing. Extinguishing liquid fuels is quite a complicated scientific and technical task. It is often necessary to deal with fire extinction during oil spills and at fuel burning in large containers outdoors and in warehouses. Recently, attention to new extinguishing methods has increased. Advances in technology of the production, storage, and transportation of inert gas hydrates enhance the opportunities of using CO2 hydrate for extinguishing liquid fuels. Previous studies have shown a fairly high efficiency of CO2 hydrate (compared to water spray) in the extinction of volumetric fires. To date, there are neither experimental data nor methods for determining the dissociation rate of CO2 hydrate powder at the time of the gas hydrate fall on the burning layer of liquid fuel. The value of the dissociation rate is important to know in order to determine the temperatures of stable combustion and, accordingly, the mass of CO2 hydrate required to extinguish the flame. For the first time, a method jointly accounting for both the combustion of liquid fuel and the dissociation rate of the falling powder of gas hydrate at a negative temperature is proposed. The combustion stability depends on many factors. This paper defines three characteristic modes of evaporation of a liquid fuel layer, depending on the prevalence of vapor diffusion or free gas convection. The influence of the diameter and height of the layer on the nature of fuel evaporation is investigated. [ABSTRACT FROM AUTHOR]

China's largest high-latitude permafrost distribution zone is in Northeast China. With the intensification of global warming and engineering construction, the carbon stored in permafrost will gradually thaw and be released in the form of methane gas. However, research on the changes in methane concentration and emission sources in this area is still unclear. In this paper, the AIRS (Atmospheric Infrared Sounder) data carried by the Aqua satellite were used to analyze the distribution and change trends in the overall methane concentration in the near-surface troposphere in Northeast China from 2003 to 2022. These data, combined with national meteorological and on-site monitoring data, were used to study the methane emission characteristics and sources in the permafrost area in Northeast China. The results show that the methane concentration in the near-surface troposphere of Northeast China is mainly concentrated in the permafrost area of the Da and Xiao Xing'an Mountains. From 2003 to 2022, the methane concentration in the near-surface troposphere of the permafrost area in Northeast China showed a rapid growth trend, with an average linear trend growth rate of 4.787 ppbv/a. In addition, the methane concentration in the near-surface troposphere of the permafrost area shows a significant bimodal seasonal variation pattern. The first peak appears in summer (June–August), with its maximum value appearing in August, and the second peak appears in winter (December–February), with its maximum value appearing in December. Combined with ground surface methane concentration monitoring, it was found that the maximum annual ground surface methane concentration in degraded permafrost areas occurred in spring, causing the maximum average growth rate in methane concentration, also in spring, in the near-surface troposphere of permafrost areas in Northeast China (with an average value of 6.05 ppbv/a). The growth rate of methane concentration in the southern permafrost degradation zone is higher than that in the northern permafrost stable zone. In addition, with the degradation of permafrost, the geological methane stored deep underground (methane hydrate, coal seam, etc., mainly derived from the accumulation of ancient microbial origin) in the frozen layer will become an important source of near-surface troposphere methane in the permafrost degradation area. Due to the influence of high-permeability channels after permafrost degradation, the release rate of methane gas in spring is faster than predicted, and the growth rate of methane concentration in the near-surface troposphere of permafrost areas can be increased by more than twice. These conclusions can provide a data supplement for the study of the carbon cycle in permafrost areas in Northeast China. [ABSTRACT FROM AUTHOR]

Atmospheric methane's rapid growth from late 2006 is unprecedented in the observational record. Assessment of atmospheric methane data attributes a large fraction of this atmospheric growth to increased natural emissions over the tropics, which appear to be responding to changes in anthropogenic climate forcing. Isotopically lighter measurements of δ13CCH4 ${\delta }^{13}{\mathrm{C}}_{\mathrm{C}\mathrm{H}4}$ are consistent with the recent atmospheric methane growth being mainly driven by an increase in emissions from microbial sources, particularly wetlands. The global methane budget is currently in disequilibrium and new inputs are as yet poorly quantified. Although microbial emissions from agriculture and waste sources have increased between 2006 and 2022 by perhaps 35 Tg/yr, with wide uncertainty, approximately another 35–45 Tg/yr of the recent net growth in methane emissions may have been driven by natural biogenic processes, especially wetland feedbacks to climate change. A model comparison shows that recent changes may be comparable or greater in scale and speed than methane's growth and isotopic shift during past glacial/interglacial termination events. It remains possible that methane's current growth is within the range of Holocene variability, but it is also possible that methane's recent growth and isotopic shift may indicate a large‐scale reorganization of the natural climate and biosphere is under way. Plain Language Summary: Atmospheric methane's unprecedented current growth, which in part may be driven by surging wetland emissions, has strong similarities to ice core methane records during glacial‐interglacial "termination" events marking global reorganizations of the planetary climate system. Here we compare current and termination‐event methane records to test the hypothesis that a termination‐scale change may currently be in progress. Key Points: The rapid growth in the atmospheric methane burden that began in late 2006 is very different from methane's past observational recordRecent studies point to strongly increased emissions from wetlands, especially in the tropicsThis increase is comparable in scale and speed to glacial/interglacial terminations when the global climate system suddenly reorganized [ABSTRACT FROM AUTHOR]

Thermodynamic hydrate inhibitors (THIs) are often used in marine gas field operations to prevent the formation of natural gas hydrate (NGH), and it is important to study the effect of THIs on hydrate synthesis characteristics. Herein, the effects of water (H2O), sodium chloride (NaCl), and ethylene glycol (EG) on NGH synthesis characteristics under different initial pressure conditions are tested using the self‐developed 1D NGH production simulation test system. The effects of each THI on the maximum synthesis rate and maximum synthesis amount of NGH are investigated using two physical quantities, peak of temperature increment and maximum gas conversion rate. The results show that the 2.65 wt% salt solution has the minimum inhibition effect on the maximum synthesis rate of NGH, and the solution with a 3:1 mixture of H2O and EG has the maximal inhibition effect on the maximum synthesis rate of NGH. When only H2O and EG or H2O and NaCl are present in the reactor, the higher the concentration of EG or NaCl, the more significant is the inhibition effect on the maximum synthesis amount of NGH. [ABSTRACT FROM AUTHOR]

The phenomenon of the formation of microheterogeneities (MHs) in solutions, which, according to chemical handbooks, are considered true solutions, has been known for a long time. MHs have been found in more than 100 binary solutions, many of which are used both in various scientific studies and in life. However, the nature of this phenomenon is largely unclear. It is only well-known that MHs are stable areas of increased concentration of one of the components of the solution. The main reason for the poor knowledge of MHs is the use of very few experimental methods, mainly light scattering methods. In this paper, the terahertz time-domain spectroscopy method was used for the first time to study MHs using the example of aqueous solutions of three sugars: glucose, fructose, and sucrose. This method gives the spectra of complex permittivity in the terahertz range, which are very informative when studying the hydrate shells of molecules in solutions. The idea of this study was that structuring sugar molecules with the formation of MHs changes their hydration. The characteristics of sugar hydration in solutions before and after filtration through a 20 nm filter, leading to the destruction of MHs, were compared. It has been shown that the water binding in the MHs of all three solutions is increased compared with the hydrate shells of individual sugar molecules. Also, for MHs' fructose solution, a decrease in the number of hydrogen bonds between water molecules and an increase in the number of free water molecules was shown, which is not observed in MH glucose and sucrose solutions. This is explained by mutarotations of fructose molecules, leading to permanent significant rearrangements of the water structure in MHs. Thus, terahertz time-domain spectroscopy provides fundamentally new information about the MHs of aqueous solutions at the level of their hydration characteristics. The presence of MHs in solutions is a significant factor that has never been taken into account when studying the hydrate shells of various molecules in solutions using THz spectroscopy. [ABSTRACT FROM AUTHOR]

Increasing carbon dioxide (CO2) concentration in the atmosphere is considered one of the most important challenges today. Therefore, capturing CO2 and producing alternative energy sources through Power-to-X (PtX) approaches have become relevant scientific topics in recent years. However, there is a significant research gap regarding water management in PtX processes, particularly in offshore operations. The present study evaluates relevant aspects and possible challenges with respect to water management as well as mass and energy balances in conceptual offshore methane and methanol production platforms. The results show that 1600 m3 of seawater must be desalinated to supply the electrolyzer and reach a daily 50-Megagram (Mg) hydrogen production. Around 1100 m3 of brine coming out of the desalination plant may be discharged to the sea as long as prior environmental impact assessments are conducted. Additionally, 273 Mg and 364 Mg CO2 need to be generated daily by direct air capture to produce 99 Mg day−1 methane and 265 Mg day−1 methanol, respectively. The daily produced methane and methanol wastewater is estimated to be 223 and 149 m3, respectively. Based on the scant literature on methanol wastewater, this is expected to contain toxic substances. Zero liquid discharge (ZLD) is proposed as wastewater method. The corresponding energy demand for the water management facilities is projected to be negligible compared to the other PtX processes. The presented management of water streams in PtX platforms would not only help recover some of the resources (water, hydrogen and methanol), but also substantially contribute to the production cycle itself while leading toward a more sustainable approach. [ABSTRACT FROM AUTHOR]

Heat storage technologies are essential for increasing the use of solar energy in the household sector. Their development can be achieved by designing new storage materials; one way is to impregnate a porous matrix with hygroscopic salts. In this article, the possibility of using biochar-based composite sorbents to develop promising new heat storage materials for efficient thermal storage is explored. Biochar-based composites with defined salt loadings (5, 10, 15, and 20%) were produced by impregnating MgSO4 into a biochar matrix derived from corn cobs. The new materials demonstrated a high water sorption capacity of 0.24 g/g (20MgCC). After six successive charging-discharging cycles (dehydration/dehydration cycles), only a negligible variation of the heat released and the water uptake was measured, confirming the absence of deactivation of 20MgCC upon cycling. The new 20MgCC composite showed an energy storage density of 635 J/g (Tads = 30 °C and RH = 60%), higher than that of other composites containing a similar amount of hydrate salt. The macroporous nature of this biochar increases the available surface for salt deposition. During the hydration step, the water molecules effectively diffuse through a homogeneous layer of salt, as described by the intra-particle model applied in this work. The new efficient biochar-based composites open a low-carbon path for the production of sustainable thermal energy storage materials and applications. [ABSTRACT FROM AUTHOR]

Plasterboard is an important building material in the construction industry because it allows for quick installation of walls, partitions, and ceilings. Although a common material, knowledge about its performance related to modern polymers and fabrication conditions is still lacking. The present work analyzes how some manufacturing factors applied during the plaster board fabrication impact on some plasterboard properties, including water absorption, flexural strength, and thermal conductivity. The manufacturing variables evaluated are the dose (D) of polymethylhydrosiloxane (PMHS), the agitation time of the mixture (H), and the drying temperature of the plaster boards after setting (T). The results suggest that factors D, H, and T induce changes in the porosity and the morphological structure of the calcium sulfate dihydrate crystals formed. Performance is evaluated at two levels of each factor following a statistical method of factorial experimental design centered on a cube. Morphological changes in the crystals of the resulting boards were evaluated with scanning electron microscopy (SEM) and the IMAGEJ image analysis program. Porosity changes were evaluated with X-ray microcomputed tomography (XMT) and 3D image analysis tools. The length-to-width ratio of the crystals decreases as it goes from low PMHS dosage to high dosage, favoring a better compaction of the plasterboard under the right stirring time and drying temperature. In contrast, the porosity generated by the incorporation of PMHS increases when going from low-level to high-level conditions and affects the maximum size of the pores being generated, with a maximum value achieved at 0.6% dosage, 40 s, and 140 °C conditions. The presence of an optimal PMHS dosage value that is approximately 0.6–1.0% is evidenced. In fact, when comparing trails without and with PMHS addition, a 10% decrease in thermal conductivity is achieved at high H (60 s) and high T (150 °C) level conditions. Water absorption decreases by more than 90% when PMHS is added, mainly due to the hydrophobic action of the PMHS. Minimum water absorption levels can be obtained at high drying temperatures. Finally, the resistance to flexion is not affected by the addition of PMHS because apparently there are two opposing forces acting: on one hand is the decrease in the length–width ratio giving more compactness, and on the other hand is the generation of pores. The maximum resistance to flexion was found around a dosage of 0.6% PMHS. In conclusion, the results suggest that the addition of PMHS, the correct agitation time of the mixture, and the drying temperature reduce the water absorption and the thermal conductivity of the gypsum boards, with no significant changes in the flexural resistance. [ABSTRACT FROM AUTHOR]

Water is a key actor of various processes of nature and, therefore, molecular engineering has to take the structural and energetic consequences of hydration into account. While the present review focuses on the target–ligand interactions in drug design, with a focus on biomolecules, these methods and applications can be easily adapted to other fields of the molecular engineering of molecular complexes, including solid hydrates. The review starts with the problems and solutions of the determination of water structures. The experimental approaches and theoretical calculations are summarized, including conceptual classifications. The implementations and applications of water models are featured for the calculation of the binding thermodynamics and computational ligand docking. It is concluded that theoretical approaches not only reproduce or complete experimental water structures, but also provide key information on the contribution of individual water molecules and are indispensable tools in molecular engineering. [ABSTRACT FROM AUTHOR]

To investigate the impact of geothermal gradient on the distribution and reserves of hydrate in permafrost regions, it is crucial to utilize the Archie formula to compute hydrate saturation and adjust parameters to enhance the model's precision under varying temperature gradient conditions. This study formed methane hydrate under four temperature gradients of 0.02 °C/cm, 0.07 °C/cm, 0.11 °C/cm and 0.18 °C/cm, and two sand particle ratios. The values of porosity index (m) and saturation index (n) were fitted according to different conditions. The water saturation and hydrate saturation were then calculated and contrasted with experimental results. Findings indicate that the influence of temperature gradient on the values of m and n is intricate, with n decreasing gradually and m fluctuating with an increase in temperature gradient. The discrepancies between the optimized Archie model and the actual calculated hydrate saturation values ranged from 0.8% to 2.5%, with average errors of less than 3%, proving its applicability. Finally, the optimized Archie model was used to investigate the hydrate saturation and its distribution in different layers, which confirmed the significant effect of temperature gradient on the assessment of hydrate storage and distribution by Archie's equation. [ABSTRACT FROM AUTHOR]

The possibility of slowing down gas hydrate nucleation by introducing additional surfaces into the system has been investigated. The process usually takes place at phase boundaries, i.e., the appearance of new surfaces (solid particles) in the system should increase the probability of hydrate formation. The effect of carboxylated cellulose nanofibrils (CNF) dispersed in water on methane hydrate formation under vigorous stirring was studied. It was found, that under identical conditions, allows""introducing 0.5 wt.% of CNF allows, first, to reduce the hydrate nucleation rate and, second, to suppress the "memory" effect characteristic of hydrate formation from distilled water (DW). The analysis of the "survival" functions made it possible to establish that the mechanism of the inhibiting action of CNF involves the reducing the number of hydrate nucleation sites. This can be explained by the involvement of the CNF in the disrupting the hydrogen bonds network: for example, mechanical destruction of subcritical nuclei by inhibitor particles with intense agitation. The obtained data indicate the possibility of developing a new class of kinetic hydrate inhibitors based on dispersions. [ABSTRACT FROM AUTHOR]

This research will look at hydrate inhibition, mainly by mono-ethylene-glycol and how this differently affects other areas, and how recovered again. The aim of this study will highlight the current monoethylene-glycol requirement in deep marine gas plant, the wells that still require mono-ethylene-glycol, and the others that do not, along with the volumes needed for inhibition. This search will also provide information of the future requirement for mono-ethylene-glycol in deep marine gas plant, and what options are available to reduce the quantity of MEG required to be injected safely without any impact on production. As it was injected about 14 cubic meter of mono ethylene glycol into the wells, the potential saving from this optimization by using HYSIS program is 3.65 Million dollar / year. Due to the rapidly decline on most wells and increasing aqueous received, the concentration of MEG in aqueous received from wells was lower than the on spec condition of existing MEG recovery unit. So, different scenarios were proposed starting from minimum concentration of MEG, required to operate MEG recovery unit and ending with the maximum concentration. HYSYS simulation program was used to estimate the saved cost of operating the MEG recovery unit at minimum and maximum concentrations which are 35,377,688 $ / year and 409,188,219 $ / year respectively. [ABSTRACT FROM AUTHOR]

The paper presents the results of modeling the problem of injecting liquid sulfur dioxide into a porous reservoir initially saturated with methane and ice. The model presented in the paper assumes the formation of three different regions, namely the near one, saturated with liquid SO2 and its hydrate; the far one, containing methane and ice; and the intermediate one, saturated with methane and water. The effects of various parameters of the porous medium and injected SO2 on the nature of the course of the hydrate formation process have been studied. It is shown that with a decrease in reservoir permeability or injection pressure, the length of the intermediate region decreases, which, in the limiting case, means the formation of SO2 hydrate in the mode without the formation of an extended region saturated with methane and water. It is shown that such a regime is also typical for the case of high initial injection pressures, as well as low values of the initial reservoir temperature and injection temperature. [ABSTRACT FROM AUTHOR]

The methods of preventing and curing gas hydrate in deepwater drilling are too preservative. In the west of the South China Sea, the gas hydrate inhibitive drilling fluid HEM used in the deepwater drilling is quite expensive and the penetration rate is low. To reduce the mud cost and shorten the drilling time, several issues were studied, including the phase equilibrium curves of hydrate generation with different gas components, the regions for gas hydrate generation under different operating conditions, and the methods of dealing with borehole blockage by the gas hydrates. All these studies were conducted with the low cost polymer drilling fluids used in the deepwater drilling in the BD block in the Yinggehai basin (South China Sea). Potential regions for the generation of gas hydrates under different operating conditions were obtained. Based on these studies, poly (M-vinyl caprolactam) was selected as the kinetic gas hydrate inhibitor to inhibit the generation of gas hydrates glycol selected as the thermodynamic inhibitor to remove blockage in a wellbore by gas hydrates. Ten new kinetic inhibitors were designed in laboratory study, of which the DS-A3 inhibitor has good inhibitive capacity for gas hydrate generation. Laboratory study and field (block BD) application showed that: 1) in operating conditions such as normal drilling, circulation and well shut-in, no gas hydrate generation region exists, as such, there is no risks of wellbore blockage. 2) Considering the inhibitive effect and cost together, 0.8% poly (M-vinyl caprolactam) has the best inhibitive effect for gas hydrate generation, and 45% glycol has the best effect for removing blockage of a wellbore by gas hydrate. 3) When there are no complex downhole operating conditions, if the rig down time does not exceed 15 hours, polymer drilling fluids can be directly used in deepwater drilling. In this way the drilling fluid cost for a single well can be reduced by 50%-70%, a good economic benefit. [ABSTRACT FROM AUTHOR]

The in‐situ stress state and geomechanical properties of hydrate‐bearing sediments impact hydrate formation and gas production strategies. We explore the uniaxial strain compression and stress evolution of natural hydrate‐bearing sandy‐silts from Green Canyon Block 955 in the deep‐water Gulf of Mexico. We performed constant rate of strain uniaxial strain experiments, interrupted by periods where we held the axial stress constant, to explore the vertical deformation and the evolution of the ratio of lateral to axial effective stress (K0) with time. The hydrate‐bearing sandy‐silt is stiffer and has a larger K0 than the equivalent hydrate‐free sediment upon loading. During stress holds, the void ratio decreases sigmoidally with the log of time, and K0 converges to isotropic conditions. We interpret that during loading, the hydrate bears the load and deforms. With time, the hydrate redistributes the load and K0 increases. We used a viscoelastic model to describe the behavior. The model accurately captures deformation and K0 trends but does not reproduce all the complex interactions of the hydrate with the porous skeleton. We anticipate that viscous effects within hydrate sediments will impact reservoir compression and stresses during production (hours to days), result in isotropic stress state over geological timescales, and explain the creeping movement in submarine landslides. Plain Language Summary: Natural methane hydrates are ice‐like crystalline solids, typically found within and beneath permafrost regions and near the seafloor in the deep ocean. They host large amounts of methane and are envisioned as a potential energy resource, a potential geo‐hazard, and an active component in the Earth's carbon cycle. We studied the geomechanical behavior of natural and intact hydrate‐bearing sandy‐silts recovered from the deep‐water Gulf of Mexico. We performed all the experiments at a high pressure and low temperature to maintain the hydrate stable during testing. This study demonstrates that these hydrate‐bearing sandy‐silts are viscoplastic; deformation and stresses are rate‐dependent. Under sustained vertical load, while allowing no lateral deformation, the lateral stress rises with time. This process is known as stress relaxation. Simultaneously, the material undergoes vertical compression with time, a process known as creep. We interpret that these systems deform by hydrate "flowing" and displacing the pore water within the sediment. The hydrate distributes the load in all directions, and stress relaxation takes place. This viscoplastic behavior has important implications for gas hydrate production models, drilling and completing wellbores safely, and may elucidate the mechanisms for submarine landslides. Key Points: Hydrate‐bearing sandy‐silts are viscoplastic materials with a relaxation time scale on the order of hoursThe in‐situ stress state in hydrate‐bearing sandy‐silts undergoing burial may be isotropicLoad‐bearing hydrate flow viscously and redistributes the load. A spring‐dashpot model captures this behavior [ABSTRACT FROM AUTHOR]

The sediments in the South China sea are mainly composed of clayey silt, characterized by weak cementation, low strength, and poor permeability. These characteristics lead to slow gas and water transport and low gas production efficiency in the production process, which is not conducive to reservoir stability. Therefore, this paper studied the influence of different factors on the displacement and permeability of hydrate-bearing sediments by using remolded cores from the South China Sea. It was found that, when the depressurization method was used for hydrate decomposition, the displacement change in sediments could be divided into three stages: depressurization stage, decomposition stage, and creep stage. During the decompression stage, sediment deformation was rapid and displacement was small. During the decomposition process of hydrates, sediment deformation was slow and displacement was maximum. The creep stage had the slowest deformation and the smallest displacement. The displacement increased with the increase in initial porosity, hydrate saturation, effective pressure, and depressurization amplitude. The permeability of the sediments was lower than that of the original sediments after hydrate decomposition. This permeability damage increased with the increase in the sediment porosity, hydrate saturation, depressurization range and effective pressure. Furthermore, the displacement of sediments was positively correlated with the permeability damage. [ABSTRACT FROM AUTHOR]

In this study, the effect of tetrabutylammonium halide aqueous solutions on the gas storage of CH4 and CO2 gases were studied with molecular dynamics (MD) simulations. The results show that the surface tension and the gas molecules adsorbed at the interface decreases and increases, respectively, in the presence of TBAX (X: Br, Cl, F) in the aqueous phase compared to pure water at similar gas pressures. Both of these factors may facilitate gas uptake into cages during semi-clathrate hydrate formation. CO2 showed a stronger intermolecular interaction with the water molecules since it was preferentially adsorbed at the interface, leading to a higher surface density as compared to CH4. Moreover, the relative increase in CH4 adsorption on the surface was because of the hydrophobic interactions between the CH4 molecules and the n-alkyl chains of the cation. The counter-ions of TBAXs can affect their surface activity. TBAX salts enhance the tetrahedral ordering of water molecules at the interface compared to the bulk, leading to a potential mechanism for forming semi-clathrate hydrates. [ABSTRACT FROM AUTHOR]

Cytochrome P450 (P450, CYP) family 51 enzymes catalyze the 14a-demethylation of sterols, leading to critical products used for membranes and the production of steroids, as well as signaling molecules. In mammals, P450 51 catalyzes the 3-step, 6-electron oxidation of lanosterol to form (4β,5a)-4,4-dimethyl-cholestra-8,14,24-trien-3-ol (FF-MAS). P450 51A1 can also use 24,25-dihydrolanosterol (a natural substrate in the Kandutsch-Russell cholesterol pathway). 24,25-Dihydrolanosterol and the corresponding P450 51A1 reaction intermediates, the 14a-alcohol and -aldehyde derivatives of dihydrolanosterol, were synthesized to study the kinetic processivity of the overall 14a-demethylation reaction of human P450 51A1. A combination of steady-state kinetic parameters, steady-state binding constants, dissociation rates of P450-sterol complexes, and kinetic modeling of the time course of oxidation of a P450-dihydrolanosterol complex showed that the overall reaction is highly processive, with koff rates of P450 51A1-dihydrolanosterol and the 14a-alcohol and 14a-aldehyde complexes being 1 to 2 orders of magnitude less than the forward rates of competing oxidations. epi-Dihydrolanosterol (the 3a-hydroxy analog) was as efficient as the common 3β-hydroxy isomer in the binding and formation of dihydro FF-MAS. The common lanosterol contaminant dihydroagnosterol was found to be a substrate of human P450 51A1, with roughly one-half the activity of dihydrolanosterol. Steady-state experiments with 14a-methyl deuterated dihydrolanosterol showed no kinetic isotope effect, indicating that C-14a C-H bond breaking is not rate-limiting in any of the individual steps. The high processivity of this reaction generates higher efficiency and also renders the reaction less sensitive to inhibitors. [ABSTRACT FROM AUTHOR]

In the Shenhu Area of the South China Sea, although some numerical studies are conducted on the gas production at well SHSC-4, the geomechanical responses have not been taken into account, and the associated impact of permeability enhancement on gas production has not been thoroughly investigated. In this study, pTOUGH+HYDRATE V1.5 coupled with the RGMS is applied to account for geomechanical responses. Based on actual geological conditions, the reservoir model has five layers: the hydrate-bearing layer (HBL), the three-phase layer (TPL), the free gas layer (FGL), the overburden, and the underburden. The numerical results match the trial production data, validating the numerical model. The analysis shows that gas production from the FGL contributed the most (72.17%) to the cumulative gas production (Vg), followed by the TPL (23.54%) and the HBL (4.29%). The cumulative water-to-gas ratio (RwgT) gradually decreased during gas production, with the HBL exhibiting the highest value. Permeability enhancement can improve gas production, with the FGL being the most responsive to such enhancement. It increased Vg by 87% and reduced RwgT to 85%. To achieve more realistic production schemes and better enhance energy recovery, it is advisable to conduct numerical investigations that incorporate geomechanical considerations due to the intricate nature of hydrate-bearing sediments. [ABSTRACT FROM AUTHOR]

The first prerequisite for the efficient and safe exploitation of gas hydrate resources is to accurately analyze the primary mechanical performance of hydrate-bearing sediments (HBSs). The mechanical performance of HBSs is complex and affected by many factors, including the reservoir environment in situ (temperature, pore pressure, salinity). Several published studies have demonstrated a correlation of the mechanical behavior of hydrates with temperature and pressure (T-PP). However, the research on the effect of salinity on the mechanical properties of hydrates or HBSs is still a relatively blank field. This study found that the strength of HBSs decreased with increasing salinity. This phenomenon can be attributed to the influence of salinity on the phase equilibrium state of hydrates. NaCl changed the relationship between the phase equilibrium curve of the hydrate and the T-PP conditions. The distance between the T-PP conditions and equilibrium curve was reduced with increasing salinity, which in turn led to a decline in sample strength. Moreover, the effect of the phase equilibrium of hydrates on the mechanical performance of HBSs was further explored. NaCl was added to HBSs to regulate the phase equilibrium state of the hydrate. When the T-PP conditions were on the phase equilibrium curve, the strength behaviors of HBSs showed a high degree of consistency. [ABSTRACT FROM AUTHOR]

Most hydrate-bearing sediments worldwide exhibit mixed pore- and fracture-filling hydrates. Due to the high exploitation value, pore-filling hydrate production is the focus of current hydrate production research, and there is a lack of systematic research on the decomposition of fracture-filling hydrates and their effects on the evolution of temperature and pressure in hydrate-bearing sediments. If only the decomposition characteristics of pore-filling hydrates are studied while the fracture-filling hydrates decomposition and its effects on the hydrate-bearing sediments production process are ignored, the obtained research results would be inconsistent with the actual situation. Therefore, in this study, the effects of fracture-filling hydrates with different dipping angles on the hydrate production process were studied, and the necessity of considering the phenomenon of mixed pore- and fracture-filling hydrates in hydrate-bearing sediments was illustrated. On this basis, the simulation of a typical site (GMGS2-16) with mixed pore- and fracture-filling hydrates was constructed, and the production process was researched and optimized. The results indicated that: (a) fracture-filling hydrates formed in shallow fine-grained sediments and gradually approached the area of pore-filling hydrates, before a stable mixed zone was formed; (b) the occurrence of fracture-filling hydrates was conducive to the hydrate-bearing sediment depressurization production, and the promoting effect of the fracture-filling hydrate with smaller dipping angles was stronger; and (c) depressurization combined with heat injection could effectively compensate for the local low temperature and secondary hydrate caused by the mass decomposition of fracture-filled hydrates. [ABSTRACT FROM AUTHOR]

Marine natural gas hydrate (NGH) can mainly be found in argillaceous fine-silt reservoirs, and is characterized by weak consolidation and low permeability. Sand production is likely to occur during the NGH production process, and fine-silt particles can easily plug the sand-control media. In view of this, experiments were conducted to assess the influence of the formation sand on the sand retention media in gravel-packed layers under gas–water mixed flow, and the plugging process was analyzed. The results show that following conclusions. (1) The quartz-sand- and ceramic-particle-packed layers show the same plugging trend, and an identical plugging law. The process can be divided into three stages: the beginning, intensified, and balanced stages of plugging. (2) The liquid discharge is a key factor influencing the plugging of gravel-packed layers during NGH exploitation by depressurization. As the discharge increases, plugging occurs in all quartz-sand packing schemes, while the ceramic-particle packing scheme still yields a high gas-flow rate. Therefore, quartz sand is not recommended as the packing medium during NGH exploitation, and the grain-size range of ceramic particles should be further optimized. (3) Due to the high mud content of NGH reservoirs, a mud cake is likely to form on the surface of the packing media, which intensifies the bridge plugging of the packed layer. These experiment results provide an important reference for the formulation and selection of sand-control schemes. [ABSTRACT FROM AUTHOR]

Hydrocarbon seeps are common manifestations of gas leakage from the seafloor. However, the fate of methane seepage within the gas hydrate stability zone at active margins is poorly constrained. This study presents a 40‐thousand‐year record of hydrocarbon seepage archived by a ∼5‐m long core composed of authigenic carbonate from the Yam Seep area, Four‐Way Closure Ridge off SW Taiwan. Different carbonate microfacies could be distinguished: Consolidated microcrystalline aragonite representing lithified host sediments intercalated by pure aragonite present in 10–50 cm thick intervals in the core. These aragonite intervals are interpreted as having precipitated within former fractures in the host rock. High resolution U‐Th dating of these aragonites is interpreted to record the minimum age of the opening of these fractures. The chronology of aragonite precipitation throughout the core suggests a record of continuous seepage from ∼41 to 2 ka that fluctuated in intensity over this time period. The chronology of putative fracturing events and observed carbonate precipitation suggest (a) an active period of fracturing and seepage from ∼37 to 27 ka, (b) a more quiescent period from ∼27 to 16 ka, followed by (c) another active period from ∼16 to 12 ka. A schematic model illustrates the evolution of carbonate formation within the core influenced by faulting, fracturing, erosion, gas hydrate accumulation, and aragonite precipitation and provides a unique 40,000‐year‐old record of methane seepage and crucial insights into the dynamics of long‐term seepage systems at active margins. Key Points: A 40‐thousand‐year history of hydrocarbon seepage at an active margin accretionary ridge off SW TaiwanUranium‐Thorium dating of authigenic carbonate reveals alternating periods of seepage activity and quiescenceDating of fracture boundaries provides evidence for episodes of tectonic and seepage activities [ABSTRACT FROM AUTHOR]

Mutagenesis is a highly efficient tool for establishing genetic variation and is widely used for genetic enhancement in various plants. The key benefit of mutation breeding is the prospect of enhancing one or several characteristics of a variety without altering the genetic background. In this study, we exposed the seeds of Salvia officinalis to four concentrations of hydrazine hydrate (HZ), i.e., (0%, 0.1%, 0.2%, and 0.3%) for 6 h. The contents of terpenoid compounds in the S. officinalis plantlets driven from the HZ-treated seeds were determined by GC-MS, which resulted in the identification of a total of 340 phytochemical compounds; 163 (87.48%), 145 (84.49%), 65 (97.45%), and 62 (98.32%), from the four concentrations of HZ (0%, 0.1%, 0.2%, and 0.3%), respectively. Furthermore, we used the qRT-PCR system to disclose the "transcriptional control" for twelve TPS genes related to terpenoid and terpene biosynthesis, namely, SoGPS, SoMYRS, SoNEOD, SoCINS, SoSABS, SoLINS, SoFPPS, SoHUMS, SoTPS6, SoSQUS, SoGGPS, and SoGA2. Altogether, results are likely to ensure some positive relationship between the concentrations of the chemical mutagen HZ used for treating the seeds, the type and amount of the produced terpenes, and the expression of their corresponding genes. [ABSTRACT FROM AUTHOR]

We report new results on the translational‐rotational (T‐R) states of the CO2 molecule inside the sI clathrate‐hydrate cages. We adopted the multiconfiguration time‐dependent Hartree methodology to solve the nuclear molecular Hamiltonian, and to address issues on the T‐R couplings. Motivated by experimental X‐ray observations on the CO2 orientation in the D and T sI cages, we aim to evaluate the effect of the CO2–water interaction on quantum dynamics. Thus, we first compared semiempirical and ab initio‐based pair interaction model potentials against first‐principles DFT‐D calculations for ascertaining the importance of nonadditive many‐body effects on such guest–host interactions. Our results reveal that the rotational and translational excited states quantum dynamics is remarkably different, with the pattern and density of states clearly affected by the underlying potential model. By analyzing the corresponding the probability density distributions of the calculated T‐R eigenstates on both semiempirical and ab initio pair CO2–water nanocage potentials, we have extracted information on the altered CO2 guest local structure, and we discussed it in connection with experimental data on the orientation of the CO2 molecule in the D and T sI clathrate cages available from neutron diffraction and 13C solid‐state NMR studies, as well as in comparison with previous molecular dynamics simulations. Our calculations provide a very sensitive test of the potential quality by predicting the low‐lying T‐R states and corresponding transitions for the encapsulated CO2 molecule. As such spectroscopic observables have not been measured so far, our results could trigger further detailed experimental and theoretical investigations leading to a quantitative description of the present guest–host interactions. [ABSTRACT FROM AUTHOR]

Submarine methane seepage can potentially be promoted by the dissociation of the marine hydrates surrounding the continental margins due to oceanic warming since the Last Glacial Maximum. This seepage could be archived by authigenic carbonates at seeping sites, but the time lag caused by heat transmission through the sediment column leads to an inconsistency between the ages of the carbonate and the period of bottom water warming. Here we present the records of the authigenic carbonate crust from drilling site D1 in the Mid‐Okinawa Trough. Uranium–thorium dating results show that the carbonate crust mainly grew downwards during 14–6 ka. Gas hydrates hosted in the relatively thin stability zone dissociated in a rapid response to bottom water warming and intensified the methane seepage. Our study better supports the hypothesis that a considerable amount of methane can be released from marine hydrates due to global climatic changes. Plain Language Summary: Methane hydrates are ice‐like crystalline compounds and often found in deep‐ocean marine sediments. Ocean warming in the past could have destabilized methane hydrates and led to a rapid discharge of free methane gas. Geological information on this methane escape could be preserved by carbonate rocks. To date, the hypothesis of the control of ocean warming on hydrate melting since the Last Glacial Maximum (19,000–26,000 years ago) has not been fully tested. To examine this hypothesis, we used the rock samples of seep‐carbonate retrieved by seafloor drilling in the Mid‐Okinawa Trough. Uranium–thorium dating results show that the seep carbonates formed between 6,000 and 14,000 years ago. It took less time for heat to diffuse downwards from warming seawater to trigger hydrate melting at this location than in most of other oceans at similar water depths. The smaller time lag makes the carbonate rock age close to the period of ocean warming. Our results better support that global ocean warming could potentially release methane from gas hydrates during glacial–interglacial transitions. The consequent methane transport into the oceans and likely also the atmosphere might impact ocean acidification and climatic warming. Key Points: Presentation of the chronology of methane seepage by dating authigenic carbonates collected from drilling core D1 in the Okinawa TroughOcean warming–induced hydrate dissociation led to the downward growth of authigenic carbonate for 14–6 ka after the Last Glacial MaximumThis carbonate record better supports the link of hydrate dissociation with ocean warming due to a smaller thermal lag effect [ABSTRACT FROM AUTHOR]

The industrial sector utilizes approximately 40% of global energy consumption. A sizeable amount of waste energy is rejected at low temperatures due to difficulty recovering with existing technologies. Thermochemical heat transformers (THT) can play a role in recovering low-temperature industrial waste heat by storing it during high supply and discharging it on demand at a higher temperature. Thus, THT will enable waste heat reintegration into industrial processes, improving overall energy efficiency and lowering greenhouse gas emissions from the industrial sector. Salt hydrate is a promising thermochemical material (TCM) because it requires a low charging temperature which can be supplied by waste heat. Furthermore, its non-toxic nature allows the implementation of a simpler and less costly open system. Despite extensive research into salt hydrate materials for thermochemical energy storage (TCES) applications, a research gap is identified in their use in THT applications. This paper aims to provide a comprehensive literature review of the advancement of THT applications, particularly for systems employing salt hydrates material. A discussion on existing salt hydrate materials used in the THT prototype will be covered in this paper, including the challenges, opportunities, and suggested future research works related to salt hydrate THT application. [ABSTRACT FROM AUTHOR]

Numerous recent studies have shown that discharging colored wastewater into the environment causes contamination, which has adverse impact due to textile, dyeing, and food industries. The current study presents experimental research on the clathrate hydrate technique used for producing pure water from of wastewater contaminated by dyes. Under constant starting conditions, the clathrate formation for binary (water + refrigerant gas) and ternary (water + refrigerant gas + promotor) systems were studied. The R134a gas was used along with Cyclohexane (2.5 vol%), Tween 80 (100 ppm), and silica gel powder as promotors (100 ppm). Moreover, povidone-iodine (500, 2500, and 5000 ppm) and potassium permanganate (10, 50, and 100 ppm) were used as colored compounds in order to prepare synthetic wastewater (model wastewater). The production of hydrates, which rapidly captured the refrigerant gas molecules in the solid phase, was primarily responsible for the pressure drop. Both povidone-iodine and potassium permanganate have a negligible impact on the hydrate formation rates. It was found that the concentration of povidone-iodine and potassium permanganate in the produced water was decreased. As far as we know, the method of using clathrate hydrate to remove the dyes in water has never been investigated. The results showed that the povidone-iodine removal efficiency ranged between 86% and 92%, and the potassium permanganate removal efficiency ranged between 90% and 95%. The removal efficiency was improved by adding promotors, which increased the dissolved gas quantity and the amount of water hydrates. The maximum removal efficiency was accomplished using silica gel powder and cyclohexane, which are more significant than in pure water and Tween 80. This study demonstrated the viability of the clathrate hydrate technique as a green technology for the treatment of colored wastewater effluents from different industries. [ABSTRACT FROM AUTHOR]

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