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This review covers the types and applications of chemical inhibitors of gas hydrate formation in the oil and gas industry. The main directions of the development of new types of highly effective and environmentally safe “green” kinetic hydrate inhibitors (KHIs) based on biopolymers are analyzed. The structure, physicochemical properties, efficiency of gas hydrate formation inhibition, and commercial prospects of polysaccharides in preventing and controlling the formation of gas hydrates are considered. The criteria for their selection, current experimental data, and the mechanism of inhibition are presented. Recent research in the development of cost-effective, efficient, and biodegradable KHIs for industrial applications in the oil and gas industry is also presented.

Helium, nitrogen and hydrogen are continually generated within the deep continental crust 1 – 9 . Conceptual degassing models for quiescent continental crust are dominated by an assumption that these gases are dissolved in water, and that vertical transport in shallower sedimentary systems is by diffusion within water-filled pore space (for example, refs. 7 , 8 ). Gas-phase exsolution is crucial for concentrating helium and forming a societal resource. Here we show that crustal nitrogen from the crystalline basement alone—degassing at a steady state in proportion to crustal helium-4 generation—can reach sufficient concentrations at the base of some sedimentary basins to form a free gas phase. Using a gas diffusion model coupled with sedimentary basin evolution, we demonstrate, using a classic intracratonic sedimentary basin (Williston Basin, North America), that crustal nitrogen reaches saturation and forms a gas phase; in this basin, as early as about 140 million years ago. Helium partitions into this gas phase. This gas formation mechanism accounts for the observed primary nitrogen–helium gas discovered in the basal sedimentary lithology of this and other basins, predicts co-occurrence of crustal gas-phase hydrogen, and reduces the flux of helium into overlying strata by about 30 per cent because of phase solubility buffering. Identification of this gas phase formation mechanism provides a quantitative insight to assess the helium and hydrogen resource potential in similar intracontinental sedimentary basins found worldwide. A modelling study shows that crustal nitrogen from the crystalline basement can reach sufficient concentrations in some sedimentary basins to form a free gas phase, into which helium partitions.

The kinetic fractionation model for hydrogen isotope fractionation for methane, ethane and propane formation is tested in this study. The model agrees very well with the current existing model of carbon isotope fractionation for coal-derived gas from the Kuqa depression, Tarim basin, China. The strong con-elation of carbon and hydrogen isotopes between theory and field data proves that it is unlikely that hydrogen isotopes will exchange with water under the gas formation condition. Using both gas carbon and hydrogen isotopes can further constrain our prediction of gas maturity, formation age and accumulation patterns for a natural gas system. Based on the carbon and hydrogen isotope fractionation model and field data, our results show the gas in the Kuqa depression was overmature in the central depression with Ro values up to 1.9–2.0% in the Kela 2 gas field and the gas maturity was much lower in the southern Front Uplift with Ro values ranging from 1.3% to 1.7%, which agree well with the distribution characteristics of the maturity of the local source rocks. However, the predicted gas maturity in the Front Uplift was relatively higher than that of the local source rocks, which probably indicates natural gases in the Front Uplift were migrated from the central depression. Our prediction demonstrates that natural gases in the Kuqa depression were formed during the last 3–5 million years and the gas formation temperature was 170–200°C, which is consistent with the burial history of the depression. According to our results, the potential accumulation pattern for the gas in the Kuqa depression is that gases were formed at depth and expelled from the Kuqa depression and migrated vertically along faults to some traps and formed giant gas fields, or migrated from north to south and accumulated in the Front Uplift or mixed with previous oil fields and formed condensate oil gas fields.

[...]current research suggests that the ELIP event is the most intense tectonic-thermal anomaly of the basin since ultra-high paleo-heat flows (~114 mW/m2) during the Late Permian have been recognized for decades2,4. [...]strong thermal anomalies combined with active tectonics were sufficient to lead to rapid and extensive pyrolysis of organic matter and followed by the release of natural gases. In addition to our evidence of high-temperature methane, the latest study suggests a maximum natural gas formation temperature of ~296 °C based on both Δ13CH3D and 12CH2D2 analysis at the same region6. [...]deep burial alone would not have been able to explain the generally high or over-high maturity and the complete natural gas production in the Sinian–Paleozoic reservoirs in the Sichuan Basin. High-temperature methane gas generation and emissions were not overestimated Approaches suggested by Huang et al., for questioning volume of high-temperature methane generation and emissions are meaningless and invalid, because they are purely based on the concept of industrial natural gas reserves.

With the widespread deployment of high-voltage cable terminals in power systems, insulating silicone oil has become a critical medium due to its superior dielectric and thermal properties. However, conventional diagnostic methods such as the three-ratio gas analysis developed for transformer oil have proven ineffective for silicone oil, owing to its distinct chemical structure and degradation behavior. To address this, this study aims to establish a fault-type identification method specifically for silicone oil to enhance the operational reliability of cable terminals. Accelerated thermal aging experiments (140°C, 30 days) were conducted to simulate long-term aging of silicone oil. By integrating partial discharge, high-energy discharge, and breakdown experiments, the gas generation patterns of silicone oil under different stresses were systematically analyzed. Gas chromatography (GC) and infrared spectroscopy (IR) were employed to track gas composition and chemical structural changes. The results propose the following diagnostic criteria: H₂/CH₄ > 1, C₂H₄/C₂H₆ > 1, and C₂H₂/C₂H₄ < 0.1 indicate overheating faults; H₂/CH₄ < 1, C₂H₄/C₂H₆ < 0.1, and C₂H₂/C₂H₄ < 0.1 correspond to partial discharge; while H₂/CH₄ > 1, C₂H₄/C₂H₆ > 0.1, and C₂H₂/C₂H₄ > 5 signify high-energy discharge. In addition, kinetic modeling based on the Arrhenius equation was applied to extract the activation energy of pyrolytic gas formation, confirming its relation to Si–O bond cleavage. This research provides a foundation for fault diagnosis in silicone oil-insulated equipment, effectively improving the operational reliability of power systems.

Natural gas is a key energy resource, and understanding how it forms is important for predicting where it forms in economically important volumes. However, the origin of dry thermogenic natural gas is one of the most controversial topics in petroleum geochemistry, with several differing hypotheses proposed, including kinetic processes (such as thermal cleavage, phase partitioning during migration, and demethylation of aromatic rings) and equilibrium processes (such as transition metal catalysis). The dominant paradigm is that it is a product of kinetically controlled cracking of longchain hydrocarbons. Here we show that C2+ n-alkane gases (ethane, propane, butane, and pentane) are initially produced by irreversible cracking chemistry, but, as thermal maturity increases, the isotopic distribution of these species approaches thermodynamic equilibrium, either at the conditions of gas formation or during reservoir storage, becoming indistinguishable from equilibrium in the most thermally mature gases. We also find that the pair of CO₂ and C₁ (methane) exhibit a separate pattern of mutual isotopic equilibrium (generally at reservoir conditions), suggesting that they form a second, quasi-equilibrated population, separate from the C₂ to C₅ compounds. This conclusion implies that new approaches should be taken to predicting the compositions of natural gases as functions of time, temperature, and source substrate. Additionally, an isotopically equilibrated state can serve as a reference frame for recognizing many secondary processes that may modify natural gases after their formation, such as biodegradation.

The rapid secondary formation of gas hydrate is a potential cause of flowline blockage in deepwater oil and gas production systems, posing serious flow assurance challenges. However, its microscopic formation mechanism remains an area of active research. Recently, the residual structure hypothesis has gained significant attention in explaining the rapid secondary formation of hydrates. In this study, massive molecular dynamics simulations are conducted to investigate the secondary formation of methane hydrates in solutions containing hydrate residual structures of varying sizes. The results indicated that residual structures, owing to their hydrate-like characteristics, facilitate the adsorption and capture of methane molecules, leading to the formation of local gas supersaturation regions. Residual structures promote hydrate formation through two key mechanisms: acting as nucleation sites and supplementing methane concentrations. Particularly, a synergy between residual structures and gas concentration was identified: high gas concentrations stabilize small residual structures, allowing them to serve as nucleation sites, while large stable structures can enrich methane even under low gas concentration. This work not only provided a detailed understanding of the mechanisms of hydrate secondary formation but also provided valuable insight for hydrate blockage prediction and control in subsea oil and gas pipelines, contributing to improved flow assurance strategies.

Gas injection into a liquid cross-flow is examined for the case where the gas is injected beneath a horizontal flat surface. For moderate Froude numbers, the gas pocket that is formed will rise toward the flow boundary under the action of buoyancy, a condition that is conducive to the formation of gas layers for friction-drag reduction on the surface. At the location of gas injection, a plume whose geometry is related to the mass and momentum flux of the injected gas and liquid cross-flow is formed, and the influence of buoyancy is minimal. However, as the gas pocket convects downstream, buoyancy brings the gas back upward to the flow boundary, and leads to the bifurcation of the pocket into two distinct branches, forming a stable ‘V’-shape. Under some conditions, the flow between the two gas branches is almost entirely liquid, while for others there exists a bubbly flow or a continuous sheet of gas between the branches. The sweep angle and cross-sectional geometry of the gas branches are related to free-stream speed and boundary-layer thickness of the liquid cross-flow, the mass-injection rate of the gas, the diameter of the injection orifice and the gas outlet mean velocity and gas–jet angle. Data for a range of experimental conditions are used to scale the flow and results are compared to numerical computations of the flow, and these data are used to illustrate the underlying flow processes responsible leading to the formation the stable and straight gas branches. A simple model based on the balance of forces around a stable gas branch is presented and used to scale the observed data, and we use the results of this analysis and the computations to discuss how the process of gas injection may interact with the formation of the stable gas pockets farther downstream.

Sodium lignin sulfonate (SLS) has been explored as a fire retardant finishing agent on cotton fabric. 30% [w/v] SLS treated cotton fabric has registered LOI value of 28.5 with minimum char length of 4 cm (self-extinguishment) whereas control cotton fabric was found to burn out with flame and afterglow within 1 min. Thermo-gravimetry of the treated cotton fabric showed 35% mass retention at 500 °C while only 8% char mass was left for the control cotton fabric at the said temperature. Volatile species liberated during burning were analyzed by GC–MS technique which demonstrated the restriction of flammable gas formation from the SLS treated fabric. Char mass left after burning also has been characterized in terms of its morphology, elemental analysis, etc. Moreover, it has also been proven that SLS treatment imparts a natural attractive yellow color, UV protective property to the treated fabric without altering physical strength of the fabric which can be considered as an added advantage over flame retardant effect. Graphic abstract

In spite of the interest in the two-dimensional electron gases (2DEGs) experimentally found at surfaces and interfaces, important uncertainties remain about the observed insulator–metal transitions (IMTs). Here we show how an explicit pseudo-proper coupling of carrier sources with a relevant soft mode significantly affects the transition. The analysis presented here for 2DEGs at polar interfaces is based on group theory, Landau–Ginzburg theory, and illustrated with first-principles calculations for the prototypical case of the LaAlO 3 / SrTiO 3 interface, for which such a structural transition has recently been observed. This direct coupling implies that the appearance of the soft mode is always accompanied by carriers. For sufficiently strong coupling an avalanche-like first-order IMT is predicted.