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1
Daghash, Shaden M., Phillip Servio, and Alejandro D. Rey. "From Infrared Spectra to Macroscopic Mechanical Properties of sH Gas Hydrates through Atomistic Calculations." Molecules 25, no. 23 (2020): 5568. http://dx.doi.org/10.3390/molecules25235568.
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The vibrational characteristics of gas hydrates are key identifying molecular features of their structure and chemical composition. Density functional theory (DFT)-based IR spectra are one of the efficient tools that can be used to distinguish the vibrational signatures of gas hydrates. In this work, ab initio DFT-based IR technique is applied to analyze the vibrational and mechanical features of structure-H (sH) gas hydrate. IR spectra of different sH hydrates are obtained at 0 K at equilibrium and under applied pressure. Information about the main vibrational modes of sH hydrates and the factors that affect them such as guest type and pressure are revealed. The obtained IR spectra of sH gas hydrates agree with experimental/computational literature values. Hydrogen bond’s vibrational frequencies are used to determine the hydrate’s Young’s modulus which confirms the role of these bonds in defining sH hydrate’s elasticity. Vibrational frequencies depend on pressure and hydrate’s O···O interatomic distance. OH vibrational frequency shifts are related to the OH covalent bond length and present an indication of sH hydrate’s hydrogen bond strength. This work presents a new route to determine mechanical properties for sH hydrate based on IR spectra and contributes to the relatively small database of gas hydrates’ physical and vibrational properties.
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Liashenko, Anna, Oleksandr Melnikov, Ruslan Petrash, and Oleksandr Petrash. "Wells Gas Hydrates Formation Analysis and Prevention Methods." International Journal of Engineering & Technology 7, no. 4.8 (2018): 328–31. http://dx.doi.org/10.14419/ijet.v7i4.8.27265.
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The article deals with laws of occurrence of gas hydrates in mining wells and prevention of their formation. The basic calculations for determining temperature regimes in wells have been described. The basic methods of struggle against hydrated deposits in wells have been demonstrated. The detailed description of hydrates occurrence causes is presented along with methods of its prevention from a technological perspective. This paper provides data on the techniques used for production string clearing from hydrate plagues. The conditions necessary for hydrates formations are presented. The technological methods of hydrates removal from a tubing have been described. Â
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Klymenko, Vasyl, Vasyl Gutsul, Volodymyr Bondarenko, Viktor Martynenko, and Peter Stets. "Modeling of the Kinetics of the Gas Hydrates Formation on the Basis of a Stochastic Approach." Solid State Phenomena 291 (May 2019): 98–109. http://dx.doi.org/10.4028/www.scientific.net/ssp.291.98.
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Recently, more attention has been paid to the development of gas hydrate deposits, the use of gas-hydrated technologies, suitable for energy-efficient transportation of natural gas, the separation of gas mixtures, production and storage of cold, desalinating of seawater, etc. Hydrate formation is one of the main processes of gas-hydrate technological installations. In the article a model is proposed that describes the kinetics of the formation of hydrate in disperse systems, which are characteristic for real conditions of operation of gas-hydrate installations, on the basis of a stochastic approach using Markov chains. An example of numerical calculations is presented on the basis of the proposed model of the dynamics of the total mass of gas hydrates, and changes in the velocity of their formation and size distribution at different values of the nucleation constants and growth rate of the gas hydrates, and results of these calculations are analyzed. It is shown that the rate of formation of hydrate has a maximum value in half the time period of the whole process. The obtained results of the calculations of the dynamics the total mass of gas hydrates are in good agreement with the results of calculations by the equation of kinetics Kolmogorov-Avrami. The proposed model can be applied to the inverse problem: the determination of the nucleation constants and the rate of growth of gas hydrates by the results of the dynamics of the formation of hydrate and the changes in the fractional composition of the generated gas hydrates.
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Daghash, Shaden, Phillip Servio, and Alejandro Rey. "First-Principles Elastic and Anisotropic Characteristics of Structure-H Gas Hydrate under Pressure." Crystals 11, no. 5 (2021): 477. http://dx.doi.org/10.3390/cryst11050477.
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Evaluating gas hydrates properties contributes valuably to their large-scale management and utilization in fundamental science and applications. Noteworthy, structure-H (sH) gas hydrate lacks a comprehensive characterization of its structural, mechanical, and anisotropic properties. Anisotropic and pressure dependent properties are crucial for gas hydrates’ detection and recovery studies. The objective of this work is the determination of pressure-dependent elastic constants and mechanical properties and the direction-dependent moduli of sH gas hydrates as a function of guest composition. First-principles DFT computations are used to evaluate the mechanical properties, anisotropy, and angular moduli of different sH gas hydrates under pressure. Some elastic constants and moduli increase more significantly with pressure than others. This introduces variations in sH gas hydrate’s incompressibility, elastic and shear resistance, and moduli anisotropy. Young’s modulus of sH gas hydrate is more anisotropic than its shear modulus. The anisotropy of sH gas hydrates is characterized using the unit cell elastic constants, anisotropy factors, and the angular dependent moduli. Structure-properties composition correlations are established as a function of pressure. It is found that compressing filled sH gas hydrates increases their moduli anisotropy. Differences in atomic bonding across a crystal’s planes can be expected in anisotropic structures. Taken together the DFT-based structure–properties–composition relations for sH gas hydrates provide novel and significant material physics results for technological applications.
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Pedchenko, Mykhailo, Larysa Pedchenko, Tetiana Nesterenko, and Artur Dyczko. "Technological Solutions for the Realization of NGH-Technology for Gas Transportation and Storage in Gas Hydrate Form." Solid State Phenomena 277 (June 2018): 123–36. http://dx.doi.org/10.4028/www.scientific.net/ssp.277.123.
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The technology of transportation and storage of gas in a gas-hydrated form under atmospheric pressure and slight cooling – the maximum cooled gas-hydrated blocks of a large size covered with a layer of ice are offered. Large blocks form from pre-cooled mixture of crushed and the granulated mass of gas hydrate. The technology of forced preservation gas hydrates with ice layer under atmospheric pressure has developed to increase it stability. The dependence in dimensionless magnitudes, which describes the correlation-regressive relationship between the temperature of the surface and the center gas hydrate block under its forced preservation, had proposed to facilitate the use of research results. Technology preservation of gas hydrate blocks with the ice layer under atmospheric pressure (at the expense of the gas hydrates energy) has designed to improve their stability. Gas hydrated blocks, thus formed, can are stored and transported during a long time in converted vehicles without further cooling. The high stability of gas hydrate blocks allows to distributed in time (and geographically) the most energy expenditure operations – production and dissociation of gas hydrate. The proposed technical and technological solutions significantly reduce the level of energy and capital costs and, as a result, increase the competitiveness of the stages NGH technology (production, transportation, storage, regasification).
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Li, Yaobin, Xin Xin, Tianfu Xu, et al. "Production Behavior of Hydrate-Bearing Sediments with Mixed Fracture- and Pore-Filling Hydrates." Journal of Marine Science and Engineering 11, no. 7 (2023): 1321. http://dx.doi.org/10.3390/jmse11071321.
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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.
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Braun, Doris, and Ulrich Griesser. "Insights into hydrate formation and stability of morphinanes." Acta Crystallographica Section A Foundations and Advances 70, a1 (2014): C991. http://dx.doi.org/10.1107/s2053273314090081.
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The formation of multi-component crystals with water (hydrates) is a widespread phenomenon among organic molecules. Hydrate formation is of high practical relevance for industrially used materials, as it affects their physicochemical properties. [1,2] To exclude water or moisture in industrial processes is often difficult. Therefore knowledge about the existence and stability of hydrates and the understanding and control of the anhydrate/hydrate balance is mandatory for avoiding manufacturing problems. In order to improve our understanding of hydrate formation we selected representative substances (morphine, codeine, ethylmorphine) from a class of molecules (morphinanes), which are prone to crystallize along with water. Stable hydrates of both, free bases and HCl salts, have been observed in this important class of drug compounds. This allowed us to investigate the influence of different functional groups, the role of water and the Cl– counterion on the structure and properties of these morphinanes. A crystallization screen on the six compounds considerably extended the total number of known solid forms from twelve [3] to 17 and the number of crystal structures from five to twelve. Anhydrous polymorphs were detected for all compounds except ethylmorphine (one anhydrate) and its HCl salt (no anhydrate). The relative stabilities of the hydrated and anhydrous forms differ considerably, which was evaluated by moisture sorption studies and thermal analytical experiments. Two different hydrates, a tri- and dihydrate, were found for morphine HCl. In the free bases, the substituents define the number of hydrogen bond donor groups and lead to differences in the sterical hindrance around polar groups, influencing the intermolecular interactions, packing and stability. Hydrate formation results in higher dimensional hydrogen bond networks, whereas salt formation decreases the packing variability of the structures among the different compounds. Calorimetric measurements and lattice energy calculations were employed to estimate the heat of hydrate/anhydrate phase transformation, showing an enthalpic stabilization of the hydrates over the anhydrates. The combination of a variety of experimental techniques with computational modelling allowed us to generate sufficient kinetic, thermodynamic and structural information to understand the principles of hydrate formation of morphinanes.
8
Sun, Jian Ye, Yu Guang Ye, Chang Ling Liu, and Jian Zhang. "Experimental Study on Gas Production from Methane Hydrate Bearing Sand by Depressurization." Applied Mechanics and Materials 310 (February 2013): 28–32. http://dx.doi.org/10.4028/www.scientific.net/amm.310.28.
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The simulate experiments of gas production from methane hydrates reservoirs was proceeded with an experimental apparatus. Especially, TDR technique was applied to represent the change of hydrate saturation in real time during gas hydrate formation and dissociation. In this paper, we discussed and explained material transformation during hydrate formation and dissociation. The hydrates form and grow on the top of the sediments where the sediments and gas connect firstly. During hydrates dissociation by depressurization, the temperatures and hydrate saturation presented variously in different locations of sediments, which shows that hydrates dissociate earlier on the surface and outer layer of the sediments than those of in inner. The regulation of hydrates dissociation is consistent with the law of decomposition kinetics. Furthermore, we investigated the depressurizing range influence on hydrate dissociation process.
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Kvamme, Bjørn, Jinzhou Zhao, Na Wei, and Navid Saeidi. "Hydrate—A Mysterious Phase or Just Misunderstood?" Energies 13, no. 4 (2020): 880. http://dx.doi.org/10.3390/en13040880.
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Hydrates that form during transport of hydrocarbons containing free water, or water dissolved in hydrocarbons, are generally not in thermodynamic equilibrium and depend on the concentration of all components in all phases. Temperature and pressure are normally the only variables used in hydrate analysis, even though hydrates will dissolve by contact with pure water and water which is under saturated with hydrate formers. Mineral surfaces (for example rust) play dual roles as hydrate inhibitors and hydrate nucleation sites. What appears to be mysterious, and often random, is actually the effects of hydrate non-equilibrium and competing hydrate formation and dissociation phase transitions. There is a need to move forward towards a more complete non-equilibrium way to approach hydrates in industrial settings. Similar challenges are related to natural gas hydrates in sediments. Hydrates dissociates worldwide due to seawater that leaks into hydrate filled sediments. Many of the global resources of methane hydrate reside in a stationary situation of hydrate dissociation from incoming water and formation of new hydrate from incoming hydrate formers from below. Understanding the dynamic situation of a real hydrate reservoir is critical for understanding the distribution characteristics of hydrates in the sediments. This knowledge is also critical for designing efficient hydrate production strategies. In order to facilitate the needed analysis we propose the use of residual thermodynamics for all phases, including all hydrate phases, so as to be able to analyze real stability limits and needed heat supply for hydrate production.
10
Horvat, Kristine, and Devinder Mahajan. "Carbon dioxide-induced liberation of methane from laboratory-formed methane hydrates." Canadian Journal of Chemistry 93, no. 9 (2015): 998–1006. http://dx.doi.org/10.1139/cjc-2014-0562.
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This paper reports a laboratory mimic study that focused on the extraction of methane (CH4) from hydrates coupled with sequestration of carbon dioxide (CO2) as hydrates, by taking advantage of preferential thermodynamic stability of hydrates of CO2 over CH4. Five hydrate formation-decomposition runs focused on CH4–CO2 exchange, two baselines and three with host sediments, were performed in a 200 mL high-pressure Jerguson cell fitted with two glass windows that allowed visualization of the time-resolved hydrate phenomenon. The baseline pure hydrates formed from artificial seawater (75 mL) under 6400–6600 kPa CH4 or 2800–3200 kPa CO2 (hydrate forming regime), when the bath temperature was maintained within 4–6 °C and the gas/liquid volumetric ratio was ∼1.7:1 in the water-excess systems. The data show that the induction time for hydrate appearance was largest at 96 h with CH4, while with CO2 the time shortened by a factor of four. However, when the secondary gas (CO2 or CH4) was injected into the system containing preformed hydrates, the entering gas formed the hydrate phase instantly (within minutes) and no lag was observed. In a system containing host Ottawa sand (104 g) and artificial seawater (38 mL), the induction period reduced to 24 h. In runs with multiple charges, the extent of hydrate formation reached 44% of the theoretical value in the water-excess system, whereas the value maximized at 23% in the gas-excess system. The CO2 hydrate formation in a system that already contained CH4 hydrates was facile and they remained stable, whereas CH4 hydrate formation in a system consisting of CO2 hydrates as hosts were initially stable, but CH4 gas in hydrates quickly exchanged with free CO2 gas to form more stable CO2 hydrates. In all five runs, even though the system was depressurized, left for over a week at room temperature, and flushed with nitrogen gas in between runs, hydrates exhibited the “memory effect”, irrespective of the gas used, a result in contradiction with that reported previously in the literature. The facile CH4–CO2 exchange observed under temperature and pressure conditions that mimic naturally occurring CH4 hydrates show promise to develop a commercial carbon sequestration system.
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Sai, Kateryna. "RESEARCH INTO PECULIARITIES OF PHASE TRANSITIONS DURING THE DISSOCIATION OF GAS HYDRATES." JOURNAL of Donetsk Mining Institute, no. 2 (2021): 51–59. http://dx.doi.org/10.31474/1999-981x-2021-2-51-59.
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Purpose. Analytical study of the dissociation process of gas hydrates taking into account the peculiarities of phase transitions occurring during their dissociation and described by the Clausius-Clapeyron equation. Methods. The research uses an integrated approach, which includes the analysis and generalization of literature sources devoted to studying the peculiarities and thermobaric properties of gas hydrates; processes of hydrate formation and accumulation; methods for the development of gas hydrate deposits and technologies for extracting the methane gas from them; analytical calculations of phase transitions of gas hydrates. Findings. The conditions for the formation of gas hydrate deposits have been analyzed and the peculiarities of stable existence of gas hydrates have been revealed. The existing experience in the development of gas hydrate technologies by leading scientists, world research laboratories, advanced design institutes and organizations is summarized. The mechanism of hydration formation in rocks is studied and some classifications of gas hydrate deposits occurring in sedimentary rock stratum are presented. It has been determined that gas hydrates in natural conditions usually occur not only in the form of pure hydrate reservoirs, but most often contain a certain share of rock intercalations, which makes the deposit structure heterogeneous. The mechanisms of hydrate formation and dissociation of gas hydrates have been revealed. It has been determined that the Clausius-Clapeyron equation in a modified form can be used to describe phase transitions both during the formation and dissociation of gas hydrates, taking into account the deposit heterogeneity. Originality. The Clausius-Clapeyron equation for the analysis of phase transformations in solid phases during hydrate formation and dissociation of gas hydrates is defined more exactly, taking into account the consumption of additional heat due to the influence of the properties of rock intercalations. Practical implications. The research results are useful for designing the rational thermobaric parameters (pressure and temperature) in the dissociation of natural or technogenic gas hydrates, as well as for optimal control of the kinetics of the process.
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Guo, Zhiqi, Xiaoyu Lv, Cai Liu, Haifeng Chen, and Zhiguang Cai. "Characterizing Gas Hydrate–Bearing Marine Sediments Using Elastic Properties—Part 1: Rock Physical Modeling and Inversion from Well Logs." Journal of Marine Science and Engineering 10, no. 10 (2022): 1379. http://dx.doi.org/10.3390/jmse10101379.
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Gas hydrates are considered a potential energy source for the future. Rock physics modeling provides insights into the elastic response of sediments containing gas hydrates, which is essential for identifying gas hydrates using well-log data and seismic attributes. This paper establishes a rock physics model (RPM) by employing effective medium theories to quantify the elastic properties of sediments containing gas hydrates. Specifically, the proposed RPM introduces critical gas hydrate saturation for various modeling schemes. Such a key factor considers the impact of gas hydrates on sediment stiffnesses during the dynamic process of the gas hydrate accumulating as pore fillings and part of the solid components. Theoretical modeling illustrates that elastic characteristics of the sediments exhibit distinct variation trends determined by critical gas hydrate saturation. Numerical tests of the model based on the well-log data confirm that the proposed technique can be employed to rationally predict gas hydrate saturation using the elastic properties. The compressional wave velocity model is also developed to estimate the gas hydrate saturation, which gives reliable fit results to core measurement data. The proposed methods could improve our understanding of the elastic behaviors of gas hydrates, providing a practical approach to estimating their concentrations.
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Du, Bing-rui, Da-wei Bai, Peng-hui Zhang, Peng Guo, and Qiang Zhang. "Physical Experiment Research on Dielectric Properties of Hydrate-bearing Sediment in Sandstone Reservoir." E3S Web of Conferences 118 (2019): 03046. http://dx.doi.org/10.1051/e3sconf/201911803046.
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Dielectric constants can be used to detect hydrates in permafrost regions. Therefore, this study investigated the relationships between the dielectric constant characteristics of sandstone reservoir hydrate and the hydrate saturation degree through physical simulation experiments, as well as the granularity of the surrounding rock. Methane and tetrahydrofuran (THF) hydrates with quartz sands were prepared, and their dielectric constants were analyzed. With different granularities of quartz sands, the dielectric constants of two different methane hydrate sediments decreased with increasing saturation degrees. At a given saturation degree, the dielectric constant of methane hydrate sediments with small granularity was larger than that with medium granularity, a result attributed to the unreacted water in the larger pores of the latter. In addition, the dielectric constant of methane hydrate sediments was larger than that of THF hydrates, which was also attributed to gas-phase factors and the presence of unreacted water. At a given granularity and saturation, the dielectric constants of both the THF and methane hydrates decreased with increasing saturation degrees. We conclude that at low temperature and under normal pressure, THF hydrates cannot be used as a substitute for methane hydrates in laboratory experiments investigating geophysical phenomena.
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Lu, Cheng, Pengfei Xie, Hui Li, et al. "Study on the Mechanical Properties of Silty Clay Sediments with Nodular Hydrate Occurrence." Journal of Marine Science and Engineering 10, no. 8 (2022): 1059. http://dx.doi.org/10.3390/jmse10081059.
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Natural gas hydrates are a strategic energy resource in China. The China Geological Survey has discovered segregated hydrate mass formations under the seepage mechanism in the South China Sea through exploration, and gas hydrates occur in nodular, massive, and vein formations in silty clay sediment. Previous work has focused on the analysis of sediment mechanical properties with respect to the uniform distribution of natural gas hydrates in pore spaces, but the mechanical properties of hydrate-bearing sediments containing segregated hydrate masses are not well understood. Spherical hydrates are used to characterize nodular hydrates, a method is proposed for the preparation of sediment samples containing segregated hydrates masses, and a series of triaxial compression tests are carried out on the samples containing spherical hydrates with two kinds of particle sizes at a certain volume fraction. The paper presents triaxial stress–strain curves for the samples containing spherical hydrates. A model for predicting elastic modulus is established. The results present two distinct stages in the triaxial compression tests of silty clay sediments containing spherical hydrates; they also show that the elastic moduli predicted by the model are in good agreement with the experimental results when the model parameters are set at α = 0.5 and β = −0.21. These results provide fundamental mechanical parameters for the safety evaluation of strata containing segregated gas hydrates.
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Li, Nan, Rezeye Rehemituli, Jie Zhang, and Changyu Sun. "One-Dimensional Study on Hydrate Formation from Migrating Dissolved Gas in Sandy Sediments." Energies 13, no. 7 (2020): 1570. http://dx.doi.org/10.3390/en13071570.
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Upward migration of gas-dissolved pore fluid is an important mechanism for many naturally occurring hydrate reservoirs. However, there is limited understanding in this scenario of hydrate formation in sediments. In this preliminary work, hydrate formation and accumulation from dissolved gas in sandy sediments along the migration direction of brine was investigated using a visual hydrate simulator. Visual observation was employed to capture the morphology of hydrates in pores through three sapphire tubes. Meanwhile, the resistivity evolution of sediments was detected to characterize hydrate distribution in sediments. It was observed that hydrates initially formed as a thin film or dispersed crystals and then became a turbid colloidal solution. With hydrate growth, the colloidal solution converted to massive solid hydrates. Electrical resistivity experienced a three-stage evolution process corresponding to the three observed hydrate morphologies. The results of resistivity analysis also indicated that the bottom–up direction of hydrate growth was consistent with the flow direction of brine, and two hydrate accumulation centers successively appeared in the sediments. Hydrates preferentially formed and accumulated in certain depths of the sediments, resulting in heterogeneous hydrate distribution. Even under low saturation, the occurrence of heterogeneous hydrates led to the sharp reduction of sediment permeability.
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Malakhova, Valentina V. "INFLUENCE OF SALT DIFFUSION ON THE STABILITY OF METHANE GAS HYDRATE IN THE ARCTIC SHELF." Interexpo GEO-Siberia 4, no. 1 (2020): 91–97. http://dx.doi.org/10.33764/2618-981x-2020-4-1-91-97.
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Suitable conditions for the formation of methane hydrates exist in the bottom sediments of shallow Arctic shelves in the presence of permafrost. Salt diffusion into hydrated bottom sediments can help accelerate hydrate degradation. An analysis of the influence of salinity of the bottom sediments of the Arctic shelf on the thickness of the methane hydrate stability zone was based on mathematical modeling. Estimates of the thickness of the stability zone were obtained in experiments with various correlations which relate the hydrate dissociation temperature in the presence of aqueous solutions containing salts.
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Li, Xian, Hongfeng Lu, Panpan Zhang, Lu Yu, Changwen Xiao, and Yan Li. "Numerical Simulation of Secondary Hydrate Formation Characteristics and Effectiveness of Prevention Methods." Energies 17, no. 20 (2024): 5045. http://dx.doi.org/10.3390/en17205045.
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The exploitation of natural gas hydrates by the pressure reduction method is affected by the decomposition heat absorption effect, and the range of the formation temperature reduction area is expanding. At the same time, the temperature reduction phenomenon is more significant around the production wells under the influence of gas throttling and expansion effects, and hydrate formation will occur under certain temperature and pressure conditions, leading to blockage of effective seepage channels in the reservoir in the region and elevation of seepage resistance, which may affect the output of hydrate decomposition gas. A numerical simulation model is constructed for the purpose of studying the secondary hydrate generation pattern around the well, analyzing the impact of secondary hydrates around wells on the production capacity, and assessing the effectiveness of prevention methods to inform the actual production of hydrates. The results demonstrate that secondary hydrate is typically formed in the near-well area of the upper part of the production well, and the secondary hydrate around the upper part of the production well is the first to be formed, exhibiting the highest saturation peak and the latest decomposition. The formation of the secondary hydrate can be predicted based on the observed change in temperature and pressure, and the rate of secondary hydrate formation is markedly rapid, whereas the decomposition rate, approximately 0.285 mole/d, is relatively slow. Additionally, the impact of secondary hydrates on cumulative gas production is insignificant, and the effect of secondary hydrates on capacity can be ignored. Hot water injection, wellbore heating, and reservoir reconstruction can effectively eliminate secondary hydrates around the well. Reservoir reconstruction represents a superior approach to the elimination of secondary hydrates, which can effectively enhance production capacity while preventing the generation of secondary hydrates.
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Okereke, Ndubuisi U., Pius E. Edet, Yahaya D. Baba, et al. "An assessment of hydrates inhibition in deepwater production systems using low-dosage hydrate inhibitor and monoethylene glycol." Journal of Petroleum Exploration and Production Technology 10, no. 3 (2019): 1169–82. http://dx.doi.org/10.1007/s13202-019-00812-4.
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AbstractIn this study, a deepwater pipeline-riser system that experienced hydrates was modelled in MAXIMUS 6.20 (an integrated production modelling tool) to understand, predict and mitigate hydrates formation in typical deepwater system. Highlights of the results from this study suggest that the injection of low-dosage hydrate inhibitors (LDHIs) into the hydrate-forming structures within the multiphase flow stream disperses the hydrates particles in an irregular manner and subsequently decreases the nucleation rate of the hydrate and prevents the formation of hydrates. This study found that the cost of using monoethylene glycol was significantly higher than that of LDHI by over $500/day although low-dosage hydrate inhibitors have initial relatively high CAPEX. In the long run, its OPEX is relatively low, making it cost-effective for hydrate inhibition in deepwater scenarios.
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Chen, Huan, Bingyue Han, Chen Lang, Min Wen, Baitao Fan, and Zheyuan Liu. "Hydrates for Cold Storage: Formation Characteristics, Stability, and Promoters." Applied Sciences 11, no. 21 (2021): 10470. http://dx.doi.org/10.3390/app112110470.
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The potential of hydrates formed from R141b (CH3CCl2F), trimethylolethane (TME), and tetra-n-butylammonium bromide/tetra-n-butylammonium chloride (TBAB/TBAC) to be used as working substances for cold storage was investigated to provide a solution for unbalanced energy grids. In this study, the characteristics of hydrate formation, crystal morphology of hydrates, and the stability of hydrate in cyclic formation under 0.1 MPa and at 5 °C were carried out. It found that the ice had a positive effect on the hydrate formation under same conditions. Upon the addition of the ice cube, the induction time of R141b, TME, and TBAB/TBAC hydrates decreased markedly, and significantly high formation rates were obtained. Under magnetic stirring, the rate at which TBAB/TBAC formed hydrates was significantly lower than that when ice was used. In microscopic experiments, it was observed that the TBAB/TBAC mixture formed hydrates with more nucleation sites and compact structures, which may increase the hydrate formation rate. In the multiple cycle formation of TBAB/TBAC hydrates, the induction time gradually decreased with the increasing number of formation cycles and finally stabilized, which indicated the potential of the TBAB/TBAC hydrates for application in cold storage owing to their good durability and short process time for heat absorption and release.
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Xu, Chun-Gang, Min Wang, Gang Xu, et al. "The Relationship between Thermal Characteristics and Microstructure/Composition of Carbon Dioxide Hydrate in the Presence of Cyclopentane." Energies 14, no. 4 (2021): 870. http://dx.doi.org/10.3390/en14040870.
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Hydrate-based carbon dioxide (CO2) separation and capture is a new technology for achieving CO2 emission reduction. However, it is still not commercially applied for the ambiguity of microscopic hydrate formation mechanism. In a constant volume experiment of hydrate formation, there are two or more pressure platforms, indicating that there might be two or more different hydrates formation in succession. In order to reveal the relationship between the microscopic process and the gas consumption in the process of hydrate formation, hydrate composition and formation mechanism of cyclopentane-CO2 (CP-CO2) system was investigated using a differential scanning calorimeter (DSC) and Raman spectroscopy. The results indicated CO2-CP binary hydrate and CO2 hydrate are formed successively, and they coexist in the final hydrate. CP-CO2 binary hydrates forms preferentially, and as crystal seeds, inducing the formation of CO2 hydrates. The two hydrates formation processes cause the two pressure-drops. The results provide a scientific basis for increasing the gas consumption in different stages of gas hydrate formation in the presence of hydrate formation promoter.
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Li, Lili, Pengwei Zhang, Ming Yang, and Baoguo Liu. "Thermal-hydro coupling model of methane hydrate reformation in porous media." IOP Conference Series: Earth and Environmental Science 1335, no. 1 (2024): 012048. http://dx.doi.org/10.1088/1755-1315/1335/1/012048.
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Abstract Methane hydrates are crystalline compounds found in marine sediments and permafrost regions. Methane hydrates remain stable under both low-temperature and high-pressure conditions. When a methane hydrate reservoir is heated or depressurized, methane hydrates become unstable and decompose into water and methane gases. The heat absorption process during the decomposition of methane hydrates influences the temperature field. Methane hydrate reformation occurs during the extraction process, significantly reducing the hydraulic conductivity of the reservoir and hindering the long-term stable extraction of methane hydrates. In this paper, a numerical model is established by coupling seepage and heat processes. The temperature variation owing to the heat absorption process of methane hydrate decomposition is quantified based on the proposed model. The effect of spatial lithology on methane hydrate conversion is also analyzed, and the results for hydrate, water, gas, and permeability in the model are summarized. The numerical model also reflects the heterogeneity of marine sediments. Finally, the sensitivities of different physical parameters (permeability and porosity) and pressure gradients to the reformation rate of methane hydrate reforming are discussed. The results of this study provide scientific data supporting the influence of secondary hydrate formation on long-term extraction efficiency in the actual engineering hydrate extraction process.
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Qi, Ying Xia, and Hua Zhang. "MD Simulation of CO2-CH4 Mixed Hydrate on Crystal Structure and Stability." Advanced Materials Research 181-182 (January 2011): 310–15. http://dx.doi.org/10.4028/www.scientific.net/amr.181-182.310.
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MD simulations are carried out on the sI CO2-CH4 mixed hydrates in the constant-NVT and constant-NPT ensembles for the two cases of CO2 occupancy. One is 75% called normal, the other is 87.5%. The simulations results show that the hydrate structure can be maintained both for the two hydrates over the temperature range of 0K to 300K. However, the equilibrium pressure, the potential energy and the MSDs of the atoms in H2O for the higher CO2 ratio hydrates is larger than that of the normal CO2 ratio hydrates, indicating that the normal mixed hydrates is more stable than the higher CO2 occupancy mixed hydrate. These results are consistent with the present experimental results.
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Gaidukova, Olga, Sergei Misyura, and Pavel Strizhak. "Key Areas of Gas Hydrates Study: Review." Energies 15, no. 5 (2022): 1799. http://dx.doi.org/10.3390/en15051799.
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Gas hydrates are widespread all over the world. They feature high energy density and are a clean energy source of great potential. The paper considers experimental and theoretical studies on gas hydrates in the following key areas: formation and dissociation, extraction and transportation technologies of natural methane hydrates, and ignition, and combustion. We identified a lack of research in more areas and defined prospects of further development of gas hydrates as a promising strategic resource. One of the immediate problems is that there are no research findings for the effect of sediments and their matrices on hydrate saturation, as well as on gas hydrate formation and dissociation rates. No mathematical models describe the dissociation of gas hydrates under various conditions. There is a lack of research into the renewal and improvement of existing technologies for the easier and cheaper production of gas hydrates and the extraction of natural gas from them. There are no models of gas hydrate ignition taking into account dissociation processes and the self-preservation effect.
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Chuvilin, Evgeny, Valentina Ekimova, Boris Bukhanov, Sergey Grebenkin, Natalia Shakhova, and Igor Semiletov. "Role of Salt Migration in Destabilization of Intra Permafrost Hydrates in the Arctic Shelf: Experimental Modeling." Geosciences 9, no. 4 (2019): 188. http://dx.doi.org/10.3390/geosciences9040188.
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Destabilization of intrapermafrost gas hydrate is one possible reason for methane emission on the Arctic shelf. The formation of these intrapermafrost gas hydrates could occur almost simultaneously with the permafrost sediments due to the occurrence of a hydrate stability zone after sea regression and the subsequent deep cooling and freezing of sediments. The top of the gas hydrate stability zone could exist not only at depths of 200–250 m, but also higher due to local pressure increase in gas-saturated horizons during freezing. Formed at a shallow depth, intrapermafrost gas hydrates could later be preserved and transform into a metastable (relict) state. Under the conditions of submarine permafrost degradation, exactly relict hydrates located above the modern gas hydrate stability zone will, first of all, be involved in the decomposition process caused by negative temperature rising, permafrost thawing, and sediment salinity increasing. That’s why special experiments were conducted on the interaction of frozen sandy sediments containing relict methane hydrates with salt solutions of different concentrations at negative temperatures to assess the conditions of intrapermafrost gas hydrates dissociation. Experiments showed that the migration of salts into frozen hydrate-containing sediments activates the decomposition of pore gas hydrates and increase the methane emission. These results allowed for an understanding of the mechanism of massive methane release from bottom sediments of the East Siberian Arctic shelf.
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Safronov, Anatolii. "KEY ASPECTS OF THERMAL METHODS FOR DEVELOPMENT OF MARINE GAS HYDRATES ON THE EXAMPLE OF THE METHODS OF USING THERMAL WATERS AND INJECTION OF HOT WATER INTO THE FORMATION." SCIENTIFIC PAPERS OF DONNTU Series: “The Mining and Geology”, no. 1(31)-2(32) (2024): 98–103. https://doi.org/10.31474/2073-9575-2024-1(31)-2(32)-98-103.
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Purpose: to highlight key aspects of thermal methods for development of marine gas hydrates when using thermal waters and their injection into the formation. Methods: the work uses one of the methods of using thermal waters for development of marine gas hydrates. Findings: The features of the use of thermal methods for development of marine gas hydrates by supplying heat to the gas hydrate decomposition zone, heating the wellbore with heaters, steam-cyclic treatment of the well, etc. are analyzed. The advantages and disadvantages of the above methods are characterized, and a conclusion is made about the relevance of their application. Originality consists in highlighting key aspects of thermal methods for development and extraction of marine gas hydrates. Practical implication. The research results can simplify the development and production of offshore gas hydrates. Keywords: gas hydrates, offshore gas hydrates, offshore gas hydrate development methods, thermal development methods, steam cyclic treatment, thermal flooding.
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de Lima Silva, Paulo H., Mônica F. Naccache, Paulo R. de Souza Mendes, Leandro S. Valim, and Adriana Teixeira. "Effect of Alcohols on the Rheological Properties of Tetrahydrofuran Hydrate Slurries." SPE Journal 25, no. 06 (2020): 3111–19. http://dx.doi.org/10.2118/201101-pa.
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Summary Hydrate formation is an issue that can have a significant negative economic impact on the oil industry. Hydrates are crystalline solids that resemble ice, usually formed in the presence of a mixture of oil/gas/water in conditions of high pressure and low temperature, similar to those found in deepwater oil production. Depending on the amount of hydrates formed, production lines can be severely affected, causing huge financial losses. Therefore, it is of great interest to understand and analyze the characteristics of the hydrates formed, and eventually identify means of mitigating hydrate formation, to reduce the production losses. In this work we analyze the effect of alcohols for hydrate mitigation through rheological characterization. We study the rheology of hydrates formed in a mixture of tetrahydrofuran (THF) and water. This is used as a model system because hydrates are formed at atmospheric pressure. Using the rheology of the model system as a baseline case, we analyze the effect of different alcohols (monoethylene glycol, ethanol, isopropanol) and concentrations on the rheology of the resulting hydrate slurries to verify and understand the capability of these additives to mitigate hydrate formation.
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Kutnyi, Bogdan, and . "Termotechnical Characteristics Determination of Enclosing Structures for Hydrates Storage." International Journal of Engineering & Technology 7, no. 3.2 (2018): 510. http://dx.doi.org/10.14419/ijet.v7i3.2.14580.
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In many countries around the world, gas hydrates use is seen as a promising alternative source of energy. The industrial infrastructure gas hydrates use requires the creation of reliable means for their storage and transportation.In the paper the research installations schemes and the dissociated gas temperature regime hydrate experimental study results are given. The surface and propane hydrate deep layers temperature regime, which decomposes under atmospheric pressure, is analyzed. Convective and radiant heat transfer at the hydrate storage reservoir inner surface is considered and the temperature at the gas hydrates surface is determined. The method for determining the resistance to the tent heat transfer is developed and the dependence for the propane hydrate dissociation intensity is established. The research results can be used to reduce gas losses during gas hydrates storage and transportation under nonequilibrium conditions.
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Wang, Yubin, Wei Liu, Bin Li, Xiaochen Yan, Yunchen Wang, and Fan Xiao. "Influence of natural gas component changes on hydrate generation temperature and pressure." Journal of Physics: Conference Series 2788, no. 1 (2024): 012007. http://dx.doi.org/10.1088/1742-6596/2788/1/012007.
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Abstract During the transportation of natural gas through pipelines, there is a potential for the formation of gas hydrates. These hydrates can result in pipeline blockages, causing economic losses and significant safety hazards. Therefore, it holds crucial reference value to understand the conditions under which hydrates are formed and to grasp the laws governing their generation for effective prevention and control. This study employs the P-P hydrate thermodynamic model to compute the temperature and pressure at which natural gas generates hydrates. We also explore the impact of changes in the composition of natural gas on the temperature and pressure required for hydrate formation. This helps us discern the sensitivity of hydrate formation conditions to various components. Our findings indicate that propane, isobutane, and H2S substantially influence hydrate formation under the same percentage of alteration. For instance, a 3% increase in these three components results in a temperature increase of 2.36°C, 2.83°C, and 2.14°C, respectively, for hydrate formation at 100 bar.
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Gabitto, Jorge F., and Costas Tsouris. "Physical Properties of Gas Hydrates: A Review." Journal of Thermodynamics 2010 (January 12, 2010): 1–12. http://dx.doi.org/10.1155/2010/271291.
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Methane gas hydrates in sediments have been studied by several investigators as a possible future energy resource. Recent hydrate reserves have been estimated at approximately 1016 m3 of methane gas worldwide at standard temperature and pressure conditions. In situ dissociation of natural gas hydrate is necessary in order to commercially exploit the resource from the natural-gas-hydrate-bearing sediment. The presence of gas hydrates in sediments dramatically alters some of the normal physical properties of the sediment. These changes can be detected by field measurements and by down-hole logs. An understanding of the physical properties of hydrate-bearing sediments is necessary for interpretation of geophysical data collected in field settings, borehole, and slope stability analyses; reservoir simulation; and production models. This work reviews information available in literature related to the physical properties of sediments containing gas hydrates. A brief review of the physical properties of bulk gas hydrates is included. Detection methods, morphology, and relevant physical properties of gas-hydrate-bearing sediments are also discussed.
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Nalyvaiko, Oleksandr, Pavlo Pysarenko, Yevhenii Nalyvaiko, and Nikolay Tanchev. "Methane gas hydrates of the Black Sea – environmental problem or energy source?" Journal of Innovations and Sustainability 6, no. 4 (2022): 04. http://dx.doi.org/10.51599/is.2022.06.04.04.
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Purpose. The purpose of this paper is to substantiate the technological solution of equilibrium conditions in the system “methane – water phase – hydrate – R-2M”; to reveal existing ecological problems of methane gas hydrate extraction from the Black Sea bottom; to determine whether gas hydrate deposits of Black Sea methane are an ecological problem or should be considered as an energy source, to explain the necessity of introduction of the effect of forced self-preservation of methane gas hydrates into development of gas hydrates from the sea bottom.
 Results. This article analyses current research on gas hydrates specifically in the Black Sea. It shows that the necessary conditions exist for the accumulation of gas hydrates in certain areas of the deep Black Sea (one of the most favourable regions among modern sea basins). This article discusses some ideas for the development of experimental studies of the metastable state of methane gas hydrates at negative temperatures: stability and mechanisms of decomposition. Despite the great variety of technological solutions and schemes of gas hydrates application proposed by the leading researchers in the world, they have been tested practically on a small number of laboratory and model installations, mainly for water desalination and concentration of water solutions, separation of two-component gas mixtures. In fact, there is no data to calculate the processes of formation and melting of ice-gas hydrate methane. The effect of self-preservation of methane gas hydrates deserves special attention.
 Scientific novelty. An attempt was made to substantiate the issue of whether gas hydrate deposits of methane in the Black Sea are an environmental problem or should they be considered as an additional source of energy and even as a “fuel of the future”. The authors for the first time introduced the concept of “forced preservation (activation) effect of methane gas hydrates”, which makes it possible to stabilize methane hydrate decomposition when the system is transferred from the area of hydrate stability to the area of thermodynamic parameters, thus significantly reducing the environmental problems of the Black Sea.
 Practical value. This article offers a technological solution for stabilization of equilibrium conditions by hydrophobic material “Ramsinks-2M” in the system “methane-water phase-hydrate-R-2M” to regulate the self-preservation effect of methane gas hydrates
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Kliner, J. R., and J. LH Grozic. "Determination of synthetic hydrate content in sand specimens using dielectrics." Canadian Geotechnical Journal 43, no. 6 (2006): 551–62. http://dx.doi.org/10.1139/t06-022.
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Gas hydrates are solid crystalline compounds (clathrates) that encage gas molecules inside the lattices of hydrogen bonded water molecules within a specific temperaturepressure stability zone. It is imperative that reliable detection and quantification modi operandi are developed, as proposed in this research, to identify hydrate-laden strata and determine economic viability of this potential energy yield. This paper presents the experimental analysis of synthetic refrigerant (R-11) hydrates in 20/30 Ottawa sand using dielectric principles to determine specific hydrate content. Hydrate specimens were constructed via moist tamped Ottawa sand, purged with carbon dioxide (CO2), saturated with de-aired water, and mixed with a known amount of R-11 to produce precise hydrate contents. The specimen's bulk dielectric constant was measured using a ThetaProbe by applying the principles of time domain reflectometry (TDR). A distinct relationship between hydrate content and the bulk dielectric constant of sand specimens is determined, as well; volumetric expansion associated with hydrate formation is also portrayed.Key words: gas hydrates, synthetic hydrates, dielectrics, Ottawa sand, laboratory testing.
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Gauteplass, Jarand, Stian Almenningen, Tanja Barth, and Geir Ersland. "Hydrate Plugging and Flow Remediation during CO2 Injection in Sediments." Energies 13, no. 17 (2020): 4511. http://dx.doi.org/10.3390/en13174511.
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Successful geological sequestration of carbon depends strongly on reservoir seal integrity and storage capacity, including CO2 injection efficiency. Formation of solid hydrates in the near-wellbore area during CO2 injection can cause permeability impairment and, eventually, injectivity loss. In this study, flow remediation in hydrate-plugged sandstone was assessed as function of hydrate morphology and saturation. CO2 and CH4 hydrates formed consistently at elevated pressures and low temperatures, reflecting gas-invaded zones containing residual brine near the injection well. Flow remediation by methanol injection benefited from miscibility with water; the methanol solution contacted and dissociated CO2 hydrates via liquid water channels. Injection of N2 gas did not result in flow remediation of non-porous CO2 and CH4 hydrates, likely due to insufficient gas permeability. In contrast, N2 as a thermodynamic inhibitor dissociated porous CH4 hydrates at lower hydrate saturations (<0.48 frac.). Core-scale thermal stimulation proved to be the most efficient remediation method for near-zero permeability conditions. However, once thermal stimulation ended and pure CO2 injection recommenced at hydrate-forming conditions, secondary hydrate formation occurred aggressively due to the memory effect. Field-specific remediation methods must be included in the well design to avoid key operational challenges during carbon injection and storage.
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Liu, Huaxin, Meijun Li, Hongfei Lai, Ying Fu, Zenggui Kuang, and Yunxin Fang. "Controlling Factors of Vertical Geochemical Variations in Hydrate-Rich Sediments at the Site GMGS5-W08 in the Qiongdongnan Basin, Northern South China Sea." Energies 17, no. 2 (2024): 412. http://dx.doi.org/10.3390/en17020412.
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Large amounts of natural gas hydrates have been discovered in the Qiongdongnan Basin (QDNB), South China Sea. The chemical and stable carbon isotopic composition shows that the hydrate-bound gas was a mixture of thermogenic and microbial gases. It is estimated that microbial gas accounts for 40.96% to 60.58%, showing a trend of decrease with the increase in burial depth. A significant amount of gas hydrates is thought to be stored in the mass transport deposits (MTDs), exhibiting vertical superposition characteristics. The stable carbon isotopic values of methane (δ13C1) in the MTD1, located near the seabed, are less than −55‰, while those of the methane below the bottom boundary of MTD3 are all higher than −55‰. The pure structure I (sI) and structure II (sII) gas hydrates were discovered at the depths of 8 mbsf and 145.65 mbsf, respectively, with mixed sI and sII gas hydrates occurring in the depth range 58–144 mbsf. In addition, a series of indigenous organic matters and allochthonous hydrocarbons were extracted from the hydrate-bearing sediments, which were characterized by the origin of immature terrigenous organic matter and low-moderate mature marine algal/bacterial materials, respectively. More allochthonous (migrated) hydrocarbons were also discovered in the sediments below the bottom boundary of MTD3. The gas hydrated is “wet gas” characterized by a low C1/(C2 + C3) ratio, from 2.55 to 43.33, which was mainly derived from a deeply buried source kitchen at a mature stage. There is change in the heterogeneity between the compositions of gas and biomarkers at the site GMGS5-W08 along the depth and there is generally a higher proportion of thermogenic hydrocarbons at the bottom boundary of each MTDs, which indicates a varying contribution of deeply buried thermogenic hydrocarbons. Our results indicate that the MTDs played a blocking role in regulating the vertical transportation of hydrate-related gases and affect the distribution of gas hydrate accumulation in the QDNB.
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Haiko, Hennadii, Oleksandr Zhivkov, and Lubov Pyha. "Application of resonant oscillatory systems for the seafloor gas hydrates development." E3S Web of Conferences 230 (2021): 01020. http://dx.doi.org/10.1051/e3sconf/202123001020.
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The prospects for the gas recovery from bottom gas hydrates are studied, and the necessity for the formation of an innovation environment and practical steps for conducting industrial experiments are formulated. The promising methods of shielded development of seafloor gas hydrate deposits are analyzed and the technical problems of their improvement are revealed. The possibilities of using resonant oscillatory systems for the shielded development of bottom gas hydrates are studied, in particular, a Helmholtz flow-excited resonator. The expediency of using high-quality oscillations of the “rotator” type has been substantiated in order to facilitate controlled gas hydrates dissociation over large areas of a gas hydrate field and to counteract the formation of new gas hydrates in the fractures of hydraulic reservoir fracturing. A method has been developed of gas recovery from bottom methane hydrates using a resonator device, which significantly reduces the energy consumption for the gas hydrates dissociation and contributes to the technological processes control.
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Kvamme, Bjørn, Jinzhou Zhao, Na Wei, et al. "Why Should We Use Residual Thermodynamics for Calculation of Hydrate Phase Transitions?" Energies 13, no. 16 (2020): 4135. http://dx.doi.org/10.3390/en13164135.
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The formation of natural gas hydrates during processing and transport of natural has historically been one of the motivations for research on hydrates. In recent years, there has been much focus on the use of hydrate as a phase for compact transport of natural gas, as well as many other applications such as desalination of seawater and the use of hydrate phase in heat pumps. The huge amounts of energy in the form of hydrates distributed in various ways in sediments is a hot topic many places around the world. Common to all these situations of hydrates in nature or industry is that temperature and pressure are both defined. Mathematically, this does not balance the number of independent variables minus conservation of mass and minus equilibrium conditions. There is a need for thermodynamic models for hydrates that can be used for non-equilibrium systems and hydrate formation from different phase, as well as different routes for hydrate dissociation. In this work we first discuss a residual thermodynamic model scheme with the more commonly used reference method for pressure temperature stability limits. However, the residual thermodynamic method stretches far beyond that to other routes for hydrate formation, such as hydrate formation from dissolved hydrate formers. More important, the residual thermodynamic method can be utilized for many thermodynamic properties involved in real hydrate systems. Consistent free energies and enthalpies are only two of these properties. In non-equilibrium systems, a consistent thermodynamic reference system (ideal gas) makes it easier to evaluate most likely distribution of phases and compositions.
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Chuvilin, Evgeny, Dinara Davletshina, Boris Bukhanov, Aliya Mukhametdinova, and Vladimir Istomin. "Formation of Metastability of Pore Gas Hydrates in Frozen Sediments: Experimental Evidence." Geosciences 12, no. 11 (2022): 419. http://dx.doi.org/10.3390/geosciences12110419.
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The Arctic permafrost and zones of hydrate stability may evolve to the conditions that allow gas hydrates to remain metastable for a long time due to self-preservation within 150 m depths. The behavior of relict (metastable) gas hydrates in frozen sediments is controlled externally by pressure and temperature and internally by the properties of hydrate particles and sediments. The sensitivity of the dissociation and self-preservation of pore gas hydrates to different factors is investigated in laboratory experiments. The observations focus on time-dependent changes in methane hydrate saturation in frozen sand samples upon the pressure dropping below phase equilibrium in the gas–hydrate–ice system. The preservation of pore gas hydrates in these conditions mainly depends on the initial hydrate and ice saturation, clay contents and mineralogy, salinity, and texture of sediments, which affect the size, shape, and structure distortion of hydrate inclusions. The self-preservation mechanism works well at high initial contents of pore ice and hydrate, low salinity, relatively low percentages of clay particles, temperatures below −4 °C, and above-equilibrium pressures. Nuclear magnetic resonance (NMR) measurements reveal considerable amounts of unfrozen pore water in frozen sediments that may hold for several days after the pressure drop, which controls the dissociation and self-preservation processes. Metastable gas hydrates in frozen sand may occupy up to 25% of the pore space, and their dissociation upon permafrost thawing and pressure drops may release up to 16 m3 of methane into the atmosphere per 1 m3 of hydrate-bearing permafrost.
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Srivastava, Shubhangi, Bernd Hitzmann, and Viktoria Zettel. "A Future Road Map for Carbon Dioxide (CO2) Gas Hydrate as an Emerging Technology in Food Research." Food and Bioprocess Technology 14, no. 9 (2021): 1758–62. http://dx.doi.org/10.1007/s11947-021-02656-5.
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AbstractGas hydrates constitute of gas as a guest molecule in hydrogen-bonded water lattices. This review covers ongoing hydrate research in food technology with a spotlight on carbon dioxide (CO2) application as a hydrate. The application of gas hydrates in the concentration of juices, desalination, carbonation, and food preservation has been covered in the review. One of the applications of CO2 hydrate technology was in the concentration of orange juice which gave a dehydration ratio (DR) of 57.2% at a pressure of 4.1 MPa. Similarly, one study applied it for the tomato juice concentration and had a DR of 65.2%. The CO2 hydrate rate constants recorded were 0.94 × 10−8 and 1.65 × 10−8 J−1 mol2 s−1 at a feed pressure of 1.81 and 3.1 MPa respectively. Hence, CO2 hydrate can be used effectively for the juice concentration as well as for other applications too. The review will cater insights on the generic trends of hydrates in food research with respect to their kinetics properties and their role in food applications. Despite the fact that there are no technology stoppers to exploit CO2 hydrates, a downright technological quantum leap is the need of the future in this riveting field. Thus, the perspectives and key challenges in food research are also discussed. The food applications of CO2 gas hydrates are still very scarce so there is an urge to carry through more theoretical and experimental analysis to elucidate various applications of hydrates in food and to positively validate its sustainability.
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Vorozhtsova, Yulia S., Alexander V. Melent'ev, Alexander A. Uspensky, Dmitry V. Kremnev, Mikhail A. Radin, and Alexander A. Slobodov. "THERMODYNAMIC PROPERTIES OF GAS HYDRATE COMPOUNDS." Bulletin of the Saint Petersburg State Institute of Technology (Technical University) 59 (2021): 12–20. http://dx.doi.org/10.36807/1998-9849-2021-59-85-12-20.
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The most stable forms (compositions) and thermodynamic characteristics of gas hydrates СН4•6Н2О, С2Н6•8Н2О, С3Н8•17Н2О, i-С4Н10•17Н2О, СO2•6Н2О, O2•6Н2О, H2S•6Н2О, N2•6Н2О, Ar•6Н2О were defined based on the analysis of literature data and own research on the composition and thermodynamic properties of gas hydrate compounds. Correlation dependences of thermodynamic characteristics of gas hydrates depending on the composition were graphed. All the main thermodynamic characteristics of gas hydrates – standard enthalpies and Gibbs energies of formation, standard entropies, temperature dependences of isobaric heat capacity, enthalpy and entropy of dissociation (formation) of gas hydrates into hydrate-forming gas and water (ice) – were determined based on the results of the examination, assessment, calculation and data agreement
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Kalacheva, L. P., I. K. Ivanova, A. S. Portnyagin, I. I. Rozhin, K. K. Argunova, and A. I. Nikolaev. "Determination of the lower boundaries of the natural gas hydrates stability zone in the subpermafrost horizons of the Yakut arch of the Vilyui syneclise, saturated with bicarbonate-sodium type waters." SOCAR Proceedings, SI2 (December 30, 2021): 1–11. http://dx.doi.org/10.5510/ogp2021si200549.
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This paper considers the possibility of the underground gas storage facilities creating in a hydrate state on the north-western slope of the Yakut arch of the Vilyui syneclise. For this, the boundaries of the hydrate stability zone were determined for 6 promising areas of the considered geological structure. Equilibrium conditions of the natural gas hydrates formation in the model porous media containing bicarbonate-sodium type water (mineralization 20 g/l), characteristic for the subpermafrost horizons of the Yakut arch, have been studied by the method of differential thermal analysis. On the basis of the obtained results, the boundaries of the natural gas hydrates stability zone were determined. It was shown that the upper boundaries of the hydrate stability zone are located in the thickness of permafrost rocks. It was found that the lower boundaries of the natural gas hydrates stability zone in moist unsalted porous medium lie in the range from 930 to 1120 m. When the samples are saturated with mineralized water, the boundaries are located 80-360 m higher. The obtained experimental results allow us to conclude that in subpermafrost aquifers of the Yakut arch has favorable conditions for the formation of natural gas hydrates. Keywords: natural gas hydrates; aquifers; underground gas storage; hydrate stability zone; geothermal gradient; equilibrium conditions of the hydrate formation; bicarbonate-sodium type water.
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Liu, Lu, Yuanxin Yao, Xuebing Zhou, Yanan Zhang, and Deqing Liang. "Improved Formation Kinetics of Carbon Dioxide Hydrate in Brine Induced by Sodium Dodecyl Sulfate." Energies 14, no. 8 (2021): 2094. http://dx.doi.org/10.3390/en14082094.
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Due to high efficiency and low cost, hydrate-based desalination is investigated as a pretreatment method for seawater desalination. To improve the formation rate of hydrates, the effect of sodium dodecyl sulfate (SDS) on CO2 hydrate formation from a 3.5 wt.% NaCl solution was measured at 275 K and 3 MPa. X-ray diffraction (XRD) and cryo-scanning electron microscopy (cryo-SEM) were used to measure the crystal structure and micromorphology of the formed hydrates. The results showed that the induction time of CO2 hydrate formation reduced from 32 to 2 min when SDS concentration increased from 0.01 to 0.05%, the hydrate conversion rate increased from 12.06 to 23.32%, and the remaining NaCl concentration increased from 3.997 to 4.515 wt.%. However, as the SDS concentration surpassed 0.05 wt.%, the induction time increased accompanied by a decrease in the hydrate conversion rate. XRD showed that the CO2 hydrate was a structure I hydrate, and SDS had no influence on the hydrate structure. However, cryo-SEM images revealed that SDS promoted the formation of hydrates by increasing the specific surface area of the formed hydrates and folds; rods and clusters could be found on the surface of the CO2 hydrate. Thus, the best SDS concentration for promoting CO2 hydrate formation was approximately 0.05 wt.%; desalination was most efficient at this concentration.
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Chuvilin, Davletshina, Ekimova, Bukhanov, Shakhova, and Semiletov. "Role of Warming in Destabilization of Intrapermafrost Gas Hydrates in the Arctic Shelf: Experimental Modeling." Geosciences 9, no. 10 (2019): 407. http://dx.doi.org/10.3390/geosciences9100407.
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Destabilization of intrapermafrost gas hydrates is one of the possible mechanisms responsible for methane emission in the Arctic shelf. Intrapermafrost gas hydrates may be coeval to permafrost: they originated during regression and subsequent cooling and freezing of sediments, which created favorable conditions for hydrate stability. Local pressure increase in freezing gas-saturated sediments maintained gas hydrate stability from depths of 200–250 meters or shallower. The gas hydrates that formed within shallow permafrost have survived till present in the metastable (relict) state. The metastable gas hydrates located above the present stability zone may dissociate in the case of permafrost degradation as it becomes warmer and more saline. The effect of temperature increase on frozen sand and silt containing metastable pore methane hydrate is studied experimentally to reconstruct the conditions for intrapermafrost gas hydrate dissociation. The experiments show that the dissociation process in hydrate-bearing frozen sediments exposed to warming begins and ends before the onset of pore ice melting. The critical temperature sufficient for gas hydrate dissociation varies from −3.0 to −0.3 °C and depends on lithology (particle size) and salinity of the host frozen sediments. Taking into account an almost gradientless temperature distribution during degradation of subsea permafrost, even minor temperature increases can be expected to trigger large-scale dissociation of intrapermafrost hydrates. The ensuing active methane emission from the Arctic shelf sediments poses risks of geohazard and negative environmental impacts.
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Soromenho, Mário R. C., Anastasiia Keba, José M. S. S. Esperança, and Mohammad Tariq. "Effect of Thiouronium-Based Ionic Liquids on the Formation and Growth of CO2 (sI) and THF (sII) Hydrates." International Journal of Molecular Sciences 23, no. 6 (2022): 3292. http://dx.doi.org/10.3390/ijms23063292.
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In this manuscript, two thiouronium-based ionic liquids (ILs), namely 2-ethylthiouronium bromide [C2th][Br] and 2-(hydroxyethyl)thiouronium bromide [C2OHth][Br], were tested at different concentrations (1 and 10 wt%) for their ability to affect CO2 (sI) and tetrahydrofuran (THF) (sII) hydrate formation and growth. Two different methods were selected to perform a thermodynamic and kinetic screening of the CO2 hydrates using a rocking cell apparatus: (i) an isochoric pressure search method to map the hydrate phase behavior and (ii) a constant ramping method to obtain the hydrate formation and dissociation onset temperatures. A THF hydrate crystal growth method was also used to determine the effectiveness of the ILs in altering the growth of type sII hydrates at atmospheric pressure. Hydrate–liquid–vapor equilibrium measurements revealed that both ILs act as thermodynamic inhibitors at 10 wt% and suppress the CO2 hydrate equilibria ~1.2 °C. The constant ramping methodology provides interesting results and reveals that [C2OHth][Br] suppresses the nucleation onset temperature and delays the decomposition onset temperatures of CO2 hydrates at 1 wt%, whereas suppression by [C2th][Br] was not statistically significant. Normalized pressure plots indicate that the presence of the ILs slowed down the growth as well as the decomposition rates of CO2 hydrates due to the lower quantity of hydrate formed in the presence of 1 wt% ILs. The ILs were also found to be effective in inhibiting the growth of type sII THF hydrates without affecting their morphology. Therefore, the studied thiouronium ILs can be used as potential dual-function hydrate inhibitors. This work also emphasizes the importance of the methods and conditions used to screen an additive for altering hydrate formation and growth.
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Freij-Ayoub, R., M. Rivero, and E. Nakagawa. "HYDRATES—A CHALLENGE IN FLOW ASSURANCE FOR OIL AND GAS PRODUCTION IN DEEP AND ULTRA-DEEP WATER." APPEA Journal 46, no. 1 (2006): 395. http://dx.doi.org/10.1071/aj05022.
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Offshore exploration and production is going to deep and ultra deep waters, driven by the depletion of continental shelf reserves and the high demand for hydrocarbons. This move requires the continued extension of existing technologies and the development of new technologies that will make the investment economically viable. Innovative flow assurance technology is needed to support ultra deepwater production, particularly within the concept of platform free fields where there is a need to minimise interventions.Hydrates present one of the major challenges in flow assurance. Deep and ultra deep water operations together with long tiebacks present the ideal conditions for the formation of hydrates which can result in pipeline blockage and serious operational and safety concerns. Methods to combat hydrates range between control and management. One main technique has been to produce the hydrocarbons outside of the thermodynamic stability domain of hydrates. This is achieved by keeping the temperature of the hydrocarbon above the stability temperature of hydrates by insulating the pipe line, or by introducing heat to the hydrocarbon. Another efficient way of combating hydrates has been to shift the hydrate phase boundary to lower temperatures by using chemicals like methanol and mono ethylene glycol (MEO) which are known as thermodynamic inhibitors. Within the last decade a new generation of hydrate inhibitors called low dosage hydrate inhibitors (LDHI) has been introduced. One type of these LDHI are kinetic hydrate inhibitors (KHI) that, when used in small concentrations, slow down hydrate growth by increasing the induction time for their formation and preventing the start of the rapid growth stage. Another approach to managing hydrates has been to allow them to form in a controlled manner and transport the hydrate-hydrocarbon slurry in the production pipe. In this paper we describe the various approaches used to combat hydrates to ensure flow assurance and we discuss the cons and pros of every approach and the technology gaps.
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Pavlenko, Anatoliy. "Self-preservation Effect of Gas Hydrates." Rocznik Ochrona Środowiska 23 (2021): 346–55. http://dx.doi.org/10.54740/ros.2021.023.
Full textAbstract:
This work was performed to improve the storage and transportation technology of gas hydrates in nonequilibrium conditions. At atmospheric pressure and positive ambient temperature, they gradually dissociate into gas and water. Simulation of the gas hydrate dissociation will determine optimal conditions for their transportation and storage, as well as minimize gas loss. Thermodynamic parameters of adiabatic processes of forced preservation of pre-cooled gas hydrate blocks with ice layer were determined theoretically and experimentally. Physical and mathematical models of these processes were proposed. The scientific novelty is in establishing quantitative characteristics that describe the gas hydrates thermophysical parameters thermophysical characteristics influence on the heat transfer processes intensity on the interphase surface under conditions of gas hydrates dissociation. Based on the results of experimental studies, approximation dependences for determining the temperature in the depths of a dissociating gas hydrate array have been obtained. Gas hydrates dissociation mathematical model is presented.
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Pan, Mengdi, and Judith M. Schicks. "Unraveling the Role of Natural Sediments in sII Mixed Gas Hydrate Formation: An Experimental Study." Molecules 28, no. 15 (2023): 5887. http://dx.doi.org/10.3390/molecules28155887.
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Considering the ever-increasing interests in natural gas hydrates, a better and more precise knowledge of how host sediments interact with hydrates and affect the formation process is crucial. Yet less is reported for the effects of sediments on structure II hydrate formation with complex guest compositions. In this study, experimental simulations were performed based on the natural reservoir in Qilian Mountain permafrost in China (QMP) due to its unique properties. Mixed gas hydrates containing CH4, C2H6, C3H8, and CO2 were synthesized with the presence of natural sediments from QMP, with quartz sands, and without sediments under identical p–T conditions. The promoting effects of sediments regardless of the grain size and species were confirmed on hydrate formation kinetics. The ice-to-hydrate conversion rate with quartz sand and natural QMP sediments increased by 23.5% and 32.7%, respectively. The compositions of the initial hydrate phase varied, but the difference became smaller in the resulting hydrate phases, having reached a steady state. Beside the structure II hydrate phase, another coexisting solid phase, neither ice nor structure I hydrate, was observed in the system with QMP sediments, which was inferred as an amorphous hydrate phase. These findings are essential to understand the mixed gas hydrates in QMP and may shed light on other natural hydrate reservoirs with complex gas compositions.
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Xie, Ying Ming, Jin Ming Gong, Tao Tang, Dao Ping Liu, Ni Liu, and Ying Xia Qi. "Experimental Research on Hydrogen Storage Characteristics of TBAB Hydrates." Advanced Materials Research 415-417 (December 2011): 1697–702. http://dx.doi.org/10.4028/www.scientific.net/amr.415-417.1697.
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The hydrogen storage characteristics of Tetra Butyl Ammonium Bromide (abbr. TBAB) hydrates were studied in a high pressure gas hydrate experimental apparatus. The effects of temperature and pressure on hydrogen storage characteristics under the condition of constant volume were discussed. The results showed that lower reaction temperature or higher reaction pressure can cause to a rapid formation of hydrogen hydrate and a larger hydrogen storage density, Comparing with tetrahydrofuran (abbr. THF) hydrates under same temperature and pressure, TBAB hydrates have faster hydrogen storage rate and larger hydrogen storage density.
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Zaripova, Yulia, Vladimir Yarkovoi, Mikhail Varfolomeev, Rail Kadyrov, and Andrey Stoporev. "Influence of Water Saturation, Grain Size of Quartz Sand and Hydrate-Former on the Gas Hydrate Formation." Energies 14, no. 5 (2021): 1272. http://dx.doi.org/10.3390/en14051272.
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The development of technologies for the accelerated formation or decomposition of gas hydrates is an urgent topic. This will make it possible to utilize a gas, including associated petroleum one, into a hydrate state for its further use or to produce natural gas from hydrate-saturated sediments. In this work, the effect of water content in wide range (0.7–50 mass%) and the size of quartz sand particles (porous medium; <50 μm, 125–160 μm and unsifted sand) on the formation of methane and methane-propane hydrates at close conditions (subcooling value) has been studied. High-pressure differential scanning calorimetry and X-ray computed tomography techniques were employed to analyze the hydrate formation process and pore sizes, respectively. The exponential growth of water to hydrate conversion with a decrease in the water content due to the rise of water–gas surface available for hydrate formation was revealed. Sieving the quartz sand resulted in a significant increase in water to hydrate conversion (59% for original sand compared to more than 90% for sieved sand). It was supposed that water suction due to the capillary forces influences both methane and methane-propane hydrates formation as well with latent hydrate forming up to 60% either without a detectable heat flow or during the ice melting. This emphasizes the importance of being developed for water–gas (ice–gas) interface to effectively transform water into the hydrate state. In any case, the ice melting (presence of thawing water) may allow a higher conversion degree. Varying the water content and the sand grain size allows to control the degree of water to hydrate conversion and subcooling achieved before the hydrate formation. Taking into account experimental error, the equilibrium conditions of hydrates formation do not change in all studied cases. The data obtained can be useful in developing a method for obtaining hydrates under static conditions.
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Yang, Bo, Xiangyun Hu, Wule Lin, Shuang Liu, and Hui Fang. "Exploration of permafrost with audiomagnetotelluric data for gas hydrates in the Juhugeng Mine of the Qilian Mountains, China." GEOPHYSICS 84, no. 4 (2019): B247—B258. http://dx.doi.org/10.1190/geo2018-0469.1.
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In China, gas hydrates in onshore permafrost areas have so far only been found in the Juhugeng Mine of the Qilian Mountains. However, their subsurface distribution remains unclear. Electrical resistivity logs have revealed that zones containing gas hydrates have higher resistivity than surrounding zones, which makes electromagnetic methods viable for detecting gas-hydrate deposits. We have deployed a natural-source audio-magnetotelluric (AMT) survey at the Juhugeng Mine. AMT data were collected at 176 sites along five profiles, and resistivity models were derived from 2D inversions after detailed data analysis. After the available geologic and geophysical observations were combined, the inversion results from profile 1 suggested that permafrost near the surface with high resistivity and thickness is essential for underlying gas hydrates to be present. The decrease in resistivity and/or thickness of permafrost due to climate change may lead to gas-hydrate dissociation. The other four AMT transects suggested three prospective gas-hydrate sites. Our results indicate that the AMT survey technique is suitable for exploring gas hydrates in permafrost areas and analyzing the impact of permafrost characteristics on gas-hydrate occurrence.
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Wang, Lei, Shu Li Wang, and Tian Tian Kang. "Surfactant Effect of Promoting Research on Hydrate Formation." Advanced Materials Research 1092-1093 (March 2015): 220–25. http://dx.doi.org/10.4028/www.scientific.net/amr.1092-1093.220.
Full textAbstract:
Gas hydrates are a major concern in oil and gas industry, Gas hydrates form in small amounts of water, gas, and the appropriate pressure and temperature conditions. Gas hydrate storage and transportation technology starts a new way for energy storage and transportation industry. The most critically technical problem is how to improve the hydrate formation rate, storage capacity and form continuously. The influences of surfactants on induction time in three types of solution with equal concentration were studied by means of visual hydrate experimental equipment, and generalized induction time was measured by direct observation method. Specific effects of different surfactants on hydrate formation were summarized, as well as the hydrate formation mechanism of surfactants . The lack of research and the research direction of the future were concluded . The further study of surfactant mechanism and build kinetics model containing surfactant have important theoretical value . The result shows that the gas molecules saturated due to the solubilization of surfactant, which promotes the progress of mass transfer in the hydrates. And driving force is provided for the complexation of host molecules and guest molecules during the formation progress of gas hydrates.
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Liang, Shuai, and Peter G. Kusalik. "The nucleation of gas hydrates near silica surfaces." Canadian Journal of Chemistry 93, no. 8 (2015): 791–98. http://dx.doi.org/10.1139/cjc-2014-0443.
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Understanding the nucleation and crystal growth of gas hydrates near mineral surfaces and in confinement are critical to the methane recovery from gas hydrate reservoirs. In this work, through molecular dynamics simulation studies, we present an exploration of the nucleation behavior of methane hydrates near model hydroxylated silica surfaces. Our simulation results indicate that the nucleation of methane hydrates can initiate from the silica surfaces despite of the structural mismatch of the two solid phases. A layer of intermediate half-cage structures was observed between the gas hydrate and silica surfaces, apparently helping to minimize the free energy penalty. These results have important implications to our understanding of the effects of solid surfaces on hydrate nucleation processes.