Study of gas hydrate metastability and its decay for hydrate samples containing unreacted supercooled liquid water below the ice melting point using pulse NMR

Мадыгулов, М. Ш.; Nesterov, A. N.; Reshetnikov, A. M.; Власов, В. А.; Zavodovsky, A. G.

doi:10.1016/j.ces.2015.06.039

Cited by 30 publications

(7 citation statements)

References 30 publications

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“…It should be noted that there also exists an alternative explanation of an increase in the efficiency of self-preservation with a decrease in temperature. It is known that liquid water is an intermediate product of hydrate decomposition at a temperature below 0 °C. , Evidently, the probability of water freezing rapidly increases with a decrease in temperature. Thus, the probability of water freezing at a temperature of −5 °C is substantially lower than the probability of water freezing at −20 °C.…”

Section: Resultsmentioning

confidence: 99%

Decomposition Kinetics and Self-Preservation of Methane Hydrate Particles in Crude Oil Dispersions: Experiments and Theory

et al. 2019

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The self-preservation phenomenon may be used for storage and transportation of natural gas in the form of gas hydrate. In this work, decomposition kinetics and self-preservation of methane hydrate dispersions in two types of crude oils were studied. Hydrate particle sizes in both dispersions did not exceed 30 μm. The experiments were performed at constant temperatures from −4 to −20 °C without preliminary deep-freezing of the samples. The kinetic curves of the methane hydrate decomposition were recorded as depending on methane pressure in the autoclave vs time. In the experiments with the first dispersion, it was shown that at the decomposition degree of 50%, the hydrate decomposition rates decreased by 1–2 orders of magnitude in comparison to the rates at the start of the decomposition process; therefore, hydrate self-preservation took place. Estimated thickness of the ice shell providing self-preservation did not exceed 1.3 μm at the decomposition degree of 50%. Self-preservation was less pronounced in experiments with the second dispersion. It may be explained by the presence of the surfactant in the second dispersion, which was added to stabilize the water-in-oil emulsion from which the dispersion was obtained. Possible mechanisms and the effect of various factors on the efficiency of self-preservation are discussed in this work. A mathematical model of hydrate decomposition process taking into account self-preservation of hydrate particles in the dispersion is suggested. A time-dependent (decreasing) diffusion coefficient of methane in ice shell was used in the model.

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Section: Resultsmentioning

confidence: 99%

Decomposition Kinetics and Self-Preservation of Methane Hydrate Particles in Crude Oil Dispersions: Experiments and Theory

et al. 2019

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“…Two distinctions between the supercooled water-gas-hydrate metastable system and the self-preservation system were concluded as follows: One is that ice shell generation is essential for self-preservation; while in the supercooled water-gas-hydrate metastable system the hydrate persistence may be attributed to the kinetic difficulty of ice nucleation which could result in the decay of the hydrate metastability. Another is that the dissociation of metastable hydrates into supercooled water and gas is reversible; however, self-preserved hydrates would slowly and irreversibly dissociate into ice and gas [77]. In addition, the selfpreservation effect depends on the hydrate particle size, while the dependency in the supercooled water-gas-hydrate metastable system is not well consolidated.…”

Section: More Mechanisms Of Hydrate Metastabilitymentioning

confidence: 99%

Metastable state of gas hydrate during decomposition: A novel phenomenon

Sun

Fan

Yang

et al. 2020

Chinese Journal of Chemical Engineering

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Natural gas hydrates are solid compounds with cage-like structures formed by gas and water. An intriguing phenomenon that gas hydrates can dissociate at a low rate below the ice freezing point has been viewed as the metastability of hydrate. The mechanisms of hydrate metastability have been widely studied, and many mechanisms were proposed involving the self-preservation effect, supercooled water-gas-hydrate metastable equilibrium, and supersaturated liquid-gas-hydrate system etc. The metastable state of hydrate could be of crucial significance in the kinetics of hydrate formation and decomposition, heat and mass transfer during gas production processes, and the application of hydrate-based technique involving desalination, energy storage and transportation, and gas separation and sequestration. Few researches have systematically considered this phenomenon, and its mechanism remains unclear. In this work, various mechanisms and hypothesis explaining the metastable state of gas hydrates were introduced and discussed. Further studies are still required to reveal the intrinsic nature of this metastable state of gas hydrate, and this work could give some implications on the existing theory and current status of relevant efforts.

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“…Since the relative change in temperature for the processes under consideration is small, the reduced diffusion coefficient D will be considered constant. It should be mentioned that many factors can influence the intensity of the hydrate decomposition and formation, such as the introduction of various surfactants, the exposure of the shock and electromagnetic waves [46][47][48][49][50][51][52][53], etc. The empirical parameter D depends both on the hydrate structure and on the porous medium skeleton features.…”

Section: Description Of the Ch 4 -Co 2 Replacement Kinetics In The Hymentioning

confidence: 99%

Mathematical Model of Carbon Dioxide Injection into a Porous Reservoir Saturated with Methane and Its Gas Hydrate

2020

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In this paper, the process of methane replacement in gas hydrate with carbon dioxide during CO2 injection into a porous medium is studied. A model that takes into account both the heat and mass transfer in a porous medium and the diffusion kinetics of the replacement process is constructed. The influences of the diffusion coefficient, the permeability and extent of a reservoir on the time of full gas replacement in the hydrate are analyzed. It was established that at high values of the diffusion coefficient in hydrate, low values of the reservoir permeability, and with the growth of the reservoir length, the process of the CH4-CO2 replacement in CH4 hydrate will take place in the frontal regime and be limited, generally, by the filtration mass transfer. Otherwise, the replacement will limited by the diffusion of gas in the hydrate.

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Study of gas hydrate metastability and its decay for hydrate samples containing unreacted supercooled liquid water below the ice melting point using pulse NMR

Cited by 30 publications

References 30 publications

Decomposition Kinetics and Self-Preservation of Methane Hydrate Particles in Crude Oil Dispersions: Experiments and Theory

Decomposition Kinetics and Self-Preservation of Methane Hydrate Particles in Crude Oil Dispersions: Experiments and Theory

Metastable state of gas hydrate during decomposition: A novel phenomenon

Mathematical Model of Carbon Dioxide Injection into a Porous Reservoir Saturated with Methane and Its Gas Hydrate

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