Self-preservation Effect Research Articles

Kinetic study on the effect of ice nucleation and generation on methane hydrate dissociation below the quadruple point

Natural gas hydrates (NGHs) have captured worldwide attention because of its huge resources and high energy density. Deep depressurization by dropping the pressure below the quadruple point is recognized as a promising exploitation method. However, the impact of ice formation on NGHs dissociation within depressurization is still controversial. Thus, we examine the dissociative behavior of NGHs at low temperature below the quadruple point using a high-pressure reactor. It primarily focuses on how ice formation affects heat and mass transfer, as well as the kinetics of hydrate dissociation. The results indicate that during the hydrate dissociation process, liquid water initially transforms into metastable supercooled water, which then transitions to solid ice under external disturbance. Ice nucleation predominantly occurs in two locations: within the free water phase and on the surface of hydrate particles. A double-edged effect of ice on NGHs dissociation is observed: the latent heat released by ice nucleation and generation could accelerate the hydrate breakdown (positive effect), while the decrease in permeability along with the self-preservation effect from ice formation tends to inhibit the NGHs dissolution (negative effect). In addition, a higher pressure drawdown rate can accelerate both ice nucleation and formation, which in turn shortens the freezing induction time. The increase of water saturation (SA) and the decrease of hydrate saturation (SH) can significantly reduce the mining time and strengthen both the hydrate dissociation rate (QH) and gas production rate (QP). Therefore, hydrate sediments with higher SA or lower SH are more conductive to gas recovery of low-temperature NGHs deposits in permafrost regions.

Microscopic experimental study on the effects of NaCl concentration on the self-preservation effect of methane hydrates under 268.15 K

It is known that salt ions are abundant in the natural environment where natural gas hydrates are located; thus, it is essential to investigate the self-preservation effect of salt ions on methane hydrates. The dissociation behaviors of gas hydrates formed from various NaCl concentration solutions in a quartz sand system at 268.15 K were investigated to reveal the microscopic mechanism of the self-preservation effect under different salt concentrations. Results showed that as the salt concentration rises, the initial rate of hydrate decomposition quickens. Methane hydrate hardly shows self-preservation ability in the 3.35% (mass) NaCl and seawater systems at 268.15 K. Combined the morphology of hydrate observed by the confocal microscope with results obtained from in situ Raman spectroscopy, it was found that during the initial decomposition stage of gas hydrate below the ice point, gas hydrate firstly converts into liquid water and gas molecules, then turns from water to solid ice rather than directly transforming into solid ice and gas molecules. The presence of salt ions interferes with the ability of liquid water to condense into solid ice. The results of this study provide an important guide for the mechanism and application of the self-preservation effect on the storage and transport of gas and the exploitation of natural gas hydrates.

Dissociation of methane from a layer of methane-hydrate particles: A new simple model

A simple model of the dissociation of methane from a layer of methane-hydrate particles is suggested. The model is based on the assumption that methane-hydrate particles form a flat porous film lying on an adiabatic wall. This film is heated by ambient air convection. It is assumed that when the temperature inside a certain region within the methane-hydrate reaches the critical temperature for the release of methane from the methane-hydrate, all methane is released from the methane-hydrate and the latter turns into ice. The contribution of heat required for the release of methane is considered. The model is based on the analytical solution to the one-dimensional heat transfer equation in the two-layer (methane-hydrate/ice) system. This solution is incorporated into the numerical code and used at each time step of the calculations. Model predictions are compared with experimental data for the heating of a layer of methane-hydrate of porosity 0.3 and thickness 5 mm. It is shown that good agreement between the predictions of the model and experimental data is observed at the initial stage of the process. At longer times, the model predicts faster methane release than observed experimentally unless the effect of self-preservation can be ignored. This deviation between modelling results and experimental data is attributed to the main assumption of the model that all methane is instantaneously released from the methane-hydrate when the methane-hydrate temperature reaches the above-mentioned critical temperature.

Dry Water as a Promoter for Gas Hydrate Formation: A Review.

Applications of clathrate hydrate require fast formation kinetics of it, which is the long-standing technological bottleneck due to mass transfer and heat transfer limitations. Although several methods, such as surfactants and mechanical stirring, have been employed to accelerate gas hydrate formation, the problems they bring are not negligible. Recently, a new water-in-air dispersion stabilized by hydrophobic nanosilica, dry water, has been used as an effective promoter for hydrate formation. In this review, we summarize the preparation procedure of dry water and factors affecting the physical properties of dry water dispersion. The effect of dry water dispersion on gas hydrate formation is discussed from the thermodynamic and kinetic points of view. Dry water dispersion shifts the gas hydrate phase boundary to milder conditions. Dry water increases the gas hydrate formation rate and improves gas storage capacity by enhancing water-guest gas contact. The performance comparison and synergy of dry water with other common hydrate promoters are also summarized. The self-preservation effect of dry water hydrate was investigated. Despite the prominent effect of dry water in promoting gas hydrate formation, its reusability problem still remains to be solved. We present and compare several methods to improve its reusability. Finally, we propose knowledge gaps in dry water hydrate research and future research directions.

Modeling the Accumulation and Transition to the Relic State of Methane Hydrates in the Permafrost of Northwestern Siberia

This paper presents the results of numerical modeling of the permafrost thermal regime and thermobaric conditions of methane hydrates in the north of Western Siberia over the past 70 thousand years. The area of hydrate formation was determined and the rate of accumulation of hydrates was estimated in connection with the migration of fluid from the underlying gas-saturated layers under the conditions of cover glaciation. The estimates obtained for the change in hydrate saturation as a result of fluid migration during the 10 thousand-year glaciation period, depending on the permeability of the soil, are from 6 to 40% in the upper 350 m. Based on quantitative characteristics of the equilibrium and metastable states of methane hydrates, the conditions for the preservation of relict methane hydrates in permafrost under the paleoclimatic scenario were determined, taking into account periods of ice cover and transgression. It is shown that due to the effect of self-preservation at temperatures below –4°C, it is possible to preserve relict methane hydrates in the upper 200 m of soil under non-equilibrium conditions. The effect of lowering the temperature while the hydrates dissociate prevents the complete decomposition of the deposit and leads to an increase in the thickness of the frozen soil.

Molecular hydrogen storage in binary H2-CH4 clathrate hydrates

Clathrate hydrate has emerged as a promising candidate for hydrogen storage, but the major challenge is the high pressure required for its formation. The addition of natural gas can significantly reduce the formation pressure, but also can improve the energy density. In this work, we estimated the hydrogen storage capacity of the H2-CH4 binary hydrate by performing the first-principles calculations and simulations. The thermodynamical and mechanical stability of the hydrate was studied as a function of the cage occupancy of both 512 and 51264 cages. For the most stable structure, the molar ratio of H2 and H2O is 0.353:1. The H2-CH4 binary hydrate can maintain its structure during dynamics under the moderate temperature and pressure. The self-preservation effect was observed at ∼270 K, which can be used for the hydrogen storage and transport. These findings provide a better understanding of the mixed hydrate as a viable hydrogen storage technology, which could enable us to achieve a sustainable hydrogen economy.

Влияние поливинилпирролидона на эффект самоконсервации гидрата пропана

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

Methane gas hydrates of the Black Sea – environmental problem or energy source?

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

Mathematical Model of the Decomposition of Unstable Gas Hydrate Accumulations in the Cryolithozone

We present a generalization of the mathematical model of gas discharge from frozen rocks containing gas-saturated ice and gas hydrates in a metastable state (due to the self-preservation effect) caused by the drop in external stress associated with various geodynamic factors. These factors can be attributed, for example, to a decrease in hydrostatic pressure on a gas-bearing formation due to glacier melting, causing an isostatic rise, or to the formation of linear depressions in the bottom topography on the shelf due to iceberg ploughing. A change in external pressure can also be associated with seismic and tectonic deformation waves propagating in the lithosphere as a result of ongoing strong earthquakes. Starting from the existing hydrate destruction model, operating at the scale of individual granules, we consider a low-permeable hydrate and ice-saturated horizontal reservoir. Generalization is associated with the introduction of a finite threshold for the external pressure drop, which causes the destruction of the gas hydrate and gas-saturated microcavities of supramolecular size. This makes it possible to take into account the effect of anomalously high pressures occurring in the released gas as a result of partial hydrate dissociation. Numerical and approximate analytical solutions to the problem were found in the self-similar formulation. A parametric study of the solution was carried out, and regularities of the hydrate decomposition process were revealed.

A covering liquid method to intensify self-preservation effect for safety of methane hydrate storage and transportation

In this work, experiments and comprehensive insights into the proposed covering liquid method to intensify self-preservation effect for methane (CH 4 ) storage are presented. The CH 4 hydrate decomposition percentage was 17.6% with the pressure of 0.61 MPa after 12 h at 266.0 K without a covering liquid, which can be reduced to 12.4%, 13.8%, 13.0%, and 8.3% with the pressure of 0.26 MPa, 0.33 MPa, 0.51 MPa, and 0.37 MPa by covering with tetrahydrofuran (THF), cyclopentane (CP), cyclohexane, and n-tetradecane, respectively. When the temperature for CH 4 hydrate decomposition was 274.2 K, covering with THF, CP, cyclohexane, and n-tetradecane failed to inhibit CH 4 hydrate decomposition. The results suggested that the covering liquid may form a new solid layer (a hydrate layer or other solidified layer) around the CH 4 hydrate, which inhibit CH 4 transfer below the freezing point of water. However, the new solid layer cannot resist the fast transfer of CH 4 from decomposed CH 4 hydrate above the freezing point of water. The same phenomenon was also observed in a sodium dodecyl sulfonate (SDS)-dry solution CH 4 hydrate formation system. Therefore, the covering method can only intensify the self-preservation effect below the freezing point of water, but cannot generate a self-preservation effect.

Experimental Study on Influences of Self-Preservation Effects and Memory Effects on the Hydrate Decomposition Process

Abstract In order to explore the characteristics of the hydrate decomposition behavior at the pore scale, this study carries out a pore-scale experimental study of methane hydrate decomposition based on the high-pressure visual model under the etched glass. A mathematical model is also constructed to analyze the behavioral characteristic of the self-preservation effect and memory effect during the hydrate decomposition period. This study draws the following conclusions: (1) The self-preservation effect and memory effect exist during the methane hydrate decomposition lead by depressurization, which generally inhibits the hydrate decomposition process. (2) The hydrate self-preservation effect is a transition of the surface water film’s phase state to inhibit the methane hydrate decomposition, in which the liquid phase transforms into a metastable “quasiliquid film”. (3) The multiple syntheses induced by the hydrate memory effect are a periodic attenuation process. The times of synthesis are a critical factor affecting the hydrate gas production and decomposition rate. (4) The self-preservation and memory effects during the hydrate decomposition period are associated with each other. The two are correlated at some degree with playing a dominant role alternately at different stages. The self-preservation effect is an abnormal behavior of the hydrate, which refers to the hydrate’s transition from the solid phase to the gas-liquid mixed phase. The memory effect is another abnormal behavior, which refers to the transition from the gas-liquid mixed phase to the solid phase. The sustaining pressure drop is the key reason of the disappearance of the two effects. This research was aimed at providing a theoretical basis for the exploitation and optimization of marine natural gas hydrates.

Self-preservation effect exceeding 273.2 K by introducing deuterium oxide to form methane hydrate

• D 2 O was introduced as host molecular to form methane hydrate. • Self-preservation effect was first observed above 273.2 K for methane hydrate. • Self-preservation was improved at least 3.5 K for methane hydrate. • Mixed cages were first found during methane hydrate formation in (D 2 O + H 2 O) system. Self-preservation effect of hydrate is an advantage for gas storage by using hydrate-based technology. Unlike focusing on guest molecules in previous publications, deuterium oxides (D 2 O) were introduced as one of host molecules to form methane hydrate. Methane hydrate dissociated percentage was 92.2% after 12 h of dissociation at 273.7 K without the addition of D 2 O, while the methane hydrate dissociated percentage decreased to 55.2 % with the addition of 30 wt% D 2 O. The methane hydrate dissociated percentage reduced to 15.7% when methane hydrate formed in D 2 O system. The results suggested that the self-preservation effect of methane hydrate was improved to above 273.2 K for the first time since this abnormal phenomenon was found in 1986. The temperature of self-preservation effect for (CH 4 + D 2 O) hydrate was improved at least 3.5 K higher than that for (CH 4 + H 2 O) hydrate. From the simulation results, some (D 2 O + H 2 O) mixed cages with different D 2 O and H 2 O molecules formed, and CH 4 inserted into the mixed cages to form CH 4 hydrate as sI structure. The (D 2 O + H 2 O) mixed cages may explain the self-preservation effect of (CH 4 + D 2 O + H 2 O) hydrate above 273.2 K to some extent. Finally, it was also found from the simulation results that (CH 4 + D 2 O + H 2 O) hydrate not only formed from hydrate/(D 2 O + H 2 O) contact, but also nucleated independently.

Enhancement of hydrocarbon recovery from CH4-C2H6-C3H8 mixed hydrates via gas sweep

Mixed hydrates have been found in some ocean and permafrost deposits, and the dissociation of mixed hydrates by depressurization alone has been reported to be difficult and inefficient. However, most studies in the field of mixed hydrate decomposition have mainly focused on dissociation behaviors at the crystal lattice and guest molecular levels, but there has been little discussion about recovery efficiency. The dissociation of CH4-C3H8 or CH4-C2H6-C3H8 mixed hydrates in sandy sediments using depressurization followed by the gas sweep method was investigated to determine the underlying mechanism of difficulty in decomposition and to enhance hydrocarbon recovery. It was found that CH4 and C2H6 were preferentially released over C3H8 from mixed hydrates in the depressurization stage. Particularly, the dissociation of mixed hydrates tended to stop despite substantial hydrates remaining above the water freezing point, which was similar to the self-preservation effect of CH4 hydrates below the ice point. Interestingly, when gas sweep was performed, mixed hydrates continued to decompose, and more C3H8 was recovered at the beginning of the gas sweep. Compositional analysis of the dissociated gas confirmed that the gradual formation of C3H8-rich hydrate shell led to the cessation of hydrate decomposition, which hinders the diffusing hydrocarbons in the internal hydrate to be released. Furthermore, continuous gas sweep resulted in continuous and rapid decomposition of mixed hydrates, but when it was stopped, the decomposition of mixed hydrates gradually slowed down and tended to stop, and the C3H8-rich hydrate shell was re-formed. This suggested that the formation and decomposition of the C3H8-rich hydrate shell may control the decomposition rate of mixed hydrates. These results are of significance for guiding successful and efficient hydrocarbon recovery from mixed hydrates.

Key Areas of Gas Hydrates Study: Review

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.

Self-preservation of small gas hydrate particles in oils under stirring: Experimental results and computational model

In this work, the self-preservation of small (tens of μm) methane hydrate particles dispersed in oils was studied. The results of this work show that stirring in itself has no effect on the self-preservation of hydrate particles in oil suspensions. The particles undergo self-preservation under both static and stirred conditions. However stirring can lead to redistribution of oil components which may result in the disappearance of self-preservation. Accordingly to developed analytical model, it was shown that the effectiveness of self-preservation is determined by the value of the diffusion coefficient of methane in the pores of the ice crust. It was shown that for the samples with weak self-preservation, the diffusion coefficient of methane in the pores of the ice layer is close to 10−15 m2/s, while for the samples with effective self-preservation this value is an order of magnitude lower. Thus, the pore structure of the ice layer formed on the hydrate particles completely determines whether the self-preservation effect is manifested in a single experiment. The oil environment can allow for the formation of dense ice layers that can provide effective self-preservation. Our data show that the process of the appearance of ice layer and of evolution of its pore system on the surface of hydrate particles suspended in oils and thus the hydrates decomposition rates is of a stochastic nature. Therefore, the efficiency of self-preservation may differ significantly under similar external conditions.

Dissociation of gas hydrate for a single particle and for a thick layer of particles: The effect of self-preservation on the dissociation kinetics of the gas hydrate layer

To date, prediction of the dissociation of single gas hydrate particles at positive temperatures is found to be effective. Meanwhile, there are no reliable approaches that would allow modeling the dissociation at negative temperatures, taking into account the heat flux, the thickness of the powder layer, as well as the diameter of the cylinder or tablet, consisting of small particles. These studies are relevant for the development of technologies for storing and transporting methane hydrate. This paper deals with modeling the dissociation of the methane hydrate, taking into account the temperature in the self-preservation region, and considers the influence of four characteristic scales: the layer thickness (or the cylinder diameter), the average diameter of a single particle, the average pore diameter in a particle, and the porosity in a layer or in a consolidated sample. Experimental and theoretical studies of dissociation in a wide temperature range are carried out. It is shown that for efficient storage of methane hydrate, the most optimal conditions correspond to the packing of small particles in a cylinder, tablet or thick layer. The ways of reducing the dissociation rate due to the multilevel consolidation of particles in a large sample are proposed. The results obtained may be useful for improving the efficiency of storage and transportation of gas hydrates at negative temperatures.

Investigation of natural gas storage and transportation by gas hydrate formation in the presence of bio-surfactant sulfonated lignin

The hydrate-based solidified natural gas (SNG) technology is a promising approach for natural gas storage and transportation. One challenge of this technology is to enhance the hydrate formation kinetics and achieve mild storage conditions. This work employed a biomass surfactant sulfonated lignin (SL) to enhance CH4 hydrate formation. Meanwhile, the self-preservation effect of CH4 hydrate formed in the presence of SL was investigated using a high-pressure micro-differential scanning calorimeter (HP μ-DSC). The results indicate that 500 ppm SL is an optimum concentration for improving CH4 hydrate formation kinetics among the five SL concentrations (300, 500, 700, 900, and 1000 ppm) tested. At 500 ppm SL, the CH4 hydrate formation rate was increased significantly, and the largest gas consumption was obtained, which was 2.7 times larger than that obtained in pure water under the same temperature and pressure conditions. The gas consumption was also larger than that obtained in the presence of other surfactants (sodium dodecyl sulfate, silicone surfactant, and ethylene diamine tetraacetamide). CH4 hydrate formed in the presence of SL can be stably preserved at 0.1 MPa and 268.15 K due to the self-preservation effect. Therefore, the energy costs, such as system cooling and gas compression, for SNG using SL are lower than conventional natural gas storage and transport technologies.

Thermodynamic properties of propane and methane hydrates doped with sodium hydroxide

Pure and sodium hydroxide doped with single-component hydrates of methane and propane are studied using molecular and lattice dynamics methods. Vibration density of states and the dependence of Helmholtz free energy on temperature and cell volume are calculated. Dynamic stability of empty and filled by gas sI and sII structures doped with 1 or 2 NaOH molecule is shown in the wide range of temperature values. Comparison of free energy values allows calculating the thermal expansion coefficient and demonstrating the possibility of self-preservation effect in NaOH-doped methane and propane hydrates with ~1.8 and ~1.4 mol% of sodium hydroxide, respectively.

Fluid production behavior from water-saturated hydrate-bearing sediments below the quadruple point of CH4 + H2O

Driven by the large resource volume, extraction of CH4 from hydrate reservoirs has received worldwide attention. Depressurization is a feasible method and has been widely used in past field tests. However, fluid production behavior from water-saturated hydrate-bearing sediments below the quadruple point of CH4 + H2O has not been well understood and warrants investigation. In this study, we designed a series of experiments using ultra-deep depressurization with bottom hole pressure (BHP) of 1.0 MPa, 1.5 MPa and 2.1 MPa in water-saturated hydrate-bearing sediments to investigate the fluid production behavior, particularly in the region with potential ice or secondary hydrate formation. The effect of hydrate saturations and pressure drawdown rates on fluid production below the quadruple point were systematically examined. Our experimental results show that ice formation was likely based on the temperature response, however, the self-preservation effect by ice formation prevents a further drop in temperature to its equilibrium temperature at the corresponding BHP. The gas and water recovery ratios increased by 6.5% and 49.1%, respectively for BHP below the quadruple point. No significant benefit of water trapping due to ice formation was observed. Faster pressure drawdown rate results in a more substantial temperature drop, which could trigger ice formation. Still, interestingly gas production was continuous and not affected in the phase diagram of ice + CH4. Higher hydrate phase saturation improves gas production rate and final gas recovery ratio, yielding a lower water-gas ratio for more economic-viable CH4 recovery. Our results indicate that ultra-deep depressurization could be one technical feasible option for increasing both gas production rate and final recovery ratio. The findings provide valuable information for designing an ultra-deep depressurization scheme based on SH of interest in future production tests.

Kinetic study of methane hydrate development involving the role of self-preservation effect in frozen sandy sediments

The dissociation of natural gas hydrate in permafrost areas is a kinetic reaction process associated with the existence of ice and the accompanied self-preservation effect. The kinetic decomposition behaviors of methane hydrate below freezing point are investigated through both experimental and numerical simulations in this work. Dissociation experiments have been conducted in a high-pressure reactor (HPR) by depressurization and wellbore heating methods. Two kinetic models are employed for the prediction of gas recovery and hydrate dissociation in frozen sandy sediments. The modified new model which takes into account the protection effect of ice is found to predict more accurately than the traditional one. When the deposit is situated under frozen state, the hydrate particles can be maintained at a relatively stable state even when the external pressure has dropped below the equilibrium level. Such self-preservation effect is the main factor resulting in the undesirable recovery efficiency of frozen gas hydrate by pure depressurization, and it can be only eliminated by external heat injection. However, the heated wellbore has a limited influencing area, and lots of the provided heat is wasted outside through the boundary. Secondary ice formation exists in the cold regions far away from the well, which leads to incomplete decomposition of methane hydrate. The kinetic decomposition of frozen hydrate is mainly dominated by its self-preservation effect and the injected heat, and the dissociation process is not sensitive to the production pressure when it is adjusted below the equilibrium level.