Gas Hydrate Formation Process Research Articles

A new approach to producing a prospective energy resource based on coalmine methane

The paper describes topical issues of a prospective method for coalmine methane utilization for obtaining an additional valuable energy resource for the regional development of coal-mining areas. It is noted that the development of the extraction of methane resources is very urgent and is of great economic importance for ensuring the energy independence of Ukraine. The experience and technologies of using methane and coalmine gas by global coal-mining companies are analyzed. Modern prospects and opportunities for using coal gas are studied. There is a need to transform the coalmine methane removal system and directions for maximizing the use of its resources in a wide range of concentrations in the composition of gas-air mixtures based on the development of innovative technologies to improve the efficiency and cost-effectiveness of functioning coal-mining enterprises. Attention is focused on the advantages of using gas hydrate technologies for obtaining additional energy resource under conditions of changing coalmine methane concentrations. The specifics of the process of mixed gas hydrate formation from gas mixtures of various geneses have been studied. It has been revealed that it is the coalmine gas-methane composition that determines and forms the basic condition for hydrate formation. The thermobaric conditions for the hydrate formation process at different methane concentrations in gas mixtures of degassing systems have been experimentally determined. The results obtained are the basis for further research on efficiency of creating gas hydrates from coalmine methane and determining its minimum permissible concentration in the gas mixture of degassing systems according to the technological and economic criteria of hydrate formation.

Diffusion model of gas hydrate formation from ice considering the gas pressure drop

A kinetic model of the process of gas hydrate formation from ice that considers the gas pressure drop caused by this process is presented. This model is based on the diffusion equation. The issues during the formation of gas hydrate from ice powder and that from a flat ice layer are considered separately. For each of these problems, a solution in the framework of a quasi-stationary approximation is obtained, allowing for the calculation of the gas pressure drop in the gas phase. The calculated data are compared with available experimental data on the kinetics of CO2 hydrate formation from pure ice powder and ice powder with the addition of sodium dodecyl sulfate (SDS) at a mass concentration of 240 ppm: the calculated and experimental curves of CO2 pressure drop are compared with each other. From this comparison, the values of the diffusion coefficient of CO2 through a layer of CO2 hydrate formed from pure ice and ice with the addition of SDS at a mass concentration of 240 ppm were determined. Based on these values, it was found that SDS molecules present in the gas hydrate affect the rate of gas diffusion through the gas hydrate layer.

Microscopic study on the key process and influence of efficient synthesis of natural gas hydrate by in situ Raman analysis of water microstructure in different systems with temperature drop

Gas hydrate technology has considerable potential in many fields. However, due to the lack of understanding of the micro mechanism of hydrate formation, it has not been commercially applied so far. Gas hydrate formation is essentially a gas-liquid-solid phase transition of water and gas molecules at a certain temperature and pressure. The key to the hydrate formation is the transformation of water molecule from disordered arrangement to ordered arrangement. In this process, weakly hydrogen bonded water will be correspondingly converted to strongly hydrogen bonded water. Through in situ Raman analysis and experiments, the position change of the corresponding peaks of the strongly hydrogen bonded water and the weakly hydrogen bonded water was compared in this work, and the key microscopic process and influence of gas hydrate formation in different systems were comprehensively studied and summarized. It is found that, with the decrease of temperature, the OH of the weakly hydrogen bonded water remains unchanged when the temperature drops to a certain value, which is the key to the transformation of water into cage hydrate rather than ice. The conversion from the weakly hydrogen bonded water to the strongly hydrogen bonded water is closely related to the gas-liquid interface force, the hydrophilicity/hydrophobicity of the promoter, the ionization degree of liquid, and the electrostatic field of the system. Among the four most common promoters, tetrahydrofuran (THF) has the highest efficiency in promoting methane (CH4) hydrate formation. Therefore, this study provides a scientific direction and basis for the development of high efficient hydrate formation promoters, which can effectively weaken the hydrogen bond of weakly hydrogen bonded water and promote the conversion of weakly hydrogen bonded water to strongly hydrogen bonded water.

Mathematical Model of the Process of Non-Equilibrium Hydrate Formation in a Porous Reservoir during Gas Injection

Increasing the efficiency of natural gas storage in geological formations is possible by transferring gas from a free state to a gas hydrate state, since gas hydrates have a number of unique properties. For example, 1 m3 of methane hydrate contains 164 m3 of gas under normal conditions. It is possible to store a sufficiently large amount of gas in a small volume at a relatively low pressure. To study the regularities of the process of formation of underground gas hydrate gas storage, this article presents a mathematical model of the process of methane injection into a natural reservoir saturated with methane and water, accompanied by the formation of gas hydrate. Unlike previous works, the constructed mathematical model additionally takes into account a number of factors: the filtration flow of water, the real gas properties, the Joule–Thomson effects and adiabatic compression. The process of gas hydrate formation is considered as a non-equilibrium phase transition. Numerical solutions of the problem are constructed that describe the distributions of parameters (temperature, pressure, phase saturations) in a reservoir. Dependences are obtained that reveal the regularities of the process of non-equilibrium formation of gas hydrate in a natural reservoir during gas injection. The influence of gas injection pressure and temperature, as well as reservoir porosity and permeability, on the distributions of pressure, temperature, water saturation and hydrate saturation in the reservoir, as well as on the dynamics of changes in these parameters and the mass of gas hydrate formed in the reservoir over time, are analyzed.

Investigation of the formation behaviors of CO2 hydrate in porous media below the freezing point

AbstractThe formation process of gas hydrate is a stochastic phenomenon considered to be significant for its application in the areas such as hydrate‐based technology and natural gas hydrate exploitation. The formation behaviors of CO2 hydrate were studied in porous media below the freezing point. In addition, the formation experiments were conducted in the high‐pressure vessel under different temperature and pressure conditions. The formation process of CO2 hydrate showed different formation behaviors in the porous media under different experimental conditions. The results showed that the formation rate was higher in earlier stage and the largest formation rate attained 7.18 × 10−4 mol h−1. The influence of initial pressure on the formation rate was indistinctive in porous media below the freezing point. Particle size of the porous media played an important role in affecting the formation characteristic of CO2 hydrate below the freezing point. The results indicated that, the smaller the particle size of porous media was, the larger the formation rate and the conversion rate of CO2 hydrate. The maximum conversion rate was attained 90.61%. The results also indicated that CO2 hydrate had a good gas storage capacity in porous media below the freezing point. The gas storage capacity was close to 160 L/L in frozen quartz sand with the particle size of 250 μm in the experiments. The relative results will provide some insight for sequestration and storage process of CO2 gas in the form of hydrates into sediments.

Mathematical Modeling of the Gas Hydrate Formation Process in a Porous Reservoir, Taking into Account Nonequilibrium Phase Transition

Mathematical Modeling of the Gas Hydrate Formation Process in a Porous Reservoir, Taking into Account Nonequilibrium Phase Transition

Methane Hydrate Formation in Hollow ZIF-8 Nanoparticles for Improved Methane Storage Capacity

Methane hydrate has been extensively studied as a potential medium for natural gas storage and transportation. Due to their high specific surface area, tunable porous structure, and surface chemistry, metal–organic frameworks are ideal materials to exhibit the catalytic effect for the formation process of gas hydrate. In this paper, hollow ZIF-8 nanoparticles are synthesized using the hard template method. The synthesized hollow ZIF-8 nanoparticles are used in the adsorption and methane hydrate formation process. The effect of pre-adsorbed water mass in hollow ZIF-8 nanoparticles on methane storage capacity and the hydrate formation rate is investigated. The storage capacity of methane on wet, hollow ZIF-8 is augmented with an increase in the mass ratio of pre-adsorbed water and dry, hollow ZIF-8 (RW), and the maximum adsorption capacity of methane on hollow ZIF-8 with a RW of 1.2 can reach 20.72 mmol/g at 275 K and 8.57 MPa. With the decrease in RW, the wet, hollow ZIF-8 exhibits a shortened induction time and an accelerated growth rate. The formation of methane hydrate on hollow ZIF-8 is further demonstrated with the enthalpy of the generation reaction. This work provides a promising alternative material for methane storage.

Advances in Characterizing Gas Hydrate Formation in Sediments with NMR Transverse Relaxation Time

The formation process, structure, and distribution of gas hydrate in sediments have become focal points in exploring and exploiting natural gas hydrate. To better understand the dynamic behavior of gas hydrate formation in sediments, transverse relaxation time (T2) of nuclear magnetic resonance (NMR) is widely used to quantitatively characterize the formation process of gas hydrate and the change in pore characteristics of sediments. NMR T2 has been considered as a rapid and non-destructive method to distinguish the phase states of water, gas, and gas hydrate, estimate the saturations of water and gas hydrate, and analyze the kinetics of gas hydrate formation in sediments. NMR T2 is also widely employed to specify the pore structure in sediments in terms of pore size distribution, porosity, and permeability. For the recognition of the advantages and shortage of NMR T2 method, comparisons with other methods as X-ray CT, cryo-SEM, etc., are made regarding the application characteristics including resolution, phase recognition, and scanning time. As a future perspective, combining NMR T2 with other techniques can more effectively characterize the dynamic behavior of gas hydrate formation and pore structure in sediments.

Nuclear magnetic resonance study of the formation and dissociation process of nature gas hydrate in sandstone

In this work, the authors monitored the formation and dissociation process of methane hydrate in four different rock core samples through nuclear magnetic resonance (NMR) relaxation time (T2) and 2D imaging measurement. The result shows that the intensity of T2 spectra and magnetic resonance imaging (MRI) signals gradually decreases in the hydrate formation process, and at the same time, the T2 spectra move toward the left domain as the growth of hydrate in the pores of the sample accelerates the decay rate. The hydrate grows and dissociates preferentially in the purer sandstone samples with larger pore size and higher porosity. Significantly, for the sample with lower porosity and higher argillaceous content, the intensity of the T2 spectra also shows a trend of a great decrease in the hydrate formation process, which means that high-saturation gas hydrate can also be formed in the sample with higher argillaceous content. The changes in MRI of the sample in the process show that the formation and dissociation of methane hydrate can reshape the distribution of water in the pores.©2022 China Geology Editorial Office.

Sequestration and Storage of Carbon Dioxide Using Hydrate Formation Method in the Presence of Copper Oxide Nanoparticles

The nanofluid-based gas hydrate formation process employing copper oxide (CuO) nanoparticles have been experimentally investigated in this work. Different concentrations of nanofluids are injected into the reactor at the operating condition of 29 bar, 274.15 K, and impeller speed of 100 rpm. It was observed that the kinetics of the carbon dioxide hydrate formation process was greatly affected by the nanoparticles. The remarkable point was that at a very low concentration of 20 ppm, a considerable improvement on the carbon dioxide hydrate formation kinetic without using any surfactant was obtained. At the concentration of 20 ppm, the values of the initial rate of hydrate formation, growth time, and induction time were 0.0495, 194.5, and 4.4 min, respectively, which these results can be of great importance for the use of carbon dioxide hydrate in various industries. The results indicated that the kinetics of gas hydrate formation was also severely influenced by the impeller speed and initial gas pressure. The rate of CO2 captured in the hydrate crystalline lattice is also modeled by the first-order kinetic model. It was seen that this model can be used to predict the rate of hydrate formation with considerable accuracy.

Controlled Production of Natural Gas Hydrates in an Experimental Device with an Internal Circulation Circuit

For countries with limited access to conventional hydrocarbon gases, methane hydrates have emerged as a potential energy source. In view of the European Union’s requirements to reduce the energy intensity of technological processes and increase energy security, it appears promising to accumulate natural gas and biomethane in the form of hydrate structures and release them if necessary. Storing gas in this form in an energy-efficient manner creates interest in developing and innovating technologies in this area. Hydrates that form in gas pipelines are generated by a more or less random process and are an undesirable phenomenon in gas transportation. In our case, the process implemented in the proposed experimental device is a controlled process, which can generate hydrates in orders of magnitude shorter times compared to the classical methods of generating natural gas hydrates in autoclaves by saturating water only. The recirculation of gas-saturated water has been shown to be the most significant factor in reducing the energy consumption of natural gas hydrate generation. Not only is the energy intensity of generation reduced, but also its generation time. In this paper, a circuit diagram for an experimental device for natural gas hydrate generation is shown with complete description, principle of operation, and measurement methodology. The natural gas hydrate formation process is analyzed using a mathematical model that correlates well with the measured hydrate formation times. Hydrates may become a current challenge in the future and, once verified, may find applications in various fields of technology or industry.

Intensification of Gas Hydrate Formation Processes by Renewal of Interfacial Area between Phases

This paper presents the analysis of the main reasons for a significant decrease in the intensity of diffusion processes during the formation of gas hydrates; solutions to this problem are proposed in a new process flow diagram for the continuous synthesis of gas hydrates. The physical processes, occurring at the corresponding stages of the process flow, have been described in detail. In the proposed device, gas hydrate is formed at the boundary of gas bubbles immersed in cooled water. The dynamic effects arising at the bubble boundary contribute to the destruction of a forming gas hydrate structure, making it possible to renew the contact surface and ensure efficient heat removal from the reaction zone. The article proposes an assessment technique for the main process parameters in the synthesis of hydrates based on the criterion of thermodynamic parameters optimization. The optimization criterion determines the relationship of intensity of heat and mass transfer processes at the phase contact interface of reacting phases, correlating with the maximum GH synthesis rate, and makes it possible to determine optimum thermodynamic parameters in the reactor zone.

Mathematical Modeling of the Gas Hydrate Formation Process in a Zonal Heterogeneous Porous Reservoir

Mathematical Modeling of the Gas Hydrate Formation Process in a Zonal Heterogeneous Porous Reservoir

Gasification of Remote Settlements Using Technology of Artificial Gas Hydrate Production

Currently there are a number of problems in the Republic of Sakha (Yakutia) connected with energy supply to remote residential areas and industrial facilities. Taking into account the logistical difficulties of gasification of remote settlements existing in our region, the authors study modern gasification methods. The object of their study is artificially produced gas hydrates. In order to expand the use of hydrates for storage and transportation of natural gas it is important to take into consideration the features of gas hydrate formation process in high-pressure chambers when laboratory settings of gas hydrate synthesis are being realised. The analysis show that gas hydrates can be prospective and effective new source of energy. In addition, since the territory of Yakutia is located in the permafrost zone, there is a scientific, industrial and socio-economic expediency to study the features of gas hydrates. The following work illustrates the study of ways of natural gas artificial hydrate production, analysis of options of its use as a new energy resource in the conditions of the Far North and the process of its synthesis in Federal Research Center of the Devision of Institute of Oil and Gas Problems of Siberian Branch of the Russian Academy of Science.

Thermodynamic Features of the Intensive Formation of Hydrocarbon Hydrates

This paper presents the results of a study on the influence of pressure and temperature of the gas–water medium on the process of hydrocarbon gas hydrate formation occurring at the phase interface. Herein, a mathematical model is proposed to determine the optimum ratios of pressure, gas temperatures, water, and gas bubble sizes in the bubbling, gas ejection, or mixing processes. As a result of our work, we determined that gas hydrate in these processes is formed at the gas–water interface, that is, on the boundary surface of gas bubbles. Moreover, there is a gas temperature range where the hydrate formation rate reaches its maximum. These study findings can be used to optimize various technological processes associated with the production of gas hydrates in the industry.

CO2 hydrate heat cycle using a carbon fiber supported catalyst for gas hydrate formation processes

In order to contribute to utilization expansion of unused energy and renewable energy, a heat cycle of the small difference in temperature which used unique dissociation expansion property of CO2 hydrate is proposed. However, the formation speed of CO2 hydrate needs to be accelerated drastic to realize the proposed heat cycle. Therefore, application of a powdery iron oxide catalyst for gas hydrate formation, 150% or more of CO2 hydrate formation speed has realized. On the other hand, the powdery catalyst jumped out of the reactor with high pressure dissociated gas, stability of the catalytic effect was important subject. In this study, the carbon fiber supported catalyst is developed and performance stabilization of CO2 hydrate heat cycle is tried. The effect of the carbon fiber supported catalyst developed newly is comparable as conventional powdery catalyst, and the effect stable in repeating operation of heat cycle is obtained. Moreover, when pressure conditions of the gas hydrate heat cycle were set highly, the generated amount of CO2 hydrate increased from the proposal catalyst system.

Dynamic in-situ imaging of methane hydrate formation and self-preservation in porous media

We present the results of dynamic in-situ 3D X-ray imaging of methane hydrates microstructure during methane hydrate formation and dissociation in sand samples. Short scanning times and high resolution provided by synchrotron X-rays allowed for better understanding of water movement and different types of gas-hydrate formation. Complementing previous observations, we conclude that the process of gas-hydrate formation is accompanied by the water movements caused by cryogenic water suction that happens in sequences of short fast movements with longer equilibrium states in between (when the water is immobile). Based on the 3D microstructure we identified two distinct types of gas-hydrate formation: (i) into the gas pockets and (ii) inside water volumes. For both mechanisms we do not see problems in gas or water supply to support the gas-hydrate formation. The rate of dissociation in the self-preservation mode (pressure drop at negative temperatures) appears to be different for these two types of gas hydrates. This means that the history of the gas-hydrate formation may influence its behaviour at the dissociation stage (e.g. gas-hydrate production). • Different types of hydrate growth mechanisms in porous media: shells, growth into gas pockets and inside water volumes. • Hydrates formed in water volumes show better self-preservation than hydrate grown into gas pockets. • Multiple fast incremental water flows were captured during hydrate formation resembling the Haines jumps.

Evaluation on the natural gas hydrate formation process

Abstract Gas hydrates have endowed with great potential in gas storage, and rapid formation of gas hydrates is critical to use this novel technology. This work evaluated the natural gas hydrate formation process, which was compared from six parameters, including conversion of water to hydrate, storage capacity, the rate of hydrate formation, space velocity (SV) of hydrate reaction, energy consumption and hydrate removal. The literature was selected by analyzing and comparing these six parameters mentioned above, meanwhile placing emphasis on the three parameters of storage capacity, the rate of hydrate formation and space velocity of hydrate reaction. Through analysis and comparison, four conclusions could be obtained as follows. Firstly, the overall performance of the stirring process and the spraying process were better than other processes after analyzing the six parameters. Secondly, the additive types, the reactor structure and the reactor size had influence on the natural gas hydrate formation process. Thirdly, the energy consumption via reciprocating impact in the hydrate formation process was higher than that via stirring, spraying and static higee. Finally, it was one key for hydrate removal to realize the hydrate industrial production.

ON THE PROCESS OF GAS HYDRATE FORMATION IN A POROUS MEDIUM SATURATED WITH METHANE AND ICE

Background Currently, the energy potential of natural gas hydrates is the main incentive for their comprehensive study. Estimates of the amount of gas contained in natural hydrates vary widely by different researchers, but they all agree that this amount is much higher than the existing and explored gas reserves. The mathematical modeling of the formation of gas hydrate during gas injection into a porous medium initially saturated with gas and ice was carried out earlier. It should be noted that the process of hydrate formation is considered for porous media of semi-infinite length in a self-similar approximation. However, all real formations have a sufficient length, but are still limited in size. Therefore, self-similar solutions turn out to be valid only for the initial times of the hydrate formation process, when the influence of the right boundary is not yet significant. Aims and Objectives: - to investigate the process of gas hydrate formation in a porous medium of finite length, initially saturated with methane and ice; - to consider the cases of hydrate formation on the frontal surface and in the extended area. Methods Math modeling. Results On the basis of the presented mathematical model, the problem of gas hydrate formation during gas (methane) injection into a porous layer of finite length, initially saturated with methane and ice, is considered. Cases where hydrate formation occurs both on the frontal surface and in an extended area have been investigated. It has been established that a part of the gas hydrate formed in an extended region can further dissociate, and an extended hydrate formation region can degenerate into a frontal surface.

Characteristics and dynamics of gas hydrate systems in the northwestern South China Sea - Results of the fifth gas hydrate drilling expedition

Abstract In 2018, Guangzhou Marine Geological Survey conducted the fifth gas hydrate drilling expedition (GMGS5) in the northwestern continental slope of South China Sea. We use pore water geochemistry, pressure core CT scanning, degassing quantification, seismic data and in situ temperature test at four drill sites (W01, W07, W08 and W09) to investigate the gas hydrate characteristics and discuss the dynamics of the gas hydrate system. Based on the CT scanning and pressure core degassing, we demonstrate the coexistence of pore-filling and vein-like gas hydrates. Gas hydrate saturation estimated based on the chloride concentration (0–92%) is higher than that based on the degassing quantification (0–52.9%). The saturation discrepancy is mainly resulted from the sampling discrimination. Based on the average gas hydrate saturation estimated using chloride concentration and degassing, the methane gas volume contained in the gas hydrate of one cubic meter sediment at drill sites W07, W08 and W09 are calculated to be 13.7 m3, 26.82 m3 and 22.24 m3 and 3.03 m3, 14.30 m3 and 16.25 m3. The geothermal gradients estimated based on the in situ temperature measurements at sites W07, W08 and W09 (102–111 °C/km) are more than 50% higher than that at the background site W01 (65 °C/km). It is inferred that the fractures and faults in the gas chimney at sites W07, W08 and W09 are the major contributors for the efficient fluid pathways and high geothermal gradients. The pore water sulfate profiles and inferred sulfate-reduction methane-oxidation interface (SMI) depths indicate that methane flux is lowest at site W01 and highest at site W08. The SMI depths and top of gas hydrate occurrence is linearly correlated which provides an experienced function for understanding the local gas hydrate distribution. Kick-type sulfate profiles at sites W07 and W09 indicate an ongoing increase of methane flux and corresponding shoaling SMI depths. In addition, chloride enrichment in the shallow sediment at site W08 indicates a recent fast gas hydrate formation process. The kick-type sulfate profiles, positive chloride anomalies and authigenic carbonates at multiple depths suggest that the system experienced dynamic changes in fluid flux and multi-stage gas hydrate evolution on time scale from months to thousands of years. Understanding the controlling mechanism and periodicity of the composite pressure system is important for evaluating the gas hydrate resource and carbon cycling.