Influence of Particle Size on the Heat and Mass Transfer Characteristics of Methane Hydrate Formation and Decomposition in Porous Media

Abstract

In nature, permafrost regions and deep ocean sediments contain a large amount of gas hydrate. As a basic property of the sediments, the particle size of the porous media is a critical factor affecting hydrate production. In this study, methane hydrate formed and dissociated in the sediments with different particle sizes, including the particle sizes of 14–20 mesh, 35–60 mesh, 80–120 mesh, and 400–500 mesh. The experimental results showed that two stages were included during the hydrate formation process. In the first stage, the hydrate was mainly formed in the upper of the sediments, which hindered the further contact of gas/water and resulted in the decrease of the hydrate formation rate in the second stage. As the particle size of the porous media decreased, the induction time for the hydrate nucleation decreased and the hydrate formation rate increased. In the porous media with 400–500 mesh, the hydrate started forming while the gas was injected into the hydrate simulator. It was found that the hydrate formation rate in the sediments was limited by the mass transport rate of gas and water. In the constant pressure stage (CPS) of the hydrate dissociation, the maximum value of the hydrate dissociation rate was obtained in the porous media with 35–60 mesh. It was found for the first time that the change characteristics of the average hydrate dissociation rate with the medium particle size of the porous media were similar to those of the effective thermal conductivity with the medium particle size of the porous media. This demonstrated that the heat transfer rate of the sediments determined the hydrate dissociation rate, and the influences of the capillary force and the hydrate distribution on the hydrate dissociation were minor. The experimental results also suggested that the coarse-dominated sediments are more advantageous for gas hydrate production.

Research Advances, Maturation, and Challenges of Hydrate-Based CO2 Sequestration in Porous Media

“…Currently, there are limited studies on the stability or dissociation of CO 2 hydrates in porous media. However, in this section, relevant findings on the dissociation of methane hydrates from hydrate-bearing sediments have been used as basics to understand the dissociation of CO 2 hydrates in porous media. − According to Yang et al, the time taken to release an arbitrary amount of CO 2 at any given time in silica sand is about two times shorter in the brine system than in pure water. The effect of clays on hydrate kinetic dissociation has not been investigated in the literature and remains unknown.…”

“…The response of these petrophysical properties to heat transfer cannot be ignored. The heat transfer rate within the CO 2 storage sediment affects the hydrate dissociation rate . Therefore, understanding the thermal properties of the CO 2 storage site is an essential parameter that needs to be considered to ensure stable hydrate storage.…”

“…The heat transfer rate within the CO 2 storage sediment affects the hydrate dissociation rate. 127 Therefore, understanding the thermal properties of the CO 2 storage site is an essential parameter that needs to be considered to ensure stable hydrate storage. et al, 129 argued that high heating rates or porous media properties with high thermal conductivity would cause rapid CO 2 hydrate dissociation.…”

“…et al, 129 argued that high heating rates or porous media properties with high thermal conductivity would cause rapid CO 2 hydrate dissociation. According to Li et al, 127 sediments with particle sizes ranging from 35 to 60 mesh size show low stability with a high hydrate dissociation rate compared to particle sizes below 35 and above 60 mesh size. On the other hand, porous media with larger pore sizes could provide stable hydrate storage.…”

Influence of the Particle Size of Porous Media on the Formation of Natural Gas Hydrate: A Review

“…In summary, under conditions of ideal gas water distribution, compared to a large size, small particle size has a larger specific surface area and more contact interface between gas and water, the hydrate formation process into the presence of a nuclear matrix play a prominent role in the formation of hydrate nucleation, and the hydrate induction period was shortened. 54,55 At the same time, the connectivity of pore space formed by the medium with small particle size is better, which promotes the migration of gas and water in the system, allows the system to reach a supersaturation state faster, and quickly creates nucleation.…”