Strengthening and weakening of methane hydrate by water vacancies

Abstract

Gas clathrate hydrates show promising applications in sustainable technologies such as future energy resources, gas capture and storage. The stability of clathrate hydrates under external load is of great crucial to those important applications, but remains unknown. Water vacancy is a common structural defect in clathrate hydrates. Herein, the mechanical characteristics of sI methane hydrates containing three types of water vacancy are investigated by molecular dynamics simulations with four different water forcefields. Mechanical properties of methane hydrates such as tensile strength are dictated not only by the density but also the type of water vacancy. Surprisingly, the tensile strength of methane hydrates can be weakened or strengthened, depending on the adopted water model and water vacancy density. Strength enhancement mainly results from the formation of new water cages. This work provides critical insights into the mechanics and microstructural properties of methane clathrate hydrates under external load, which is of primary importance in the recovery of natural gas from methane hydrate reservoirs.

Proposing Crystallographic Theory to Deparameterize Hydrate Phase Description: Physical Insights and Validation

“…However, this potential difference in the former case (5 12 ) is larger than the latter one (5 12 6 2 ), which reveals that a guest enclosed in the smaller cavity exhibits more interactions with the surrounding molecules. This, in turn, indicates the higher stability of 5 12 cages, and similar insights are reported in the literature (e.g., Tang et al 32 and Lin et al 33 ).…”

“…This, in turn, indicates the higher stability of 5 12 cages, and similar insights are reported in the literature (e.g., Tang et al . and Lin et al).…”

Insights into the mechanical stability of tetrahydrofuran hydrates from experimental, machine learning, and molecular dynamics perspectives

“…Previous studies have demonstrated the dynamic transfer of unconventional cages in hydrate systems. 61 Consistent with previous findings, 62,63 the present study reveals that the compressive load induces the formation of unconventional clathrate cages in polycrystalline THF hydrates. Fig.…”

Mechanical Destabilization and Cage Transformations in Water Vacancy-Contained CO2 Hydrates

“…For example, Sveinsson and Malthe-Sørenssen reported via MD simulations that crack fracture of the nanocrack-contained CH 4 clathrate hydrate shows two stages including slow and fast crack propagations; as the stress intensity factor approaches , the slow crack growth disappears. Lin et al revealed that the adopted water model and water vacancy density can alter the tensile strength of water vacancy-contained methane hydrates via MD simulations. Similar to CH 4 clathrate hydrate, these defects have a significant impact on the performance of CO 2 clathrate hydrates. ,,,, For example, using MD simulations, cage-to-cage hopping behaviors were observed for CO 2 hydrates under elevated temperatures.…”