Title
Microscopic insights into poly- and mono-crystalline methane hydrate dissociation in Na-montmorillonite pores at static and dynamic fluid conditions
Author
Fang, B. (China University of Geosciences, Wuhan)
Lü, Tao (China University of Geosciences, Wuhan)
Li, Wei (China University of Geosciences, Wuhan)
Moultos, O. (TU Delft Engineering Thermodynamics) 
Vlugt, T.J.H. (TU Delft Engineering Thermodynamics)
Ning, Fulong (China University of Geosciences, Wuhan)
Date
2024
Abstract
Knowledge on the kinetics of gas hydrate dissociation in clay pores at static and dynamic fluid conditions is a fundamental scientific issue for improving gas production efficiency from hydrate deposits using thermal stimulation and depressurization respectively. Here, molecular dynamics simulations were used to investigate poly- and mono-crystalline methane hydrates in Na-montmorillonite clay nanopores. Simulation results show that hydrate dissociation is highly sensitive to temperature and pressure gradients, but their effects differ. Temperature changes increase thermal instability of water and gas molecules, leading to layer-by-layer dissociation from the outer surface. Under flow conditions, laminar flow predominates in nano-pores, and non-Darcy flow occurs due to clay-fluid interactions. Viscous flow disrupts hydrogen bonding at the hydrate surface, enhancing kinetic instability of water. Grain boundaries of polycrystalline hydrates are less stable compared to bulk phases and preferentially decompose, forming new dissociation fronts. This accelerates dissociation compared to monocrystalline hydrates. Fracture occurs at the grain boundaries of polycrystalline hydrate in the fluid, resulting in separate hydrate crystal grains. This fracture process further accelerates hydrate dissociation. In flow systems, methane nanobubbles form in fluid and readily transport with fluid flow. Unlike surface nanobubbles at static conditions, these liquid nanobubbles exhibit mobility. The findings of this study can contribute to a better understanding of the complex phase transition behavior of hydrate in confined environment, and provide theoretical support for improving production control technology.
Subject
Dissociation behaviors
Molecular simulation
Na-montmorillonite pore
Poly- and mono-crystalline hydrates
Static and dynamic fluid conditions
To reference this document use:
http://resolver.tudelft.nl/uuid:0b60e20e-0a0a-476f-8e36-d09db39a28bd
DOI
https://doi.org/10.1016/j.energy.2023.129755
Embargo date
2024-05-27
ISSN
0360-5442
Source
Energy, 288
Bibliographical note
Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.
Part of collection
Institutional Repository
Document type
journal article
Rights
© 2024 B. Fang, Tao Lü, Wei Li, O. Moultos, T.J.H. Vlugt, Fulong Ning