Molecular insights into two-phase flow in clay nanopores during gas hydrate recovery: Wettability-induced multiple pathways of water lock formation
Abstract
A comprehensive understanding of the intricate water/gas two-phase flow in sedimentary pores is essential for accurately predicting gas production following the in-situ dissociation of natural gas hydrates, as it is crucial for optimizing resource extraction strategies. This study constructed three typical clay slit nanopore models with distinct wettability characteristics – hydrophilic, relatively hydrophobic, and Janus hybrid-wettability – and used molecular dynamics simulations to investigate the spatial distribution and transport dynamics of two-phase fluids under varying water saturation conditions. The results revealed a significant negative correlation between water saturation and gas relative permeability. When water saturation reaches a critical threshold, the water lock effect occurs, blocking gas flow. Pore wettability plays a key regulatory role in water/gas phase dynamics via influencing the formation pathways of water locks. In relatively hydrophobic pores, weaker solid-water interactions promote the rapid clustering of water molecules, forming water locks, while hydrophilic surfaces enable water lock formation through gradual thickening of the liquid film. In Janus pores with low water saturation, strong electrostatic interactions between oppositely charged pore walls facilitate the formation of discrete water bridge networks, maintaining “gas windows” that allow gas flow, although these windows eventually close as saturation increases. The lower the water saturation, the more favorable it is for gas transport; in contrast, hydrophilic pores exhibit higher gas transport efficiency. Our findings provide valuable molecular-scale insights into how wettability governs multiphase flow transport, offering a theoretical foundation for reservoir modification and seepage control in natural gas hydrate recovery.
Document Type: Original article
Cited as: Fang, B., Zhang, Z., Zhang, Q., Guo, G., Jiang, J., Ning, F. Molecular insights into two-phase flow in clay nanopores during gas hydrate recovery: Wettability-induced multiple pathways of water lock formation. Advances in Geo-Energy Research, 2025, 17(1): 17-29. https://doi.org/10.46690/ager.2025.07.02
Keywords:
Natural gas hydrate, molecular dynamics simulation, two-phase flow, surface wettability, water bridgeReferences
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