Understanding Hysteresis and Gas Trapping in Dissociating Hydrate-Bearing Sediments Using Pore Network Modeling and Three-Dimensional Imaging

Hysteresis behavior is a key factor in exploring dynamic water and gas flow in dissociating hydrate-bearing sediments (HBS). In this study, we combined microfocus X-ray computed tomography and a pore network model to investigate the effect of hydrate dissociation on gas trapping and hysteresis in capillary pressure, Pc and relative permeability, k(r) in different wettability systems. The results show that the hydrate dissociation process involves secondary hydrate formation, which promotes gas trapping. The effective residual gas saturation in the water-wet system was significantly higher than that in the gas-wet system due to snap-off. Gas trapping has a huge impact on the hysteresis in P-c and k(r) between the drying and wetting cycles in HBS. This work will improve the fundamental understanding of the permeability properties of HBS so that gas and water production can be better assessed.

Automated summary

This study investigates the effect of hydrate dissociation on gas trapping and hysteresis in capillary pressure and relative permeability. It finds that secondary hydrate formation promotes gas trapping, with higher residual gas saturation in water-wet systems compared to gas-wet systems. Gas trapping has a significant impact on hysteresis between drying and wetting cycles.