Negative Effects of Inorganic Salt Invasion on the Dissociation Kinetics of Silica-Confined Gas Hydrate via Thermal Stimulation

Negative Effects of Inorganic Salt Invasion on the Dissociation Kinetics of Silica-Confined Gas Hydrate via Thermal Stimulation

Fang, B. (TU Delft Engineering Thermodynamics; China University of Geosciences, Wuhan)
Lu, T. (China University of Geosciences, Wuhan; Hubei Key Laboratory of Advanced Control and Intelligent Automation for Complex Systems,)
Cheng, Liwei (China University of Geosciences, Wuhan)
Wang, Dongdong (China University of Geosciences, Wuhan)
Ni, Yang (China University of Geosciences, Wuhan)
Fan, Bowen (China University of Geosciences, Wuhan)
Meng, Jiuling (China University of Geosciences, Wuhan)
Vlugt, T.J.H. (TU Delft Engineering Thermodynamics)
Ning, Fulong (China University of Geosciences, Wuhan; Qingdao National Laboratory for Marine Science and Technology)

2022

Methane hydrate dissociation kinetics can be inhibited in NaCl solutions; however, this effect is reversed by promoting bubble formation that enhances dissociation. The negative and positive effects of inorganic salt injection on gas production from hydrate-bearing sediments are still controversial. Here, molecular dynamics simulations were performed to investigate the characteristics of NaCl solution invasion into hydrate-occupied nanopores and the effects on the confined hydrate dissociation kinetics. Two initial configurations comprising liquid and silica pore phases were studied with a low or high NaCl concentration, respectively. The results show that, under the simulation conditions, salt invasion decelerated hydrate dissociation within the silica pore as NaCl invasion into the pore is stepwise. Initially, few ions can diffuse into the pore phase, and gas nanobubbles form on the solid surface mainly via confinement and surface effects, independent of NaCl solution invasion. Subsequently, gradual salt diffusion immersed the residual hydrate in the salt solution and hindered hydrate decomposition until the dissociation finished. More ions could diffuse into the pore phase at the high NaCl concentrations with a low diffusion efficiency, leading to surface nanobubble growth toward the residual hydrate and somewhat accelerated hydrate dissociation. This severely hinders the escape of released methane from the pore. This study yields molecular-level insight into the origin of the negative effect of salt invasion on hydrate dissociation, which should be avoided during gas production from hydrate reservoirs with low permeabilities via salt injection combined with thermal stimulation.

http://resolver.tudelft.nl/uuid:a32cf0fc-92cb-42c5-8581-4eb240c10930

https://doi.org/10.1021/acs.energyfuels.2c00978

2023-07-01

0887-0624

Energy & Fuels, 36 (12), 6216-6228

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.

Institutional Repository

journal article

© 2022 B. Fang, T. Lu, Liwei Cheng, Dongdong Wang, Yang Ni, Bowen Fan, Jiuling Meng, T.J.H. Vlugt, Fulong Ning