Gas recovery from low-permeability muddy silt gas hydrate reservoirs by depressurization coupled with hot water injection: Impact of hydro-lock effect

Hongyu Ye, Jingyu Chen, Yuanxin Yao, Daoyi Chen, Xuezhen Wu, Dayong Li and Mucong Zi

Energy, 2025, vol. 316, issue C

Abstract: Thermal stimulation via injecting hot water can assist depressurization in natural gas hydrate (NGH) exploitation. However, whether depressurization coupled with the thermal stimulation (DP + TS) model can enhance gas production in muddy silt NGH reservoirs is still debated. In this study, we aimed to perfect research on the DP + TS model by proposing a hydro-lock effect that can delay pressure propagation and hinder heat and mass transfer in NGH reservoirs. In addition, we established a THMC model to simulate NGH reservoirs located at Site W17 to investigate the production enhancement of the DP + TS model in the initial state and the hydraulic fracturing state. Results indicate that (i) injecting water into reservoirs may cause pressure-holding, NGH reformation, and permeability damage, making the DP + TS model fail to enhance gas recovery and produce additional water. (ii) Hydraulic fracturing enhances permeability, maintaining higher hot water injection rates, easing hydro-lock, and promoting efficient heat and mass transfer. (iii) The DP + TS model can only enhance production when the permeability of the fractured area exceeds a certain value, but its energy efficiency is still lower than that of pure depressurization. These key findings can fill knowledge gaps in the DP + TS model and provide guidance in future NGH exploitation.

Keywords: Natural gas hydrate; Thermal stimulation; Muddy silt; Hydro-lock effect; Fracturing (search for similar items in EconPapers)
Date: 2025
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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:316:y:2025:i:c:s0360544225000556

DOI: 10.1016/j.energy.2025.134413

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