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<p>Continental margins contain substantial methane stored as hydrates within sediment layers. While methane release from hydrate dissociation is commonly viewed as the primary driver of subsea methane seepage, deep methane leakage may also stem from overpressure accumulation due to hydrate-induced sealing. In this study, we employed the TOUGH+hydrate (T+H) multiphase flow model to investigate the formation of deeply buried hydrate seals under varying sediment conditions and methane fluxes, as well as the modifications in hydrate seals under deep overpressure. Results indicate that the methane hydrate stability zone (MHSZ) initially thins due to changes in salinity and temperature, followed by a phase of thickening due to overpressure caused by hydrate formation. The expansion of the hydrate stability zone facilitates hydrate recrystallization in the lower MHSZ, alters flow dynamics, and shifts the peak overpressure (the hydrofracture-prone point) to greater depth, thereby increasing the horizontal effective stress that must be overcome before methane leakage. Thus, although overpressure increases, sediment susceptibility to fracturing decreases. This self-regulating behavior of hydrate systems effectively prolongs and complicates methane release from the seabed.</p>

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Hydrate sealing of overpressured gas: delaying methane leakage

  • 期刊论文

  • 发表日期：

    2026年2月7日

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  • Zihan Zheng,
  • Yuncheng Cao,
  • Duofu Chen

摘要

Continental margins contain substantial methane stored as hydrates within sediment layers. While methane release from hydrate dissociation is commonly viewed as the primary driver of subsea methane seepage, deep methane leakage may also stem from overpressure accumulation due to hydrate-induced sealing. In this study, we employed the TOUGH+hydrate (T+H) multiphase flow model to investigate the formation of deeply buried hydrate seals under varying sediment conditions and methane fluxes, as well as the modifications in hydrate seals under deep overpressure. Results indicate that the methane hydrate stability zone (MHSZ) initially thins due to changes in salinity and temperature, followed by a phase of thickening due to overpressure caused by hydrate formation. The expansion of the hydrate stability zone facilitates hydrate recrystallization in the lower MHSZ, alters flow dynamics, and shifts the peak overpressure (the hydrofracture-prone point) to greater depth, thereby increasing the horizontal effective stress that must be overcome before methane leakage. Thus, although overpressure increases, sediment susceptibility to fracturing decreases. This self-regulating behavior of hydrate systems effectively prolongs and complicates methane release from the seabed.