Hydrate bearing clayey sediments: Formation and gas production concepts

Jaewon Jang, J. Carlos Santamarina

Research output: Contribution to journalArticle

22 Scopus citations

Abstract

Hydro-thermo-chemo and mechanically coupled processes determine hydrate morphology and control gas production from hydrate-bearing sediments. Force balance, together with mass and energy conservation analyses anchored in published data provide robust asymptotic solutions that reflect governing processes in hydrate systems. Results demonstrate that hydrate segregation in clayey sediments results in a two-material system whereby hydrate lenses are surrounded by hydrate-free water-saturated clay. Hydrate saturation can reach ≈2% by concentrating the excess dissolved gas in the pore water and ≈20% from metabolizable carbon. Higher hydrate saturations are often found in natural sediments and imply methane transport by advection or diffusion processes. Hydrate dissociation is a strongly endothermic event; the available latent heat in a reservoir can sustain significant hydrate dissociation without triggering ice formation during depressurization. The volume of hydrate expands 2-to-4 times upon dissociation or CO2[Formula presented]4 replacement. Volume expansion can be controlled to maintain lenses open and to create new open mode discontinuities that favor gas recovery. Pore size is the most critical sediment parameter for hydrate formation and gas recovery and is controlled by the smallest grains in a sediment. Therefore any characterization must carefully consider the amount of fines and their associated mineralogy.

Original languageEnglish (US)
Pages (from-to)235-246
Number of pages12
JournalMarine and Petroleum Geology
Volume77
DOIs
StatePublished - Nov 1 2016

Keywords

  • Clayey sediments
  • Frozen ground
  • Gas hydrate
  • Hydrate lenses

ASJC Scopus subject areas

  • Oceanography
  • Geophysics
  • Geology
  • Economic Geology
  • Stratigraphy

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