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TitreOccurrence of high salinity fluids associated with massive near-seafloor gas hydrate deposits
AuteurTorres, M E; Kim, J H; Choi, J Y; Ryu, B J; Bahk, J J; Riedel, M; Collett, T S; Hong, W L; Kastner, M
SourceProceedings of the 7th International Conference on Gas Hydrates (ICGH 2011); 2011 p. 1-19
Séries alt.Secteur des sciences de la Terre, Contribution externe 20110048
Réunion7th International Conference on Gas Hydrates (ICGH 2011); Edinburgh; GB; juillet 17-21, 2011
Mediaen ligne; numérique
ProvinceRégion extracotière de l'ouest
Lat/Long OENS-128.0000 -124.0000 49.0000 44.0000
Lat/Long OENS 80.0000 86.0000 20.0000 15.0000
Lat/Long OENS130.0000 131.0000 37.0000 35.5000
Sujetshydrate; milieu sédimentaire; chlorure; salinité; saumure; interpretations sismiques; résistivité électrique; fluides des pores; hydrates de gaz; géologie marine; géophysique; sédimentologie; combustibles fossiles
ProgrammeHydrates de gaz, Caractérisation des Hydrates de gaz
Résumé(disponible en anglais seulement)
Since the report of the presence of brines associated with massive gas hydrate deposits on Hydrate Ridge (Oregon), there have been additional observations of pore fluids highly enriched in dissolved chloride at sites of massive gas hydrate occurrence in northern Cascadia accretionary margin (Canada), the Krishna-Godavari Basin (India) and the Ulleung Basin (Korea). Dissolved chloride (up to 1440 mM in the Ulleung Basin) generally extends from near-seafloor (~1 mbsf) to depths of ~100 mbsf. Below the depth of chloride maxima, chloride values approach concentrations that are lower or equal to seawater values, with minor negative chloride anomalies superimposed on baseline that reflect discrete gas hydrate bearing horizons. The Ulleung Basin and northern Cascadia sites were all drilled on seismic acoustic chimneys, indicative of methane transport in the gas phase. None of these sites, however, show any evidence for the formation of a salinity front that can shift the thermodynamic equilibrium and sustain gas transport through the gas hydrate stability front, as postulated by current models. More likely, hydrofracturing and critical gas pressures below the GHSZ support the gas transport. The composition of gases sampled after gas hydrate dissociation from massive shallow deposits is similar to those of disseminated hydrate within the sediment column, indicating that the gas source for the massive hydrate is not different than that for other gas hydrate deposits.