Pore water anomalies of submarine gas-hydrate zones as tool to assess hydrate abundance and distribution in the subsurface What have we learned in the past decade?

Hesse, Reinhard

doi:10.1016/s0012-8252(02)00117-4

Cited by 157 publications

(102 citation statements)

References 78 publications

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“…Surrounding pore waters initially become more saline during the process of hydrate formation. During hydrate crystallization the exclusion of salinity (chlorine) and intake of δ 18 O is due to the solidfluid isotope fractionation that causes preferential uptake of the heavy isotope δ 18 O in the solid phase and depletion in the fluid (Hesse, 2003 pore waters. The δ…”

Section: Geochemical Explorationmentioning

confidence: 99%

Review of exploration and production technology of natural gas hydrate

Cui

Lü

et al. 2018

Adv. Geo-Energy Res.

107

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Abstract:Natural gas hydrate is an ice-like substance which is sometimes called "combustible ice" since it can literally be lighted on fire and burned as fuel. Natural gas hydrate is characterized by widespread distribution, large reserves and little pollution. This paper introduced the distributions of hydrate, hydrate reserves and properties of hydrate. The main exploration methods, such as geophysical exploration and geochemical exploration have been presented. In addition, the main production techniques of natural gas hydrate including depressurization, thermal stimulation and chemical injection have been summed up. Finally, the challenges and outlooks of natural gas hydrate production have been proposed.

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Section: Geochemical Explorationmentioning

confidence: 99%

Review of exploration and production technology of natural gas hydrate

Cui

Lü

et al. 2018

Adv. Geo-Energy Res.

107

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“…This process has been used widely to estimate gas hydrate concentrations (e.g., Hesse and Harrison, 1981;Hesse, 2003;Kastner et al, 1995;Ussler and M. Riedel et al Gas hydrate on the northern Cascadia margin Paull, 2001). The limitation of the method, however, is the problem of estimating the background (or reference) in situ pore fluid chlorinity/salinity before gas hydrate dissociation upon recovery.…”

Section: Pore Water Chlorinity/salinitymentioning

confidence: 99%

Gas hydrate on the northern Cascadia margin: regional geophysics and structural framework

Riedel¹,

Willoughby²,

Chen³

et al. 2006

Proceedings of the IODP

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Integrated Ocean Drilling Program Expedition 311 is based on extensive site survey data and historic research at the northern Cascadia margin since 1985. This research includes various regional geophysical surveys using a broad spectrum of seismic techniques, coring and logging by the Ocean Drilling Program Leg 146, heat flow measurements, shallow piston coring, and bottom video observations across a cold-vent field, as well as novel controlled-source electromagnetic and seafloor compliance surveying techniques. The wealth of data available allowed construction of structural cross-sections of the margin, development of models for the formation of gas hydrate in an accretionary prism, and estimation of gas hydrate and free gas concentrations. Expedition 311 established for the first time a transect of drill sites across the northern Cascadia margin to study the evolution of gas hydrate formation over the entire gas hydrate stability field of the accretionary complex. This paper reviews the tectonic framework at the northern Cascadia margin and summarizes the scientific studies that led to the drilling objectives of Expedition 311 Cascadia gas hydrate.

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“…This process has been used widely to estimate gas hydrate concentrations (e.g. Hesse and Harrison, 1981;Hesse, 2003;Kastner et al, 1995;Ussler and Paull, 2001). However, the limitation of the method is the problem of estimating the in situ pore fluid chlorinity/salinity.…”

Section: Chlorinity and Pore-water Fresheningmentioning

confidence: 99%

Gas hydrate concentration estimates from chlorinity, electrical resistivity and seismic velocity

Riedel

Collett²,

Hyndman

2005

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Gas hydrate beneath the N. Cascadia continental slope off Vancouver Island occurs as a regional diffuse layer above the BSR and as local high concentrations in large vent or upwelling structures. Regional concentrations of gas hydrate beneath the N. Cascadia continental slope off Vancouver Island have been estimated earlier using multichannel seismic, seafloor electrical, and IODP Leg 146 downhole data. The concentrations of between 15 and 30% of pore saturation in a 100 m thick layer above the BSR are much higher than estimated elsewhere where there is good data, especially the Blake Ridge and central Cascadia off Oregon on ODP Leg 204. Although both of these other studies involved different sediment environments, a careful re-evaluation of the N. Cascadia estimates seemed desirable. We have re-evaluated the methods used to calculate the gas hydrate concentrations from pore-water chlorinity (salinity), electrical resistivity, and seismic velocity, describing in detail the assumptions and uncertainties. Use of the porewater chlorinity/salinity and electrical resistivity directly have low reliability because of the effect on the no-hydrate reference of hydrate formation and dissociation, and the effect of pore fluid freshening by clay dehydration. At ODP Site 889/890 hydrate concentrations range from 5-10% to 30-40%, depending on the no-hydrate reference salinity used. Use of core salinity data along with the downhole and seafloor electrical resistivity data allows calculation of both the in situ reference salinity and the hydrate concentrations. The most important uncertainty in this method is the relation between 2 resistivity and porosity, i.e., Archie's Law parameters. Significantly different relations were determined from the ODP Leg 146 core and downhole log data, the log data resistivity-porosity relation giving much lower concentrations. Finally, seismic velocities from sonic-logs and multichannel data can be used to calculate gas hydrate concentrations, if an appropriate no-hydrate velocity-depth profile can be estimated. A velocity-hydrate concentration relation is also required. Depending on which nohydrate/no-gas velocity baseline is used, estimated hydrate concentrations range from as low as 5% to above 25% saturation. In spite of having three nearly independent methods of estimating hydrate concentrations, it is concluded that the data allow regional concentrations in the 100 m layer above the BSR from less than 5% to over 25% saturation (3-13% of sediment volume). ODP drilling in the region scheduled for the fall of 2005 should help resolve the uncertainties.

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Pore water anomalies of submarine gas-hydrate zones as tool to assess hydrate abundance and distribution in the subsurface What have we learned in the past decade?

Cited by 157 publications

References 78 publications

Review of exploration and production technology of natural gas hydrate

Review of exploration and production technology of natural gas hydrate

Gas hydrate on the northern Cascadia margin: regional geophysics and structural framework

Gas hydrate concentration estimates from chlorinity, electrical resistivity and seismic velocity

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