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icon IODP Leg 311 - Cascadia Margin Gas Hydrates

Gilles Guerin, Alberto Malinverno

Expedition 311 of the Integrated Ocean Drilling Program (IODP) investigated the occurence and the formation of gas hydrate in the accretionary prism of the northern Cascadia margin. The five sites visited during the expedition defined a SW-NE transect across a ~30km wide Bottom Simulating Reflector (BSR) that runs parallel to the coast alongmost of the continental slope (see Figure 1).

From Site U1326, at the SW tip of the accretionary prism, to Site U1329, the shallowest site located at the landward limit of the BSR, the transect was designed to sample the complexity of the evolution of a gas hydrate system (see Figure 2).

To constrain the formation of gas hydrates in subduction zones, Expedition 311 had an ambitious drilling program including extensive pressure coring to recover gas hydrate at in situ conditions. Because of the unstability of gas hydrate at surface conditions, and of the strong response of some logging tools such as electrical and acoustic logs to the presence of gas hydrate, logging was a critical component of the operations. The logging program consisted of two phases - the first week of the expedition was dedicated to Logging While Drilling (LWD), in order to identify intervals likely to contain gas hydrate where pressure coring tools should be deployed; the second phase consisted in wireline logging following coring operations in order to complete the geophysical characterization of the sites.

Fig. 1

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A location of IODP Expedition 311 on the Cascadia margin. B) Bathymetry and location of the different sites visited (bathimetry courtesy of D. Kelley, J. Delaney, and D. Glickson, University of Washington, and C. Barnes, C. Katnick, NEPTUNE Canada, University of Victoria; funded by the University of Washington and the W.M. Keck Foundation.

Fig. 2

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Seismic section (line 89-08) showing the position of the Expedition 311 sites across the accretionary front.

Expedition 311 Proceedings

Expedition 311 Logging Summary

Log Data

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icon IODP Leg 204 - Hydrate Ridge

Dave Goldberg, Gilles Guerin

During Ocean Drilling Program (ODP) Leg 204, a total of nine sites were drilled through the gas hydrate stability zone on the southern part o Hydrate Ridge on the Cascadia accretionary margin, offshore Oregon. For further information regarding gas hydrates and the background geological setting see the Leg 204 Preliminary Report. The first part of Leg 204 was dedicated entirely to logging while drilling (LWD) to identify potential gas hydrate bearing intervals prior to coring. The data were of excellent quality, thus allowing optimization of the use of time-consuming special tools to measure in situ temperature and pressure and to retrieve cores at in situ pressure. The leg also included an extensive wireline logging program and a two-ship seismic program with the R/V Maurice Ewing to acquire offset and walkaway vertical seismic profiles (VSP). The log data are available from the ODP Logging Services database.

Initial Report

Scientific Results

Logging Summary

Log Data

 

icon Electrical and Nuclear Resonance measurements of Tetrahydrofuran Hydrate

Ann Cook, Dave Goldberg

Tetrahydrofuran (THF) hydrate (20% weight THF with 80% weight deionized water) was synthesized in the laboratory at LDEO and brought to the Schlumberger-Doll research laboratory in Ridgefield, Connecticut for measurements of their surface area, nuclear magnetic relaxivity, and dielectric properties. Surface area data was collected at liquid nitrogen temperatures. NMR and dielectric experiments were conducted at about 0° Celsius.

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Borehole Research Group at Lamont-Doherty Earth Observatory of Columbia University, 61 RT 9W, Palisades, NY 10964