First Shear Strength Measurements on Gas Hydrate Cemented Sediments Are Part of Preliminary Results of Tests on Gas Hydrate Cores from the Mackenzie Delta, NWT, Canada

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First Shear Strength Measurements on Gas Hydrate Cemented Sediments Are Part of Preliminary Results of Tests on Gas Hydrate Cores from the Mackenzie Delta, NWT, Canada

By William J. Winters
January 1999

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Bill Winters at research well Bill Winters, trying to stay warm, at the Mallik 2L-38 gas hydrates research well, Northwest Territories, Canada.

Using GHASTLI (Gas Hydrate And Sediment Test Laboratory Instrument), Bill Winters, Dave Mason, Monica Relle, and Ingo Pecher (University of Texas, Austin) have successfully completed an initial suite of tests on gas hydrate cores obtained from the Mallik Research Well in the Northwest Territories, Canada, and have collected the first triaxial strength measurements on a gas hydrate-cemented sediment ever made.

A number of U.S. and international commercial and government organizations have begun studying gas hydrates, which are located on many continental margins, because of their resource and hazards potential. However, determining properties of hydrates is greatly complicated by their instability after removal from the typical low temperature/high pressure natural environment. With logistical cooperation from the Geological Survey of Canada (GSC), we have preserved the natural hydrate-containing samples from the Mackenzie Delta and have reestablished in-situ conditions using GHASTLI so that acoustic, strength, permeability, and electrical resistance properties could be measured before, during, and after controlled dissociation. We have calculated that a very high percentage of the pore voids was occupied by hydrate and have measured its significant effect on acoustic velocity and strength properties. Initial interpretation of results confirm that the hydrate from the Mackenzie Delta greatly increases p-wave velocity and increases shear strength by at least 5 times. This is the first known experiment that measured shear strength of natural hydrate under triaxial confining conditions and compared it to nearby non-hydrate containing cores.

The samples were obtained from an 1150-m-deep well that was drilled adjacent to the Beaufort Sea in a cooperative effort of the Geological Survey of Canada (GSC), the Japan National Oil Corp. (JNOC), the U.S. Geological Survey, the Japan Petroleum Exploration Co (JAPEX), and numerous other government organizations and companies. Scott Dallimore (GSC, Ottawa), Tim Collett (USGS, Denver), Takashi Uchida (Japex), chief scientists, provided field support and assistance with recovery of the samples. Tom Lorenson and Keith Kvenvolden (USGS, Menlo Park) are performing isotopic analyses on the gas recovered from GHASTLI during the hydrate dissociation phases of the experiments. Tom and Bill Winters of the C&MGP gas hydrates project traveled to the Canadian Arctic in February and March, 1998, to collect data during the drilling.

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January 1999

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in this issue: Gas Hydrate Shear Strength

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Coastal SWATH Tests

Cape Cod Seafloor Imagery

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New Program-Wide Newsletter

Lecture: Tsunami!

Lecture: Navassa Island

Seminar: South Florida Ecosystem Restoration

NAS/NRC Review

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Director Visits Menlo Park

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Note From the Editor

January Publications List