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Gas-Hydrate Research Wells Completed in the Canadian Arctic
Gas hydrates have been of global interest for much of the past decade because of their potential impact on energy reserves, global climate change, continental-margin slope stability, and petroleum-drilling hazards. High pressures and low temperatures, associated with many continental margins and Arctic regions, can form gas hydrate in the presence of an adequate supply of certain gas molecules and water. The drilling project, involving more than 60 scientists and engineers and 250 support staff from six countries, overcame huge logistical problems compounded by the drillsite's extremely remote location and harsh winter conditions, including temperatures below Ð40°C. The drill holes, spaced 40 m apart, were located in the Mallik gas-hydrate field next to the Beaufort Sea on the northern part of Richards Island, and were near the Mallik 2L-38 well drilled in 1998. All major equipment was delivered by way of a project ice road constructed on the frozen Mackenzie River.
The recently completed Mallik project consisted of several different phases. Drilling of the first observation well began on Christmas Day. One after the other, the two observation wells were drilled and instrumented with fiber-optic temperature sensors; then the main well was begun. The 640-m-deep permafrost section in the main well was drilled and cased before the start of continuous coring, which completely penetrated the gas-hydrate section between about 890-m and 1,150-m depth. Because recovery of sediment cores containing gas hydrate was extremely good, more than 50 pressure vessels and four liquid-nitrogen dewar flasks were filled to capacity. Other aspects of the project consisted of well logging, downhole temperature profiling, microbiologic studies, seismic crosshole tomography (yielded information about sediment density and elastic properties), and the first intentional production tests of a gas-hydrate reservoir involving both pressure drawdown and thermal stimulation. These last tests were conducted to determine the relation between pressure reduction and dissociation of inplace gas hydrate, and to measure gas release for a given input of thermal energy.
The infrared temperature measurements were part of a pilot program involving Frank Rack of Joint Oceanographic Institutions (JOI) and Bill Gwilliam (DOE). During a giant-piston-coring cruise in July 2002, researchers will use the French research vessel Marion Dufresne to obtain 50-m-long cores from potential gas-hydrate zones in the Gulf of Mexico. During recovery, gas hydrate in the cores will begin to dissociate because of the reduction in pressure and contact with warm gulf surface water and air. It is hoped that infrared measurements of the type obtained in the Arctic will help the Gulf of Mexico researchers quickly pinpoint and preserve sections of the core that may contain gas hydrate (hydrate dissociation, an endothermic reaction, will cool surrounding sediment). Whole-round gas-hydrate sediment sections were preserved in pressurized vessels for future testing in the Gas Hydrate And Sediment Test Laboratory Instrument (GHASTLI) located at the Woods Hole Field Center. Other members of the Woods Hole gas-hydrate group include Debbie Hutchinson, Bill Dillon, Bill Waite, and Dave Mason.
Bennett Raley (Assistant Secretary of the Interior for Water and Science), Pat Leahy (Associate Director for Geology), and Suzanne Weedman (USGS Energy Program Coordinator) were among the dignitaries that visited operations at both the drillsite and the Inuvik Research Center. Canadian VIPs included Peter Harrison (Deputy Minister of Natural Resources Canada), Assistant Deputy Ministers Irwin Itzkovitch and Ric Cameron, and Jan Boon (Director General for the Geological Survey of Canada). We were also honored by visits from the president of the Japan National Oil Corp. and members of other Japanese organizations involved in the project. Widespread media coverage involved days of filming by both the Canadian Broadcasting Corp. and SFB, a German broadcasting company, as well as interviews by reporters from Canadian Press (a Canadian wire service similar to the Associated Press) and U.S. News and World Report. The current and previous drilling projects resulted in several scientific and technical accomplishments, discussed in more detail at the Related Web Sites below:
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in this issue:
Marine Environmental Careers Symposium Congressional Briefing on Wetlands Talks—DOE and College of William and Mary
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U. S. Department of the Interior | U.S. Geological Survey
cover story:
