IN-SITU SAMPLING AND CHARACTERIZATION OF NATURALLY OCCURRING MARINE METHANE HYDRATE USING THE D/V JOIDES RESOLUTION

• Main Authors: Rack, Frank R., Francis, Tim, Schultheiss, Peter, Long, Philip E., Freifeld, Barry M.
• Other Authors: United States
• Format: Report
• Language: English
• Published: Joint Oceanographic Institutions (United States) 2005
• Subjects: Subduction Zones; Diffusion; Oxidation; Sediments; Gas Hydrates; Fluid Flow; Clathrates; Hydrates; Sampling; Methane; Prisms; Stability; Drilling; Climates; Plumes; 03 Natural Gas; Permeability; Resolution; Methane hydrate
• Online Access: https://doi.org/10.2172/840101; https://digital.library.unt.edu/ark:/67531/metadc781339/

The primary activities accomplished during this quarter were continued efforts to develop plans for Phase 2 of this cooperative agreement based on the evolving operational planning for IODP Expedition 311, which will use the JOIDES Resolution to study marine methane hydrates along the Cascadia margin, offshore Vancouver Island. IODP Expedition 311 has been designed to further constrain the models for the formation of marine gas hydrate in subduction zone accretionary prisms. The objectives include characterizing the deep origin of the methane, its upward transport, its incorporation in gas hydrate, and its subsequent loss to the seafloor. The main attention of this expedition is on the widespread seafloor-parallel layer of dispersed gas hydrate located just above the base of the predicted stability field. In a gas hydrate formation model, methane is carried upward through regional sediment or small-scale fracture permeability, driven by the tectonic consolidation of the accretionary prism. The upward moving methane is incorporated into the gas hydrate clathrate as it enters the methane hydrate stability zone. Also important is the focusing of a portion of the upward methane flux into localized plumes or channels to form concentrations of near-seafloor gas hydrate. The amount of gas hydrate in local concentrations near the seafloor is especially important for understanding the response of marine gas hydrate to climate change. The expedition includes coring and downhole measurements at five sites across the Northern Cascadia accretionary prism. The sites will track the history of methane in an accretionary prism from (1) its production by mainly microbiological processes over a thick sediment vertical extent, (2) its upward transport through regional or locally focused fluid flow, (3) its incorporation in the regional hydrate layer above the BSR or in local concentrations at or near the seafloor, (4) methane loss from the hydrate by upward diffusion, and (5) methane oxidation and incorporation in seafloor carbonate, or expulsion to the ocean. This expedition builds on the previous Cascadia gas hydrate drilling of ODP Leg 146 and on more recent ODP Leg 204 off Oregon. Important experiments being considered for DOE/NETL funding as part of the JOI cooperative agreement include, (1) Logging-While-Drilling/Measurements-While-Drilling (LWD/MWD), (2) Pressure Core Sampling (PCS/HYACINTH) of gas hydrate, and fluid recovery under in situ conditions, (3) X-ray CT logging of whole cores under in situ conditions, and (4) Infrared thermal imaging of whole round cores to map temperature variations resulting from the presence of hydrate. Preliminary budget estimates have been made for each of these tasks and discussions are ongoing with DOE/NETL program managers to develop a final plan that can be implemented within the constraints of the available funding and logistical considerations.