New Seismic Constraints on the Distribution of Methane Hydrate on the U.S. Mid-Atlantic Margin
Abstract
In summer 2018, the U.S. Geological Survey (USGS), in collaboration with the Bureau of Ocean Energy Management (BOEM) and the U.S. Department of Energy, acquired more than 1500-line-km of high-resolution multichannel seismic (MCS) and wide-angle reflection data between Hudson Canyon and Cape Hatteras using an airgun source array up to 840 in3, a 120-channel streamer over 1 km long, and sonobuoys. The Mid-Atlantic Resource Imaging Experiment (MATRIX) was designed to constrain the distribution of deepwater gas hydrates and shallow methane gas in continental slope sediments. Data acquisition focused on areas previously identified as good prospects for gas hydrates based on BOEM's analysis of legacy seismic data and also targeted imaging beneath upper slope sites associated with widespread, recently-discovered methane seepage. The new MCS data are the first collected in this area for more than 30 years and fill a gap in modern seismic coverage of the slope/upper rise, between a 2014 Extended Continental Shelf survey conducted by the USGS to the north and the 2014 Eastern North American Margin (ENAM) survey sponsored by the National Science Foundation to the south. The newly-acquired MATRIX data are also useful for analysis of margin structure, marine geohazards, and patterns of sedimentation/erosion that affect gas accumulation and release.
Here we report the first results of the MATRIX survey and provide a preliminary map of gas hydrate distributions for the U.S. Mid-Atlantic margin based on delineation of bottom simulating reflectors and other hydrate-related features in the new MCS data. We adjust the boundaries of the gas hydrate prospects previously defined by BOEM and identify new areas where elevated gas hydrate saturations are likely to be found. Where possible, we also map the landward (updip) extent of gas hydrate, an important feature for assessing the susceptibility of natural gas hydrate deposits to dissociation during changes in ocean temperature or sea level. The new MCS data also reveal geologic structures beneath some of the vigorous deepwater (>600 m water depth) methane seeps identified within the gas hydrate stability zone since 2012 and allow us to assess whether deeper gas accumulations feed the seeps and whether features such as diapirs play a role in fluid migration at these locations.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMOS54A..04R
- Keywords:
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- 1051 Sedimentary geochemistry;
- GEOCHEMISTRYDE: 3004 Gas and hydrate systems;
- MARINE GEOLOGY AND GEOPHYSICSDE: 3022 Marine sediments: processes and transport;
- MARINE GEOLOGY AND GEOPHYSICSDE: 3036 Ocean drilling;
- MARINE GEOLOGY AND GEOPHYSICS