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Abstract

DOI: 10.1306/05212019052

Pressure coring a Gulf of Mexico deep-water turbidite gas hydrate reservoir: Initial results from The University of Texas–Gulf of Mexico 2-1 (UT-GOM2-1) Hydrate Pressure Coring Expedition

Peter B. Flemings,1 Stephen C. Phillips,2 Ray Boswell,3 Timothy S. Collett,4 Ann E. Cook,5 Tiannong Dong,6 Matthew Frye,7 David S. Goldberg,8 Gilles Guerin,9 Melanie E. Holland,10 Junbong Jang,11 Kevin Meazell,12 Jamie Morrison,13 Joshua I. O’Connell,14 Ethan G. Petrou,15 Tom Pettigrew,16 Peter J. Polito,17 Alexey Portnov,18 Manasij Santra,19 Peter J. Schultheiss,20 Yongkoo Seol,21 William Shedd,22 Evan A. Solomon,23 Carla M. Thomas,24 William F. Waite,25 and Kehua You26

1Institute for Geophysics and Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas; [email protected]
2Institute for Geophysics, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas; [email protected]
3National Energy Technology Laboratory (NETL), Department of Energy (DOE), Pittsburgh, Pennsylvania; [email protected]
4US Geological Survey (USGS), Central Energy Resources Science Center, Denver Federal Center, Denver, Colorado; [email protected]
5School of Earth Sciences, The Ohio State University, Columbus, Ohio; [email protected]
6Institute for Geophysics and Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas; [email protected]
7Resource Evaluation Division, Bureau of Ocean Energy Management (BOEM), Washington, District of Columbia; [email protected]
8Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York; [email protected]
9Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York; [email protected]
10Geotek, Ltd., Daventry, Northamptonshire, United Kingdom; [email protected]
11Integrated Statistics, Inc., contracted to USGS, Woods Hole, Massachusetts; [email protected]
12Institute for Geophysics and Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas; [email protected]
13Institute for Geophysics, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas; [email protected]
14Institute for Geophysics, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas; [email protected]
15Institute for Geophysics, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas; [email protected]
16Pettigrew Engineering, PLLC, Milam, Texas; [email protected]
17Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas; [email protected]
18School of Earth Sciences, The Ohio State University, Columbus, Ohio; [email protected]
19Institute for Geophysics, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas; [email protected]
20Geotek, Ltd., Daventry, Northamptonshire, United Kingdom; [email protected]
21NETL, DOE, Morgantown, West Virginia; [email protected]
22Office of Resource Evaluation, BOEM, New Orleans, Louisiana; [email protected]
23School of Oceanography, College of the Environment, University of Washington, Seattle, Washington; [email protected]
24Institute for Geophysics, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas; [email protected]
25USGS, Woods Hole Field Center, Woods Hole, Massachusetts; [email protected]
26Institute for Geophysics, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas; [email protected]

ABSTRACT

The University of Texas Hydrate Pressure Coring Expedition (UT-GOM2-1) recovered cores at near in situ formation pressures from a gas hydrate reservoir composed of sandy silt and clayey silt beds in Green Canyon Block 955 in the deep-water Gulf of Mexico. The expedition results are synthesized and linked to other detailed analyses presented in this volume. Millimeter- to meter-scale beds of sandy silt and clayey silt are interbedded on the levee of a turbidite channel. The hydrate saturation (the volume fraction of the pore space occupied by hydrate) in the sandy silts ranges from 79% to 93%, and there is little to no hydrate in the clayey silt. Gas from the hydrates is composed of nearly pure methane (99.99%) with less than 400 ppm of ethane or heavier hydrocarbons. The δ13C values from the methane are depleted (−60‰ to −65‰ Vienna Peedee belemnite), and it is interpreted that the gases were largely generated by primary microbial methanogenesis but that low concentrations of propane or heavier hydrocarbons record at least trace thermogenic components. The in situ pore-water salinity is very close to that of seawater. This suggests that the excess salinity generated during hydrate formation diffused away because the hydrate formed slowly or because it formed long ago. Because the sandy silt deposits have high hydrate concentration and high intrinsic permeability, they may represent a class of reservoir that can be economically developed. Results from this expedition will inform a new generation of reservoir simulation models that will illuminate how these reservoirs might be best produced.

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