Scientific Objectives of the Gulf of Mexico Gas Hydrate JIP Leg II Drilling

Authors: E. Jones, T. Latham, D. McConnell, M. Frye, J. Hunt Jr. W. Shedd, D. Shelander, R. Boswell, K. Rose, C. Ruppel, D. Hutchinson, T. Collett, B. Dugan, W. Wood

Venue: 2008 Offshore Technology Conference held in Houston, Texas, U.S.A., May 5-8, 2008 ( http://www.otcnet.org/2008/c4p/index.html [external site])

Abstract: The Gulf of Mexico Methane Hydrate Joint Industry Project (JIP) has been performing research on marine gas hydrates since 2001, and is sponsored by both the JIP members and the U.S. Department of Energy. In 2005, the JIP drilled the Atwater Valley and Keathley Canyon exploration blocks in the Gulf of Mexico to acquire downhole logs and recover cores in silt- and clay-dominated sediments interpreted to contain gas hydrate based on analysis of existing 3-D seismic data prior to drilling. The new 2007-2009 phase of logging and coring, which is described in this paper, will concentrate on gas hydrate-bearing sands in the Alaminos Canyon, Green Canyon, and Walker Ridge protraction areas. Locations were selected to target higher permeability, coarser-grained lithologies (e.g., sands) that have the potential for hosting high saturations of gas hydrate and to assist the U.S. Minerals Management Service with its assessment of gas hydrate resources in the Gulf of Mexico.

This paper discusses the scientific objectives for drilling during the upcoming campaign and presents the results from analyzing existing seismic and well log data as part of the site selection process. Alaminos Canyon 818 has the most complete data set of the selected blocks, with both seismic data and comprehensive downhole log data consistent with the occurrence of gas hydrate-bearing sands. Preliminary analyses suggest that the Frio sandstone just above the base of the gas hydrate stability zone may have up to 80% of the available sediment pore space occupied by gas hydrate.

The proposed sites in the Green Canyon and Walker Ridge areas are also interpreted to have gas hydrate-bearing sands near the base of the gas hydrate stability zone, but the selection of specific drill sites is not yet complete. The Green Canyon site coincides with a 4-way closure within a Pleistocene sand unit in an area of strong gas flux just south of the Sigsbee Escarpment. The Walker Ridge site is characterized by a sand-prone sedimentary section that rises stratigraphically across the base of the gas hydrate stability zone and that has seismic indicators of gas hydrate.

Related NETL Project:
This presentation is related to the NETL project DE-AI26-05NT42496, “Scientific Studies in Support of DOE Efforts to Evaluate and Understand Methane Hydrates.” The objective of this project is to conduct scientific studies of natural gas hydrates to support DOE efforts to evaluate and understand methane hydrates, their potential as an energy resource, and the hazard they may pose to ongoing drilling efforts.

Project Contacts
NETL – Robert Vagnetti (RobertVagnetti@netl.doe.gov or 304-285-1334)
USGS – Deborah R. Hutchinson (dhutchinson@usgs.gov or 508-427-2263)