Resource-quality gas-hydrate deposits found in gulf

A 21-day expedition discovered highly saturated gas-hydrate-bearing sands in two of three sites drilled in the Gulf of Mexico, according to the Office of Fossil Energy's National Energy Technology Laboratory (NETL).

Guntis Moritis
OGJ Production Editor

HOUSTON, May 14 -- A 21-day expedition discovered highly saturated gas-hydrate-bearing sands in two of three sites drilled in the Gulf of Mexico, according to the Office of Fossil Energy's National Energy Technology Laboratory (NETL).

The expedition was a collaborative effort of NETL, US Geological Survey, US Minerals Management Service, and an industry research consortium led by Chevron Corp.

"Prior to this expedition there was little documentation that gas hydrate occurred in resource-quality accumulations in the marine environment," NETL said.

This was the second leg of a joint industry project. The first leg in 2005 focused on the drilling hazards related to gas hydrates in fine-grained sediments, while this second leg targeted sediments thought to contain high-quality, thick, porous, and permeable sands.

The expedition found gas hydrates at saturations ranging from 50% to more than 90% in high-quality sand deposits in close accordance with the project's predrilling predictions. This increased the confidence in gas hydrate exploration and appraisal technologies, NETL said.

NETL noted that these two sites were the first finds in the world of resource-quality marine gas-hydrate deposits.

The hydrates found were in sand reservoirs, thick sequences of fracture-filling gas hydrates in shales, and potential partially saturated gas hydrates in younger sediments.

NETL said this second leg also had several technical advances, including the use of an advanced suite of logging-while-drilling tools that provided 3D images of hydrate-bearing sediments. In addition, the wells at Walker Ridge, drilled 3,500 ft below the seafloor, were more than 1,000 ft deeper than any previous gas-hydrate research wells, NETL said.

NETL's Ray Boswell said, "The expedition was completed on time, with no incidents, and below the planned $11.2 million dollar budget." The other two sites drilled were in the Green Canyon and Alaminos Canyon planning areas.

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