New data gathered during a 15-day research expedition in the northern Gulf of Mexico (GOM) are being used to refine estimates of natural gas hydrates.

“This expedition represents a significant milestone,” said U.S. Geological Survey (USGS) Energy Resources Program Coordinator Brenda Pierce. “The data and imagery provide insight into the entire petroleum system at each location, including the source of gas, the migration pathways for the gas, the distribution of hydrate-bearing sediments, and the traps that hold the hydrate and free gas in place.”

The expedition and the data and imagery collected resulted from cooperation between the USGS and the Bureau of Ocean Energy Management (BOEM) and the U.S. Department of Energy (DOE). The trio of agencies are working to expand understanding of hydrates so that they may become a future energy resource.

Gas hydrates are ice-like substances formed when certain gases combine with water at specific pressures and temperatures. Deposits of gas hydrates are widespread in marine sediments beneath the ocean floor and in sediments within and beneath permafrost areas, where pressure-temperature conditions keep the gas trapped in the hydrate structure. Methane is the gas most often trapped in these deposits, making gas hydrates a potentially significant source for natural gas around the world.

The recently completed expedition, which was planned by USGS, DOE and BOEM, was executed by USGS. Using low-energy seismic sources, USGS scientists collected details about the nature of the gas hydrate reservoirs and about geologic features of the sediment between the reservoirs and the seafloor. The new data also provide information about how much gas hydrate exists in a much broader area than can be determined from using standard industry seismic data, which is typically designed to image much deeper geologic units.

“Understanding the nature and setting of deepwater gas hydrates is central to the National Methane Hydrates R&D Program, which is led by DOE and managed by Fossil Energy’s National Energy Technology Laboratory,” said DOE’s Christopher Smith, acting assistant secretary for fossil energy. “Over the past eight years, research carried out under this program has resulted in significant advances in our understanding of methane hydrates, their role in nature, and their potential as a future energy resource.”

Data were collected at two locations in the Gulf of Mexico where the three federal agencies partnered with an industry consortium to conduct a drilling expedition in 2009 (see Daily GPI, May 15, 2009). That expedition discovered gas hydrate filling between 50% and 90% of the available pore space between sediment grains in sandy layers in the subsurface. These reservoirs are expected to be representative of the 6,700 Tcf of gas that BOEM estimates is housed in gas hydrates in sand-rich reservoirs in the northern GOM.

The new data are being used to refine estimates of the nature, distribution, and concentration of gas hydrate in the vicinity of the 2009 drill sites, USGS said. This will help assess how useful specialized seismic data may be to estimating hydrate saturations in deepwater sediments.

USGS maintains a web page detailing hydrate research activities.

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