US Gas Hydrates Find Has Worldwide Implications



In a 21-day expedition led by Chevron, DOE's National Energy Technology Lab (NETL), the US Geological Survey, the Minerals Management Service, in addition to a host of other industry experts, the most prospective gas hydrates reservoirs yet found have been located and drilled.

"Gas hydrates for a long time have been the most elusive and confounding of hydrocarbon deposits to find," said Dan McConnell, vice president of AOA Geophysics, one of the companies selected for the site selection committee. "This is the very first time that thick hydrates accumulations have been drilled by design, that those hydrates were where they were predicted to be."

The Gulf of Mexico Gas Hydrates Joint Industry Program (JIP) was formed by US governmental groups and petroleum companies to investigate the occurrence of gas hydrates and develop technologies for reliable detection and safe drilling.

"The goal of the DOE program is to determine the scale at which gas hydrates exist in potentially recoverable reservoirs in the Gulf," said Ray Boswell, the project leader from NETL. "This expedition is a major success in that effort."

"In the pursuit for gas hydrates, which has been put on by Japan, India, Korea and China, it was thought for a while that the US had lagged in its efforts," said McConnell. "But we have in this one expedition found the most promising hydrates that can actually be produced -- the thickest, most saturated hydrates that have yet been encountered. So, it really is a landmark expedition."

"These sites represent a range of gas hydrate occurrences, including not only the prospective gas hydrate saturated sands," said the USGS' Tim Collett. "In addition to their resource implications, they should serve as excellent research sites to advance our understanding of the nature and evolution of gas hydrate systems."

Helix Q4000 Semisub
Helix Q4000 Semisub

Through April and May 2009, Helix's Q4000 semisub drilled seven deepwater wells in Walker Ridge, Green Canyon and Alaminos Canyon in the US Gulf of Mexico. Ranging in water depths of 4,800 to 6,600 feet, four of the wells encountered concentrations of hydrates in porous, permeable sands; two discovered low concentrations of gas hydrates in sands; and one intersected promising sands yet no hydrates.

Locating Gas Hydrates

The 21-day expedition proved that under the US Gulf of Mexico is a new source of energy. Gas hydrate is an icy combination of water and natural gas, which is thought to be found in abundance in both marine environments and the Arctic, but has been historically difficult to find in commercial quantities. Coming in below the budget of $11.2 million, this US expedition has potentially changed the face of the petroleum industry as it exists now.

Gas Hydrate Composition
Gas Hydrate Composition (USGS)

Following a 2005 JIP Leg II program to determine the potential drilling hazards related to gas hydrate in fine-grained sediments, the recent expedition started with determining where to drill. AOA Geophysics was brought into the fold as a part of the site selection committee because of previous published papers outlining how to locate gas hydrates.

"They recognized that we brought a set of skills that was needed in the site selection committee," provided McConnell. "We end up looking at a lot of data, and we are always looking at the interface between gas and gas hydrates as we work for our clients. So when Chevron asked us using their supplied data to prospect for gas hydrates, we had really good ideas of where to look for them and were actually able to guide them toward two of the successful sites."

AOA Geophysics helped to put forth two successful sites, on the Walker Ridge 313 and the Green Canyon 955 locations. In fact, the Walker Ridge site was one that the company had identified in a 2002 paper.

Gas Hydrate Composition
Blocks drilled for gas hydrates in the US GOM

"Prior to this paper, researchers would look for a bottom simulating reflector and were puzzled on why it seemed to be absent in the GOM," explained McConnell, the author of the research.

The programs discovered gas hydrate in saturations ranging from 50 percent to more than 90 percent in high-quality sands.

"And those gas hydrates were in a sand which should have excellent reservoir characteristics," added Adrian Digby, vice president of business development at AOA Geophysics. "So, if you are going to find a producible gas hydrate, we believe this is the sort of places you should look. This is the first step. We believe that we've found the most likely location yet drilled. There's still a lot of work to be done to actually get the gas out commercially, but this is the place to start."

Producible Quantities

There are a number of implications for this marine gas hydrate find, especially since the hydrates were found near existing infrastructure. One way gas hydrates can help the industry, is by powering this infrastructure.

"It can benefit some of the deepwater developments," explained McConnell. "The deepwater developments are far flung, and they actually need energy to run themselves. So one possibility is the gas hydrates can be used to help run platforms. If you have a platform that's 200 miles offshore, you have to supply it with energy to run it."

Additionally, gas hydrates may one day produce through existing infrastructure for domestic needs.

"If you look at the deepwater Gulf of Mexico map, you find more and more pipelines, more and more platforms," McConnell continued. "There will be the infrastructure out there to help gather some of these otherwise stranded hydrocarbons."

Processing the gas hydrates is a difficult challenge because of the thermodynamics involved in melting the energy crystals to bring them to the surface.

"You've got three different ways that you can get it out," said Digby. "You've got to increase the temperature, decrease the pressure or use some sort of solvent which would decrease the temperature of the gas hydrates in the water in which they are locked up."

The pressure and the temperature of the hydrates pose a challenge, but there are teams currently working on developing techniques to produce gas hydrates. In fact, this winter, the DOE and Alaska North Slope operators are planning to conduct gas hydrate production tests in the Arctic. Furthermore, international teams are trying to unlock the gas hydrate mystery, as well.

International Implications

There are a number of countries collaborating in the gas hydrates research. Although the Gulf of Mexico has just pulled out in front, other regions have been earnestly developing ways to locate and process this new frozen resource, including the Asian countries of Japan, India, Korea and China.

Gas hydrates have been produced or tested in Siberia and Alaska. There are major efforts under way to test and produce gas hydrates in Siberia, Japan and India, but the process for finding them was coincidental. An additional focus of the American program included establishing a genuine methodology for locating the resource that can be used worldwide, and that has been accomplished.

"The same technologies, the same methodology to finding gas hydrates is applicable to other basins," concluded McConnell.



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