The work done in Alaska will inform the potential extraction of methane hydrates believed to lie beneath the seabed of the U.S. Gulf of Mexico--and if successful--could also provide a feasible way to store molecules of carbon dioxide and remove them from the atmosphere.

Industry and science have long known about methane hydrates: natural gas that has been trapped beneath the ground in molecular lattices of frozen, pressurized water. Estimates vary, but the globe is thought to contain a massive abundance of methane hydrates--tens of thousands of trillion cubic feet estimated in the Arctic alone.

But since no commercially viable method has been found to recover the trapped gas, the U.S. Department of Energy's (DOE) research and development program has focused on two priorities:

  • The need to detect and quantify methane hydrate deposits prior to drilling; and
  • The demonstration of methane production from hydrate at commercial volumes.

The DOE's National Energy Technology Laboratory--in partnership with ConocoPhillips Co.--completed installation of a well they call "Ignik Sikumi," using Iñupiaq terms for "fire in the ice."

So the Ignik Sikumi field trial well tackled the first of the DOE’s priorities, documenting the location and concentration of methane hydrate deposits in saturated sandstone beneath the North Slope.

"The data confirm the occurrence of 160 feet of gas-hydrate-bearing sand reservoirs in four separate zones, as predicted, and provide insight into their physical and mechanical properties," the DOE stated.

Once extraction begins this winter, the team hopes to tackle the agency’s second priority over the next year.

Coaxing Fuel from Icy Crystals

In January 2012, the U.S. Department of Energy (DOE) will begin about 100 days of experiments into carbon exchange and methane harvesting from methane hydrates--lattices of ice that trap molecules of natural gas deep underground.

The project is small in terms of capital. The DOE is investing US$5 million, while an additional $7 million will come from the Japan Oil, Gas and Metals National Corp., a government entity. ConocoPhillips Co. will contribute $5.3 million to the research project.

In contrast, the DOE invested about $150 million over 14 years on research into extracting shale gas.

The Energy Department has been conducting research into methane hydrates since at least 2005, although the resource has been on the radar of the industry for years.

Hydrates would often be found as companies drilled for oil and gas around the Gulf of Mexico, and initial research was done to ensure the material didn’t become a hazard to drilling.

Late last year, the DOE drilled a well on an ice pad in Alaska, and this winter, scientists will return to the well to conduct two rounds of tests to verify their theories on how methane hydrates will perform.

This next phase of recovering natural gas from methane hydrates on Alaska's North Slope is expected to last until at least March 2012, according to an October 24 statement from the DOE's Fossil Energy Office (FEO).

Tests will include the initial field trial of a technology that involves injecting carbon dioxide (CO2) into methane hydrate-bearing sandstone formations, resulting in the swapping of CO2 molecules for methane molecules in the solid-water hydrate lattice, the release of methane gas and the permanent storage of CO2 in the formation, the FEO said.

It's been done in a laboratory, and scientists hopes to repeat that success on the North Slope.

Once the exchange tests are completed, the team will conduct a one-month evaluation of an alternative methane-production method called depressurization, the FEO said. The process involves pumping fluids out of the borehole to reduce pressure in the well, which results in dissociation of methane hydrate into methane gas and liquid water.

The method was successfully demonstrated during a one-week test conducted by Japan and Canada in northwestern Canada in 2008, the agency noted.

A Glowing Promise

According to the U.S. Geological Survey (USGS), 100,000 to 300 million trillion cubic feet (Tcf) of methane exist globally in hydrate form--most of it in the ocean floor.

"The worldwide volume of methane held in methane hydrate is immense and poorly known. Estimates range from 100,000 Tcf to more than 1,000,000 Tcf of natural gas," according to the U.S. Department of Energy (DOE). "There's more energy potential locked up in methane hydrate formations across the world than in all other fossil energy resources combined."

In the U.S. Exclusive Economic Zone, up to 200,000 Tcf of methane is in hydrates, the agency said. Two Rhode Island-sized areas in the Blake Ridge--east of the Carolinas--contain more than 2,012 Tcf--110 times the country’s annual natural gas consumption, according to the DOE.

Hydrates form and stabilize in a very specific zone of high pressure and low temperature, where water solidifies around gas molecules to form a crystalline structure. A goal of many expeditions in recent years has been to study the factors controlling where this phenomenon occurs. And as it turns out, the type of sediment where hydrates occur is crucial, the DOE says.

To-date, two main extraction methods have been successfully tested at an experimental site on Canada's Mackenzie Delta. The first, called depressurization, involves drilling a hole into the hydrate layer to draw down the pressure, causing hydrates to dissociate and gas to flow up the pipe. Thermal injection, the second technique, destabilizes hydrates by pumping hot water into the deposit. Because depressurization requires less energy, many scientists call it the "lowest-hanging fruit."

A third method appears promising, too, but has so far only been tested in a lab. Injecting carbon dioxide into a hydrate formation displaces methane, and has the added benefit of locking away an abundant greenhouse gas, according to the DOE.

A Dark Paradox

But if methane gas escapes directly to the atmosphere--as a byproduct of extraction, an earthquake or warming ocean waters--the consequences could be dire, some researchers say.

A "potent" greenhouse gas, methane is 21 times more effective at trapping heat than carbon dioxide, according to the U.S. Department of Energy's National Energy Technology Laboratory (NETL).

"Clearly, methane hydrate has a significant role in the global carbon cycle, and it is gaining recognition as an important player in global climate processes and climate change," the NETL said. "Beyond these basic assertions, many questions remain."

With that in mind, the DOE said it has stepped-up efforts to address the many questions that surround methane hydrate deposits.

"In addition to these technical challenges, production of natural gas from methane hydrate would need to be carried out with attention to the potential environmental impacts and safety concerns associated with this unique resource," the NETL say. "Any future development would need to use techniques that minimize the release of methane to the atmosphere, and development activities in both arctic and marine settings would need to be carried out in ways that maximize protection of these environments.

"Significant scientific work must be completed before methane hydrate can be considered a producible natural gas resource," NETL scientists said. "Testing must demonstrate that methane can be produced safely from hydrate deposits, at commercial rates, over extended time periods and with minimal environmental impacts."

Contact the author, Kristie Sotolongo, at ksotolongo@hartenergy.com.