The world has a lot of methane hydrate. A Minerals Management Service study in 2008 estimated methane hydrate resources in the northern Gulf of Mexico at 21,000 trillion cubic feet, or 100 times current U.S. reserves of natural gas. The combined energy content of methane hydrate may exceed all other known fossil fuels, according to the DOE.
Not all is accessible, but high concentrations in permeable rock where there's existing drilling infrastructure would be among early candidates for development. The USGS in 2008 estimated 85 trillion cubic feet of undiscovered, technically recoverable gas within methane hydrate deposits on Alaska's North Slope.
It will not be simply dug out of the ground, Boswell said.
“One of the basic messages is, we're not mining,” he said. “It's using existing drilling techniques.”
Methane could be extracted by lowering pressure or increasing temperature in an underground reservoir.
“One of the issues with that, though, is that you are melting the ice, and adding a lot of gas and water to the reservoir, which can compromise the reservoir's strength,” Boswell said.
The Alaska research focused on a method aimed at preserving the underground ice structure. The extraction technique was based on studies done by ConocoPhillips and the University of Bergen in Norway. Researchers in a laboratory injected carbon dioxide into methane hydrate. CO2 molecules swapped places with methane molecules, freeing the methane to be harvested but preserving the ice.
The DOE worked with ConocoPhillips and Japan Oil, Gas and Metals National Corp. to see if it would work in the field. They named the North Slope well Ignik Sikumi, an Inupiat Eskimo phrase that translates as “fire in the ice.”
Researchers injected 210,000 cubic feet of carbon dioxide and nitrogen into the underground reservoir through perforated pipe. Instruments measured pressure, temperature and produced gases. They tracked injected gases without fracturing the formation.
Scientists collected data from 30 days of methane production, five times longer than anyone had done before. They are now trying to determine if methane produced was from an exchange with CO2, a reaction to the nitrogen, or a reaction to pressure changes down the hole.
Researchers are optimistic.
“From the lab data we had, it seemed like it was some strong evidence that it was not a lot of wholesale destruction of the solid hydrate,” Boswell said.