DAN JOLINGANCHORAGE, Alaska (AP) â¿¿ A half mile below the ground at Prudhoe Bay, above the vast oil field that helped trigger construction of the trans-Alaska pipeline, a drill rig has tapped what might one day be the next big energy source. The U.S. Department of Energy and industry partners over two winters drilled into a reservoir of methane hydrate, which looks like ice but burns like a candle if a match warms its molecules. There is little need now for methane, the main ingredient of natural gas. With the boom in production from hydraulic fracturing, the United States is awash in natural gas for the near future and is considering exporting it, but the DOE wants to be ready with methane if there's a need. "If you wait until you need it, and then you have 20 years of research to do, that's not a good plan," said Ray Boswell, technology manager for methane hydrates within the DOE's National Energy Technology Laboratory. The nearly $29 million science experiment on the North Slope produced 1 million cubic feet of methane. Researchers have begun the complex task of analyzing how the reservoir responded to extraction. Much is unknown but interest has accelerated over the last decade, said Tim Collett, a research geologist for the U.S. Geological Survey in Denver. U.S. operators in Alaska, he said, may want to harvest methane so they can re-injected it into the ground. Crude oil is more lucrative than natural gas, which is routinely injected into North Slope fields to maintain underground pressure to aid in oil extraction. Japan, Korea, India and China, however, want to cut down on natural gas imports by burning methane. Japan is setting up for a production test on a gas hydrate accumulation in the Nankai Trough south of Honshu, its main island.