"In recent years, natural gas producers in the United States have struggled, mostly in vain, to be taken more seriously in the energy world. Big oil companies like Exxon had concluded that natural gas reserves in the United States were not sufficiently abundant to warrant big investments in exploration and drilling. When small independent gas producers argued otherwise, they were often ridiculed. ...
But the natural gas folks now have numbers on their side due to new successes in getting gas out of shale rock. Geologists have always known that shale rock, often found in combination with coal and oil deposits, holds substantial amounts of natural gas. If a piece of shale rock is broken and lit with a match, it will actually burn for a few moments with a small flame.
The shale gas was previously considered unreachable, but advances in drilling techniques have changed that assessment. The result is a dramatic increase in estimated natural gas reserves. The Potential Gas Committee, loosely affiliated with the Colorado School of Mines, reported in June that natural gas reserves in the United States are actually 35 percent higher than believed just two years ago, and some geologists say even that estimate is too conservative."