User:Magnetiks/advres article

Unconventional gas resources, which consist of tight gas sands, coalbed methane, and gas shales are extremely important to the industry of natural gas production. As little as 10-12 years ago, this was a new resource that was overlooked by natural gas companies. This is now a very important resource for natural gas companies today.

"Though tight gas sands, coalbed methane, and gas shales were historically overlooked in search of more economical, conventional reserves, the growing maturity of these plays in the U.S. has led to increased investment in unconventional gas exploration. In 2005, unconventional gas represented 44% of U.S. lower-48 onshore production."

References:

1. Advanced Resources International Unconventional Resources