For the first time in more than 10 years of commercial production in Wyoming, the coal-bed methane industry is being asked to prove "beneficial use" in regard to how much groundwater it dumps on the surface compared to how much gas it reaps from the activity.

This week, State Engineer Patrick Tyrrell requested a "show cause" explanation from a number of producers about why some wells have yielded only water and no coal-bed methane gas.

The order involves some 296 wells more than five years old in the Clear Creek and Crazy Woman Creek drainages of the Powder River Basin, according to the state engineer's office.

"Approval of a permit to use ground water for CBM production carries with it an expectation that the production of gas will proceed in a timely fashion and in such a way as to minimize the impact to the ground water resource," Tyrrell wrote in his letter.

Tyrrell said his office will begin imposing a threshold water-to-gas ratio of 10 barrels of water per thousand cubic feet of gas, which must be achieved in the first two to three years of water production.