After a natural-gas boom in the Powder River Basin here petered out several years ago, few energy companies were interested in the leftover wells pockmarking the prairie. Then Ed Presley came along. The burly, bearded speculator acquired roughly 3,000 idle wells, many for a few dollars. With a salesman’s charm, he vowed to revive the wells with a contraption called the Gazmo. But Mr. Presley’s plan never produced any gas. He says he couldn’t raise enough money for his company, High Plains Gas Inc., to follow through. Last year, Wyoming seized most of his wells to ensure they didn’t pollute groundwater or soil, declaring them abandoned. […]