With Fort Worth sitting on one of the nation's largest natural gas fields, 150-foot drilling rigs are rising over golf courses, churchyards, even tree-lined neighborhoods. "If you don't have a gas well ... get one!" a billboard urges commuters zipping along a busy interstate near downtown. But not everyone is celebrating the natural gas bonanza here, despite the 55,000 new jobs and extra $5.2 billion it brings to the North Texas economy each year. Once confined to the lonely prairies, oil and gas exploration has gone urban. In Fort Worth, Los Angeles and other densely populated places, that sometimes pits...