A new technique for natural gas extraction eliminates fears about contaminated water and stops opponents in their tracks. In a major energy security speech this March, President Barack Obama had some nice things to say about a new technique for extracting domestic natural gas deposits: “Recent innovations have given us the opportunity to tap large reserves—perhaps a century’s worth of reserves, a hundred years worth of reserves—in the shale under our feet.” The innovation that has unlocked those vast new reserves of natural gas is a process known as hydrofracking—or fracking for short—in which horizontal drilling is combined with blasts...