Idle oil wells may be the source of massive methane emissions — study A methane detector reads a sample of water in a demonstration. (Image by Jay Yocis, courtesy of the University of Cincinnati). A study published in the journal Environmental Research Letters states that uncapped, idle oil wells could be leaking millions of kilograms of methane each year into the atmosphere and surface water. The authors of the paper studied 37 wells located on private property in the Permian Basin of Texas, the largest oil-producing region on Earth. Of these wells, seven had methane emissions of as much as 132 grams per hour, while the average rate was 6.2 grams per hour.