Low-yielding US Oil Wells Emit Half of Methane, Survey Says

Methane is the second most significant contributor to climate change, behind carbon dioxide.

Environmental organizations criticized the proposed regulation because it required corporations to monitor just major well sites spewing an estimated three tons of methane per year or more, which the government said accounted for 86 percent of leaks.

Marginal wells produce fewer than 15 barrels of oil equivalent per day and release methane at a rate six to twelve times that of the national average, the research said. This is comparable to losing 10% of their gas into the atmosphere.

It demonstrates how, by exempting those wells from regulation, the EPA would be oblivious to a massive source of methane.

"The methane impact of these little wells is huge and cannot be disregarded," said Mark Omara, co-author of the research and an environmental scientist with the Environmental Defense Fund.

According to EPA spokesman Nick Conger, the agency received the report's information during the public comment period on the November proposal.

"We are taking it into account, as well as all other comments received, as we create a supplementary proposal that the Agency anticipates issuing later this year," he said in an e-mailed statement.

The oil and gas industry lobbied the EPA to exempt smaller wells from the regulations, citing the sheer volume of such wells and the associated costs of monitoring and repair.

Field observations revealed that "negligence and degradation" of equipment was the predominant source of methane emissions at low-production well sites, indicating that they might be prevented with more regular monitoring and site inspections, the research said.

The proposed EPA methane rule would be the first to control methane emitted by existing oil and gas operations, requiring oil and gas firms to periodically check and fix methane leaks at 300,000 of their largest well sites and other equipment.