Shale gas companies in Pennsylvania reported leaking 9,681 tons of methane in 2013, a 41 percent increase over the prior year. But the real amount of methane that went into the air may have little to do with that estimate.
Leaks, or fugitive emissions, aren’t measured at oil and gas facilities. Those emissions are estimated based on a 20-year-old formula that plugs in the number of components on a well site and the volume of gas flowing through.
The increase from 2012 to 2013 reflects only that more wells were producing gas, not necessarily that those were leaking more gas.
More than a dozen studies measuring emissions from shale gas sites, in the Marcellus region that underlies much of Appalachia and elsewhere in the country, have come up with varying conclusions about leak rates. But the equalizer has been the finding that a small number of very leaky wells skew the curve.
“The type of phenomenon you have is the majority of wells do pretty well and don’t leak much,” said Rob Altenburg, director of PennFuture’s Energy Center in Harrisburg. “But those that do leak, potentially leak a lot.”
The issue will be on the table Tuesday at a public hearing the Environmental Protection Agency is holding in Downtown to hear comments on a recently proposed suite of federal regulations meant to curb emissions of methane and volatile organic compounds at oil and gas production, processing and transmission operations.
Pennsylvania’s Department of Environmental Protection is looking at ways to beef up reporting of all emissions at oil and gas sites, leaks included, said DEP Secretary John Quigley, allowing that its current inventory relies on some outdated measures.
“We need to get a better handle on all emissions,” he said.
The DEP has not provided details of how that would be done, but the department is preparing comments on the new federal proposal.
The EPA agency’s new rules could standardize leak detection and repair programs to mitigate fugitive methane emissions.
A growing number of oil and gas companies already do that, employing inspectors who tour sites with mobile sensors at quarterly or annual intervals.
Cecil-based Consol Energy Inc. started its leak detection program in 2013, but it doesn’t inventory the emissions it finds or try to quantify them. The focus is on immediate treatment.
“We don’t look at how severe the leak is,” said Brian Aiello, a spokesman for the company. “If there is a leak, it’s fixed.”
Consol, along with every other oil and gas company that submitted emissions data to the DEP last year, let the agency fill in its leak estimates.
The DEP relied on an EPA-sanctioned emission factor that was derived from an industry study measuring leaks in 24 oil and gas wells in 1993. That study looked at methane coming from 24 connectors, nine flanges and 84 valves, a fraction of such parts in a single Marcellus Shale well.
“This approach is prone to systematic error since emissions are highly variable across production facilities, over time, and between operators,” reads an introduction to an ongoing Department of Energy-funded effort to measure emissions by aircraft, vehicle and stationary monitors.
“Accurate, regionally comprehensive, and continuous monitoring of the actual rate of leakage from shale gas production is required both to document the [greenhouse gas] impact of gas production and evaluate efforts to reduce emissions,” it states.
Methane is 84 times more potent than carbon dioxide at trapping heat in the atmosphere over a 20-year period, which climate scientists say is the most critical time to keep emissions at bay.
Anya Litvak: alitvak@post-gazette.com or 412-263-1455.
First Published: September 28, 2015, 4:00 a.m.
