Certain types of Pennsylvania’s scores of abandoned oil and gas wells are associated with higher emissions of the greenhouse gas methane, according to a study published Monday that could help government agencies prioritize efforts to plug the biggest leaks.
Laura Legere reports for PowerSource: The study of 88 wells across Western Pennsylvania led by Mary Kang, a postdoctoral fellow at Stanford University, revealed that high-emitting wells tend to be natural gas wells that are either unplugged or that are plugged but vented in coal-rich areas.
Abandoned oil wells had consistently lower emissions than the abandoned gas wells in the study. Proximity to active natural gas storage fields or new shale gas wells appeared unrelated to methane flow rates from abandoned wells, according to the report in the Proceedings of the National Academy of Sciences.
The highest emitters are a particularly valuable target in efforts to curb releases of the powerful greenhouse gas, which has 86 times the heat-trapping potential of carbon dioxide in the atmosphere over a 20-year period.
Researchers found that wells with high methane emissions were leaking at steadily high rates across years of sampling, indicating that they “may have been emitting at these levels for many decades and will likely continue for decades into the future.”
Ms. Kang and her fellow researchers first reported the significant but largely uncounted contribution that abandoned wells can have on total methane emissions in a 2014 paper. That drew the attention of both state and federal regulators, who are now trying to begin to account for abandoned wells in their official inventories of emissions.
The earlier paper also showed that the bulk of measured emissions was coming from only 10 percent of the smaller sample of wells, which inspired the researchers from Stanford, Princeton and other institutions to dig deeper to define attributes of the biggest leakers.
“There are hundreds of thousands of wells in Pennsylvania. That’s a lot of wells to fix,” Ms. Kang said. “But if we only have to fix 10 percent of those, that’s a huge cost benefit.”