Researchers from Princeton University have discovered that oil and natural gas wells can continue to emit substantial quantities of methane even after they are decommissioned and abandoned.
Nineteen such wells were studied in Pennsylvania’s McKean and Potter counties and all of them tested positive for methane emissions. The findings were published Monday in the Proceedings of the National Academy of Science.
The study arose by happenstance after Mary Kang, then a doctoral candidate in Princeton’s school of civil and environmental engineering, noticed a lack of data on methane emissions from decommissioned gas wells. Stanford University estimates that there are approximately three million wells across the United States, though records of the wells are not reliable. Notably, only one of the 19 wells Princeton researchers surveyed was actually present on the state’s list of abandoned wells.
“I was looking for data,” said Kang in a University news release, “but it didn’t exist.”
While wells are in operation, there are many precautions and environmental standards that operators take. Once a well is abandoned, however, such precautions are no longer deemed necessary.
Methane is a potent greenhouse gas, produced by both natural and man-made means. It arises from the decomposition of organic matter and constitutes the main ingredient in natural gas. Unlike carbon dioxide, it does not linger in the atmosphere for an indefinite length of time, dissipating instead after about 12 years. However, it is at least 20 times better at trapping heat than carbon dioxide, making it a significant factor in raising atmospheric temperatures worldwide.
Kang and her fellow Princeton researchers placed flux chambers over the tops of abandoned methane wells and discovered that each of them still emitted some amount of methane. In 15 percent of the cases, emissions were thousands of times greater than the lower-level wells.
Extrapolating from their current data, the researchers estimate that abandoned wells could constitute as much as 10 percent of the state’s methane emissions and, in some cases, have been leaking for decades.
“This may be a significant source,” said Denise Mauzerall, a Princeton professor and member of the research team. “There is no single silver bullet but if it turns out that we can cap or capture the methane coming off these really big emitters, that would make a substantial difference.”
The team has called for more measurements to be taken across Pennsylvania, as well as in California and Texas, where oil and gas development has existed since the 19th century.