A new study conducted by researchers at Princeton University suggests that the more than 3 million abandoned oil and gas drilling wells in the United States could be a major contributor to our overall methane emissions.

The researchers selected wells in different kinds of environments including grasslands, wetlands and forests and took measurements both from wells and from surrounding areas to serve as controls. The wells and the control areas were covered with a plastic chamber that sealed off the wellheads while measuring anything released from below. They analyzed the air for a bevy of chemicals such as methane, ethane, propane and butane (the last three help pinpoint whether the methane comes from natural organic processes or if it was released as a result of drilling) and what they found is not good.

Wellheads, more or less, are significant contributors to the release of methane, a potent greenhouse gas. The researchers found that wellheads had, on average, a mean flow rate of 11,000 mg/hour/well while the mean flow rate for the control locations was 0.19 mg/hour/location.

11,000 mg/hour for each abandoned well


0.19 mg/hour for each control location

That's a significant difference.

The team found that a smaller subset of the wells they studied were super emitters, pumping out far more methane gas than the average well. Through the powers of extrapolation, the researchers estimate that the roughly 300,000 to 500,000 abandoned wells in just Pennsylvania alone could have been responsible for 4 to 7 percent of the state's total anthropogenic methane emissions in 2010.

Princeton researchers in the field

Princeton researchers capped the wells with special tents that measured gasses being emitted. (Photo: Robert Jackson/Stanford University)

Another recent study found that the U.S. could have as many as 3 million abandoned gas and oil wells. There are no laws regulating the monitoring of abandoned wells and just about zero oversight on how drilling companies close up their operations upon completion of their work. With so many abandoned wells littering the American landscape, we need to know what's bubbling up from those pipes to best respond to it. This study is an important first step.

The findings of the Princeton team, where a smaller percentage of the abandoned wells are found to be far more active than an average well, could be a good thing, relatively. While testing millions of abandoned wells in the U.S. would not be cheap or easy, the idea of capping "just" thousands of them is eminently more achievable than having to deal with all of them.

You can click over to the Proceedings of the National Academy of Sciences to read the full report yourself (PDF).

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