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Gas leaks: America’s leaky wells

There are an estimated three million abandoned oil and gas wells across the US There are an estimated three million abandoned oil and gas wells across the US Richard Thornton/Shutterstock
04 Jan
Abandoned oil and gas wells in the US are leaking significant quantities of methane

The US Department of the Interior recently announced a new Methane and Waste Prevention Rule, part of the Obama administration’s Climate Action Plan. This new legislation, ‘which will be phased in over time’, updates existing 30-year-old regulations on venting, flaring and leaks from operational oil and gas wells. It is hoped this will eliminate up to 180,000 tons of methane emissions per year, roughly equivalent to 4.5 million metric tons of carbon dioxide.

However, even after an oil or gas well has ceased drilling, it can still leak vast quantities of methane, which has a global warming potential up to 86 times greater than carbon dioxide over a 20-year period. Studies in western Pennsylvania – a hotspot for drilling in the US – found that gas escaping from abandoned wells (which are unaccounted for on national inventories) made up between five to eight per cent of the state’s total methane emissions. The number of such leaky wells in Pennsylvania is estimated to be between 470,000 and 750,000, with over three million to be found across the entire US. There are also likely to be many more that are undocumented, raising the total number even further.

Our goal was to identify well characteristics that would help identify high emitters, and avoid the cost of plugging abandoned wells with low or no emissions

Crucially, some abandoned wells are considerably more leaky than others, with roughly ten per cent of abandoned US wells believed to be responsible for 90 per cent of the methane produced by them all. Recent work by researchers from Princeton, Stanford, Ohio State and the Lawrence Berkeley National Laboratory found the main causes of leaks to be that they were either left unplugged (because of the vast costs involved in plugging abandoned wells), or they were plugged but still being allowed to vent (venting of plugged wells is required in coal areas).

‘Our goal in this work was to identify well characteristics that would help identify high emitters, and thus provide an opportunity to target them for mitigation and avoid the cost of plugging abandoned wells with low or no emissions,’ says Denise Mauzerall, Professor of Environmental Engineering and International Affairs at Princeton. ‘We hope this approach can be used across the United States and abroad to identify high emitters and target them for remediation.’

This was published in the January 2017 edition of Geographical magazine.

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