An improved understanding of abandoned oil and gas wells as a methane emission source may help bridge the current gap in local, regional, and global methane budgets.
Three million abandoned oil and gas wells in the US appear to be leaking substantial amounts of the powerful greenhouse gas methane into the atmosphere, a study by Princeton University reveals.
"The research indicates that this is a source of methane that should not be ignored", said Michael Celia, Professor of both Environmental Studies and Civil and Environmental Engineering at Princeton, adding "We need to determine how significant it is on a wider basis."
The study, 'Direct measurements of methane emissions from abandoned oil and gas wells in Pennsylvania', estimates that methane emissions from abandoned wells will increase total emissions to double that of the oil and gas industry's current output, concluding:
"These measurements show that methane emissions from abandoned oil and gas wells can be significant. The research required to quantify these emissions nationally should be undertaken so they can be accurately described and included in greenhouse gas emissions inventories."
After studying samples taken from 19 wells in northwestern Pennsylvania, most of them out of production for 50 years or more, the researchers found all of them to be emitting varying levels of methane gas, with 15% of the wells releasing far higher levels than predicted.
There are currently 3 million abandoned wells dotted across the US, with no standard way of 'capping' or sealing them, says Denise Mauzerall, a Princeton professor and a member of the research team:
"This may be a significant source. 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."
With the UK coalition government's hard-line pursuit of shale gas as a viable energy investment, increasing numbers of environmental groups and local communities have expressed deep concern at the effects of hydraulic fracturing on the local environment.
Talking to DeSmogUK, Greenpeace UK's chief scientist Professor Doug Parr expresses similar concerns with fracking in the UK and the fossil fuel industry's track record with environmental impacts, stating:
"The life cycle of many fossil fuels shows that their impacts on communities and people are much greater than from just the carbon dioxide when they are burnt.
"The study shows that even conventionally extracted oil and gas could be having a greater climate impact than anticipated. This particular problem could be fixed - but here fossil fuel producers have run off with their cash and left the public purse to clean up their mess."
"The risk remains that the untried UK fracking industry could exploit political hype to do the same", Parr added.
The 'long tail' of fugitive methane emissions
The researchers have stressed that the study is in its early stages, but have estimated that the effects could be extreme, with abandoned wells leaking harmful gases for decades after being abandoned:
"Methane emissions from abandoned oil and gas wells appear to be a significant source of methane emissions to the atmosphere. An improved understanding of abandoned oil and gas wells as a methane emission source may help bridge the current gap in local, regional, and global methane budgets.
"Additional measurements are required to characterize and determine the distribution of methane flow rates from these wells. Also, lost wells must be identified, located, and recorded to improve estimates of the number of abandoned oil and gas wells.
"The measured wells presented in this paper are likely to be half a century old or older, and the positive flow rates measured at these wells indicate that the methane emissions from these wells may have been occurring for many decades and possibly more than a century.
"Therefore, the cumulative emissions from abandoned wells may be significantly larger than the cumulative leakage associated with oil and gas production, which has a shorter lifetime of operation."
The study also notes: "There is no regulatory requirement to monitor or account for methane emissions from abandoned wells in the United States ... existing monitoring is focused on detecting large concentrations. The result is a lack of information to quantify methane emissions from abandoned oil and gas wells."
The paper: 'Direct measurements of methane emissions from abandoned oil and gas wells in Pennsylvania' by Mary Kang et al.
This article has been edited and extended by The Ecologist with additional quotations from the paper.