Abandoned and unplugged oil and gas wells are likely responsible for less than 1 percent of reported methane emissions from the state’s oil and gas operations, according to new research published by the University of Wyoming’s Enhanced Oil Recovery Institute (EORI).
Sampling conducted at 10 such “orphan” wells in Wyoming’s Powder River Basin showed emission of minute amounts of methane, averaging 651 milligrams per hour. By comparison, the average dairy cow emits 11,900 milligrams per hour.
Based upon that data and other considerations, the researchers calculated that the approximately 1,900 abandoned and unplugged wells in the state emit a total of 3.83 metric tons of methane per year. That’s less than 1 percent of reported methane emissions from all Wyoming oil and gas operations in the most recent National Emissions Inventory conducted by the Environmental Protection Agency.
The UW researchers note that their estimate does not take into account the approximately 18,000 plugged wells in the state.
The issue of methane emissions from orphan wells has gained prominence in recent years, as methane has a much higher global warming potential impact than carbon dioxide. “Fugitive” methane emissions are a byproduct of normal oil and gas production, but wells can emit methane after production ends.
When oil and gas companies retire wells, they typically include proper abatement procedures to prevent further emissions. However, with the boom and bust of the oil and gas industry in the past decade, an increase in bankruptcy filings by companies has resulted in a rise in orphan wells.
EORI’s study, results of which may be found here, was conducted by Jeffrey Nivitanont, Dana Caulton, Shane Murphy and Matt Burkhart, of UW’s Department of Atmospheric Science, along with EORI researchers Eric Robertson and Graeme Finley.
As one of the Centers of Excellence in UW’s School of Energy Resources, EORI facilitates meaningful and measurable increases in recoverable reserves, and production of oil and natural gas in Wyoming that may otherwise not be realized.