Scientists from the U.S. Geological Survey recently released research showing where groundwater is most at risk of contamination by orphan oil and gas wells.
Appalachia – including parts of eastern Ohio – is high on the list.
“There’s been a long history of oil and gas drilling in the Appalachian Basin, and especially in parts of Ohio,” said Josh Woda, a hydrologist with the USGS New York Water Science Center and one of the study’s authors.
Orphan wells are no longer used to produce oil and gas, and they don’t have an identifiable owner, so the responsibility to take care of them often falls to the state or federal governments. There are more than 20,000 of these wells in Ohio, according to a USGS database.
“But these are just the documented orphan wells,” Woda said. “So there may be more where we actually don’t know where the locations are.”
In Ohio, many orphan wells were drilled a long time ago, when there were fewer regulations in place to protect aquifers.
Woda said both the high number and age of wells in the area make it more likely for them to contaminate groundwater.
How can orphan wells contaminate groundwater?
Orphan wells provide a pathway for contaminants deep underground to get into shallower aquifers.
“So you can imagine if an orphan well was drilled through an underground coal mine that's since collapsed, there might be some concerns there,” Woda said.
The study found that about half of the country’s documented orphan wells are in aquifers that supply over 90% of the water we consume.
“And a fair portion of that consumptive use is from privately owned wells,” said Karl Haase, a research chemist with the USGS and another author of the study. “That means that there is one house or one farm that is drawing from this well. [The water] is not being treated. The aquifer is the treatment system, so if an orphan well leaks into this aquifer that a homeowner is using, that can directly impact them.”
What aquifers are most at risk nationally?
Other areas where aquifers are more susceptible to contamination from orphan wells include the Gulf Coast.
“A lot of orphan wells there were within wetlands or open water, which is an interesting aspect,” Woda said.
He said the California aquifers also stood out because there are orphan wells in areas with intense groundwater withdrawals.
The study doesn’t provide recommendations on how to prevent groundwater contamination, but Haase says it could be used as a launching point for additional research.
“We feel like it helps provide a framework to expand thinking and build on local data that [stakeholders] have about orphan wells,” he said. “It also helps them see where their risks are relative to other parts of the United States. One of the things we wanted to do was provide a national assessment to put everybody on the same scale, so that maybe one municipality could draw on knowledge from another group that may have already been addressing the problem.”
