John Stolz, prof environmental microbiology, Duquesne U, Pittsburgh (currently studying a “frack-out” in Freeport):
“The industry refuses to admit this stuff happens,” he said. “The reality is it happens on a somewhat regular basis.”
A geospatial analysis of water-quality threats from orphan wells in principal and secondary aquifers of the United States by Joshua Woda, Karl B. Haase, Nicholas J. Gianoutsos, Kalle Jahn, and Kristina Gutchess, Volume 976, 10 May 2025, 179246, Science of The Total Environment
https://doi.org/10.1016/j.scitotenv.2025.179246Get rights and content
Highlights
- Orphan wells can pose threats to water quality in the nation’s aquifer systems.
- Contaminants can migrate from deeper geologic formations to freshwater aquifers.
- Some aquifers contain many orphan wells, multiple well integrity threats, and high withdrawals.
- We identify susceptible aquifers using common factors.
- 54 % of studied orphan wells are within aquifers supplying 94 % of the nation’s groundwater use.
Abstract
Throughout the history of oil and gas production in the United States, millions of wells have been drilled for exploration and energy production. Hundreds of thousands of unplugged wells are no longer actively producing and are currently under orphan status, with no responsible party obligated for plugging. Orphan wells can pose threats to water resources by providing pathways for contaminants such as hydrocarbons and brines to migrate into water-supply aquifers. In this study, we investigate the potential threats to groundwater resources posed by orphan wells at the national scale. Water-quality data are sparse in relation to orphan wells nationally and may not be suitable for identifying contamination from oil and gas development. We used geospatial and statistical methods to evaluate which principal and secondary aquifer systems may be most susceptible to contamination from orphan wells. Analysis involved three sets of susceptibility factors including: 1) factors related to the number and density of orphan wells; 2) factors that can threaten well integrity and contribute to transport of contaminants; and 3) factors related to groundwater withdrawal rates and the affected populations/communities in the event of water quality disturbances.
From a dataset of 117,672 documented orphan wells, 64,203 are located within a principal aquifer system, while the remainder fall within a secondary aquifer system.
By assessing the combination of well integrity and hydrogeologic factors within these aquifer systems, five groupings of principal aquifers were identified, where groups ranged from aquifer systems with high numbers of orphan wells, multiple well integrity threats and high withdrawals, to aquifers with a relatively low number of orphan wells, limited well integrity threats and minimal water use. Three regions of the country emerge containing aquifers with higher susceptibility to contamination from orphan oil and gas wells. These regions include 1) The Appalachian Basin (including the Pennsylvanian Aquifer system), 2) The Gulf Coast Aquifers (including the Coastal Lowlands Aquifer system) and 3) The California Aquifers (including the California Coastal Basin Aquifer system). This work is the first multivariate geospatial investigation of orphan wells and groundwater resources on a national scale and identifies which aquifers are most susceptible to groundwater contamination from orphan wells.
Graphical abstract
…
5. Conclusion
Oil and gas wells pose an array of contamination possibilities ranging from oil and gas migration to providing a connection of deeper brine rich aquifers to shallow freshwater aquifers. Although the threats OW pose are similar in many ways to other types of oil and gas wells, OW pose a unique concern to water quality due to the large number of unknowns surrounding these wells, particularly related to construction, well integrity, and spatial distribution. Over 64,000 OW currently are known to intersect a principal aquifer system, the aquifers where >90 % of the nation’s groundwater withdrawals occur, while most of the remaining roughly 55,500 OW occur within secondary aquifer systems. The overarching goal of this study was to evaluate which aquifer systems may be most susceptible to contamination from OW. Relevant groundwater quality factors were explored in the context of OW and the primary/secondary aquifers to understand the relations between OW and aquifer characteristics.
This work highlights aquifer systems where leaking OW have higher likelihood of potential movement of contaminants, and where further studies might find additional connections between OW and groundwater quality. Several regions were identified to have primary and secondary aquifers with a confluence of factors present: (1) the Appalachian Basin, where aquifers contained both the largest number and some of the oldest wells in the nation, combined with corrosive waters and an abundance of wells that overlie known coal formations; (2) the Gulf Coast aquifers, with a high percentage of OW located within land use types susceptible to contamination for OW, including wetlands, open water, and a moderate to high proportion of OW located within a census block identified as socio-economically disadvantaged; and (3) the California Coastal aquifers and Central Valley, characterized by a high density of old OW within heavily urbanized and agricultural aquifer areas with high groundwater withdrawal rates.
Finally, OW are only one aspect of understanding how historical drilling activity influences environmental concerns associated with oil and gas production and water quality. For example, leaking unplugged idle and abandoned wells, leaking plugged and abandoned wells, surface spills, and other releases from production activities could also be present.
The United States contains as many as five million active, marginal, and abandoned wells (including OW) in various geographic settings (U.S. Environmental Protection Agency, 2022). The factors examined in this study and many additional factors may be relevant to the nexus of water resources and oil and gas wells of all types.
Scientists Map Where Orphan Wells Pose Threats to Aquifers, A new study from the U.S. Geological Survey finds that groundwater in Appalachia, the Gulf Coast and California is susceptible to contamination from orphaned oil and gas wells by Martha Pskowski, May 4, 2025, Inside Climate News
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For the first time, scientists have mapped groundwater variables nationally to understand which aquifers are most vulnerable to contamination from orphan wells.
Just 100 years or more too late. Mapping after the harms are done doesn’t benefit the harmed, it just benefits industry
Oil and gas wells with no active owner that are no longer producing and have not been plugged are considered orphan wells. These unplugged wells can create pathways for contaminants like hydrocarbons and brine to migrate from the oil and gas formation into groundwater zones. Plugging a well seals off these potential pathways.Except, those plugs and seals, do not last long, and studies have shown that newer wells leak worse than older ones
USGS scientists Joshua Woda, Karl Haase, Nicholas Gianoutsos, Kalle Jahn and Kristina Gutchess published a geospatial analysis of water-quality threats from orphan wells this month in the journal Science of the Total Environment.
They found that factors including large concentrations of orphaned wells and the advanced age of wells make aquifers in Appalachia, the Gulf Coast and California susceptible to contamination.
Using a USGS dataset of 117,672 documented orphan wells nationwide, the researchers found that 54 percent of the wells are within aquifers that supply 94 percent of groundwater used nationally.
“No matter where you live across the nation, you can go look at what’s happening in your backyard, how your aquifers compare to other aquifers and what the threats are,” said Gianoutsos.
Orphan Wells Pockmark Major U.S. Aquifers
The researchers mapped the locations of orphaned wells over principal and secondary aquifers using Geographic Information Systems datasets. They then analyzed the aquifers based on factors that could contribute to vulnerability to groundwater contamination, such as the average age of the orphan wells.
Older wells were subject to less regulation and are more prone to failure.Studies have shown that newer wells leak worse than older ones! The authors found that Pennsylvanian aquifers, which span several Appalachian states including Pennsylvania, present the “maximum confluence” of risk factors. The first oil wells in the country were drilled in Pennsylvania. Orphan wells can be over 100 years old and located near coal seams and residential water wells.
The Gulf Coast aquifers, including the Coastal Lowlands aquifer system, which stretches from Texas to the Florida Panhandle, were found to be susceptible in part because wells are located in areas like wetlands and open water that are more prone to contamination.
The analysis also considered the rates of pumping from each aquifer. That led them to the California Coastal aquifers and the Central Valley, where a high density of old orphan wells overlaps with highly urbanized areas and intensive groundwater use for agriculture.
The researchers found that the Ada-Vamoosa aquifer, in central Oklahoma, has the highest concentration of orphan wells per square mile of any principal aquifer in the country.
The authors note the paper is not an analysis of the amount of groundwater contamination from orphan wells or the number of leaking orphan wells. But they suggest that policymakers and researchers could use it as a basis to target aquifers for additional investigation.
“This could be a good starting point if someone wanted to do a local investigation,” said Woda.
Gianoutsos noted that the active list of orphan wells is changing as research into orphan wells and well plugging advances. He said some 40,000 orphan wells have been added to the national list since their dataset was created. Another approximately 10,000 orphan wells have been plugged in that time.
“The threats are still there,” he said. “Just as we discover more wells, we discover additional threats.”
The research was part of the U.S. Department of the Interior Orphaned Wells Program Office through the Bipartisan Infrastructure Law.
Parts of Pennsylvania Look like “Swiss Cheese” From Drilling
Orphan wells have been linked to groundwater contamination in states including Pennsylvania, Ohio and Texas. A 2011 Ground Water Protection Council study found that orphan wells caused 41 groundwater contamination incidents in Ohio between 1983 and 2007. The study found orphan wells and sites caused 30 groundwater contamination incidents in Texas between 1993 and 2008.
The Pennsylvania Department of Environmental Protection (DEP) has reported several recent cases of orphan wells contaminating groundwater. An orphan well in Vowinckel in Clarion County contaminated a family’s drinking water before it was plugged last year, according to the DEP. Another orphan well in Shinglehouse, in Potter County, was plugged by DEP in 2024 with emergency funds after a homeowner reported contamination of their water well.
John Stolz, a professor of environmental microbiology at Duquesne University in Pittsburgh, has researched how fluids from oil and gas wells can migrate underground with unintended consequences.
Stolz said some of the wells in Pennsylvania are so old they were cased with wood or metal, unlike the cement that has been standard for decades. He said the wooden casings have often deteriorated completely. He said conventional drilling and more recent fracking have left much of Pennsylvania “looking like Swiss cheese.”
“It’s good to see a study that focuses on the water resources,” he said in response to the USGS study.
“We are going to have greater periods of drought, and these water resources are going to become far more valuable.”
Stolz is studying a “frack-out” in the town of New Freeport in southwestern Pennsylvania. An unconventional well being fracked communicated with an orphan well over 3,000 feet away, forcing fluids to the surface. Residents of the town resorted to drinking bottled water, according to NBC News.
“The industry refuses to admit this stuff happens,” he said. “The reality is it happens on a somewhat regular basis.”
Refer also to:
2024:
2017:
Note the red dotted line in Alberta Health’s graph above
2006:
Later testing by Alberta Environment found 110 mg/l of methane in Debbie Signer’s water
1996:
