Pennsylvania is sitting on what many experts describe as one of the largest abandoned oil and gas well problems in the United States, and the full scale of it still is not completely understood.

State officials and researchers estimate Pennsylvania may contain anywhere from 300,000 to 700,000 abandoned or orphaned oil and gas wells, most of them concentrated in the western portion of the state. Many were drilled decades ago, long before modern environmental regulations existed. Some date back to the earliest days of America’s oil boom in the late 1800s.

The challenge is not just the number of wells. It is the fact that many of them were never properly documented in the first place.

While Pennsylvania officially has records for roughly 30,000 orphan wells, experts believe hundreds of thousands more may exist underground without clear locations or ownership records. In many cases, companies that originally drilled the wells no longer exist, leaving taxpayers and state agencies responsible for cleanup.

That uncertainty has turned abandoned wells into both an environmental and public safety concern.

Many of the wells leak methane, a greenhouse gas significantly more potent than carbon dioxide in the short term. Others can release contaminants into groundwater, soil, and nearby air. Heavy metals, brine, and other chemicals tied to historical oil and gas production can migrate through damaged or aging well structures over time.

The location of many of these wells only adds to the concern.

According to researchers and state data, roughly 93% of Pennsylvania’s orphaned and abandoned wells are located within 3,280 feet of buildings. Some sit near homes, schools, farms, parks, and waterways. Others remain hidden in forests or buried beneath overgrown land where nobody realizes they exist until a problem emerges.

In some cases, wells have reportedly leaked gas into basements or created risks during construction and land development projects.

The problem is especially severe in western Pennsylvania, where generations of drilling activity supported some of the earliest oil and natural gas development in the country. Thousands of wells were drilled during periods when recordkeeping standards were minimal or nonexistent.

As a result, locating abandoned wells has become one of the biggest challenges facing cleanup efforts today.

Billions in Cleanup, But Decades of Work Ahead

Pennsylvania is now receiving more than $400 million in federal funding through the Bipartisan Infrastructure Law to accelerate plugging operations and reduce environmental risks tied to orphan wells.

The Pennsylvania Department of Environmental Protection, or DEP, has been actively working to identify and plug wells across the state. The agency has also partnered with researchers and contractors to improve detection efforts for undocumented wells.

New technologies are beginning to play a major role in that process.

Drone surveys, remote sensing systems, aerial methane monitoring, and historical mapping techniques are all being used to help locate hidden wells, particularly in heavily wooded areas of northwestern Pennsylvania where old drilling sites may no longer be visible from the ground.

Still, the reality of the cleanup effort remains daunting.

Properly plugging a well is expensive and technically difficult, especially when dealing with aging infrastructure or incomplete records. Plugging operations typically involve filling wells with cement to prevent methane migration and fluid leakage. Some wells are unstable or collapsed, making remediation even more complicated.

Despite the increase in funding, progress remains slow compared to the estimated scale of the problem.

According to state reporting, the DEP plugged just 308 wells over a recent two-and-a-half-year period. At that pace, experts warn it could take decades to significantly reduce the state’s orphan well inventory, particularly if estimates closer to 700,000 wells prove accurate.

Courtesy / Office of Pa. Gov. Josh Shapiro

The issue also continues growing.

Environmental groups and policymakers have raised concerns that low financial bonding requirements for oil and gas operators may allow additional wells to become orphaned in the future. In some cases, companies abandon aging wells after production declines, leaving cleanup responsibilities behind when operators go bankrupt or dissolve.

That long-term liability is becoming a larger focus nationwide as states attempt to balance energy production, environmental protection, and public safety.

Beyond methane emissions, orphan wells have increasingly become part of broader climate discussions. Federal agencies and environmental researchers view plugging programs as one potential method for reducing greenhouse gas emissions while also protecting local communities and water resources.

For Pennsylvania, however, the issue is deeply tied to the state’s industrial history.

The same oil and gas development that helped shape portions of the state’s economy also left behind a sprawling network of aging infrastructure underground. Some wells remain relatively harmless. Others continue leaking decades after they stopped producing.

The challenge now is identifying where those wells are, determining which pose the greatest risks, and finding enough funding and manpower to address them.

Even with new federal investment and advancing detection technology, Pennsylvania’s orphan well problem is increasingly being viewed not as a short-term cleanup project, but as a long-term environmental management challenge that could stretch across generations.