Thousands of sites hidden underground could be silently poisoning our atmosphere

From John D. Rockefeller to the Beverly Hillbillies, Americans have been drilling oil for over a century. All that drilling has left millions of abandoned wells pockmarking the land across the country.

Wells of course contribute to climate change when we extract the oil and burn it for fuel, but they can have an unsettling impact after they've stopped producing, too.

In fact, scientists think oil wells that have been abandoned may be a major source of methane emissions, silently poisoning our atmosphere long after they've been forgotten.

Methane is classified as a greenhouse gas because it is contributing to global warming. It actually has more potent effects than carbon dioxide does in the short term because it warms much faster in the first few decades it's released into the atmosphere. And without special tools, you can't even tell it's there: It's odorless and invisible to the naked eye.

When researchers estimate how much methane gas is polluting the planet, they calculate it two ways. In top-down analyses, they look at the total emissions coming from a particular area. Bottom-up studies measure emissions from specific sources.

But the top-down estimate always seems to be higher than the bottom-up one. That means there has to be a major source missing from the calculation.

Abandoned wells could be the source of this gap. Around 3 million abandoned oil and gas wells across the US could potentially be leaking methane into the atmosphere.

Just in Pennsylvania, a 2014 study found, abandoned wells could account for 4-7% of the total man-made methane emissions in the state.

What's more, these major sources of pollution are often totally invisible.

Briana Mordick, a senior scientist with the Natural Resources Defense Council, told Tech Insider that depending on how a company abandons a well, you may not be able to tell it was there at all.

If they cut the top off and bury it, for instance, it could be leaking to the air or underground without anyone knowing. Abandoned wells not only have the potential to poison our atmosphere; they could contaminate drinking water, too.

"Often the state may not even know where all these wells are if the records have been lost over time," she said. "You could have a well leaking, but no one knows that it's there."

The best way to plug up a well is with steel casing and cement. There is no federal standard for what companies should do with a well once they're done drilling, though, so they follow a patchwork of state laws instead.

But many of these state laws were enacted in the last few decades, meaning many wells probably didn't have to follow any standards before then. Mordick said she's even seen wells plugged with tree trunks because the steel was removed when the country needed it during World War II.

In Texas these days, most companies plug their own wells, media relations officer Ramona Nye from the state's Railroad Commission told Tech Insider in an email. If the company can't pay for it, the state plugs the well using fees collected from the oil and gas industry.

A similar program exists in Pennsylvania, but it's only scratching the surface. It doesn't come close to addressing all the retired wells that could be out there, most of which have simply been lost to history.

"Since the inception of the program, approximately 3,000 of the 12,000 identified orphan or abandoned wells have been plugged," Pennsylvania's Department of Environmental Protection program manager Seth Pelepko said in an emailed statement. "Historical drilling estimates for the state suggest that there may be upwards of 200,000 abandoned wells that are not presently accounted for."

It's these missing abandoned wells that could really be causing a problem, because we don't even know where they are. If we can find them, we can plug them properly.

The AP reported that many of the state agencies tasked with finding and plugging these wells are under-funded, partly due to the worst oil bust in decades the industry is experiencing now.

"You could be talking about thousands or tens of thousands of wells that no longer have an owner of record that are now the state's responsibility to deal with, but they most likely don't have adequate resources to actually deal with those," Mordick said. "Then we have a potentially enormous environmental problem on our hands."