More than a million oil and natural gas wells were drilled in this country before anyone really knew how to plug them, according to the Bartlesville (OK) Examiner-Enterprise.

Some have been open holes in the ground since the 1800s. Others are plugged with little more than dirt and logs. For decades, old abandoned wells have leaked oil, natural gas and brine into soil and drinking water, and posed an explosion risk.

Hundreds of thousands of abandoned wells were never properly mapped. Many of the companies that drilled them no longer exist.

Abandoned wells lurk beneath homes and buildings in Ohio; under the busy streets of Los Angeles and the sparse Oklahoma plains; and in parks, backyards, forests, cornfields and cemeteries from Appalachia to the Pacific Ocean, according to the report.

Those old wells pose a new danger as the country rides a petroleum boom driven by hydraulic fracturing techniques that unlock vast new reserves.

Between 2009 and 2014, U.S. annual oil production jumped 62 percent to 3.2 billion barrels. Annual natural gas production grew 26 percent to 27 trillion cubic feet. Together that’s $1.8 trillion of new production, at contemporary prices.

Most drilling is concentrated in Texas, Oklahoma, North Dakota, Colorado, Pennsylvania, Ohio, West Virginia and Louisiana — a list that includes states with large numbers of abandoned wells.

To frack a well, water, sand and chemicals are injected underground with enough force to break rock. When abandoned wells are near the rock layer being fractured, the increased underground pressure can cause the old wells to leak oil and gas.

Potentially toxic fracking fluid also can flow though old wellbores to other underground layers.

But at the same time, new drilling generates money that states can use to find and plug abandoned wells.

In Pennsylvania, the state is turning to citizen volunteers, scientists, drillers and archivists to find hundreds of thousands of abandoned wells.

At least 4 million wells have been drilled since 1859. Of those, a million are still producing oil and natural gas. New wells are drilled each day.

Old abandoned wells often fall short of modern plugging standards, or lack any plugs at all.

The oldest wells have casings made of wood instead of steel. Other old wells had their steel casings pulled from the ground for scrap metal during World War II.

Abandoned wells without proper plugs put the public and the environment at risk, according to the report.

Oil, natural gas and brine seeping from the old wells can pollute groundwater, and flow to the surface to contaminate soil, rivers and lakes. Natural gas leaked from an abandoned well is a potent greenhouse gas, and can collect inside a building and explode.

In 2011, a Groundwater Protection Council study found that abandoned wells caused 41 incidents of groundwater contamination in Ohio between 1983 and 2007, and another 30 in Texas between 1993 and 2008. None of those incidents was related to fracking.

A U.S. Geological Survey study from 1988 found that brine from abandoned wells polluted part of the groundwater supply for 50,000 people in West Point, Kentucky, and nearby Fort Knox.

Each state regulates oil and gas drilling within its borders. So the responsibility of ensuring abandoned wells are identified and plugged resides at the state level. States differ in terms of the number of abandoned wells and the resources to plug them.

Companies that own wells are responsible for plugging them, but bankruptcies and the passage of decades can make ownership difficult to determine.

Abandoned wells without identifiable owners are called “orphan wells.” States first started plugging orphan wells in the 1960s. In the 1970s, passage of the federal Safe Drinking Water Act strengthened state rules on plugging to better protect groundwater.

According to the Interstate Oil and Gas Compact Commission, at least half of the states have some sort of plugging program today, usually within the agency that regulates oil and gas drilling.

Source: Bartlesville (OK) Examiner-Enterprise