The Pressure Zone

Written by, | Feb 26, 2013 1:23 PM

Photo by Scott Detrow

TIOGA ENFLAMED - Shell flares off natural gas in an effort to stop a methane migration problem in Tioga County.

This article was adapted from a StateImpact Pennsylvania investigative effort called “Perilous Pathways.”

Since 1859, some 300,000 oil and gas wells have been drilled in Pennsylvania. An unknown number of them remain — hidden holes in the ground — and serve as potential pathways for gas to make its way to the surface while tapping the Marcellus Shale formation.

In February 1932, the United States was in the midst of the Great Depression. Franklin Roosevelt was planning a run for the White House. And in Union Twp., Tioga County, the Morris Run Coal company had just finished drilling a gas well on a farm owned by W.J. Butters. The Butters well was 5,385 feet deep and lined with four layers of metal casing.

Eighty years and four months later, the Butters well was tied to a major news event, even though it had been inactive for generations. It played a key role in a methane gas leak that led to a 30-foot geyser of gas and water that sprayed out of the ground for more than a week.

The geyser wasn't the only way the methane leak manifested itself. At the Ralston Hunting Club, a water well inside a cabin overflowed and flooded the building. Methane bubbled out from a nearby creek, as well. Royal Dutch Shell asked a handful of nearby landowners to temporarily evacuate their homes while the company worked with well control specialists, a fire department and state environmental regulators to bring the leak under control.


WEAK LINK - A geyser of methane and gas sprays out of the ground near a Shell drilling site in Tioga County. StateImpact Pennsylvania obtained this photo from a landowner that lives nearby.

The gas didn't come from the Butters well, nor did it originate from the Marcellus Shale formation that a nearby Shell well had recently tapped into. What most likely happened to cause the geyser, Shell and state regulators say, was something of a chain reaction. As Shell workers were drilling and then hydraulically fracturing its nearby well, the activity displaced shallow pockets of natural gas. The gas disturbed by Shell's drilling moved underground until it found its way to the Butters well, and then shot to the surface.

Companies have been extracting oil and gas from Pennsylvania's subsurface since 1859, when Edwin Drake drilled the world's first commercial oil well. During that 150-year span, as many as 300,000 wells have been drilled with an unknown number of them being left behind as hidden holes in the ground. Nobody knows how many because most of those wells were drilled long before Pennsylvania required permits, record-keeping or any kind of regulation.

It's rare for a modern drilling operation to intersect -- the technical term is "communicate" -- with an abandoned well. But incidents like Shell's Tioga County geyser are a reminder of the dangers these many unplotted holes in the ground can cause when Marcellus or Utica shale wells are drilled nearby. And while state regulators are considering requiring energy companies to survey abandoned wells within a 1,000- foot radius of new drilling operations, the location of nearby wells is currently missing from the permitting process.

Fred Baldassare worked at Pennsylvania's Department of Environmental Protection for 25 years. He spent more than half his career investigating more than 200 cases of methane migration. Only a handful of them involved an active drilling site communicating with an abandoned oil or gas well. But when the new and old operations did intersect, Baldassare said, the results were often "dramatic."

When energy companies drill down to the Marcellus Shale, their wells pass through several smaller, shallow gas formations. Drillers go to great lengths to seal off their gas wells, and Pennsylvania regulations require companies to bond their multiple layers of steel casing with topgrade cement. Shell's Guindon well, located a few thousand feet from the old Butters well, was lined with more than 1,200 sacks of cement, along with four layers of casing.

Most of the time, this buffer prevents the shallow gas from moving to the surface. But if an old, unplugged gas well has been drilled into the same formation already, the new activity can displace pockets of gas through pressure changes and physical interaction.

"Gas always wants to go from high pressure to low pressure," Baldassare continued. "That old well represents a low pressure zone. Much like water wants to move downhill, gas wants to move to low pressure zones." The lowest pressure is near the surface, so once the gas reaches an old well, it will shoot straight up.

Depending on how old the abandoned well is, the casing can be leaky, rotted or nonexistent. Methane can easily move into natural faults and cracks, following a path toward the surface that can travel through aquifers. That's likely how gas ended up bubbling into a creek, out of a water well and up into the 30-foot geyser in Union Twp.

The damage caused by Shell's methane leak was relatively minimal largely because the gas bubbled to the surface in a sparsely populated rural area. That wasn't the case in 2008 in Dayton, Armstrong County, when a gas leak led to the evacuation of an elementary school and two houses.

Then, an active vertical gas rig -- not a shale operation -- hit a pocket of gas linked to an undocumented abandoned well. The displaced gas shot straight through 90 feet of gravel, dirt and other fill material, pushing the material to the surface when it spewed out of the ground.

Department of Environmental Protection officials worked with the gas operator to vent off nearby wells in order to lower underground gas pressure. They also installed vents on the homes to keep methane from gathering in a concentrated place. The efforts brought the well under control.

The way to ensure an abandoned well does not create a gas leak is to make sure the well is plugged. When wells are cemented shut, they are less likely to create a methane pathway to the surface.

In Union Twp., Shell officials knew about the old Butters well before it began drilling nearby. "As part of our well location screening process, we did map that abandoned well, which we understood had been properly plugged and abandoned," Shell spokeswoman Kelly op de Weegh said. "It was determined, due to that, that the old well would not pose any additional risk."

Like most of StateImpact Pennsylvania’s reporting, the project had multimedia components. Reporter Scott Detrow laid out the details of Shell’s Tioga County gas spill and examined how many abandoned wells dot Pennsylvania, how investigators track these wells and why Pennsylvania’s permitting process doesn’t require drillers to avoid them. In addition to publishing four articles, StateImpact Pennsylvania developed a map plotting all known abandoned wells and aired multiple broadcast reports on witf 89.5 and 93.3 FM as well as on National Public Radio’s national network. That’s the type of online and on-air investigative reporting that earned StateImpact Pennsylvania a prestigious duPont-Columbia Silver Baton. The collaboration among witf, WHYY and NPR was honored for “[showing] the significant impact of natural gas drilling on Pennsylvania residents, and [providing] an important model for reporting on local issues.” The duPont-Columbia Award is considered the broadcast equivalent of the Pulitzer Prize, which Columbia University also administers. The StateImpact Pennsylvania website is dedicated to explaining the environmental and economic impact of the state’s booming energy industry. It’s updated multiple times a day, and hosts extensive multimedia features that break down the complicated details of hydraulic fracturing and other complicated energy issues. StateImpact Pennsylvania’s reports also can be heard on Morning Edition, All Things Considered and Radio Smart Talk.
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