HARRISBURG - Natural gas and polluted wastewater blasted out of a well in Northwestern Pennsylvania for 16 hours before being contained Friday in what officials say was the state's most alarming drilling-related accident in recent years.
No injuries were reported and no fire broke out, a grave risk with large amounts of airborne natural gas.
The well ruptured at 8 p.m. Thursday, sending a gas plume 75 feet into the air and wastewater cascading into the ground just as the gas contractor was preparing to begin production at the well, the officials said.
The accident happened as EOG Resources Inc. of Houston was preparing to start production at a deep well in the Marcellus Shale, the rich gas reserve underlying most of the state. The site is on private land at the edge of the Moshannon State Forest. The nearest house is more than a mile away.
State officials said they were still trying to determine exactly what happened, but said unexpectedly high gas pressure caused drilling crews to lose control of the well. They also said a safety device known as a blowout preventer had failed.
Workers at the site were evacuated, and contaminated wastewater, a by-product of the hydraulic fracturing, or fracking, process used to extract underground gas, was eventually contained, according to Department of Environment Protection officials.
"When we arrived . . . natural gas and 'frack' fluid was flowing off the well pad and heading toward tributaries to Little Laurel Run, and gas was shooting into the sky, creating a significant fire hazard," said DEP Secretary John Hanger, who promised an aggressive investigation.
The risk of fire prompted state officials to close roads and cut off electrical service to the area. State emergency officials were alerted and hazmat teams scrambled. The Federal Aviation Administration restricted airspace over the area for two hours.
Crews halted the leak at noon Friday, EOG officials said.
EOG spokeswoman Elizabeth Ivers said the company was conducting an internal investigation. "Public safety and protection of the environment continue to be of utmost importance to our company," an EOG statement said.
EOG, one of the largest gas contractors in Pennsylvania, has leased 230,000 acres and has drilled 43 wells in the Marcellus Shale.
DEP officials said that when their investigation is complete, they may consider fining the company or suspending or revoking its drilling permit.
"The event at the well site could have been a catastrophic incident that endangered life and property," Hanger said. "This was not a minor accident, but a serious incident that will be fully investigated by this agency with the appropriate and necessary actions taken quickly."
Gas wells are equipped with blowout preventers, a series of valves to control unexpected surges in pressure during drilling. The failure of a blowout preventer was one of the causes of the oil spill in the Gulf of Mexico.
"There was a blowout preventer" at the Pennsylvania site, DEP spokesman Neil Weaver said Friday night in an e-mail. "It failed. The reason for the failure is going to be part of the investigation."
News of the accident comes at a time of heightened interest in the historic "gas rush" that Pennsylvania and other Marcellus Shale states are experiencing, thanks to new technology in tapping gas reserves. Environmentalists and some legislators said the accident evidenced the need for tougher regulations on deep-well drilling.
"Drilling in the shale is a whole different animal from shallow-well drilling," said Jan Jarrett, president of the environment group PennFuture. "Things can go wrong."
The accident-site location gave rise to concerns about fouling waterways. The well is near the headwaters of the west branch of the Susquehanna River, and any discharge could flow east into the Susquehanna or west into the Ohio River.
Jarrett, whose group wants a moratorium on further leasing of state lands to drillers, said deep gas wells are under higher pressure then traditional shallow gas wells and use enormous amounts of water in the drilling process. "We are so early on with [Marcellus] Shale drilling, and already we're seeing all kinds of problems with wastewater and methane gas leaks," she said.
Central to deep-gas drilling is the hydraulic fracturing process, in which millions of gallons of water are blasted into rock formations to release the gas. Pollution issues arise from the wastewater that must be treated before it can be released into waterways.
There is debate about what toxins, if any, wastewater from fracking contains. Environmentalists say toxins such as arsenic, along with methane gas, oil, and metals may be released. Industry officials say they use a process to contain and dilute any potentially hazardous chemicals used in the drilling, and that any other contaminants, such as methane, occur naturally.
State regulators are in the process of approving tougher standards for gas drilling, including improved well-construction requirements, that could go into effect as early as this summer. Also, on Tuesday, a state Senate committee is to take up proposed drilling regulations, including wastewater-treatment standards.
State Rep. Camille "Bud" George, in whose Clearfield County district the accident happened, said it helped make the case for why the state needs a tax on gas extraction from deep wells - something Gov. Rendell wants as part of his proposed state budget.
"Giving the gas industry a free ride at the expense of Pennsylvania taxpayers, water resources, roads, and economy is a poor deal for everyone but the gas industry," said George, a Democrat.
Senate Republican leaders, who control the higher chamber and who last year felt it would be harmful to tax a burgeoning industry, said Thursday that they were willing to discuss a gas tax as part of the budget process.
Contact staff writer Amy Worden at 717-787-2584 or firstname.lastname@example.org.
Inquirer staff writers Andrew Maykuth and Angela Couloumbis contributed to this article.