Deadly H2S gas worrying residents and state regulators

Foul-smelling hydrogen sulfide (H2S) has escaped from oil wells near Dover, Okla., in recent weeks, starting in November. State officials say the emissions have been reduced to safe levels, and the companies that operate the wells say they never reached levels high enough to require notifying the public.

That isn’t reassuring to Karen Smilie, who lives across the street from one of the wells.

“They’re not issued a violation. Nobody tells the public,” Smilie said in a phone interview. “Not one person knocked on my door.”

She and her neighbors are especially concerned, she said, because many more wells are planned in the area that is in Kingfisher County, part of what’s called the “STACK” play.

Officials say hydrogen sulfide could become a topic in the coming weeks as oil and gas regulators at the Oklahoma Corporation Commission (OCC) draft new regulations for approval by the state Legislature next year. Agency spokesman Matt Skinner said H2S emissions have usually been in remote rural areas.

“The SCOOP and the STACK involve populated areas,” Skinner said. “We are looking at the H2S rules.”

STACK stands for “Sooner Trend (oil field), Anadarko (basin), Canadian and Kingfisher (counties).” Along with neighbor play the “SCOOP” (South Central Oklahoma Oil Province), it has led the revival of Oklahoma’s oil industry. Both plays reach the western side of the Oklahoma City area.

The Oklahoma Department of Environmental Quality is also investigating complaints about the situation in Dover, according to a spokeswoman.

Smilie and her neighbors are organizing a community meeting in Dover on Monday night to discuss the hydrogen sulfide situation.

The gas can cause “nearly instant death” at levels as low as 1,000 parts per million (ppm) in the air, according to the Occupational Safety and Health Administration.

The well across the road from Smilie’s house registered 900 ppm, according to OCC records. But that is a measure of the H2S flowing up with the fluids inside the wellhead. It’s not a measure of how much H2S was escaping into the air.

Chaparral Energy Inc., which operates the well, said it immediately began treating to reduce the H2S level.

“At no time did the radius of exposure reach the threshold for public notification,” said company spokeswoman Brandi Wessel. There is no OCC notification threshold for Dover, which is not a known H2S area. The threshold for notification in known H2S areas is 300 ppm measured 50 feet from the wellhead.

Chaparral works with regulatory agencies, Wessel said, “to ensure we protect the local communities and environments where we operate.”

Hydrogen sulfide, also called “sour gas,” is a known killer in the oil field. It is often identified by its rotten-egg smell.

It has killed at least seven oil field workers since the beginning of 2013 and in 1975 was responsible for one of the worst oil field accidents in the country. Nine people died in the Denver City, Texas, tragedy, eight of them in a home about 600 feet from the leaking well.

“I basically tell people if they’re living in these areas, they should move,” said Neil Carman, clean air director for the Sierra Club in Texas and a former state inspector. “Hydrogen sulfide is just bad stuff.”

He said there has been concerns for years that the gas could kill children at levels far below what it takes to kill an adult. But there has long been debate about whether frequent exposure to low levels is harmful.

‘It hit me’

The oil and gas industry says such chronic exposure is not dangerous.

“While the smell can be unpleasant, the odor itself is not cause for health concerns,” the American Petroleum Institute (API) states on its website. In a 2010 regulatory filing with other trade groups, API said that chronic health effects are unlikely at levels at or below 5 ppm.

Regulatory agencies, however, say there can be health problems at lower concentrations. OSHA says prolonged exposure to levels as low as 2 to 5 ppm can cause nausea, headaches or loss of sleep. U.S. EPA says lifetime exposure to H2S is unlikely to cause problems as long as the concentration is at or below 0.001 ppm.

The Oklahoma Department of Environmental Quality sets the limit at 0.2 ppm. But oil and gas is generally regulated by OCC, which allows higher amounts.

As the concentration increases, the gas deadens people’s sense of smell, making it hard for them to detect the danger.

Smilie said she was at the hospital in mid-November with her husband, who’d had a heart attack, when a neighbor sent her a message that a yellow flag was flying over the well near her house. She didn’t know what that meant, but the neighbor told her it was a warning for hydrogen sulfide.

A few days later, she woke up with a headache. When she walked downstairs and into her kitchen, she said, “it hit me.” She started seeing double and retching. A neighbor took her to the hospital. Heavier than air, H2S often collects in low-lying areas. After that, she and her husband left and stayed for a week in a recreational vehicle they own on property near Stillwater, Okla.

Her house, she said, is 500 feet or less from the wellhead at the Chaparral site. Oklahoma doesn’t have setback rules for oil and gas wells, so they can be built as close to homes as the drillers want. But a home cannot be built within 150 feet of a well.

Corporation commission records indicate Chaparral installed an H2S alarm system, a vapor recovery system, and scrubbers to treat the gas at the wellhead and water tank. Because it took appropriate measures, OCC officials said, the company didn’t violate any rules.

Another well operated nearby by Gastar Exploration Inc. had similar sour gas levels, according to the OCC records, and was the subject of a complaint. Gastar CEO Russ Porter said in an interview that what neighbors smelled was H2S from the well’s produced water. Company officials hadn’t realized it was in the wastewater and have now begun treating it.

Porter added that there have been oil and gas production operations in the area since at least the 1950s.

But many of Smilie’s neighbors told her and friends they didn’t know the odors were caused by a dangerous gas. They also didn’t know that red and yellow flags flying over the well sites were warnings. On Wednesday night, the smell returned, Smilie said, alarming her and her neighbors.

Hydrogen sulfide emissions have been rising during the oil and gas boom that started in the United States around 2010 (Energywire, Oct. 21, 2014).

In Kansas, state regulators received 15 requests to flare gas containing hydrogen sulfide in 2013, up from three in 2012 and none from 2009 to 2011, state records show. Most of those cases involved the Mississippi Lime field, which also underlies Oklahoma.

Oklahoma regulators calculated that oil and gas operators emitted 594 tons of hydrogen sulfide in 2011 and are planning to do more monitoring of air emissions overall. In New Mexico, which shares patches of the sour-gas-producing Permian Basin with Texas, state officials received reports of five hydrogen sulfide releases in 2013, after receiving none in 2012 and four in 2011.

In Texas, the amount of gas from H2S-containing fields rose 48 percent in the five years before 2015, to 1.7 trillion cubic feet.

Shale fields, where the boom has focused, have been known to have high levels of H2S. Parts of the Eagle Ford field in Texas have a maximum concentration of 68,000 parts per million, according to state data, 130 times the lethal level.

EPA has tried to tighten regulations on hydrogen sulfide, with limited success.

Hydrogen sulfide was on the original list of hazardous substances to be included in the Clean Air Act of 1990, which would have required it to be treated and monitored as an air pollutant. But it was removed before the act became law, after heavy lobbying from industry.

In 2011, EPA reinstated reporting requirements for H2S under the Toxics Release Inventory. But most oil and gas wells are exempt because they are small sources that fall below the reporting thresholds.