MANSFIELD -- The unexpected venting of natural gas at a Carrizo Oil & Gas well site Friday morning, which briefly put two schools on alert, shows the need for gas inspection and training programs, Arlington Fire Chief Don Crowson said.
"What this incident shows today is this: Things do happen at well sites," Crowson said.
Arlington and Mansfield firefighters were called to the site, 1751 E. Debbie Lane, near Matlock Road just before 8 a.m. after residents called 911 to report "smoggy mist" and noise. Students were kept indoors at James Coble Middle School and Brockett Elementary for about 45 minutes during the release, which created a loud hissing and sent a white vapor cloud through surrounding neighborhoods.
No injuries were reported, and firefighters did not detect natural gas in neighborhoods or near the schools downwind.
Carrizo and fire officials say they believe corrosive sand in the pipeline of a newly producing well caused a small rupture in a valve and allowed water and natural gas to vent at high pressure for about 20 minutes before the system automatically shut down.
Crowson said that the primary and secondary automatic safety valves failed after the rupture but that a third valve eventually shut off the gas flow.
For Crowson, the incident illustrates why he pushed the Arlington City Council to impose a gas well fee that will pay for an inspection and training program designed to help the Fire Department better understand energy industry operations and prevent and respond to natural gas well emergencies.
"We want to build a system that equips our team with advanced, pre-planned knowledge of a well site and information about potential exposure risks around a well site," he said. "If we did have a worse type of emergency, like a fire, our goal is to be prepared for those types of things and maintain neighborhood integrity and keep the incident as isolated as possible."
Arlington has more than 300 gas wells and is called to assist at wells along the borders with neighboring cities, such as Mansfield.
'Choke valves ... fail'
The first firefighters arrived about six minutes after the first 911 call, Crowson said. It took about 30 minutes for a Carrizo representative to arrive after being contacted by firefighters, officials said.
By then, the automated shutoff system had kicked in and "there was no imminent danger," according to a Carrizo report.
"This kind of stuff happens. You will have choke valves that will fail," said Rusty Ward, Carrizo's vice president of regulatory affairs. "There are so many redundant safety devices on these well sites. If one thing doesn't shut it down, something else will."
School officials kept children indoors for about 45 minutes and turned off air intake vents at Coble and Brockett as a precaution, officials said.
"At Brockett there was some odor in the air, but our students were not in any danger," Principal Chuck Roe said in an e-mail to parents.
Richie Escovedo, a spokesman for the Mansfield school district, said: "Our district police took swift action to make sure, out of an abundance of precaution, that the campus was put on red alert. They didn't feel anybody was in danger. They just wanted to make sure they were following safety procedures."
The City Council this month approved Crowson's proposed preparedness and response plan, the first of its kind in the Barnett Shale.
This year, the city will begin charging drillers in Arlington $2,397 annually per gas well.
That fee will generate an estimated $781,450 a year for additional firefighters, industry-specific training and equipment. Arlington plans to create a new fire captain position to oversee the program as well as a new gas well inspector position and six additional firefighter positions. The city will also begin sending 42 other firefighters for training in Houston this summer, Crowson said.
'Never any danger'
By Friday afternoon, the damaged section of pipe had been repaired and the well was returned to production, according to a Carrizo report. An estimated 3,400 cubic feet of natural gas and about two barrels of water were vented. The well produces about 6 million cubic feet of natural gas a day, Ward said.
The steam reaching the residential contained no natural gas, and any odor reported could have been sulfur that is added to natural gas so it can be detected, Ward said.
"That small amount of gas was completely on top of the atmosphere by the time you got to the wall of the drill site. There was never any danger to a kid or residents," Ward said.
No other gas release has been reported at the site, which has multiple wells.
Susan Schrock, 817-709-7578