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.
…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 (latent) 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 (30 min spewing per TCEQ report #166368) 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.
…..’Choke valves … fail’ (Dan Petri of Carrizo emailed TCEQ to report that the sand blowout created a 1/2 inch hole in the wellhead)
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 (and former UTA VP of finance who was instrumental in the 22 oncampus gaswells). “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, (TCEQ reported no odor when they arrived 3 hours later) but our students were not in any danger,” Principal Chuck Roe said in an e-mail to parents.
……’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 (70,000 cubic feet on final report) of natural gas and about two barrels (2.7 barrels on final report) of water (toxic, produced water) were vented. The well produces about 6 million cubic feet of natural gas a day, Ward said. (Third party consultant on final report calculated only 4.4 pounds of VOC’s in total were released which is under the “reportable quantity” of 5,000 pounds in 24 hours so this was a non-reportable emissions event.)
The steam (aerosol, toxic brine) reaching the residential contained no natural gas, and any odor reported could have been sulfur (H2S?) that is added to natural gas so it can be detected, Ward said. (Mercaptans are not usually added until a utility processes the gas for shipping to the ultimate customer, via pipeline.)
“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.
March 24, 2012 – 1:56 am
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Subject: just rec’d Debbie Lane emission event report