CHARLESTON, W.Va. -- Open hatches on a series of wastewater tanks allowed a buildup of gases that fueled two explosions that left a pair of workers dead last month at a Doddridge County natural gas production site, Antero Resources said this week in a report to West Virginia regulators.
Antero said that a "flash fire" erupted near a contractor's pump, sending a "flame trail" toward a collection of four "flow-back" tanks, which then blew up.
In a letter Wednesday to the West Virginia Department of Environmental Protection, Antero cited witness statements and some physical evidence that company officials believe support its theory about how the July 7 incident at the Hinterer 1H well near New Milton happened.
Witnesses described an initial "flame cloud" from one tank, Antero said, followed 10 to 15 minutes later by the explosion of a second tank. Both tanks were damaged and "show evidence that one the one or both (sic) were a probable source of the combustible vapors."
Antero said witness statements "note fires burning from at least two of the four tanks until they were extinguished by the fire department."
Killed in the incident were Jason Mearns, 37, of Beverly, and Tommy Paxton, 45, of Walton. Mearns was employed by Antero contractor Nabors Completion & Production Services, and Paxton by Antero contractor C&R Downhole Drilling, according to the U.S. Occupational Safety and Health Administration.
Last week, DEP Office of Oil and Gas Chief James Martin ordered Denver-based Antero to provide more information about the company's findings after Antero submitted a two-page letter with few details. Operations at the well site remain halted by DEP order while agency officials review the follow-up report, officials said.
In its latest letter to the DEP, Antero said the four tanks were tied into a flare system, which would be used to vent and burn off excess gases from the liquids that return to the surface from the drilling and hydraulic fracturing process.
DEP officials said flowback tanks are equipped with access "hatches" that allow the tanks to be inspected and cleaned but that those hatches also are the potential source of air emissions.
The hatches on all four tanks were open at the time of the incident, Antero said, but the company will now institute a policy of latching the hatches "to minimize potential for gas releases directly to the atmosphere."
Reach Ken Ward Jr. at kw...@wvgazette.com or 304-348-1702.