Wyoming regulators said Thursday a mechanical failure was the root cause of a natural gas well blowout late in April at a Chesapeake Energy Corp. drilling site, but operating errors also were contributing factors. The incident, in which no one was injured, lasted about three days (see Daily GPI, April 30).

No regulatory action is planned pending the final drill pad and impacted area clean up, Wyoming officials said. Chesapeake was credited with “cooperating fully.”

The state estimated that the amount of natural gas released as less than 2,000 Mcf over 66 hours. The total volume of oil-based drilling mud displaced from the well as liquid and atomized as mist did not exceed the amount of drilling mud in the well at the time of the incident.

A Denver-based spokesperson for Chesapeake told NGI that the company “continues to investigate the incident and is fully cooperating with OGCC’s review of the matter.”

The Wyoming Oil and Gas Conservation Commission’s (OGCC) investigation concluded that a “mechanical failure of the B section wellhead resulted in the loss of well control,” said OGCC Supervisor Tom Doll. Equipment pieces, including the lockdown pin, were taken for analysis by Chesapeake to a metallurgical laboratory in Baton Rouge, LA.

“Identification of the mechanical failure of the lockdown pin or the B section wellhead itself awaits the metallurgical lab analysis,” said Doll. The B section wellhead is below the blowout preventer stack, choke spool and blind ram, he noted. The investigation also identified two contributing factors, said Doll, a “delay [by the operator] in observation of, and response to, a gain in drilling mud in the pits during the running of the production casing prior to the incident,” and “improper engagement” of wellhead lockdown pins.

“OGCC personnel continue monitoring, sampling and inspection of the ongoing area clean up [near the town of Douglas, WY, in part of the Niobrara Shale formation in Converse County],” Doll said. A four-acre area was most immediately impacted at the drill pad site, as well as a broader area of about 52 acres.

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