Wyoming state investigators said Thursday a mechanical failure in the well was the main cause of a natural gas well blowout late in April at a Chesapeake Energy Corp. drilling site. However, operating errors also contributed. The incident lasted about three days; no one was injured (see Shale Daily, April 30).

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

According to a preliminary review by state officials, the amount of gas released was estimated at less than 2,000 Mcf over 66 hours. It also estimated that 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 (750 bbl).

A Denver-based spokesperson for Chesapeake told NGI’s Shale Daily that the gas exploration/production 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 (lockdown pin, etc.) were taken 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, who clarifyed that the B section wellhead is below the blowout preventer stack, choke spool and blind ram.

The investigation identified two contributing factors, said Doll — “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. He estimated that a four-acre area was most immediately impacted at the drill pad site, along with a broader area of 52.2 acres.