Chesapeake blowout; State issues preliminary investigation results

A preliminary investigation of the April 24 blowout of a Chesapeake Energy oil well suggests the cause was a mechanical failure, or “improper engagement of wellhead lockdown pins,” according to the Wyoming Oil and Gas Conservation Commission.

There were no injuries reported in the incident, but dozens of nearby residents were asked to voluntarily evacuate their homes during the 66 hour event.

Commission supervisor Tom Doll issued this report Thursday morning:

Summary of the OGCC Incident Investigation Report (Chesapeake Combs Ranch Unit Well 29-33-70 1H, Converse County, WY API 49-009-28568):

OGCC investigators conclude that a mechanical failure of the B section wellhead resulted in the loss of well control.  The B section wellhead and the lockdown pin recovered onsite have been transported by Chesapeake to a metallurgical laboratory in Baton Rouge, Louisiana.  Identification of the mechanical failure of the lockdown pin or the B section wellhead itself awaits the metallurgical laboratory analysis.  The B section wellhead is located below the blowout preventer stack, choke spool and blind ram.

The OGCC investigation also identifies contributing factors to the incident:  1) delay 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 2) improper engagement of wellhead lockdown pins.

The OGCC estimates that the total volume of natural gas released to the atmosphere was less than 2,000 MCF total throughout the entire 66 hour incident.  The OGCC estimates 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 which is estimated at 750 barrels.  OGCC personnel continue monitoring, sampling and inspection of the ongoing area clean-up.  The affected area is estimated at 4 acres (drill pad site) and the impacted area is estimated at 52.2 acres.

No OGCC regulatory action is planned pending final drill pad and impacted area cleanup, sampling results and site inspection confirmation of proper handling of materials.  Chesapeake continues to cooperate fully with the OGCC investigation.

The full OGCC Incident Investigation Report can be found on the Wyoming Oil and Gas Conservation Commission web page http://wogcc.state.wy.us by clicking on the Bucking Horse Icon “Notices, Memos and Details” on the upper right side of the page.

— See the full report by clicking this link.

— See related WyoFile story from April 25.

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Published on May 10, 2012

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