The move to start withdrawing heavy drilling fluid that prevents gas from escaping the well, despite some worrisome tests and before a final cement plug could be placed in the well, raises questions about the judgments made on the rig in the hours before an explosion erupted into the night air of April 20, killing 11 and eventually leaving oil pouring into the Gulf of Mexico.
Accounts from two contractors say drilling “mud” was withdrawn before placement of a final cement plug, which would have been one more safeguard against natural gas surging from the well. Once mud came out, the last safeguard, a giant set of valves called a blowout preventer, didn’t do its job, possibly because of a defect such as leaking hydraulics or because it was jammed by debris from the well, documents produced by congressional investigators show. The rig was soon engulfed in flames.
A senior BP executive and the chief executive of rig owner Transocean Ltd. told lawmakers Wednesday that discrepancies in key pressure tests on the afternoon of the explosion should have raised alarms.
They should “lead to a conclusion that there was something happening in the well bore that shouldn’t be happening,” Transocean CEO Steven Newman told the House Energy and Commerce Committee.
BP America Chairman Lamar McKay told the panel “that discrepancy is critical, and the investigation will have to tear that apart piece by piece.”
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