A series of warning signs revealed troubles at BP’s Macondo well during the hour leading up to its blowout April 20 and the resulting explosion of the Deepwater Horizon rig, according to details BP provided today to a House panel investigating the incident.
BP delivered the preliminary report — based on its internal investigation — to the House Energy and Commerce Committee, which is investigating the incident.
“The information from BP identifies several new warning signs of problems,” Committee Chairman Henry Waxman, D-Calif., told panel members in a memo this evening.
According to the panel, the irregular activity at the well head included:
- when fluid began flowing out of the well than was being pumped in, at 51 minutes before the explosion.
- when the pump was shut down for a sheen test 41 minutes before the blast and the well continued to flow (while drill pipe pressure also increased)
- when abnormal pressures and mud returns were observed and the pump “was abruptly shut down” 18 minutes before the explosion.
Based on a review of internal documents and interviews with staff from companies involved in operating or outfitting BP’s Macondo well, the committee already revealed a series of equipment failures, anomalous pressure readings and warning signs in the hours leading up to the blast.
According to Waxman’s memo:
As early as 5:05 p.m., almost 5 hours before the explosion, an unexpected loss of fluid was observed in the riser pipe, suggesting that there were leaks in the annular preventer in the BOP. Two hours before the explosion, during efforts to begin negative pressure testing, the system gained 15 barrels of liquid instead of the 5 barrels that were expected, leading to the possibility that there was an “influx from the well.”
The committee’s earlier examination focused on “significant pressure discrepancies” that were recorded during testing of the integrity of cement barriers at the well bore beginning at 5 p.m. on the day of the explosion. A process called “negative pressure” testing showed major differences in the pressure exerted on different components of the well, which should have been equal.
The negative pressure testing by Transocean occurred just before well operators were sealing the exploratory well so a full production facility could be hooked up later.
Questions also have been raised about a decision to change the customary order for plugging the well hole, effectively allowing drilling mud to be removed and displaced by seawater before a final cement plug was installed.
And, lawmakers also documented a significant leak in a key hydraulic system that provides emergency power to the shear rams in the blowout preventer that is designed to seal the well. They also discovered unexpected modifications of the device that were not reflected on schematics Transocean provided BP. In one case, shear rams had been replaced by test equipment, and workers spent a day after the blowout trying to activate the ineffective components.