Unusual pressure tests preceded Deepwater Horizon disaster

Cement barriers on BP’s Macondo well failed a key pressure test hours before a surge of explosive gas and the April 20 explosion of the Deepwater Horizon rig in the Gulf of Mexico, according to documents and testimony provided to a congressional committee, lawmakers said today.
James Dupree, the BP senior vice president for the Gulf of Mexico, told the House Energy and Commerce Committee this week that nearly 17 hours after three initial so-called “positive pressure” tests, the well failed a “negative pressure” test. Dupree told committee aides that the test result was “not satisfactory” and “inconclusive,” said Rep. Henry Waxman, D-Calif., the panel chairman.
“Significant pressure discrepancies were recorded,” Waxman said.
The anomalous test result could provide a major clue about what went wrong April 20 when gas flowed uncontrollably out of the well, unchecked by multiple cement barriers and well casing.
“This is an important test,” Waxman said. “During a negative pressure test, the fluid pressure inside the well is reduced and the well is observed to see whether any gas leaks into the well through the cement or casing.”
Waxman outlined the information in documents prepared by BP and provided by Dupree:

  • The initial negative pressure test was conducted around 5 p.m. April 20, with a “not satisfactory” or “inconclusive” result.
  • As a result, a subsequent negative pressure test was conducted. “During this test, 1,400 psi was observed on the drill pipe, while 0 psi was observed on the kill and the choke lines,” according to a BP outline. Dupree told committee staf that was also an unsatisfactory test result.

“In the test, the pressures measured at any point from the drill rig to the blowout preventer should be the same in all three lines,” Waxman said. “But what the test showed was that pressures in the drill pipe were significantly higher.”
Waxman acknowledged that what happened in the moments after the second negative pressure test “is murky.”
Dupree told committee staff “that he believed the well blew moments after the second pressure test,” Waxman said. But lawyers for BP contacted the committee with “a different account” on Tuesday and said that additional pressure tests were completed by 8 p.m. and the results apparently “justified ending the test and proceeding with well operations.”

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