There were plenty of signs that all was not right with the Macondo well before it exploded on April 20: The cement mixture that Halliburton had provided to seal it flunked every laboratory test the company had conducted. A pressure test on the well failed multiple times as well. There were indications that oil and gas had made their way into the well, which should have been sealed. But all of these warnings went unheeded—a tragedy, since they could have helped avoid the blowout, or at least given workers some time to prevent an accident from becoming a disaster.
On Monday, the chief counsel for the National Oil Spill Commission laid out a detailed timeline of the decisions—and missteps—that likely took place on the Deepwater Horizon rig to the commission. In the first of two days of hearings in Washington, counsel Fred Bartlit and his staff outlined a number of human errors and oversights that they believe led to a disaster that took the lives of 11 men and unleashed 4.9 million barrels of oil on the Gulf of Mexico. But "don't put too much import on any one event," Bartlit stressed, suggesting that it was the sum of these missteps that caused the event rather than any one decision (see the full list of preliminary conclusions here).
In what was painted as among the most dramatic failures, workers misinterpreted the results of a test of pressure in the well. On April 20, several tests indicated upward pressure in the well, a sign that the cement job was not was not properly containing the oil and gas. Yet BP and Transocean workers treated the test "as a complete success," the commission investigators concluded. "The question is why these experienced men on this rig talked themselves into thinking this was a good test result," said Sean Grimsley, assistant lead counsel for the Oil Spill Commission. "None of these men out on the rig wanted to die."
According to BP workers on the rig that have talked to commission investigators, Transocean staffers blamed the pressure buildup on something called the "bladder" effect—which, according to their investigation, doesn't actually exist, said Bartlit. But figuring out why exactly this happened on that night has proven difficult, since several of the Transocean employees involved died in the blast, and two of BP's top men on the rig have declined to testify, invoking their Fifth Amendment rights against self-incrimination.
Bartlit did note, however, that while the negative pressure test is a crucial step in establishing that the well is stable, it is not required by federal regulations or industry standards, and there are no set procedures or training requirements when it comes to this test. Thus, BP and Transocean weren't even obligated to conduct this test in the first place.
Oil Spill Commission staff also spoke at length about indications that the cement mix from oil services giant Halliburton had failed numerous tests before it was used on this well. The commission's investigation has found that all studies of the mix completed before the explosion found it to be unstable. At the point when workers made the final moves to close the well, only the compromised cement barrier stood between the oil and gas and the Gulf.