The national Oil Spill Commission said BP and Transocean rig workers misinterpreted the only test they had to determine if cement had properly sealed the bottom of BP’s wild Gulf well and that BP created additional, unnecessary risk by removing drilling mud and surface plugs that should have acted as barriers against gas blowing out.
While many decisions and issues conspired to caused the April 20 explosion that killed 11 men and started the worst oil spill in U.S. history, the commission’s investigators painted a picture Monday that BP’s risks, the misread test and unstable cement were probably the most devastating errors.
Sean Grimsley, assistant lead counsel for the Oil Spill Commission, said the evidence is clear that BP changed plans and “introduced risk that may not have been necessary” just days before the accident.
The key decision was to remove heavy drilling mud that acted as an important barrier against the natural gas that flowed up to the rig and caused the explosion. The mud was removed to an unprecedented depth in the well more than a mile below the rig, leaving more light seawater rather than heavy mud. At the same time, BP changed a previous plan to place a cement plug in the top of the well before removing the mud barrier.
“It puts a very large premium on the cement job at the bottom of the well and the test that checks the integrity of that cement job,” Grimsley said.
Robert Kaluza, the top BP man on the rig, has invoked his Fifth Amendment right not to testify before Marine Board investigators, but investigators’ notes from eight days after the accident show that Kaluza was befuddled by the decision and believed the company was trying to save time.
“It was a different sequence,” Kaluza said, according to notes that were partly read aloud by a lawyer at investigative hearings in July. “The team in town wanted to do something different. They decided to do the displacement (of heavy drilling mud with seawater) and the negative test together; I don’t know why. Maybe they were trying to save time. At the end of the well sometimes they think about speeding up.”
The commission’s lead counsel and investigator, Fred Bartlit Jr., said that in spite of Kaluza’s statement, he has no reason to believe anyone made decisions to sacrifice safety for money.
Still, Bartlit’s team of investigators say there was a leak in the bottom cement, not in the sides of the well, and a final test that clearly showed there was a problem was inexplicably accepted as a success by highly trained men on the rig.
The men, led by two BP company men who have declined to testify and several drill team members from Transocean who died in the accident, ran the so-called “negative pressure test” several times. A successful test would show no upward pressure down in the well, but each time, the test run on Deepwater Horizon showed high pressure of 1,400 psi exerted on the drill pipe that ran into the top of the hole.
And yet, at 8 p.m., about two hours before the explosion, the BP and Transocean rig leaders decided the test was successful.
Grimsley said there’s no good explanation for that.
“Why did experienced men talk themselves into believing this was a good test? None of the men wanted to die. None of the men out on that rig wanted to jeopardize their safety,” he said.
But Grimsley said nobody on the rig shared any concerns with engineers in Houston during those hours. Grimsley said one theory is that a leaking valve allowed heavy viscous fluid called “spacer” to get into a hose and created erroneous test results that gave rig workers a false sense of security.
“Nobody thought they were taking a chance, nobody thought the negative test was screwed up. For some reason or another they thought the test had succeeded,” said the commission’s lead counsel, Fred Bartlit.
Bartlit called the commission’s conclusions “preliminary,” repeatedly asking people to correct him if they are wrong. Grimsley also said the commission would not be assessing blame. But the misinterpreted test and changed procedures for closing off the well were clearly the strongest statements from the independent, presidentially appointed commission to date about human errors causing the accident.
“The negative pressure test repeatedly showed the cement had not successfully isolated hydrocarbons … and BP’s procedures introduced additional risk,” Bartlit said as he summarized a morning of highly technical findings.