HOUSTON Before rig workers aboard a doomed drilling platform performed a procedure that BP Plc says may have been a "fundamental mistake," there was a "skirmish" between BP and Transocean staff about whether to proceed, the rig's chief mechanic told federal investigators on Wednesday.
Around 10:53 p.m. EDT on April 20, Swiss-based Transocean Ltd's Deepwater Horizon rig exploded while it was drilling a well a mile beneath the Gulf of Mexico under contract for London-based BP Plc. Eleven rig workers are presumed dead.
The Transocean mechanic's account could give the company more ammunition in its verbal battle with BP to assign blame for the disaster, which caused what is likely the biggest oil spill in U.S. history.
Around noon, rig workers met in a room adjacent to the rig's galley and "there was a slight argument that took place and a difference of opinions," said Douglas Brown, the rig's chief mechanic, speaking to a federal board of investigators in Kenner, Louisiana.
Brown said "a skirmish" took place between "the company man" from BP -- whose name he said he did not know -- and three Transocean employees.
"The company man was basically saying, 'Well this is how it's going to be,'" and Transocean rig workers "reluctantly agreed," Brown said.
The argument concerned "displacing the riser," Brown said, a reference to a decision made by rig personnel to remove heavy drilling mud from the drill pipe and replace it with water, in an attempt to wrap up drilling operations and plug the well with cement.
Drilling mud is a mixture of synthetic ingredients that is pumped into the well to exert downward pressure and prevent a column of oil and gas from rushing up the pipe.
Because water is lighter and less dense than mud, the procedure allowed a flood of flammable methane gas to surge up the drill pipe, which ignited and led to a catastrophic fire, according to documents from the House of Representatives Energy and Commerce Committee.
Congressional investigators say BP and Transocean made a decision late on April 20 to begin removing mud from within the drill pipe despite pressure tests from within the well that a BP official described as "not satisfactory" and "inconclusive."
Earlier in the day, well pressure tests showed an imbalance between the drill pipe choke and kill lines running from the drill deck to the blowout preventer. The pressure in the drill pipe was 1,400 pounds per square inch, while the choke and kill lines read zero PSI, according to BP documents gathered by the House Energy and Commerce Committee.
In BP's internal investigation, made public by the committee, BP said it might have been a "fundamental mistake" to continue with the procedure because there was an "indication of a very large abnormality."
As methane surged up the drill pipe and enveloped the rig, Brown said, a loud hiss of gas escaped from the well, which set off a stream of alarms.
"Gas alarms just kept piling up on top of each other more and more and more," Brown said. The rig was hit by a power blackout, and the explosion came soon after, he said.
"The first explosion basically threw me up against the control panel that I was standing in front of," Brown said.
As Brown raced to reach the rig's lifeboats, "it was just complete mayhem, chaos, people were scared, they were crying," Brown said.
The rig worker taking a muster of workers boarding the lifeboat, a man that Brown said he had known for nine years, did not recognize him.
"This is a man that has known me for nine years and he cannot even remember my name," Brown said.
"It was just completely chaotic and nobody was really paying attention in my opinion," Brown said. "They were more concerned about just getting off the rig - escaping."
(Reporting by Chris Baltimore; editing by Mary Milliken and Mohammad Zargham)