“Tim Probert, Halliburton’s president of global business lines, plans to testify Tuesday that his company had finished an earlier step, cementing the casing, filling in the area between the pipe and the walls of the well; pressure tests showed the casing had been properly constructed, he will testify.
At this point it is common practice to pour wet cement down into the pipe. The wet cement, which is heavier than the drilling mud, sinks down through the drilling mud and then hardens into a plug thousands of feet down in the well.
The mud then is removed and displaced by seawater; the hardened cement plug holds back any underground gas.
In this case, a decision was made, shortly before the explosion, to perform the remaining tasks in reverse order, according to the expected Senate testimony of Mr. Probert, the Halliburton executive.
“We understand that the drilling contractor then proceeded to displace the riser with seawater prior to the planned placement of the final cement plug…,” Mr. Probert says in the prepared testimony, which was reviewed by The Wall Street Journal. The “riser” is part of the pipe running from the sea floor up to the drilling rig at the surface.
Lloyd Heinze, chairman of the petroleum engineering department at Texas Tech University, agrees that this is an unusual approach. “Normally, you would not evacuate the riser until you were done with the last plug at the sea floor,” he said in an interview.
A worker who was on the drilling rig said in an interview that Halliburton was getting ready to set a final cement plug at 8,000 feet below the rig when workers received other instructions. “Usually we set the cement plug at that point and let it set for six hours, then displace the well,” said the worker, meaning take out the mud.
According to this worker, BP asked permission from the federal Minerals Management Service to displace the mud before the final plugging operation had begun. The mud in the well weighed 14.3 pounds per gallon; it was displaced by seawater that weighed nearly 50% less. Like BP, the MMS declined to comment on this account.
As the heavy mud was taken out and replaced with much lighter seawater, “that’s when the well came at us, basically,” said the worker, who was involved in the cementing process.
The worker’s account is corroborated by an email account sent by another person on the rig. He said that engineers wanted to flood the well with sea water before setting the final plug. As they were taking out the mud, the blowout began with a flood of drilling fluid being pushed out of the well, followed by a series of explosions.”
What did MMS know, and did it give BP permission to proceed without placing the final cement plug?
