BP Plc plans this week to inject mud down its Macondo well in the Gulf of Mexico and begin permanently plugging the source of the largest oil spill in U.S. history.
The process will start tonight or tomorrow, National Incident Commander Thad Allen told reporters Sunday on a conference call. Once mud injected into the well overpowers pressure coming up from the reservoir of oil and gas feeding Macondo, BP may use cement to plug the well from the top.
The technique will make it safer to permanently plug the leak later the month, using a shaft drilled to intercept the damaged well about 13,000 feet (4,000 meters) beneath the ocean floor. BP has started installing steel casing in this so-called relief well in preparation for the injection of mud and cement for final plugging, it said yesterday.
“I give a reasonable chance of success to this operation,” Arthur Berman, who owns Houston-based Labyrinth Consulting Services Inc., which specializes in subsurface petroleum geology, said by telephone July 31. “Nothing is 100 percent, but I think we’re all hoping that the relief well is the final solution.”
BP will know “within hours” whether the injection of mud into the top of the well, known in the industry as a static kill, is successful, Allen said. If the plan works, bringing pressure from Macondo to zero, it will make it easier for BP to permanently plug the well from the bottom with cement, he said.
Work on a final seal would begin as soon as five days after the static kill is completed, Allen said.
Success would ensure that no more oil leaks from a well that killed 11 workers in an April 20 drilling-rig explosion, led to a record loss at BP and prompted the departure of Chief Executive Official Tony Hayward. The flow of crude from Macondo has been stopped since BP sealed it on July 15 through a valve stack placed atop the well.
The pressure at the well is around 6,980 pounds per square inch and will increase slightly during the static kill, Allen said. BP will stop the procedure if pressure rises above 8,000 pounds per square inch to avoid damaging the well, he said.
BP planned to finish plugging Macondo by the middle of this month before Tropical Storm Bonnie, which forced evacuations of drilling vessels on July 22 and caused some debris to fall into the relief well drilled to intercept with the damaged shaft.
Mud at Site
BP said it will have 12,000 barrels of 13.2-pound-per- gallon mud ready to inject into the well near the site, 40 miles (64 kilometers) off the Louisiana coast, six times more than the company expects will be needed.
Before being sealed last month, Macondo was spewing 35,000 to 60,000 barrels of crude into the Gulf, according to a government estimate made in June.
Allen said July 30 that the government will release a new calculation within a few days for the amount of oil that was leaking into the Gulf, as well as for how much oil has been dispersed.
BP used chemicals called dispersants to break up the oil and contain the spill.
The Coast Guard allowed the company to use excessive amounts of the “toxic” chemicals, U.S. Representative Edward Markey, chairman of Select Committee on Energy Independence and Global Warming, said July 31 in a statement. BP often exceeded amounts for which it had sought approval, the Massachusetts Democrat said.
Allen said the dispersant-permitting process was “very strict” and that he was in constant discussions with the Environmental Protection Agency Administrator Lisa Jackson about use of the chemicals. The Coast Guard reduced BP’s use of dispersants in May, he said.
“We have always worked hand-in-hand with the Coast Guard,” BP spokesman Daren Beaudo said yesterday in an e- mailed statement.
The flow estimate will probably widen from the range announced in June, researcher Ira Leifer, a member of the panel of scientists advising the U.S. Energy Department on the spill’s size, said in a July 30 interview.
“There’s just a lot of uncertainty because there was no monitoring system put in place,” said Leifer, a University of California, Santa Barbara researcher.
The Obama administration imposed a six-month moratorium on new deepwater drilling permits in the wake of the spill.
The U.S. Senate may act on oil-spill legislation this week after the U.S. House pushed through its version of offshore safety and environmental rules on July 30. The House bill would eliminate a $75 million cap on liability for companies responsible for spills, and bar BP from new offshore leases.