WASHINGTON — BP started pumping heavy drilling mud into its Deepwater Horizon well in the Gulf of Mexico in an effort to force oil in the well back into the rock formation that it came from, the company said Tuesday. If successful, the so-called "static kill" could lead to the permanent sealing of the well with cement.
In a brief statement, BP said the static kill began at 4 p.m. EDT, less than two hours after technicians had begun a test to see at what rate they should add the mud to force the oil down in what they called an injectivity test.
The static kill involves dumping drilling mud that weighs 13.2 pounds per gallon — almost double the weight of a gallon of crude oil — into the well at relatively low rates to force the oil back into rock formations 13,000 feet below the seafloor.
BP did not say at what speed the mud was being added. BP officials have said they expect to use about 2,000 barrels of drilling mud in the procedure, or about 84,000 gallons.
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If the oil is successfully returned to the reservoir, engineers will decide whether to dump in cement that would seal the well.
BP said in a statement that it continues to plan to complete a relief well, which, the statement said, "remains the ultimate solution to kill and permanently cement the well."
"Depending upon weather conditions, mid-August is the current estimate of the most likely date by which the first relief well will intercept the Macondo well annulus," BP said, referring to the area between the rock wall of the wellbore and the casing pipe inside.
The oil well dumped 4.9 million barrels of oil into the Gulf over 87 days, government scientists now estimate. The well exploded on April 20, killing 11 workers. Initially, it leaked 62,000 barrels a day, government scientists have concluded, but had slowed slightly to 53,000 barrels a day by the time it was contained with a special capping device July 15.