HOUSTON (Reuters) - BP Plc has more testing ahead before it can finally kill its ruptured Gulf of Mexico oil well, the top official overseeing the spill response said on Wednesday.
Retired Coast Guard Admiral Thad Allen declined to give timelines on upcoming steps, which will likely push the final plugging to late August or early September.
BP said it began a procedure on Wednesday afternoon to flush the seabed equipment on the Macondo well and fill it with seawater in advance of a pressure test.
“This will be one of the final vital signs that we will need in order to make a determination on how to go forward,” Allen said.
The Macondo well has been sealed for more than a month. Nearly two weeks ago, BP injected drilling mud and cement into the top to plug it, intending to follow up with more mud and cement injected into the bottom through a relief well.
But he said BP engineers and government scientists were concerned the cement may have trapped up to 1,000 barrels of oil in the space between the well pipe and the surrounding rock layers.
The teams want to make sure pumping in mud and cement through the relief well will not increase pressure and force that oil up, where it could leak into the sea or damage a failed blowout preventer central to various investigations of the April 20 blowout.
Allen said officials may install a pressure venting system on the seabed equipment or swap the failed blowout preventer for another before relief well drilling resumes.
The upcoming pressure test -- expected to take 48 hours -- should help officials choose between those options, he said.
“That will all be conditions-based and I can’t tell you how many days it will take to do that,” Allen said. “We will do it when we’re comfortable moving ahead.”
Additional reporting by Eileen O'Grady; Editing by Peter Cooney