BP engineers Thursday stopped oil flowing into the Gulf of Mexico for the first time since April as they shut all valves on a new cap placed on top of a fractured wellhead, a BP official said.
“It is good to see no oil going into the Gulf of Mexico,” said senior vice president Kent Wells, but he cautioned: “We are just starting the test.”
He said the oil flow stopped as the last of three valves on a huge capping stack was shut at around 2:25 (1925 GMT) Thursday, but engineers were keeping a close eye on the operation to see whether any oil began leaking again.
It was the biggest step forward in halting the worst oil spill in US history which has been flowing into the sea since a BP-leased rig sank on April 22, two days after a major explosion on the deepwater drilling platform.
Experts have estimated some 35,000 to 60,000 barrels a day have been flowing into the Gulf for some 13 weeks, leaving millions of gallons sloshing around in the waters, threatening vulnerable wildlife and fouling the shores of five Gulf states.
BP’s chief operating officer Doug Suttles warned however it was not yet time to celebrate, saying more time was needed as a 48-hour test is completed.
“I think it’s an encouraging sign. In a couple of more days it may even be more encouraging, but no celebrations,” Suttles told reporters. “If you go talk to these people that live here, celebration is the wrong word.”
Wells reminded reporters the aim of the pressure tests was to “assess the integrity of the well” as it is not known whether the wellbore which stretches deep below the seabed was damaged in the April 20 explosion.
US President Barack Obama, whose administration has led pressure on BP to stop the oil flow, welcomed the news as “a positive sign,” but cautioned: “We’re still in the testing phase.”
Over the next 48 hours, engineers will be closely monitoring the pressures inside the giant 30-foot (10-meter) cap placed on the well earlier this week.
High pressures will show that there is no other leakage underground, whereas low pressures may indicate that the casing of wellbore has cracked and is leaking.
“We would like the result that says there is perfect integrity,” Wells said, but cautioned it was too early to say whether the leaking well had been completely choked off.
“We are not sure exactly what we will be able to determine” from the data which will be gathered during the tests, Wells said, cautioning the company may need to reopen the well again.