BP started shutting off the flow of oil through a new cap on its gushing Gulf of Mexico oil well Wednesday, possibly coming within hours of stopping the gusher for the first time since April.
Company vice president Kent Wells said at a news briefing in Houston that BP has closed the first of three openings that have been letting oil flow through the a new cap. Wells said it will take hours before all three are closed.
At that point, what BP calls the official test of the well's capabilities begin, Wells said. The company will be monitoring pressure inside the device, in part to make sure no new leaks develop. They will review at six hour intervals over a 48-hour period whether the new cap works as planned.
National Incident Commander Thad Allen said that after the test, all the valves will be reopened and BP and federal officials will decide whether to close off the well again or keep it open, with the oil that pours out again being collected by vessels floating on the surface of the Gulf.
Allen said at a separate news conference in New Orleans that the decision to go ahead with testing came after a 24-hour delay prompted by an "overabundance of caution" about the effect the pressure could have on the leaking well.
"This has been a substantial impact on our environment, this has been a substantial impact on the Gulf Coast, the people, the culture," Allen said. "What we didn't want to do is compound that problem by making an irreversible mistake."
Federal officials were concerned that the pressure could further damage the well, including below the seafloor. A mapping of the seafloor around the well allayed those fears, Allen said.
Scientists will be closely monitoring the pressure inside the well during the test. Higher pressures are good; they indicate there is one leak. But if pressure fails to rise above 6,000 pounds per square inch, that could mean there are more leaks deeper in the well.
Once all the openings in the cap are shut off, it will be the first time no oil has flowed into the Gulf since an explosion on the Deepwater Horizon on April 20 that killed 11 workers and began what has become one of the worst environmental disasters in U.S. history.
BP shares lost almost 2 percent of their value in New York Wednesday after recouping some of their oil spill losses earlier this week.