US official doubles prior estimate of oil gushing into Gulf
Gov’t analysis “still a work in progress,” official claims
As much as 40,000-plus barrels of oil per day were pouring from BP’s ruptured well into the Gulf of Mexico before the latest containment device was fitted, a US official said Thursday, more than doubling the previous government estimate.
“The lowest estimate that we’re seeing that the scientists think is credible is probably about 20,000 barrels, and the highest that we’re seeing is probably a little over 40,000,” Marcia NcNutt, director of the US Geological Survey and chair of a US-government-led flow rate assessment team, told reporters.
The figures — which estimate the flow rate prior to BP cutting a busted riser pipe June 3 in order to attach a containment device — are more than double the previous estimate of 12,000 to 19,000 barrels per day.
“Our scientific analysis is still a work in progress,” McNutt said.
US Coast Guard Admiral Thad Allen, who is overseeing response to the worst oil spill in American history, said the device had captured 15,800 barrels in the 24 hours ending midnight Wednesday.
This means a minimum of 4,200 barrels, and possibly up to 25,000 barrels, or more than one million gallons, are still spewing into the sea each day.
There were also fears that the operation to shear the pipe could effectively unkink the gusher and significantly increase the flow rate.
McNutt said teams were still assessing an estimate for the present rate of flow, but the latest figures mean at least 40 million gallons of crude has already poured into the Gulf, making the disaster almost four times the size of the Exxon Valdez spill in Alaska in 1989.
“In coming days we will analyze the new data and bring together the various scientific methodologies to develop an updated estimate of how much oil is currently flowing from BP’s leaking oil well in the Gulf of Mexico,” McNutt said.
The Flow Rate Technical Group headed by McNutt is comprised of leading federal scientists including Energy Secretary Steven Chu and college and university researchers, and is divided into several sub-teams pursuing independent approaches to assess the flow rate from the well head.
Three of the teams analyzed broad sets of technical data from the air, on the surface and coast, and under water, and plugged the bits and pieces into computer models in order to formulate their revised estimates.
The methodologies included analyzing video to help estimate velocity of the oil-gas mixture escaping from the damaged well, taking pressure readings from the blowout preventer using acoustic technologies, and analyzing geological formations, composition and oil pressure at the well and in the reservoir below the sea bed.
The teams studied satellite imagery and data from infra-red image spectrometers to determine the amount of oil on the ocean surface.
They also had to assess the amount of oil that has evaporated or has been skimmed, burned and dispersed since the disaster began when the BP-leased Deepwater Horizon oil rig exploded on April 20, killing 11 workers.
McNutt at one point said the upper bound estimate from one of the teams, the Woods Hole Oceanographic Institution (WHOI) which analyzed acoustic data and imagery from the leak, was “about 50,000” barrels per day.
But she dialed back on the figure, stressing that the 50,000 would be based on “some assumptions (about the images) that they weren’t quite willing to make.”
“This is obviously a challenging scientific issue, since the leak is located a mile (1.6 kilometers) beneath the ocean,” she said.
Earlier Thursday Allen told AFP that the US Coast Guard and BP were seeking to boost capacity on the scene “to about 28,000 barrels a day,” and that over the next three to four weeks they would be “moving from the containment cap to a more fitted cap so we can capture all the product.”
But even with better data in hand to do a revised estimate, he insisted that none of the flow figures would be absolute until all the gushing oil is siphoned to the containment vessel.
“I am not sure we are ever going to know until we actually measure full production what the leak is,” Allen said.