The X factor: Measuring BP’s oil spill progress
It’s like using a kitchen scale to weigh adults and concluding that the average person weighs somewhere between zero and ten pounds.
“That operation has gone extremely well. We are very pleased.”
That was BP VP Bob Fryar’s assessment yesterday of his company’s success in capturing some of the oil gushing from its wild well on the bottom of the Gulf of Mexico.
On Friday, we said that the cap seemed headed for failure. So who’s right?
As usual, it gets down to how you define “success” and “failure” (and on how you do the math).
Downsizing the Mission
First, it’s important to note that BP has moved the goal posts after the process known as “Top Kill” failed. Actually, it’s more like they started playing a different game altogether, and they managed to did it without drawing media attention. Top Kill was the last in a long line of attempts to shut the well down — as the word “kill” implies. BP’s new game is designed, at best, to divert a portion of the oil up a pipe to the surface. Killing the well won’t be accomplished until relief wells tap into the existing pipe far below the ocean floor and inject cement there. BP has said that will take until August. (Some experts believe it will take longer, perhaps an additional six months.)
“Containing” the oil using the cap is much more manageable. Then again, maybe not. Yesterday, BP’s Doug Suttles was optimistic that the cap would ultimately bring over 90 percent of the oil to the surface where it would be pumped into a tanker. To get anywhere near that figure, four vents on the cap need to be closed, a job that was supposed to happen on Friday.
At a Saturday morning press conference, however, Coast Guard Adm. Thad Allen confirmed that all of the vents remained open, for fear of increasing the pressure on the cap too quickly, causing it to malfunction or break apart. On Sunday, it appears that all vents remain open.
Even so, BP reports today that they have succeeded in bringing up 10,500 barrels of oil in the last 24 hours, a figure they say represents over half of the 19,000 barrels the government estimates is leaking each day.
BP’s Kinky Math
There are some problems with these numbers.
First, the 10,500 barrels can’t simply be subtracted from the estimated flow at the wellhead. The flow was from a smaller opening in a pipe narrowed by a kink. As they moved from killing the well to containing the oil, BP said that the flow would increase by an estimated 20 percent. Anyone watching one of the live cams noticed a surge in the volume of oil after the cut was made. So, if their estimates are correct, by the time the cap was put in place the flow had increased by 3,800 barrels per day.
Which means BP’ has reduced the amount of oil flowing into the Gulf by 6,700 barrels per day.
But even that overstates the success of the current effort.
Before Top Kill, BP had started a very low-tech process: siphoning oil through a six-inch tube stuck into the broken riser. The amount of oil “contained” by that tube was 2,000 barrels per day.
So, after all that BP has done since May 18th (when the tube was drawing oil), they are, as of this morning, capturing a net gain of 4,700 barrels of oil a day.
Government’s Hinky Math
After weeks of maintaining that the flow was just 5,000 barrels per day, the government dramatically upped that range. On May 27, Dr. Marcia McNutt, chair of the federal Flow Rate Technical Group, said that the range of oil being released had been upped to between 12,000 and 19,000 barrels of oil per day.
Those numbers seem as suspect as the government’s initial estimate was. First, they come from a preliminary draft report, based, in part, on low quality videos of the plume, provided by BP. The Task Force managed to pry loose a higher quality video, but the estimates based on that more accurate information won’t be released for as long as several weeks, according to McNutt.
Further, the estimates were based on the measurements of two groups of scientists. The numbers from one of the groups were estimates of the minimum amounts only. It was not possible, they concluded, to make a meaningful estimate of the maximum amount of oil spewing into the gulf.
Dr. Ira Leifer, a member of both panels (and team leader of one), has said that the government figures are “lower bound” estimates.
“It’s safe to say that the total amount is significantly larger, from some fraction to multiples of that lower bound number,” Leifer said. “I do not feel comfortable yet to provide an upper bound.”
The yardstick used to measure the percentage of oil being captured by BP isn’t a yardstick at all. It’s like using a kitchen scale to weigh adults and concluding that the average person weighs somewhere between zero and ten pounds.
At yesterday’s press conference I asked Coast Guard Adm. Thad Allen if he could clear up the misunderstandings about the range of estimates given by the government task force.
There were two different models used to produce two different ranges. The low end is the same in both models. It’s 12,000 barrels a day. The two different models produce 12,000 to 19,000 barrels a day.
The other model produced 12,000 to 25,000 barrels a day. I don’t think it’s a bad idea to have competing models because it gives you a higher fidelity answer as you move forward. Hopefully, we’ll start moving those ranges into a more acceptable representation of what’s actually flowing.
Allen’s answer is technically correct — but misleading. He says that the low end is the same in both models (12,000 barrels a day), but fails to mention that the estimate of 12,000 to 25,000 barrels per day shows only the group’s range of low end estimates.
So, how much of the spewing oil is BP currently capturing? IF X is the total number of barrels, then, according to the best scientific evidence available at the moment, BP is capturing X – 10,000 barrels.
The only problem is that — 47 days after the lethal failure of BP’s oil rig in the Gulf of Mexico — we still have no idea what number X represents.