Important update about the Gulf oil spill

An article in the McClatchy newspapers challenges the official oil estimates, but the careful words of the cited expert are easily exaggerated: “BP well may be spewing 100,000 barrels a day, scientist says“, 7 June 2010 — Red emphasis added. Excerpt:

BP’s runaway Deepwater Horizon well may be spewing what the company once-called its worst case scenario — 100,000 barrels a day, a member of the government panel told McClatchy Monday. “In the data I’ve seen, there’s nothing inconsistent with BP’s worst case scenario,” Ira Leifer, an associate researcher at the Marine Science Institute of the University of California, Santa Barbara, and a member of the government’s Flow Rate Technical Group, told McClatchy.

Leifer said that based on satellite data he’s examined, the rate of flow from the well has been increasing over time, especially since BP’s “top kill” effort failed last month to stanch the flow. The decision last week to sever the well’s damaged riser pipe from the its blowout preventer in order to install a “top hat” containment device has increased the flow still more far more, Leifer said, than the 20% that BP and the Obama administration predicted.

Leifer noted that BP had estimated before the April 20 explosion that caused the leak that a freely flowing pipe from the well would release 100,000 barrels of oil a day in the worst-case scenario. The oil was not freely flowing before the top kill or before they cut the pipe, Leifer said, but once the riser pipe was cleared, there was little blocking the oil’s rise to the top of the blowout preventer. Video images confirm that the flow of black oil is unimpeded. “If the pipe behaved as a worst-case estimate you would have no visual change in the flow, and I don’t see any obvious visual change,” Leifer said. “How much larger I don’t know but let’s just quote BP.”

… A team of experts from government science agencies and universities estimated last week that at a minimum 12,000 to 25,000 barrels a day were flowing from the well, but the team declined to estimate an upper end for the flow because the information they received from BP was inadequate.

Leifer’s comments are interesting and important. But in the last paragraph McClatchy mis-represents the findings of the Flow Rate Technical Group. Of the three methods used, only two estimated only the minimum amount of oil released. As explained in the Summary Preliminary Report from the Flow Rate Technical Group, by Team Leader Marcia McNutt (U.S. Geological Survey) — Red emphasis added. Excerpt:

Three independent methods considered by the FRTG place the minimum oil flow rate at greater than 12,000 barrels per day. Two of the methods determine that the flow rate could be as high as 19,000 barrels per day. The team using video to analyze the plume believes that the flow rate could be at least 12,000 to 25,000 barrels per day. Therefore, the area of overlap of all three methods ranges between 12,000 to 19,000 barrels per day. These are all preliminary estimates.

In arriving at this preliminary range of values, the FRTG pursued entirely independent strategies, each of which yielded it own range of values. The values from the independent methods were combined to find the mostly likely flow rate for the well from the intersection of different methods. The Plume Team pursued the approach of observing video of the oil/gas mixture escaping from the kinks in the riser and the end of the riser pipe, using particle image velocimetry analysis to estimate fluid velocity and flow volume. The Mass Balance Team used remote sensing data from deployment of the Airborne Visible InfraRed Imaging Spectrometer (AVIRIS) and satellite to calculate the amount of oil on the ocean surface on a certain day. The team then corrected the value for oil evaporated, skimmed, burned, and dispersed up to that day and divided by time to produce an average rate. Each method has its own limitations and biases as described below. …

Mass Balance: 12,000 to 19,000 barrels per day …

Plume Modeling: at least 12,000 to 25,000 barrels per day (range of lower bounds) …

Reality Check: at least 11,000 barrels per day {the lower bound is the amount actually collected}

Posts about the Deepwater Horizon disaster on the FM website