1st peer-reviewed estimate of BP oil spilled in Gulf -->> 4.4 MILLION BARRELS

[nashville_brook]

http://news.firedoglake.com/2010/09/25/bp-spilled-4-4-million-barrels-into-gulf-according-to-new-estimate/

BP Spilled 4.4 Million Barrels Into Gulf, According to New Estimate


Kate Sheppard reports on an independent estimate of the BP oil disaster which again raises the amount of oil spilled into the Gulf:

An independent estimate concluded this week that the BP spill dumped 4.4 million barrels of crude oil into the Gulf of Mexico. The new study, published this week in Science, is the first peer-reviewed analysis of the total amount spilled over the nearly three months of the disaster. The scientists used high-resolution video of the leaking well to estimate the rate of the spill.

The estimate is slightly higher than the estimate from the government’s flow rate team, which concluded in August that 4.1 million barrels were spilled into the Gulf and another 800,0000 barrels was removed from the water.

The difference of 300,000 barrels equals the total amount of oil spilled in the Exxon Valdez disaster.

And this has a monetary cost to BP as well. Many penalties under the Clean Air Act base their amounts on a per-barrel rate. As much as $4,300 a barrel could be owed to the government by BP, especially if they were found liable of gross negligence in the disaster, so this increase could mean up to $1.29 billion to BP’s bottom line.

The estimate published in Science has a plus/minus of 20%. At the initial time of the spill, BP estimated that just 1,000 barrels a day flowed into the Gulf. This estimate would reflect at least 50 times that.





http://www.sciencemag.org/cgi/content/abstract/science.1195840

Magnitude of the 2010 Gulf of Mexico Oil Leak

To fully understand the environmental and ecological impacts of the Deepwater Horizon disaster, an accurate estimate of the total oil released is required. We used optical plume velocimetry to estimate the velocity of fluids issuing from the damaged well, both before and after the collapsed riser pipe was removed. We then calculated the volumetric flow rate under a range of assumptions. Using a liquid oil fraction of 0.4, we estimated that the average flow rate from 22 April to 3 June was 5.6 x 104 ±21% barrels/day (1.0 x 10–1 meter3/second), excluding secondary leaks. After the riser was removed, the flow was 6.8 x 104 ±19% barrels/day (1.2 x 10–1 meter3/second). Taking into account the oil collected at the seafloor, this suggests that 4.4 x 106 ±20% barrels of oil (7.0 x 105 meter3) was released into the ocean.

1 Lamont–Doherty Earth Observatory, Columbia University, Palisades, NY 10964, USA.
2 Department of Earth and Environmental Sciences, Columbia University, Palisades, NY 10964, USA.

[DirkGently]

1. So, BP & the administration were just off by 1 "Valdez?" And to think we doubted . . .

[nashville_brook]

2. 1 Valdez here, a couple over there...soon we'll be talking about a lot of oil!

[SidDithers]

4. The study estimate is accurate to 3 Valdez spills in either direction...nt

Sid

[bherrera]

8. no assurance they were off

The data does not say they were off. As more data is obtained, the figure can be refined, and some uncertainty will always remain, due to the nature of the problem. It is likely the volume will be revised to a lower figure if the study of valve erosion confirms the rate was increasing as the well valves became eroded.

[SidDithers]

3. 4.4 million barrels +/- 20%....

They're saying the amount spilled is somewhere between 3.52 million barrels and 5.28 million barrels. The estimate of 4.1 million is well within that range.

Edit: typical of FDL to sensationalize the story, and downplay the very wide range given to the estimate. Quibbling about a 7% difference between 2 studies, when the "accurate" study estimate has a +/- 20% variable is comical.

Sid

[bherrera]

5. Their technique is limited - figure may be quite different

I am going to quote from their abstract:

"We used optical plume velocimetry to estimate the velocity of fluids issuing from the damaged well, both before and after the collapsed riser pipe was removed. We then calculated the volumetric flow rate under a range of assumptions. Using a liquid oil fraction of 0.4, we estimated that the average flow rate from 22 April to 3 June was 5.6 x 104 ±21% barrels/day (1.0 x 10–1 meter3/second), excluding secondary leaks. After the riser was removed, the flow was 6.8 x 104 ±19% barrels/day (1.2 x 10–1 meter3/second). Taking into account the oil collected at the seafloor, this suggests that 4.4 x 106 ±20% barrels of oil (7.0 x 105 meter3) was released into the ocean."

The concern arises because their liquid oil fraction, 0.4, is not supported. The liquid oil fraction at the study point (the point where the oil was escaping into the ocean), is a function of the hydrocarbon temperature, and of the hydrocarbon properties. We know the pressure is set by the water column. But the authors did not report what simulations they used to establish the 0.4 value, which is suspiciously rounded. Since they use one significant figure for this very important parameter, their answer therefore has only one significant figure. Which then tells us their study, as you Americans like to say, is bullshit. I am surprised Science published it with this fundamental flaw.

The conclusions:

1. The government figure, which utlized velocimetry and other techniques (including a nodal simulation of the well, to match the observed temperature at the sea floor), is more reliable. Further analysis of the data, including the valves removed from the sea floor, will provide a better understanding of the cumulative oil spilled by the BP well.

2. Particle velocimetry is a good technique if there is proper accounting of the flow properties, but it is not so accurate. Nodal analysis is more accurate, but it is a technique with which many scientists are not familiar, and therefore they can not practice. Nodal analysis is a technique used by engineers, who are probably not going to publish in Science. It is also very complex and in this case requires an understanding of the thermal properties of the rocks from the sea floor to the oil reservoir. This is information which only a petrophysicist and a person with a doctorate in geomechanics would be able to develop, working together. Such combinations are rare in academia.

[Name removed]

6. Deleted message

Message removed by moderator. Click here to review the message board rules.

[bherrera]

7. The government scientists should be trusted

I believe the initial government scientist group has a more reliable figure - at this time. I am indeed ordered to study this oil spill. My employer is a department of the City of Alicante, in Spain. We have very nice beaches, and they decided we should have internal documentation of the type of actions we should take if there is an oil spill which may damage our beaches. I am an engineer, but I see this problem (an oil spill and its consequences) as a combination of science and engineering.

Your inadequate response tells me you may not be familiar with the topic. I suggest the following reading to improve your education:

http://en.wikipedia.org/wiki/Significant_figures

http://en.wikipedia.org/wiki/Particle_image_velocimetry

http://en.wikipedia.org/wiki/Flow_Rate_Technical_Group (see section 4, Nodal Analysis).

[SidDithers]

9. Yup. The .4 figure jumped out at me too...

if it's .38 instead of .4, then the 4.4 million barrels +/- 20% becomes 4.18 million barrels, +/- 20%.

The study is interesting, and is probably a very accurate gauge of what was spilled. It isn't, however, a smoking gun that the government is lying to us about what was spilled, as some posters would have you believe.

Sid