How Much Oil is Leaking in the Gulf?

The oil continues to leak, and we are now starting see the oil hit the shores.  We have live images from the leak 5,000 feet below the water surface.  But how much oil is actually leaking from the wellhead?

Initial estimates (Day 5) from the US Coast Guard and BP placed the estimate at 1,000 barrels/day.  Last week, the “official” government group revised the estimates at 20,000 – 40,000 barrels/day.  Less than a week later, the estimate is now at 35,000 – 60,000 barrels/day.

When the late May estimates came out, there was an interesting quote from Ira Leifer, University of California, Santa Barbara: “It would be irresponsible and unscientific to claim an upper bound, …it’s safe to say that the total amount is significantly larger.”  He wants to make sure the estimate has an asterisk because he wants “to stand up for academic integrity.”  In fact, there’s a whole document available by the university that will explain how the scientists came up with their estimate.  (from WSJ article here)

But I suspect that most of us will not care too much for the actual method or the details.  Maybe a chart like below is helpful since it summarizes the “growth” of the estimates over time.  By doing so, I am (on purpose? inadvertently?) suggesting a story and a conclusion.  What do you read from it?

Report Date Barrels/Day Source / Reported by Method Link
April 24 (Day 5) 1,000 USCG, BP, thru cbc.ca Info from ROV (remote operating vehicles) and surface oil slick Link
April 28 (Day 9) 5,000 NOAA Satellite pictures Link
May 12 (Day 23) 70,000 Steven Wereley, Purdue, for an NPR story particle image velocimetry, based on videotape Link
May 12 (Day 23) 20,000 – 100,000 Eugene Chang, UC-Berkeley, for an NPR story “Pencil and paper” based on pipe diameter (from video) Link
May 27 (Day 34) 12,000 – 19,000 12,000 – 25,000
(depending on source)
Flow Rate Technical Group
(NOAA, USCG, Minerals Mgt)
Based on multiple methods
(blog entry author’s guess)
Link 1

Link 2

Jun 10 (Day 52) 20,000 – 40,000
25,000 – 30,000
(depending on source)
Plume Modeling Team of The Flow Rate Technical Group Revised from earlier, based on additional video from BP Link
Jun 15 (Day 57) 35,000 – 60,000 Deepwater Horizon Incident Joint Information Center, reported by cnn “based on updated information and scientific assessments,” Link

So what can we learn from this?  We all (think we) want lots of data.  It’s helpful when it’s summarized in a way that seems to make sense.  But when we are confronted with data that we are not used to seeing (how may of us deal in BARRELS of oil, or work with flow rates?) we need some anchor, some comparisons, something that helps us make sense of numbers.

No matter how you count it, this is a lot of oil.  But does it really matter that it’s 15,000 or 60,000 barrels/day?  If you are part of cleanup or doing planning for the the collection, it may help you with the planning.  But you’re also going to want to know some other info, such as how long will it flow, how the flow has changed over time and the related “total leakage”.  Even with this last bit of info, you’re more interested in the amount that ends up on the shore or the amount that actually possible to reclaim.

For most of us, the accuracy of the flow rates do not matter so much.  It’s a lot of oil, and we need some way to get a handle on it.  Most of us will not remember the actual number (or in this case, the changing range of numbers).

Besides, no one will really know the true amount that has spilled.

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Comments

  • Alan  On July 1, 2010 at 3:35 PM

    This is well written, thanks.

    I believe the flow rates are important, but I doubt the accuracy of the numbers provided in the news. One of the reasons the rates are important is to use as a comparison for other disasters, like the Valdez, in order to get some ideas of the long term impact. Also, it’s useful to put the cleanup in perspective. If BP says that Z amount (units do not matter) of oil is leaking and they are cleaning up 40% and it later turns out the flow was ten times Z, then they were only really removing 4% of the oil, and quite a great deal more is left in the environment.

    While I believe the scientists are providing accurate information, I believe it gets muddled and summarized on the way to us through management and the media so that it is no longer very reliable. For example, when the media says that some amount of barrels of oil have been recovered, is that separated oil or is it diluted with sea water. If it is diluted, then it would be inaccurate to imply that it reduced the amount of oil released by the full number of barrels recovered.

    This news story details some other reasons the flow rates are important: http://news.yahoo.com/s/ap/20100701/ap_on_bi_ge/us_gulf_oil_spill

  • htomfields  On September 16, 2010 at 2:17 PM

    Several different velocimetry techniques are used at Idaho National Laboratory’s MIR Lab, including Laser Doppler velocimetry (LDV), particle image velocimetry (PIV) and stereoscopic PIV. Learn more about the world’s largest flow facility here.

    http://www.inl.gov/velocimetry

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