1. Deepwater disaster: how the oil spill estimates got it wrong

2. Outline Background of the oil spill
Ways to analyse the amount of oil spill
Why were the estimates so wrong?
The case for underestimation and the reason why
Difference in estimation standards
What were the consequences for the management of the disaster?
Take home message

3. Background of the oil spill
A drilling rig called Deepwater Horizon exploded and sunk on 20th April 2010.
11 people died
Caused an eruption of oil and gas from BP’s Macando well in Grand Island, Louisiana
Discharge of oil on the sea continued for 84 days, till 15 July
Official reports on the release and discharge rates were issued by authorities of the Unified Command, and they took a very long time to get the rate right
There had been an increase in the estimated values of leaked oil from the start to the end of the disaster.
Discharge ended when until a steel cap was installed and successfully closed.
Many fluctuations of their estimates
Disaster lasted for three months but this was because they didn’t believe in the worst case. They feared an overestimation and wastage of resources → worsen the matter.

4. oil and gas that escapes into the environment.
oil and gas that leaves the reservoir
Discharge is less than release because BP were eventually able to capture a total of barrels of oil and a large amount of gas before it escaped.
The discrepancies →
The facts show that during the first five weeks or more of the emergency, the official rate of release grossly underestimated the true rate that would eventually be determined. Particularly troubling is the interval from April 28th to May 27th – a complete month during which authorities were responding to an estimated release rate of 5000 bopd, which was more than an order of magnitude lower than the true rate as efforts went forward. Clearly this estimate must have hampered effective relief.

5. Why were the estimates so wrong?
The case for underestimation and the reason why:
Oil was discharging from very convoluted positions
Given the circumstances, responders had three options to estimate the total discharge.
(1) technical means ie seabed sensors and videos (to quantify the flow from the discharging jets)
(2) geological and engineering data model about the reservoir and well
(3) back-calculation from the amount of oil arriving at the surface of the ocean.
(1) and (2) were chosen.
- Oil was discharging from three locations amid the twisted tangle of pipes and other debris that collapsed to the sea floor when the rig sank. There were small but very powerful jets coming from perforations on the main 20-inch riser pipe where it made a sharp bend on the top of the 60 ft high blow-out preventer.
- Given the circumstances, they had 3 options to estimate the total discharge as follows in decreasing reliability: (1) technical means ie seabed sensors and videos (to quantify the flow from the discharging jets); (2) geological and engineering data model about the reservoir and well (already known from the exploration drilling that Deepwater Horizon had completed just before the accident); or (3) back-calculation from the amount of oil arriving at the surface of the ocean.
- Eventually, the authorities chose the first 2 because they are more reliable method (something that can quantify for you or something you can use to quantify rather than observing how much oil on the ocean and back calculating)

6. Why were the estimates so wrong?
But Thad Allen, Incident Commander said that is it not exactly accurate due to the depth of the water, and their ability to assess from remotely operated vehicles and video footage.
Even when other experts could accurately estimate the discharge rate (on their behalf), they refused to release publicly the video footage recorded at the seafloor
Claimed that accurate estimate was unnecessary as it might hinder their response activity
One limitation pointed out by Thad Allen, Incident Commander “any exact estimation of what’s flowing out of those pipes down there is probably impossible at this time due to the depth of the water and our ability to try and assess that from remotely operated vehicles and video”.
- However, even when other experts could produce accurate estimates based on even low-quality video of the oil jets, BP refused to release publicly any of the video footage.
- They even claimed that accurate estimate was unnecessary as it might hinder their response activity

7. Why were the estimates so wrong?
First framework used by BP technicians compensated for evaporation and dissipation by using a multiplier of 2 (high rate of evaporation and dissipation).
Technicians were referencing a problematic response plan that did not accurately represent the area/environment that the oil spill occurred in.
Consequently, the estimates BP technicians came up with significantly understated the extent of spillage.

8. Why were the estimates so wrong?
Second framework technicians used to estimate the oil spill was relying on contextual information such as the nature of the reservoir, the flow capacity of the pipes used, and evaluation of the condition of the reservoir and well components.
Ultimately, they had a wide range of estimated discharged bopd and they chose to give the most optimistic one (lower value). Once again the extent of spillage was being understated.

9. Why were the estimates so wrong?
The US is not a signatory of the Bonn Agreement, but they are obligated to follow the Bonn’s Standards in assessing leaks.
The Bonn Agreement is the mechanism by which the North Sea States, and the European Union (the Contracting Parties), work together to help each other in combating pollution in the North Sea Area from maritime disasters and chronic pollution from ships and offshore installations; and to carry out surveillance as an aid to detecting and combating pollution at sea.
But the BP technicians used the ASTM version instead, causing serious underestimation of oil leak.
The bonn standards will be touched on later.
The ASTM version is ambiguous if we want to estimate leaks based on area of oil on sea surface over 3 micrometers.
Also, using ASTM would mean that BP technicians were using oil thicknesses that were as much as 100 times smaller than what is prescribed by the Bonn Agreement and NOAA guidelines

10. Why were the estimates so wrong?
Difference in standards:
Bonn Standards/NOAA guidelines:
Thinnest possible layer(Sheen): no more than a few molecule thick.
Slightly thicker layers(Rainbows): 0.5 to 5 µm thick.
Thicker layers(metallic/discontinuous/true): 10 to more than 100 µm.
ASTM Standard: using colour and appearance of oil on water to judge.
The standard highlights that “the only physical change in appearance that is reliable is the onset of rainbow colours, at 0.5 to 3 µm thickness”.
ASTM standard does not provide any guideline for thicknesses above 3 µm.
Before we move on to explain more, let’s take a look at the different standards of assessing the leak.

11. What were the consequences for management of the disaster?
The BP team withheld information because they believe the worst has yet to happen.
Ignored advises and guidances from experts that could give better analysis
We know that the estimated rates were significantly lower than actual rates.
Without an accurate estimate of the problem it is difficult to come up with an appropriate solution.
Direct measurements is preferred the method to determine pump or spill rate.
Without definite numbers we end up trying to fit a square peg into a round hole.

12. When real shit happens and you need help, seek help.
Take Home Message
When real shit happens and you need help, seek help.
Hiding it will turn the situation worse. And by the time you decide to be honest, it is already too late to salvage the situation.

13. Thank You