Petrissa ECKLE, Peter BURGHERR, Edouard MICHAUX Paul Scherrer Institute, Switzerland;

1. Wir schaffen Wissen – heute für morgen
Risk of large oil spills – A statistical analysis in the aftermath
of Deepwater Horizon
Petrissa Eckle, Peter Burgherr, Edouard Michaux
Paul Scherrer Institute, Switzerland
IDRC, Davos, August 28, 2012

2. Deepwater Horizon/ Macondo, Gulf of Mexico 2010
― Largest accidental oil spill so far
― 11 workers killed, 17 injured in explosion
― Uninhibited flow for 3 months
― 680‘000 t of oil spilled
― 14 billion USD in immediate cleanup costs
― 30 billion in total so far
― Environmental and economic consequences will only become clear over coming years
IDRC, Davos, August 28, 2012 2

3. Deepwater Horizon/ Macondo, Gulf of Mexico 2010
Questions to be answered
―Outlier or not?
―How much do such single events contribute to total?
―Higher risk from drilling than other activities (e.g. tanker spills?)
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4. Context
Comparative risk assessment of energy supply options
IDRC, Davos, August 28, 2012

5. Comparative Risk Assessment
Energy Systems Analysis
Economy Environment Social
Risk of severe accidents, terrorism and
critical infrastructure protection
Risk indicators:
Average fatalities per year
Maximum historical accident
Expected fatalities per year
Exceedance at frequency F
Expected fatalities in frequency F accident
Fatalities
IDRC, Davos, August 28, 2012

6. Requirements - approach
Data based where possible – combine with modeling where necessary
– Historical data: Accident database ENSAD (mainly fossil fuels)
- comprehensive global coverage of energy related accidents since 1970
– Input from probabilistic models: Nuclear power
– Hybrid & expert judgment: New renewables, hydro power, CCS
Complete energy chains – resource extraction to waste
Exploration Extraction Transport Refining Transport Power/Heating Plant Waste Treatment & Disposal
Focus on severe accidents (≥ 5 fatalities, 10 injured, 10.000 t oil spilled..)
Top down: start with generic risk distributions – refine where possible
Core risk indicators:
- impact on human life: fatalities, injured
- impact on the environment: oil spills, land contamination (e.g. radiological for nuclear)
IDRC, Davos, August 28, 2012 6

7. Deepwater Horizon/ Macondo, Gulf of Mexico 2010
Questions to be answered
―Outlier or not?
―How much do such single events contribute to total?
―Higher risk from drilling than other activities (e.g. tanker spills?)
IDRC, Davos, August 28, 2012 7

8. Breakdown of sources
4 infrastructure categories:
- Ship spills
- Storage/refinery
- Pipeline
- Exploration/production
Number of spills: 1213 Total of oil spilled: 9.8 mio tons
Pipelines Storage/Refinery Pipelines
Storage/Refinery 870‘000 t 750‘000 t
188
113
Exploration & production
24 Exploration & production
2.2 mio t
Ship Ship
888 6.0 mio t
Accidental spills > 200 tons, 1974-2010
IDRC, Davos, August 28, 2012 8

9. Breakdown of sources
Goal: Quantify probability of spills as a function of spill amount
► expected return frequency of spill of size x
How often can we expect an event like the Deepwater Horizon accident?
Number of spills: 1213 Total of oil spilled: 9.8 mio tons
Pipelines Storage/Refinery Pipelines
Storage/Refinery 870‘000 t 750‘000 t
188
113
Exploration & production
24 Exploration & production
2.2 mio t
Ship Ship
888 6.0 mio t
Accidental spills > 200 tons, 1974-2010
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10. Distributions
RISK = Frequency x Severity
Number of accidents per year Spill amount per accident
– Mean frequency & trends – Fat tailed distribution
– Rare, independent events – Measure tail thickness
Poisson
► Model: Poisson ► Model:
– Empirical distribution
– Generalized Pareto (GPD)
IDRC, Davos, August 28, 2012

11. Risk: Frequency vs. severity
Data
Fit: Generalized Pareto (FN-curve = 1-empirical CDF*)
(1 – CDF*)
Spill amount [tons] *CDF: Cumulated density function
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12. Frequency
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13. Results: Ship Spills
1974 - 1980
1981-1990
1991-2000
2001-2010
Spill amount [tons]
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14. Results: Ship Spills
1974 - 1980
10 per year
1981-1990
1991-2000
2001-2010
0.6 per year
Spill amount [tons]
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15. Results: Overview
Ship & storage/refinery:
highest freq. for medium severity
Exploration/production:
Global frequency [1/year]
Highest freq. for high severity
DWH
Largest oil tanker
Spill amount [tons]
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16. Risk before and after Deep Water Horizon
Compare expected return frequency of the DWH spill before and after the new „data point“
Global frequency [1/year]
17 years return period*
*Uncertainty interval 5-95%: 10-70 yrs
22 years return period
Spill amount [tons]
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17. Conclusion
Structure of risk varies strongly between infrastructure subcategories:
- Transport/storage spills dominate small/medium spill risk
- Exploration/production: highest potential for very severe accidents
Top down risk assessment as a complement to bottom up engineering risk assessment
For risk of high severity events – global and long term dataset is essential
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18. Thank you for your attention www.psi.ch/gabe
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