The risk of small or medium oil spills from ships,
pipelines, storage facilities and refineries is higher than from oil
exploration and production. However, the risk of
severe oil
spills is highest from exploration and production, according to a recent
study. Furthermore, the study suggests that the Deepwater Horizon
accident, the largest recorded oil spill, cannot be considered as a
particularly rare event.
Using information contained
in the global Energy Related Severe Accident Database (ENSAD), this
study analysed over 1200 accidental oil spills that occurred between the
years 1974 and 2010. Severe accidents include those where there are
fatalities and where more than 10,000 tons of oil were spilled. This
study included oil spills larger than 200 tons in order to make
comparisons between incidents of varying scale.
Spill sources
were divided into four categories: (i) spills occurring during
exploration or production e.g. from oil wells, drilling and exploration
platforms and rigs, (ii) spills from tankers transporting crude oil and
refined products, (iii) spills from onshore and offshore pipelines
carrying crude oil and refined products and (iv) spills from refineries
and storage sites.
In this period, a total of 9.8 million tons
of oil were spilled in 1213 incidents. While exploration and production
was responsible for far fewer spills than ships, storage and refinery
and pipelines, it caused far greater quantities of oil to be released.
Six million tons of spilled oil came from 888 ship incidents; 870,000
tons from 113 spills at storage and refinery sites and 750,000 tons from
188 spills from pipelines. However, 2.2 million tons were spilled by
just 24 incidents during exploration and production.
These
figures reveal the severity of spills from exploration and production.
While the risk of small or medium spills is generally higher from ships,
pipelines and storage/refineries, the risk of large and therefore more
severe oil spills is higher from exploration and production as the
potential amount of oil that could be released is far greater.
Spills
from tankers accounted for around 75% of the total spills and volume of
oil spilled during this time. However, over time, the number of spills
and volume spilled from oil tankers fell significantly despite more oil
being carried. This is probably because better, electronic, navigation
systems have been installed in ships and ships are required to have
double hulls, which reduce the chance of spillage should the outer hull
be damaged. In contrast, the frequency of oil spills from storage or
refinery facilities and from pipelines increased over this period.
No
particular increases or decreases in the frequency of spills were found
for exploration or production operations, although it is possible that
studies with a longer time frame could reveal trends. Alternatively, a
combination of other risk factors, such as drilling in new locations or
changes in regulations and technologies, might explain a lack of trends.
By
analysing the data, the study suggests that a severe oil spill on a
similar scale as the Deepwater Horizon incident in 2010 could occur
every 23 years. The accident at the Deepwater Horizon exploration
drilling rig in the Gulf of Mexico killed 11 people and released an
estimated 680,000 tons of oil into the sea.
Source: Eckle,
P., Burgherr, P. and Edouard Michaux, E. (2012). Risk of Large Oil
Spills: A Statistical Analysis in the Aftermath of Deepwater Horizon.
Environmental Science & Technology. 46: 13002-13008. Doi.org/10.1021/es3029523
CRS Environment: Make A Difference
