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Putting the spill risk in perspective BOEM explains reasoning behind its Chukchi Sea oil spill 75% probability assessment in revised lease sale environmental analysis Alan Bailey Petroleum News
Following criticism from environmental organizations over approval for a Chukchi Sea oil and gas sale, despite recognition of offshore oil spill risks, the Bureau of Ocean Energy Management has issued a fact sheet, explaining the context and meaning of its spill probability assessment.
“The bureau supports energy independence, environmental protection and economic development through responsible management of these offshore resources based on the best available science,” BOEM says. “All offshore exploration has potential benefits and potential risks. Our goal is to maximize benefits and minimize risks - to people, wildlife and to the environment.”
In February, following a lengthy appeal against the Chukchi sale, which was held in 2008, the agency published a new supplemental environmental impact statement for the sale. And, on the basis of that new document, at the end of March the agency re-affirmed the holding of the sale.
But the media and some stakeholders have particularly homed in on one specific estimate in the environmental document, an estimate that there is a 75 percent probability of one or more oil spills of more than 1,000 barrels of oil as a consequence of the lease sale taking place, BOEM says. The fact sheet that BOEM has now issued attempts to put that 75 percent figure into perspective.
Long-term scenario Firstly, the 75 percent figure relates to a hypothetical long-term oil exploration and production scenario that BOEM analysts created for assessing the potential environmental impacts of the sale. The figure does not relate to a single oil industry program, such as Shell’s planned Chukchi Sea exploration, BOEM says. In fact BOEM views the probability of a large oil spill during exploration in the Chukchi Sea as very low, the agency says.
BOEM’s hypothetical scenario, assuming that offshore exploration meets with success, envisages the installation of eight production platforms and the drilling of more than 500 wells over the course of 77 years, resulting in the production of 4.3 billion barrels of oil. For that entire timeframe of more than seven decades, the BOEM analysts estimated a 75 percent probability of a single oil spill of more than 1,000 barrels, BOEM says. Then, in the interests of not understating the oil spill risk, the agency based its environmental impact evaluation on an assumption of the possibility of two such spills, not one.
The median estimated size of a significant spill of this scale would be 5,100 barrels from a production platform and 1,700 barrels from a production pipeline, the agency says.
By way of comparison, estimates for the size of the1989 Exxon Valdez oil spill range from 257,000 to 750,000 barrels, while 3.19 million barrels are thought to have spewed from the Macondo well following the Deepwater Horizon disaster, BOEM says.
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