Memo describes 1.4 million barrel Chukchi spill

A March 4 internal Bureau of Ocean Energy Management, Regulation and Enforcement memo which has become public and which describes the possibility of a 1.4 million barrel oil spill in the Chukchi Sea has raised some eyebrows among those with an interest in the controversy over planned Arctic outer continental shelf oil and gas exploration.

BOEMRE staff prepared the memo as part of an initiative to add a very large oil spill assessment to a new Chukchi Sea lease sale supplemental environmental impact statement. The agency is preparing the SEIS in response to a court order in an appeal against the 2008 Chukchi Sea lease sale in which Shell, ConocoPhillips, Statoil and other companies bought oil and gas leases.

The memo describes a hypothetical oil spill from an unspecified prospect in the central part of the Chukchi Sea lease sale area, in a situation with an out-of-control well penetrating an especially thick, permeable oil reservoir, and where the well blowout preventer proves completely ineffective. The envisaged spill scenario does not appear to take into account the availability of any form of spill containment device, of the type that was developed to eventually contain the Macondo well blowout in the Gulf of Mexico.

According to the memo, if the drilling vessel that is drilling the well is also able to drill a relief well, the blowout could be brought under control in about 39 days. That timeframe would extend to 44 days were it necessary to use a second drilling vessel, already positioned with the Chukchi Sea, to drill the relief well. And were it to be necessary to use an out-of-region drilling vessel for relief well drilling, the timeframe would extend to about 74 days.

Initial oil flow from the well would rapidly peak at 61,000 barrels per day, steadily tailing off thereafter and dropping to about 18,000 bpd by day 30, the memo says. By day 39, by which time the well could have been brought under control, 1.4 million barrels of oil would have spilled from the well, with that total volume of spilled oil increasing to 1.5 million barrels by day 44 and 2.2 million barrels by day 74. Were all attempts to control the well to fail, 2.4 million barrels of oil would have escaped from the well by day 90, the memo says.

Hypothetical scenario

“The numbers referenced in the memo are not from proposed drilling,” Callahan said. “They are purely hypothetical, provided to environmental analysts who will, in turn, use them to ensure that decisions are based on the best science available. Any operator that proposes drilling an actual well must conduct an independently verified analysis of potential environmental impacts, including possible oil leaks.”

And on May 3 in a University of Alaska Anchorage panel discussion of managing Arctic offshore oil risks, Jeffrey Loman, deputy director of BOEMRE Alaska region, said that the goal of assessing a very large oil spill, as envisaged in the memo, is to fully inform government decision makers of the potential risks involved in offshore exploration. BOEMRE’s new approach is to consider a worst-case scenario — the largest spill that could hypothetically occur — rather than, as in the past, use a mindset of only considering the most likely size of a spill, Loman said.

In the event of permitting a specific drilling operation, the worst-case spill volume for that specific operation at that specific site could be significantly less that the hypothetical worst-case scenario considered in the memo, Loman said.

—Alan Bailey