Shell moves to protect marine mammals offshore Alaska
Monitoring and mitigation during exploration in the Beaufort, Chukchi seas
Mark Kosiara, Michael Macrander, Ian M. Voparil - Shell
Development in the Alaskan arctic offshore requires meeting technical challenges as well as managing special environmental sensitivities related to cold regions with lots of biological diversity. The Beaufort and Chukchi seas are home to a variety of whales, seals, and other marine mammals that may be sensitive to the sounds of industrial activities.
Whales migrate into the area during the time of year when seismic operations are possible over the outer continental shelf (open, ice-free water usually the late summer and early fall). Bowhead whales, classified as endangered under US regulation, first migrate eastward in the late spring along the coast of the North Slope toward the Canadian Beaufort as leads in the ice pack develop. They return westward in the fall before the Beaufort is covered with ice. The short window of ice-free conditions means that offshore operations cannot simply be rescheduled to avoid the whales’ migrations, but must be evaluated in near real time so impacts are detected and mitigated when necessary.
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Aerial survey transects location and general pattern for the eastern Chukchi Sea, summer 2007. Specific transect start-/end-points were altered randomly from survey to survey.
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Shell has extensive experience in the arctic, which contains an estimated 25% of the world’s remaining oil and gas resources. From Shell operations in Russia, Norway, Canada, and Alaska, the company has acquired substantial and growing experience in the technical, environmental, and social challenges unique to the arctic. That includes a long history in Alaska, where, beginning almost 50 years ago, Shell operated continuously until 1998.
Shell returned to Alaska in 2005 to participate in an offshore lease sale in the Alaskan Beaufort Sea. Through this, subsequent acquisition work, and joint venture, Shell is now the largest leaseholder in the Alaska Beaufort Sea.
In 2006, Shell performed a seismic program in the Chukchi Sea, with a limited shallow hazards survey in the Beaufort Sea; other operations were cancelled due to unfavorable ice conditions. In 2007, Shell conducted two 3D seismic acquisitions (one in the Chukchi Sea and one in the Beaufort Sea) and a number of developmental assessments including shallow hazards surveys. Shell also planned to drill two exploratory wells in the Beaufort Sea, but these plans were put on hold pending resolution of a legal challenge to the environmental assessment produced by the Minerals Management Service (MMS). Shell placed a priority on preventing injury to marine mammals by sound produced by offshore operations. This involved proactively limiting sound. For example, before the seismic program even went to sea, Shell worked with the geophysical company to limit the size of the seismic energy source to only that required to meet the technical objectives, to maximize downward propagation of sound energy, and to minimize horizontal leakage by tuning the airgun array’s components.
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Deployment locations of OBHs in acoustic net array along the coast of the eastern Chukchi Sea, Alaska 2007.
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Volume 68 Issue 9
September 2008
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