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TGS delays Beaufort Sea seismic survey
Company now plans to conduct nearshore Barrow Arch 3-D survey off central North Slope during the 2019 and 2020 open water seasons Alan Bailey Petroleum News
Alaska’s Division of Oil and Gas has approved an application by TGS-NOPEC Geophysical Co. to delay from 2018 to 2019 the start of a two-year 3-D seismic survey in nearshore waters of the Beaufort Sea. The company had hoped to conduct the first phase of the survey during last year’s Arctic open water season, but now plans to carry it out this year. The survey would then be completed during the open water season of 2020. The division has also approved an increase in size of the seismic source for the surveying, coupled with larger marine mammal mitigation zones and a modified acoustic monitoring program.
Federal and state land Termed the Barrow Arch 3-D Marine Seismic Survey, the survey area covers 905 square miles of the Beaufort Sea, with about 620 square miles in waters of the federal outer continental shelf and 285 square miles in state nearshore waters. TGS has applied to the Bureau of Ocean Energy Management for a permit for the OCS component of the survey. The company will also need an incidental harassment authorization from the National Marine Fisheries Service and a letter of authorization from the U.S. Fish and Wildlife Service for the unintentional disturbance of marine mammals. TGS says that it will also require a conflict avoidance agreement with the Eskimo Whaling Commission.
The survey, extending from the eastern Harrison Bay, offshore the Colville River Delta, eastward to about four miles east of Oliktok Point, will clearly encompass an area of high hydrocarbon potential.
“Results of the 3-D seismic program will be used to identify and map potential hydrocarbon bearing formations and the geologic structures that surround them,” TGS said in its permit application.
Cable-free recording The plan for the survey involves the use of cable-free ocean bottom nodes to record the seismic signals. The nodes would be tethered on the seafloor along north-south lines. Two vessels, each with a towed seismic source array, would be available for generating the seismic signals. Source lines would run east-west, perpendicular to the recording lines. Each source vessel would tow a source system of different power, with the more powerful unit being used in deeper water.
A total of nine vessels would be involved in the survey operations, including the source vessels; node deployment and retrieval vessels; a marine mammal monitoring and crew housing vessel; and a crew transport vessel.
Mitigation actions in the event of sightings of marine mammals in the area of the survey include vessel speed and course alterations, and the potential shutdown of the seismic signal source. TGS says that the planned start on or after July 15 will result in minimal impacts on spring marine mammal migrations and on subsistence hunting. There will, however, be location and timing restrictions, to take account of fall bowhead whale hunting, TGS’s permit application says.
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