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TGS plans Beaufort Sea seismic survey
3-D survey would cover 905 square miles north of the central North Slope and take three summer open water seasons to complete
Alan Bailey Petroleum News
TGS-NOPEC Geophysical Co. has applied to the federal Bureau of Ocean Energy Management for a permit to conduct a 3-D seismic survey to cover an area of 905 square miles of the Beaufort Sea, offshore the Colville River delta region of the central North Slope. The company anticipates conducting the survey in three phases, with each phase to be completed during a single summer open water season. In its plan of operations, TGS says that about 620 square miles of the survey would take place in waters of the federal outer continental shelf, while 285 squares miles would be in state nearshore waters. The component of the survey in state waters will require state permits.
TGS anticipates its phase 1 program to start in mid-July this year and continue until late October.
“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,” the TGS plan of operations says.
The more western portion of the survey area appears to lie offshore the recent major Pikka/Horseshoe oil discovery. TGS refers to the survey as the “Barrow Arch 3D,” in reference to the regional geologic arch structure that has led to many of the oil accumulations in the coastal region of the North Slope.
Cable-free recording The survey will use cable-free ocean bottom nodes to record the seismic signals. Prior to a data gathering operation nodes will be placed in position on the sea floor, tethered at 100-foot intervals along ropes spaced 600 feet apart and laid along north-south orientations. The nodes will be retrieved for data download after the operation has been completed. The seismic sound source will consist of an eight airgun device, towed at a depth of 2 meters behind a seismic source vessel. Jet driven shallow draft vessels and bow pickers will be able to deploy and retrieve the recording nodes, the plan of operations says.
TGS proposes to deploy a total of nine vessels for the survey operations, including two seismic source vessels; the node deployment and retrieval vessels; a mitigation and housing vessel; and a crew transport vessel. Since the vessels will not have ice breaking capability, the operations will avoid any pack ice in the project area.
24-hour operation To the extent possible, taking into account the potential for shutdowns to mitigate marine mammal disturbance, operations will be conducted 24 hours per day, the operations plan says.
And, given the potential for noise from the operations to disturb wildlife and subsistence resources, the project will require an incidental harassment authorization from the National Marine Fisheries Service, a letter of authorization from the U.S. Fish and Wildlife Service, a marine mammal monitoring and mitigation plan and a conflict avoidance agreement with the Alaska Eskimo Whaling Commission.
TGS says that it has planned meetings and engagement with communities and marine mammal co-management groups on the North Slope to discuss its proposed program.
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