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BP plans new offshore seismic survey Company wants to collect 3-D seismic data on north side of Prudhoe Bay to enable more effective management of oil-field reservoirs Alan Bailey Petroleum News
BP Exploration (Alaska) has applied to the federal Bureau of Safety and Environmental Enforcement, or BSEE, for a permit to conduct a new, high-resolution 3-D seismic survey in the shallow waters of the Beaufort Sea, offshore Prudhoe Bay, starting in the summer open water season of 2013. The company says that the purpose of the proposed survey is to obtain up-to-date, high resolution seismic data for existing oil reservoirs, to allow more effective reservoir management.
129 square miles The survey would cover an area of 129 square miles, mostly in waters three to 45 feet in depth, and would use water bottom cabling for data gathering, rather than the towing of hydrophones behind a seismic vessel, as is generally done in a marine seismic survey in deeper water. The southern edge of the survey area would extend onto land along the Beaufort Sea coast. The northern edge would extend a short way beyond the three-mile limit that defines the outer edge of state waters, thus placing about 19 square miles of survey on the federal outer continental shelf — hence, presumably, the need for a federal BSEE permit.
Although the survey area primarily lies within the Prudhoe Bay unit, the area includes portions of the Northstar, Dewline and Duck Island units, and some non-unit areas, BP says in its permit application.
Start in July BP says that it anticipates mobilizing equipment for the survey to Deadhorse in the central North Slope in late May to early June, with survey operations starting at the beginning of July. Demobilization would take place by the end of September. The company does not expect to complete the survey in 2013 and would likely have to return in the 2014 open water season to finish the work.
During the survey period, the survey crew will limit potential impacts on bowhead whale migration and subsistence hunting by only conducting air-gun operations in accordance with dates specified in a conflict avoidance agreement with North Slope whale hunters, BP says.
Seismic data acquisition will take place around the clock during the dates when survey operations are in progress. The entire operation will involve about 220 people.
Cable and sound-source vessels According to BP’s permit application, five or six small cable boats will lay and later retrieve the cables with seismic sound receivers on the seafloor, with the cables running on a series of parallel lines with a minimum spacing of 1,320 feet. Three seismic sound source vessels, each about 79 feet in length, will operate two at a time, while the third vessel is in dock for operations such as refueling. The two operational sound source vessels will tow arrays of air guns along parallel lines at a minimum spacing of 320 feet, running perpendicular to the cable lines. The vessels will discharge their air guns alternately, each at intervals of eight to 10 seconds, thus causing a seismic shot to occur every four to eight seconds.
The seismic operations will require authorizations from the U.S. Fish and Wildlife Service and the National Marine Fisheries Service for the unintended, minor disturbance of marine mammals — BP proposes implementing mitigation measures designed to avoid wildlife disturbance.
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