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Shifting the OCS season Ion wants to use under-ice techniques to do seismic survey late in the year Alan Bailey Petroleum News
As the days lengthen and the short Arctic summer looms on the horizon, an annual ritual has been taking place to sort out who does what in the seas around Alaska’s northern coastline during upcoming brief period when sea ice retreats towards the northern horizon.
But this year, in the interests of avoiding conflicts with other open-water activities, and in particular to avoid the annual subsistence bowhead whale hunts, one of the would-be offshore operators, Ion Geophysical, has proposed a novel solution to conflict avoidance: Shoot a seismic survey in the Beaufort Sea late in the year, after the sea ice has formed, using special equipment that can function under the ice.
Joe Gagliardi of Ion Geophysical presented his company’s concept at the National Marine Fisheries Service Arctic open-water meeting on March 23, a meeting that forms part of the public process for the authorization of offshore activities that might disturb marine mammals.
“What’s unique about this program is that we actually intend … starting on Oct. 1 and concluding sometime in mid- or late-November,” Gagliardi said. “Really the limiting factor for us becomes land-fast ice in the Bering Straits … at the end of the season.”
Complete rethink In 2006 GX Technology, a division of Ion, conducted a regional seismic survey in the U.S. Chukchi Sea. The company planned to carry out a second Chukchi Sea survey in 2007 but during the open-water meeting of that year decided not to proceed with that survey, Gagliardi said.
Instead, the company decided to completely rethink its approach to shooting offshore seismic in the Arctic.
“Starting in 2007, when we decided to remove our permit application for our Chukchi No. 2 program, we really took a look at what it would take if we wanted to come back and work in Alaska,” Gagliardi said.
In a marine seismic survey a vessel tows arrays of air guns that periodically blast sound through the ocean water and into the rocks beneath the seafloor. The vessel also tows what are referred to as “streamers,” often several miles long, carrying special microphones called hydrophones that detect air-gun-blast echoes, reflected from rock strata deep below the sea. Computer processing of the sounds detected by the hydrophones enables the construction of detailed images of subsurface rock structures.
In a conventional marine operation, the seismic survey vessel tows the air guns and the hydrophone streamers close to the sea surface. But, to overcome the problem of conducting a survey in a near-continuous ice sheet, Ion came up with a streamer design that would ride deeper in the water, below the bottom of the ice pack.
Icebreaker in front Ion completely redesigned its equipment configuration to enable operations in situations where ice covers nine-tenths of the sea, Gagliardi said. An icebreaker and a survey vessel would work in tandem, with the icebreaker moving just ahead of the survey vessel, clearing a path through the ice as the survey vessel proceeds along the desired survey route.
“We’re talking about an icebreaker in front and seismic boat behind. … They’re not independent. They have to operate together. There is no timeframe in which the icebreaker will actually operate independently from the seismic vessel,” Gagliardi said.
And in 2009 Ion successfully demonstrated this concept in a marine survey off northeast Greenland, he said.
In October and November 2010 Ion wants to shoot 600 to 800 kilometers (375 to 500 miles) of 2-D seismic lines along much of the Beaufort Sea offshore the North Slope using its new survey technique. The survey would start at the eastern end of the U.S. Beaufort Sea, moving progressively west, starting as the last of the summers’ bowhead whales head west toward the Chukchi Sea and avoiding the October whale hunt in the Barrow area, off the western end of the North Slope.
The survey should end by late November but could continue into December, Gagliardi said.
Marine mammal observers Three marine mammal observers on the icebreaker and one observer on the survey vessel will watch for marine mammals, to ensure that the air guns are shut down if the vessels come too close to the animals. And although the observers would have powerful binoculars and the vessels would turn on floodlights at night, Ion is also considering the use of a forward-looking infrared camera for spotting wildlife in the dark, Gagliardi said.
Gagliardi said that in December Ion had introduced its concept to the North Slope Borough and had sought guidance from the borough’s wildlife department. The company had also attended other meetings with North Slope communities and with the Alaska Eskimo Whaling Commission. And in April the company plans to meet with the people in Kaktovik, the village toward the eastern end of the U.S. Beaufort Sea coast.
Some participants in the open-water meeting questioned the practicalities of observing animals at a sufficient distance from two closely spaced vessels. There were also questions relating to possible interactions with any subsistence seal hunting that might be taking place at the time of the survey, and also regarding possible disturbance to the start of polar bear denning on the sea ice. And a resident of Kaktovik expressed concern about the possible impact on the formation of multiyear sea ice of offshore ice breaking operations.
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