Anchorage - Attorneys for Royal Dutch Shell PLC presented testimony to a federal court judge on Tuesday that the company needs safety zones around its Arctic drill fleet to prevent Greenpeace USA activists from endangering company workers and themselves.An attorney for Greenpeace told US District Judge Sharon Gleason that Shell's request would usurp the maritime authority Congress gave to the Coast Guard and harm free speech rights of Greenpeace activists, who have the right to approach Shell vessels to draw attention to harmful drilling in the Arctic.Judge Gleason after a seven-hour hearing said she will consider additional briefs before deciding whether to grant Shell's request for an injunction banning Greenpeace from approaching Shell's Arctic fleet through October 31, which covers the 2015 drilling season. A ruling could come within a week.Shell is seeking federal approval to use two drill vessels for exploratory drilling this summer on federal leases in the Chukchi Sea off Alaska's northwest coast. A Shell manager testified Shell has spent upward of $7bn on its Arctic project.Arctic drilling is strongly opposed by conservation groups, including Greenpeace, that say polar regions are being hammered by climate warming at twice the rate of the rest of the planet and would be severely harmed by industrial development. The groups say oil companies have not demonstrated the ability to clean up a spill under the best of circumstances, much less in remote, cold waters far from infrastructure such as ports and Coast Guard bases.An injunction would give Shell a tool to take action against protesters in civil court rather than criminal court.Attorney Jeffery Leppo told Judge Gleason the company could seek contempt citations for illegal, direct actions taken my Greenpeace, such as boarding vessels in transit.Activists from Greenpeace International this month boarded a heavy lift ship carrying the Polar Pioneer, a vessel without propulsion that Shell plans to use this summer in the Chukchi Sea, as it crossed the Pacific from Malaysia to a staging area in Washington state. Greenpeace past actions and statements are a concern for future actions, he said."These aren't empty threats and puffery," he said.Shell is seeking a 1 000m safety zone around most of its fleet and 1 500m around drill vessels.Greenpeace Arctic campaigner Mary Sweeters testified that halting Shell drilling is a top priority for her organization and that peaceful protest that breaks trespass or other laws are a tool used to draw attention to the group's causes. Images of protests shared on social media are powerful tools, she said, and Shell's injunction request would hamper the Greenpeace mission."It would make our work very difficult, probably close to impossible," she said.Shell's proposed safety zones exceed the 500m limit that can be granted by the Coast Guard would seriously impinge on the organizations free speech rights, said attorney Matthew Pawa. Shell presented no expert testimony that the larger safety zones are needed, he said.