An oil tanker with 34 men aboard broke its mooring and drifted for five hours in the stormy North Sea today before two tugboats chased it down and began towing it back to Scotland. The tugboats attached lines to the tanker about 200 miles east of the port of Dundee, a coast guard spokesman in Aberdeen said. The tanker's engines were removed when it was permanently moored in the North Sea as a storage facility where smaller tankers picked up oil, so it drifted in strong winds and turbulent seas. The vessel was moored at a loading point in the Fulmar oil field when it broke from its mooring about 5:30 a.m. in 15-foot waves and 60 mph winds and began drifting to the southeast, said the spokesman, who demanded anonymity.