Oil firms in the final stages of testing for possible millennium disturbances on Norway's offshore oil and gas platforms say they are confident there will no major mishaps at midnight on December 31. Operators say they have tested thousands of components and replaced obsolete systems and controls where potential computer bugs may have lurked. "We cannot guarantee 100 percent but we can say that it is highly unlikely that anything will happen," said Kai Nilsen, spokesman at the state oil firm Statoil. Oil companies, along with the Norwegian Petroleum Directorate (NPD), began Y2K preparations as early as 1997. In the worst case, the NPD feared that a freak chain of computer failures could trigger an explosion.