If you really want to go to an offshore drilling platform, you should apply to CNOOC. Of course, most of the recruits now are fresh graduates. Mechanical major can be the chief engineer and mechanic of drilling platform. There is no restriction, as long as the major is recruited and the education is complete. If you recruit from the society, you must have work experience.
But I still advise you to think about it and come back. But don't go to CNOOC's drilling division. This unit is inhuman, and it sucks.