Qualifications
You need at least a high school diploma to be a roustabout or steward. Because there are few requirements for getting an entry-level position, people apply to oil rig jobs in droves, meaning that the competition can be stiff.
If you want to get a position higher in the ranks, or just want a better shot at getting in, it's best to have attended a vocational school for welding, basic mechanics, or heavy equipment operations. There are some trade schools that offer classes in oil field work. Also, the military provides oil field work training for those leaving the armed forces as part of an effort to make sure soldiers get employed after their service.
Certifications in Helicopter Underwater Escape Training (HUET) and Basic Offshore Safety Instruction and Emergency Training (BOSIET) help you get a leg up on the competition for positions. Most companies require their workers to earn an Offshore Survival & Firefighting certificate. If you want to become a specialized worker,, such as an electrician, you must have a state-issued license (source).
Applicants must be able to pass a drug test, which does not involve them saying, "Pass," when being offered the chance to take the test. For some reason, oil companies don't want to employ people drugged out of their minds to work on a flammable oil rig. Other qualifications that help your chances include good depth perception, eye-hand coordination, physical strength, interpersonal skills, and an eye for details. If the oil rig is on fire, they want you to notice.