Some years ago, my brother decided he wanted to work on an oil rig in the Gulf Coast. He headed down south, but found out the only job he could get with no experience was one of the roustabout jobs.
He got on as a roustabout and did unskilled, entry-level work, cleaning, painting, and maintenance work.
After 2 years as a roustabout, my brother became a roughneck. (I have to chuckle at this job title). In this job, he had the responsibility of connecting the pipes together as they drill down. This was hard work - his shift was sometimes 12 hours long.
He took some training classes and eventually became a supervisor on the rig. He likes his work and it pays well, too.