There is no such thing as an oil rig.
Here’s the process, in a nutshell (and greatly simplified)-
A drilling rig is moved onto likely site, and drills a narrow, but very deep hole. This process could take from a couple of days on up, depending on circumstances. If traces of oil are found, casing (constant diameter pipe) is run into the hole, and cemented in. If no traces of oil, the hole is plugged (not capped- plugged with cement).
Then a workover rig is brought in to make the cased hole into a well, and the necessary hardware is installed at the top of the hole to pump the oil.
The men who work on drilling rigs are called “roughnecks”- yes, that’s really a job description. I and all of my brothers have been roughnecks at one time or another.
Around here, we call the men who work on workover units “roustabouts”- and it’s miserable, tough work.
Just curious.