andrew mciiwain on brr @ 10:15am, page-30

"workover rig to clean out production tubing" Must be fairly advanced:

Production tubing is a tube used in a wellbore through which production fluids are produced (travel).

Production tubing is run into the drilled well after the casing is run and cemented in place. Along with other components that constitute the production string, it provides a continuous bore from the production zone to the wellhead through which oil and gas can be produced. It is usually between five and ten centimeters in diameter and is held inside the casing through the use of expandable packing devices.

If there is more than one zone of production in the well, up to four lines of production tubing can be run.