I thought I would try a bit of show and tell, when on a rig I don’t spend time with the drilling crew as I’m more on the marine side of it, so I have had to pick up snippets of information when and where, i’ll try my best, but bits of information may be wrong, but you should get the general idea.
A drill string on a drilling rig is a column, or string, of drill pipe that transmits drilling fluid (via the mud pumps) and torque (via the top drive) to the drill bit. The term is loosely applied as the assembled collection of the drill pipe, drill collars, tools and drill bit. The drill string is hollow so that drilling fluid can be pumped down through it and circulated back up the annulus (the void between the drill string and the casing/open hole).
Here is some 30 foot lengths of drill pipe laying down on the deck of the rig, the black plastic caps on the end of each pipe are there to protect the thread, these are unscrewed and used again when the pipe is removed from the hole.
The pipe is laid down for transit as we don’t want the rig to be top heavy whilst under tow, once on location and all Anchors are deployed the drill pipe can be lifted up to the derrick and screwed together, normally 3 lengths in one stand as seen below, the drill pipe is on the left side of the derrick in stacks of 3 ready to be deployed by the Top Drive. (be warned I’ll be talking about that tomorrow)
On the business end of the drill pipe is the drill bit, this is rotated by the top drive, also each cutting head is rotated by high pressure mud being pumped down the hollow centre of the drill string.