When drilling like 12 km deep into the ground, how is it possible that a 12 km long pipe (drill string) is able to turn the drill bit AND be pushed down enough to drill??

Question

A 12 km long pipe seems like a ridiculous length for any of that to be possible. Isn’t it like trying to drill a hole with a 258 ft long piece of spaghetti?

In: 1335

Answer 1

Hello, drilling engineer here! 🖐

In ELI5 terms: the pipe is thick and heavy. Over 12 kms, it’s so heavy that you don’t need to push it much. You just let the weight of the pipe work in your favour and help push the drill bit into the bottom of the hole.

The thing that rotates the pipe (top drive) is very powerful and can exert a very large turning force on the pipe.

To drill, you turn the pipe with the top drive and let the weight of the string push the bit further into the hole, thereby drilling.

This is the case in most applications. Things get trickier if the bottom of your hole is horizontal or some other crazy angle, where the full weight of the pipe no longer acts in the direction of the well bottom.