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

They drill with water, or “muds”. The bit on the end is larger than the drill rods themselves, creating an annulus for water to pass through. This film of water prevents hole drag by keeping the rods from grabbing the rock.

As far as pushing goes, after about 400 meters, the drill is no longer pushing, the weight of the rods is what’s pushing the bit into the ground. After around 800 meter, the drill is being used to hold the weight of the rods back a little bit, creating tension on the rod string which helps keep them straight.