system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:How do drilling companies drill 7000+ feet below the surface? And when it comes to fracking, how do they begin drilling horizontally that deep underground?

Basically, how do oil drilling companies manage to drill that deep into the earth?
gpt
Basically when the drillers get to the depth where they want to start deviating from vertical there are directional parts of the drill bit they start pointing in a direction other than straight down to increase the angle of inclination. The angle is usually measured in degrees per 100ft. So the transition of vertical to horizontal is relatively gradual. They are able to do this from the huge amount of weight pushing down on top of the bit. 
The joints of drill pipe from surface to drill bit are very heavy. They pump drilling mud through this hollow drill pipe and out the end of the bit this is what causes the bit to rotate and penetrate through the rock. The mud exits the drill bit and is circulated back up to the surface between the hole and the drill pipe; also carrying the rock cuttings to surface for hole cleaning purposes. 
Signals are pulsed through the mud column down to the drill bit and control the directional movement of the bit. 
Sorry the comment was a little long but things tend to get misinterpreted with this sorta thing. 
Source engineer working with a drilling co.