RE: Cumberland Well Complete...News..."Not sure, but the rig is probably a small double, not a slant rig." You drill horizontals with conventional rig. Go verticle as far as you want, then use a bent-sub to 'kick off'---been a while since I've been around this, but we used bent sub, mud motors, a special sensor to tell us which way we were drilling and the angle---
Actually, we once drilled a 5000' hole where the bit was 1300' "that-a-way" once---only problem was, it was supposed to be a straight hole! Once it kicks off, tends to keep going----when using a cable tool, bit tends to veer to soft side, if there is one-or kinda 'down formation, if it's slanted-a rotary bit goes to the hard side---just trivia, we were working in an old field, would rotary drill to about 20' from target, then unload fluids from hole and a cable tool would finish. Didn't want the fluids getting into formation.
I used to own a fairly successful calgary driller--knew the guys well--they were doing horizontals about 3000' deep. They were telling me that the layer they were trying to stay in was actually about like the floor and ceiling of a building--with floor and ceiling a little harder than their target zone and that it was actually fairly easy to stay where they wanted to be. They drilled several in a row successfully, kinda got it down. Where they were at, the verticle part was cased but horizontal leg produced 'open hole'. There was a fairly consistent thin layer of coal above their target--which was oil--and it helped as kinda a 'tracer', when the coal would come over the shaker--I imagine it drilled different also.
These wells were good--one flowed @800boe for a while--dropped off fairly fast, but payout was only about a month. They said they were actually easier to manage, once you got them on pump--if flowing well had to be shut in for a while, it took a lot of fooling around--and expense--to get it flowing again.