From the top
24" tri-cone bit-
18" tri- cone bit
28" hammer bit
18" hammer bite
Just for drilling through the upper hole.
Where I'm at, the larger drills down around 270' through all water tables.
The 18" goes to around 450' for the mine string.
Then a 12.5" for intermediate string and lastly, 8.5" the rest of the way which can go out to 17-19,000' TD
These Marcellus wells go to around 6-6,500 ft before they turn to start the horizontal run. In sw pa, that's around 370-390 million years ago. ( when the formation would have been on the surface)
Crazy when you only have to dig 2-3" for a civil war bullet.