Since I have an Oil & Gas background I did some quick calculations.

Assume shaft diameter = 12 ft or 144 inches, Depth - 1000 ft, 1 barrel = 42 US gallons

Conversion constant - 1029.414 bbls/ft

Weight of water = 8.4 lbs/gal

.052 psi/ft conversion constant

You take 144 squared divided by 1029.414 = 20.1435 bbls/ft

20.1435 bbls/ft x 1000 ft = 20,143.5 bbls water volume inside the shaft.

Bottom hole water pressure - 8.4 x 1000 x .052 = 436.8 psi

An ESP sized for 5 bbls/min and this pressure would drain the shaft in 2.8 days.

Work the shaft size and pump output numbers however you want as it is not that difficult.

Regards