They use heavy salt water during the drilling process so that in theory the standing column of water in the well is greater than the dynamic head pressure the aquifer has.Stupid question time: If that brine layer has the weight of 5000 feet of soil on top of it, does it squirt upwards when you make a hole in the clay layer? How far up?
Seems like a perfect setup for an artesian well of horrid sludge.
Also when the drill a well they grout seal the casings for several thousand feet before they hit the higher pressure water or oil formations. That way it prevents or at least greatly reduces the likelihood of an uncontrolled blowout.
As for putting the stuff back down the well the disposal stations have massive piston pumps that look just like giant triplex pressure washer pumps but they are 50 - 200+ HP and can pump several hundred GPM at 1500 - 2000 PSI to get the water to go down the well instead of come back up.
BTW around here when they get a dead oil well they plug it just below the salt water aquifer and turn it into a disposal well. The problem is there are so few bad wells here that there is a high demand for disposal well sites thus the ones that are running can earn the landowners more a year than had it been a good oil producing well.
Oil wells only run until their holding tanks are full or until whomever the pipeline is connected to stops needing oil. Disposal wells usually run 24/7 and never go bad.
I have mineral rights for some land from my moms side of the family and they are so worried that when they drill well in the next few years that we might end up with a bad well. I have told them that if that happens I will happily buy all of their mineral rights for what ever they think they are worth!