You will obviously notice any aquifer while drilling on the way down. And there may indeed well be water very deep down. But from what I understand, they are no

You will obviously notice any aquifer while drilling on the way down. And there may indeed well be water very deep down. But from what I understand, they are not connected with more surface level, and any diffusion of material takes a very long time. Keep in mind the pressure at those depths. Water is obviously lighter than rock, and if it had a way to go up, it would have.