The Kola Superdeep Borehole is 12,262 Meters (40,230 ft). That is not even through the crust yet. The water source is 700 Kilometers down. That's 700,000 Meters, and well into the mantle. There is nothing we have that could do that, let alone withstand the temperature and pressure.
The water must be really strange down there, it probably has it's own convection, pockets of intense heat and pressure... I wonder if there is life down there.Earth's mantle is a silicate rocky shell about 2,900 kilometres (1,800 mi) thick[1] that constitutes about 84% of Earth's volume.
wiki
If I'm correct, most aquifers (near the surface, anyway) are water-rich pumice or other porous rock.
Obviously wells and so on were incredibly important to the growth of civilization. I know that in Africa and Arabia people would bore tunnels underneath hills so that they would intersect with the water table and carry the water to an accessible area. These are called foggara or qanats depending on where they are. They were, I believe, crucial to places that were otherwise not arable and barren. It's my understanding that when they find water in the mantle, it's not an ocean in the usual sense of an open body of water because of the heat and the pressure. If that's the case, is there any practical or even theoretical application of drilling that deeply into the Earth? The article seems to suggest that just from knowing that there's water at that depth in that quantity is sufficient to understand its effects.