After having to pay the bill to water my lawn this summer, I sunk a shallow well in my backyard. There's a very high water table here so I only had to go 40 feet. Even at that low depth I'm still in 15 feet of water, pumping 12.5 gpm . I've been reading where some folks are running cold well water up into an evaporator and blowing a fan across it for home air conditioning. then the water is put right back in the ground through another shallow well. I'm going to do this. I already have an outside a/c package unit with a gas pack for winter. Just a few modifications and I'll drop my home cooling bill by about $500 a year.
So then I got to thinking, why not use the same thing for my computer. it will be a completely silent. No fans and the low volume pump will be outside in the pump house.
I need to have my water tested for pH and non-solubles and would have to insulate for condensation but that would be ok. With a constant flow of 60F (17C) water I think my computer would be quite happy.
There have been a few DIY geotherm WCing projects in the past with fair to good results. The problem is, that type of investment comes at a cost. Even harder when a person knows that in 5 or more years they will move out of the place. For the long haul, it's practical.
As for an open loop geothermal, that would be a pond or a holding tank that works as an open reservoir.
The distilled water bill would be alarmingly costly to do a geothermal loop. Thus, the one person I know used Berkey water twice filtered with good results with Sierra propylene glycol.
The only problem I see is the usually high water hardness of well water causing problems inside your computers cpu block. I would think it would leave deposits all over the insides of the block, eventually creating a clog. Of course if you have it tested like you say you will, and it comes back ok, I say go for it! Be sure to take some pictures of the setup too.