I have been planning MANY years to build such a system... but may never get around to it due to money shortage.So I wish you to succeed very much. Here are a few thoughts for you to ponder ....
HEAT RISES... UP in water... so the water at the TOP of your well will be warmer, and the water at the BOTTOM will be the coldest. So you would want to withdraw water from the deepest part... and dump back at the top surface. And place insulation-wrap around the UP-pipe so it doesn't RE-WARM on it way back up!
EASY PUMPING.... if you circulate the water up and back down, you will NOT need a big pump... because the water traveling down will counterbalance the water going UP... If you dump the water on the SURFACE of the ground, then you are not circulating, you are PUMPING, and that requires more amperes and a bigger motor.
DUMPING WELL... if you had a 2nd well you could dump in that one a few yards away
to keep the temperature from rising... which i am not convinced is a problem yet.
LARGE RADIATOR... I believe you will need a large-ish radiator to accomplish the heat-exchange. The fellow who suggested the made-for-the-purpose heat exchangers was well intentioned... but the $80 dollar one was only 12 inches by 12 inches. and it is made for HEAT exchange (delta-t) of very hot water from a woodstove. not COOLNESS exchange of water only 25 degrees cooler that ambient air.... so unless you can afford the BIG BIG one at several hundred bucks... i suggest you get a car or truck radiator or other options that would be cheaper.
PUMP--AND---DUMP... some say is ILLEGAL... I say so what! You could place a
closed loop pipes into the well, and you are not really "pumping." you are just
circulating water up and back down through the same pipe adding a few degrees
warmth to the ground. The earth contains GIGANTIC amounts of tonage of rocks and water down there... I dont believe your "puny" radiator will warm the EARTH enough to worry about germs and mold contamination of the aquefer. I have a few other suggestions,(easy well drilling, other pumping methods,etc) but dont want to make this too long.. email me at framistan@sbcglobal.net (If you would like to discuss further).. the picture is me drilling a 20ft hole using a post hole twist drill.