They can either recharge naturally (i.e. with earth conduction), but it takes a lot of time.
Or you can also recharge them during the summer, either with solar thermal panels, or on a small measure, by running your HVAC "backwards" (i.e. cooling your home and thus heating the wells)
The wells would recharge even without Earth's existing surrounding heat reserves. Moon (and Sun) induced tidal forces do manifest not only in the body of water but also in the Earth's crust, and the resulting tension/friction is quite a source of energy/heat.