Geothermal wells depend on the availability of a suitable underground aquifer or river. It must be deep enough underground to provide the necessary heat, and the water supply must be steady and plentiful so that the cooling effect of the geothermal system does not negatively effect any ecosystems dependent on the aquifer.
Since the requirements for a geothermal well can be difficult to meet, several wells may need to be dug before the perfect candidate is found. They may be relatively shallow or they could be several hundred feet deep. The deeper the well, the costlier it is to drill and the more technically difficult to operate.
