olympic dam project, page-21

Great topic people. If you go to

http://en.wikipedia.org/wiki/Enhanced_Geothermal_System

this gives a good summary on the technology, however if you scroll down to the bottom of the page there's a pdf:

"The Future of Geothermal Energy in the United States".

This document looks to be highly informative, I'm just getting into it now. For now here's a primer:

"Although somewhat simplistic, the geothermal resource can be viewed as a continuum in several
dimensions. The grade of a specific geothermal resource would depend on its temperature-depth
relationship (i.e., geothermal gradient), the reservoir rock’s permeability and porosity, and the amount of
fluid saturation. High-grade hydrothermal resources have high average thermal gradients, high rock
permeability and porosity, sufficient fluids in place, and an adequate reservoir recharge of fluids – all
EGS resources lack at least one of these. For example, reservoir rock may be hot enough but not produce
sufficient fluid for viable heat extraction, either because of low formation permeability/connectivity and
insufficient reservoir volume, and/or the absence of naturally contained fluids."