Knowing how to reliably and replicably engineer a geothermal reservoir, or develop an "engineered geothermal system (EGS)", is the critical skill that needs to be developed if geothermal energy is going to play a major role in the world's future energy mix. EGS systems have been generated in a small number of projects in the past, and the knowledge gained from these projects points the way to exploiting resources in many parts of the world. It all comes down to rock mechanics and the way fractures respond to applied stresses. This forum is set up to explore, explain and develop these ideas.