Operating geothermal power plants utilize fluids that flow through fracture networks of heated subsurface rock which creates reservoirs of hot fluid or steam. Prior to constructing and connecting a geothermal plant to the grid, developers must go through several steps to locate and harness these reservoirs. The steps to subsurface resource development are: 1) exploration, 2) drilling, and 3) reservoir management.
Successful completion of these steps involves the employment of numerous subsurface technologies. These technologies, which include both the tools used and approaches taken to develop a given resource are effective in only the best of conditions. To utilize most of the geothermal resource base subsurface technologies would need to be improved, new exploration technologies developed, and costs for drilling significantly reduced.

  Geothermal Technology Part I - Subsurface Technology (Nov 2007).pdf