This method has major disadvantages. It is very expensive and there is significant environmental impact from the roads, large drill sites and fluid-handling requirements. And if the operator hopes to turn an exploration well into a production well, it may be located at the fringe of the resource, where it is not convenient for eventual construction of the power plant.
Drilling production-size holes for geothermal exploration also puts a large expense at the beginning of the project, and thus requires a long period of debt service before those costs can be recaptured from power sales. If a reservoir is defined and proved with slimholes, production well drilling can be delayed until the power plant is under construction, saving years of interest payments. High exploration costs also limit the number of poten-tial new resource areas that can be evaluated, preventing significant expansion in the nat-ion's proven geothermal reserves.