Supercritical Fluids - Learning about the Deep Roots of Geothermal Systems from IEA Geothermal Collaboration

In recent years, projects in several member countries of the International Energy Agency (IEA) Geothermal Technology Collaboration Programme (TCP), Working Group 12, have undertaken research into the deep, high-temperature roots of conventional geothermal systems. The objective is to source and evaluate higher value energy resources for future use. These countries include: Iceland (IDDP2), Italy (DESCRAMBLE), Japan (Super-Critical), USA (NW Geysers EGS), Mexico (GEMex), Switzerland (COTHERM) and New Zealand (HADES). This paper compares the learnings from these projects to help guide future research programs. These learnings will enable researchers to focus on the technical problems that remain and to share the benefits of knowledge already acquired. The huge potential energy resource of 'deep roots' is undisputed; it can be estimated in terms of gigawatts of electricity generation per resource area, over minimum lifespans of 30 years. The most important remaining issues are related to: drilling problems at high temperature and pressure (casing, drill-string, cement and mud fluids); material selection to cope with corrosion from gassy supercritical fluid; well-bore stability under super-critical operating conditions; and finding, creating, and sustaining permeability in ductile conditions.