Exploitation of geothermal heat energy from rocks at depths of several km has been the goal of vari-ous projects since the mid-1970s. To exploit the energy in these deep rocks poses technical challenges in drilling, well completion, creation of the heat exchange reservoir at depth, and control of seismicity. In spite of the difficulties, what are now known as enhanced/engineered geothermal systems (EGS) offer almost limitless clean energy, so it is not surprising that this technology continues to attract investors. However, commercial energy production from the greatest potential resource, hot rock at depths >5 km or temperatures >200°C, remains elusive.

You do not currently have access to this article.