超臨界地熱開発のための掘削技術課題

抄録

Supercritical geothermal power generation is a next-generation geothermal power generation using geothermal fluid that exists in deeper formation than conventional geothermal reservoir and is in a supercritical or subcritical state in subsurface environment. The steam production capacity per production well of supercritical geothermal power generation is estimated to be several times higher than that of conventional geothermal power generation. Drilling and completion of supercritical geothermal wells under harsh conditions assuming an ultra-high temperature above 400°C and H₂S and/or HCl acidic corrosion environment with very low pH, and maintaining the well integrity for about 40 years of commercial power generation, are a challenge to overcome the extremely difficult technical issues compared to the conventional geothermal development. In this lecture paper, current status of domestic and worldwide supercritical geothermal resource development is reviewed and the technical issues in drilling and completion of supercritical geothermal wells are discussed.