Innovative Drilling Technology for Supercritical Geothermal Resources Development

Abstract

Supercritical geothermal system originated in Japan Trench subduction zone has the potential to generate a terawatt-scale of energy in Japan. For development of the supercritical geothermal system, technologies to efficiently drill into the deep ductile formation with temperature over 400°C and to complete wells with sufficient integrity are indispensable. A concept of well stimulation method to create fracture clouds that uses rock failure phenomena induced by the thermal-shock or thermal-stress generated by a decompression, boiling and consequently a rapid cooling of the completion fluid in the wellbore has been previously presented. In the current research project, the authors are extending the concept to develop a new innovative drilling method that uses thermal-shock failure phenomena artificially induced at the bottomhole. An industrial-government-academia joint study project is now in progress which consists of the following five subtasks: (1) development of a new drilling tool that can generate a thermal-shock failure of rock induced by depressurization, boiling and cooling at the bottomhole, (2) experimental and simulation studies on the mechanism of thermal-shock failure of high temperature rock, (3) development of wellbore hydrothermal simulation technology applicable under supercritical formation condition, (4) development of a new concept casing packer, and (5) study on acid- and corrosion-resistant materials against supercritical environment.