High temperature instruments and methods developed for supercritical geothermal reservoir characterisation and exploitation—The HiTI project

•New Na/Li geothermometric relationships were discovered and tracer tests performed.•Televiewer and gamma tool with casing thickness evaluation field tested to 300 °C.•Pressure, temperature and spinner tool made for 400 °C.•Wireline temperature sensor field tested to 300 °C.•Laboratory core deformation studies and rock resistivity measurements.

During the early years of the Iceland Deep Drilling Project (IDDP), development of three distinctive technological and scientific approaches were formalised and then carried out until 2010 within a European funded project called HiTI (high temperature instruments for supercritical geothermal reservoir characterisation and exploitation). These approaches were: (1) development of several downhole instruments allowing them to function up to 300 °C and 400 °C, (2) identification of two new Na/Li cation ratio geothermometric relationships valid at very high temperature, (3) tracer testing with high temperature tolerant organic isomers and finally and (4) basalt rock deformation and petrophysical properties laboratory investigations at high temperature and pressure conditions.

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