Thermometry in geothermal wells: an optical approach

A temperature measuring system based on purely optical devices is described, which exploits the temperature dependence of the physical properties of a birefringent crystal. The system is expected to measure the temperature profile in geothermal wells up to 500° C and with a resolution better than 0.1 ° C. The maximum expected depth is 3500 m. Technological solutions of the problems related to the use of optical fibers for this application are also discussed. A prototype for field use has been implemented and will be described, and preliminary experimental results will be reported.