Pressure measurements deep in geothermal wellbores provide some of the most valuable data for measuring the productivity of geothermal wells and for assessing reservoir characteristics. Wellbores have very high pressure and very low pH, but, most significantly, they have very high temperatures (up to 350ø C) that preclude present pressure measuring instrumentation from operating adequately. Instrumentation is needed that can provide improved pressure measurement resolution, accuracy, and reliability in harsh wellbore environments. To meet this need, a fiber optic interferometric pressure sensor with the following unique advantages is being developed: (1) accuracy better than 0.01%, (2) resolution better than 0.001%, (3) operation at temperatures between 150 C and 350ø C depending on the mechanical dither employed, (4) in-place calibration verification capability, (5) separation between sensor and electronics of up to several kilometers, (6) pressure span of 0 to 10,000 psi and above, (7) no electrical components at the sensing end, (8) immunity to electromagnetic interference (EMI), and (9) lighter weight and smaller size.Anticipated Results/Potential Commercial Applications as described by the awardee: The fiber optic pressure sensor will have a wide range of geophysical and power utility applications because of its unique advantages of high temperature operation, improved accuracy and resolution, remote sensing capability, and immunity to EMI. The sensor will enable heretofore unobtainable pressure measurements to be made in harsh environments of geophysical wellbores. Also, the sensor will be able to provide pressure measurements in the harsh EMI environments of electric utilities and radioactive environments of nuclear power plants.Topic 1: Geothermal Instrumentation
