High-Temperature Optical Seismic Sensor

Enhanced Geothermal System (EGS) technology has emerged as one of the key technologies for enabling the large-scale use of cost-competitive geothermal energy. In order to accurately map rock fractures before and after stimulation, the EGS needs seismic sensors at downhole depths. Unfortunately, due to the unavailibility of high-temperature electronics, the current generation of seismic sensors can not operate in the downhole environment where the temperature may reach 250°C.. To address this problem, this project will investigate an alternative approach in which all electronic components are eliminated from the borehole sensor. Instead, fiber optic telemetry and a state-of-the-art path-matched differential interferometer will be used to precisely measure the displacement of the seismic inertial mass. All signal processing electronics, including optical sources and detectors, will be located in the much-less-hostile environment at the surface. The resulting sensor will measure inertial mass motion with better than 1 nm resolution. Commercial Applications and other Benefits as described by the awardee:High-temperature seismic sensors should be in a great demand as the national interest in geothermal energy grows. In addition, the proposed sensor also could be used in hazardous industrial environments where conventional seismic or vibration meters fail