A MEMS Gyroscope for Reliable Long-Duration Measurement While Drilling at 300ºC

To increase the efficiency of drilling unconventional geothermal wells, new technology is needed that maximizes drilling effectiveness while minimizing cost. An important research topic is the measurement while drilling (MWD) system that navigates the drill string to the desired location underground. In conventional oil and gas drilling, MWD systems are typically designed to operate at temperatures <175°C, making them unsuitable for drilling enhanced geothermal systems where the downhole sensors and electronics may need to tolerate sustained temperatures of 300ºC or more. In this hot environment, new sensing technology is needed that results in MWD tools that operate continuously at 300°C while being safe, accurate, and reliable. To fill this need, we are developing a high temperature, MEMS-based gyroscope for continuous operation in a 300ºC geothermal drilling environment. Unlike conventional MEMS gyroscopes that are limited to relatively low temperature operation (<125ºC), the MEMS gyroscope we describe herein is capable of navigation grade performance and continuous operation at 300ºC without the use of heat shields, or other passive/active cooling hardware. To achieve this, our team at GE Research designed a new MEMS gyroscope called a Multi-Ring Gyroscope (MRG) that is specifically optimized for high temperature operation in harsh environments, and under Department of Energy (DOE) award number DE-EE0008604, we are currently fabricating test devices and working to couple them to a custom ASIC fabricated using silicon-on-insulator electronics. In this contribution, we provide an overview of our research program and give an update on our progress to date. This includes a discussion of gyroscope performance requirements, a survey of commercially available MEMS gyroscopes, an overview of the MRG design, and presentation of our latest MRG component validation results over the temperature range 25-500ºC.