DM300 - A 300°C Geothermal Directional Module Development

Abstract

Enhanced high-temperature geothermal drilling operations require accurate directional drilling measurements to efficiently configure the borehole. A rugged, 300°C capable directional drilling module, Honeywell's DM300, provides the geothermal drilling operator with accurate indications of tool-face angle, inclination, and heading of the down-hole assembly. The DM300 system incorporates two orthogonal arrays of accelerometers and magnetometers with their associated electronic circuitry as well as system level circuitry. The sensors and electronics are packaged in a sealed 1 ¼″ diameter titanium housing. The DM300 high-temperature electronics approach utilizes custom Honeywell developed ASICs that leverage our proven HTSOI4™ silicon-on-insulator technology to successfully operate at 300°C. Vibrating beam MEMS accelerometers provide an inherently digital acceleration signal, through measurement of beam vibration phase using counting methods. Flux-gate magnetometers incorporate a custom voltage-to-frequency converter digitizing ASIC. The magnetometer ASIC integrates several system level functions to reduce chip count in the overall system design. Active cooling is not required for these DM300 features to operate, perform, and survive in a 300°C down-hole environment. This paper presents system concept design and implementation through a two phase development. The current development phase focuses on the development and characterization of the sensors, their associated electronics, and packaging into a 300°C capable housing. A future development phase will incorporate a 300°C capable Gate Array ASIC and EEPROM. The Gate Array functions capture the digital sensor signals and provides SPI bus interface as required for a deployable directional drilling module.