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|DM300 - A 300 degC Geothermal Directional Module Development|
|Keywords: Geothermal Drilling Directional Module, High Temperature Electronics, MEMS Geothermal Sensors|
|This work presents development efforts to realize a rugged, 300 degC capable directional module providing the driller operator with accurate indications of tool-face angle, inclination, and heading of the down-hole assembly. The DM300 system design incorporates two orthogonal arrays of accelerometers and magnetometers with their associated electronic circuitry and system level circuitry. The sensors and electronics are packaged in a sealed 1 ¼” diameter Titanium housing. The DM300 does not require any active cooling to operate, perform, and survive in a 300 degC down-hole environment. DM300 high-temperature electronics approach utilizes custom Honeywell developed ASIC’s based on the proven HTSIO4TM technology. The DM300 development has pushed this silicon-on-insulator technology to successfully operate at 300 degC. Vibrating beam 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 incorporates several system level functions to reduce chip count in the overall system design. This paper presents system concept design and implementation through a two phase development. The initial development phase focuses on the development and characterization of the sensors and their associated electronics and is the main topic of the paper. The following development phase discussed, extends the system concept to incorporate a 300°C capable Gate Array ASIC and EEPROM. The Gate Array functions to capture the digital sensor signals and provide SPI bus interface. Communication outputs are selectable as raw sensor readings, thermally compensated sensor readings, or calculated orientation angles, as desired by the drilling operator. The EEPROM provides capability of storing sensor characterization data and OM tool information. This paper contains information on the target application, component requirements, design, and fabrication approach. This material is based upon work supported by the U.S. Department of Energy under, Golden Field Office, award number DE-EE0002574.|
|Douglas C. MacGugan, Staff Engineer