A Near-real-time Electromagnetic Data-link for Geothermal Downhole Instruments

There exists a need to obtain near-real-time information in a wireless tool configuration to be used in dynamic geothermal well conditions, such as when drilling is in progress. A tool which can provide this near real-time information from sensors located near the bit of the drill string will help reduce the hazards and costs associated with geothermal well development by allowing surface monitoring of key variables such as bit vibration (for extending the bit life and penetration rates of PDC and roller bits, and verifying the operation of hammer bits); drill pipe and annular pressure (for quickly detecting and locating lost circulation and high-pressure zones); and downhole temperatures (to better match drilling fluid and cement properties to field conditions). All of these factors play critical roles in enhancing wellbore integrity under high-temperature, high-pressure conditions. The proposed near-real-time wireless tool will be achieved by modifying a commercial ElectroMagnetic Measurement While Drilling (EM MWD) System to operate in the high temperature environments associated with geothermal well applications. During Phase 1, a system architecture, based on distributed computing techniques, capable of hosting advanced digital coding protocols and adaptive digital modulation techniques will be developed using electronic components that can operate at geothermal temperatures while unprotected by thermal flasks. Specifically, silicon-on-insulator (SOI) and silicon-carbide (SiC) semiconductors will be investigated for the design of the downhole electronics with a goal to operate for extended periods of time at a maximum temperature of 250°C (which is well above the temperature specification for our current commercial packaging technology). This temperature specification should be sufficient to satisfy drilling requirements for reservoirs up to 300°C since drilling fluids dramatically cool a well below the surrounding reservoir temperature. A commercial system system that has been successfully used under air-drilling conditions will be implemented, so the new geothermal system will be fully capable of operating in CO2 reservoirs as well.