Dewarless High-Temperature Seismic Tool for EGS

Abstract

the drilled well, likely through hydraulic fracturing. Whether fracturing of the rock occurs by shear destabilization of natural fractures or by extensional failure of weaker zones, control of the fracture process will be required to create the flow paths necessary for effective heat mining. As such, microseismic monitoring provides one method for real-time mapping of the fractures created during the hydraulic fracturing process. This monitoring is necessary to help assess stimulation effectiveness and provide the information necessary to properly create the reservoir. In addition, reservoir monitoring of the microseismic activity can provide information on reservoir performance and evolution over time. To our knowledge, no seismic tool exists that will operate above 125°C for the long monitoring durations that may be necessary. Replacing failed tools is costly and introduces potential errors such as depth variance, etc. Sandia has designed a high-temperature seismic tool for long-term deployment in geothermal applications. It is capable of detecting microseismic events and operating continuously at temperatures up to 210°C. This project includes the design and fabrication of a High- Temperature (HT) seismic tool that will have the capability to operate in both temporary and long-term monitoring modes. To ensure the developed tool satisfies industry requirements for high sampling rates (>2ksps) and high-resolution, a precision highspeed 24 bit Analog-to-Digital converter (ADC) was utilized.