Applying Small footprint Borehole Electric and Magnetic Field Sensors for Geophysical Monitoring Networks

C55-13c-270336The Department of Energy’s (DOE’s) Carbon Storage program is focused on ramping up commercial scale carbon capture and geologic storage (CCUS) operations across the US to combat the release of CO2, a potent greenhouse gas responsible for global warming, into the atmosphere. Each one of these commercial scale operations will sequester greater than one metric megaton per year of CO2 in geologic reservoirs, with an initial focus on storage in brine filled aquifers. To ensure safe storage with the injected CO2 behaving as predicted, and that there is not a risk of induced seismicity that develops due to over- pressuring of the reservoir and surrounding strata, the Department of Energy’s (DOE’s) Small Business Innovative Research (SBIR) program recently has funded efforts to develop ‘turn-key passive seismic monitoring and networks services’ that are rugged and robust enough to be installed and last for up to and over 30 years. The ‘turn-key’ nature of these systems refers to the system containing an intelligent level of automatic data processing and streamlined interpretation such that there is not a post-data acquisition burden placed on operators and decision makers. In this proposal we will demonstrate the feasibility of fiber optic electrical and electromagnetic sensors which may be deployed to secure carbon storage sites. By using these sensors to map the electrical resistivity of the reservoir, the CO2 can be mapped. This is because the resistivity is significantly affected when brine is replaced by CO2 or brine displaces fresher water. Paulsson Inc. (PI) proposes a system where fiber-optic based downhole sensors are used to monitor downhole Electric and Electromagnetic fields on a continuous basis. These sensors will provide data currently unavailable to the industry for monitoring the integrity of carbon storage sites. In the SBIR Phase I, we apply optical fiber to detect strain of custom designed cores of piezoelectric material such as PZT (Lead Zirconate Titanate). The fluctuating electric fields cause dimensional changes in the PZT which are detected using the high sensitivity strain measuring capability of optical fiber. For electric field sensors, sensitivity is amplified by wrapping multiple turns of fiber around custom designed cores or by interrogating multiple fiber wrapped cores in ‘parallel’. The sensors developed in this project will allow for higher resolution subsurface mapping, which will benefit the CO2 Sequestration, Enhanced Geothermal Systems (EGS), Underground Gas Storage (UGS), and Unconventional Oil & Gas Markets. Initially the CO2 sequestration market will be small, but these sensors can also be deployed in the UGS market to help alleviate regulator concerns of another blowout such as the one that occurred in Aliso Canyon, California. Reservoir characterization and integrity monitoring will be key factors for America’s transition to clean energy.