Development of an Ultra-Sensitive Surface based Three Component Accelerometer for Efficient and Effective Passive Seismic Monitoring

Statement of the problem or situation that is being addressed. The Department of Energy (DOE) has identified, under the guidance of the Biden Administration, the need to advance America’s transition to clean energy. This will, in part, be accomplished by sequestering CO2 produced by the energy sector, for example, capturing and sequestering the CO2 from coal fired power plants which still produce about 1/3 of America’s electricity. To enable this, the IRS has created the 45Q tax credit; however, to obtain the tax credit, the CO2 must be captured and sequestered, and a monitoring plan must be in place to ensure that the CO2 is not released into the atmosphere. This monitoring requirement has led to increased interest in cost-effective site characterization for potential sequestration reservoirs. Ideally, monitoring solutions that are cost-effective will be deployed and seismicity risks evaluated before investing in developing a carbon storage reservoir. General statement of how this problem or situation is being addressed. PI is proposing to develop a fiber optic accelerometer that can be deployed at shallow depths in surface and near-surface seismic applications. The accelerometers will be embedded in 3-Component (3C) stations that will allow mapping of the passive, micro seismic activity occurring in the subsurface. By utilizing 3C stations, we will be able to map the incoming vectors, and create a high-resolution subsurface image of the surrounding faults and other geologic structures. The accelerometer will be designed for high sensitivity and high frequency acquisition to enable the detection of micro seismic events, which have much higher frequency content than larger seismic events (M>0). What is to be done in Phase I Current fiber optic accelerometer work focuses on using the fiber as a spring wound around a mass, which unfortunately makes both tuning the resonant frequency and dampening the resonant response practically impossible. PI will remove the fiber-as-a-spring from the mandrel and focus on designing a single mass, three component accelerometer that uses standard springs rather than fiber as the spring. The single mass system will utilize fiber-to-free space transitions and mirrors for the reflective components, eliminating the need for Fiber Bragg Gratings (FBGs) as reflectors. A prototype showing a single axis detection scheme will be demonstrated, and with time permitting, a full three axis detection scheme will be demonstrated. In Phase II we will embed the accelerometer into 3C surface and near-surface stations for deployment at a potential CO2 sequestration site. Commercial Applications and Other Benefits. 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.