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

Statement of the Problem. The US DOE has identified the need to transition to clean energy to reduce global warming. This will, in part, be accomplished by sequestering CO2. from coal fired power plants which still produce 1/3 of America’s electricity. To enable this transition, IRS created the 45Q tax-credit. To obtain the tax-credit, the CO2 must be securely sequestered, and monitored to ensure that the CO2 is not released into the atmosphere. This requirement has led to the need to develop cost-effective site characterization and monitoring technologies to assess the sequestration process. Thus, survey and monitoring solutions that are cost-effective must be deployed to evaluate seismicity risks before developing a carbon storage reservoir.General Statement. Paulsson, Inc. (PI) is proposing to develop a fiber optic 3C accelerometer that can be deployed on the surface and near-surface along with a fiber optic hydrophone. These sensors in combination will be deployed as 4-Component (4C) stations that will allow mapping of the micro seismic activity occurring in the subsurface in and around the CO2 storage reservoir. The sensors will be designed for high sensitivity and broad band frequency acquisition to enable the detection of small micro seismic events, which have much higher frequency content than larger seismic events (M>0).In SBIR Phase I a Fiber Optic Accelerometer (FOAC)™ was designed and laboratory tested and found to have a much better micro seismic detection capability compared with high fidelity seismic geophones or seismometers. A broadband noise floor under 10 ng/vHz, and a sensitivity of 7,800 radians/g has been demonstrated allowing 0.1µJ events at frequencies over 2,000 Hz to be detected. We have created a sensor that has a better detection capability than a standard seismometers or geophones over a much larger bandwidth, which is necessary for detection of the passive seismic signals at CO2 sequestration sites before, during, and after injection.We will begin Phase II by additional testing of the sensor prototype produced in Phase I. A fiber optic hydrophone will be designed, manufactured, and tested as an optional sensor for stations in areas where the water table is available for deployment. A seismic station with solar-power, GPS time-stamping, and solid ground coupling will be designed and deployed with partners at test sites to evaluate the 4C stations as a commercial product for sequestration sites.Commercial Applications. The sensors developed in this project will benefit the CO2 Sequestration, Enhanced Geothermal Systems (EGS), Underground Gas Storage (UGS), and UOG Markets, together a $Trillion market. Initially the CO2 sequestration market will be small, but these sensors can also be deployed in the UGS market to reduce risks for blowouts such as the Aliso Canyon disaster. Reservoir characterization and integrity monitoring will be key factors for America’s transition to clean energy.