Design of Seismic Networks for CO2 Sequestration Utilizing Pre-injection Fluid Flow, Seismicity and Ground Motion Modeling
Abstract
The purpose of passive seismic monitoring during and after CO2 injection is twofold. First, analysis of induced seismicity can be used to track the migration of subsurface pressure and the CO2 plume and provide constraints on the reservoir permeability structure using seismic tomography and by mapping earthquake hypocenters through time. Earthquake focal mechanisms can also help characterize the in situ stress state. The second purpose is to assess induced seismicity hazard and risk on an ongoing basis throughout the life of the project. Both objectives are important in optimizing the design of a seismic monitoring network before injection begins, which requires initial characterization of the seismicity that might be expected. We approach this problem together with pre-injection hazard assessment by simulating the potential range of induced seismicity behavior that might result from a given injection scenario. Our approach assumes that comprehensive site characterization, including rock and hydrological properties, in situ stress, larger faults, and dominant fracture systems, has been completed. We use the code RSQSim to simulate seismicity at reservoir scale under constant rate tectonic loading and injection-induced pressure change histories modeled using the flow code TOUGH2. Monitoring network design, including the network configuration and instrument sensitivity, can then be based on the simulated hypocenter distributions and ground motion amplitudes calculated by convolving earthquake source parameters with synthetic Green's functions determined from the velocity structure. We show examples of multiple realizations of hypocenter and frequency-magnitude distributions generated by sampling the uncertainties in model input parameters and by randomizing fault and fracture properties. The multiple realizations - which are required for probabilistic seismic hazard assessment - enable us to introduce a probabilistic element to inform network design optimization.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.S44A..05F
- Keywords:
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- 0599 General or miscellaneous;
- COMPUTATIONAL GEOPHYSICSDE: 1699 General or miscellaneous;
- GLOBAL CHANGEDE: 7290 Computational seismology;
- SEISMOLOGYDE: 7299 General or miscellaneous;
- SEISMOLOGY