S063-0013
Improved Seismic Tomography of the Brady Geothermal Field, Nevada, based upon Full Waveform Inversion Using Salvus

Wednesday, 16 December 2020
Poster
Christina Morency1, Eric Matzel1, Michael Afanasiev2, Lion Krischer3, Christian Boehm2 and Arthur J Rodgers4, (1)Lawrence Livermore National Laboratory, Livermore, CA, United States, (2)Mondaic AG, Zurich, Switzerland, (3)Mondaic AG, Munich, Switzerland, (4)Lawrence Livermore National Laboratory, Atmospheric, Earth and Energy Division, Livermore, CA, United States
Abstract:
A dense seismic array was deployed for active source tomography at the Brady Hot Springs geothermal site in Nevada for the DOE-funded PoroTomo project (Feigl and PoroTomo Team, 2017) for shallow geothermal reservoir characterization and monitoring. This rich dataset involves vibroseis sources at 196 locations, using three vibration modes (vertical, longitudinal, and transverse), recorded by 238 three-components 5-Hz FairfieldNodal receivers. This field survey was repeated four times to try and capture four different stages of power plant operation.

Here, we evaluate two velocity models, which used data recorded during normal facility operations: one based on travel time inversion (Parker et al., 2018) and one using interferometry (Matzel et al, 2017). These models show discrepancies inherent to the different methods. We use these models as priors for full waveform inversion based on adjoint method to further refine the Earth model. We also draw the scheme of 4D seismic analysis to characterize the time-dependent 3D structure related to the four different stages of operation.

Numerical simulations are performed using the high-performance software Salvus based on spectral-element method developed by Mondaic Ltd. and the Swiss Federal Institute of Technology (ETH Zürich).

References:

  • Feigl, K. L., and PoroTomo Team (2017), Overview and preliminary results from the PoroTomo project at Brady Hot Springs, Nevada: Poroelastic tomography by adjoint inverse modeling of data from seismology, geodesy, and hydrology, presentation at the 42nd Workshop on Geothermal Reservoir Engineering, Stanford University, CA
  • , E., X. Zeng, C. Thurber, Y. Luo and C. Morency (2017), Seismic Interferometry Using the Dense Array at the Brady Geothermal Field, presentation at the 42nd Workshop on Geothermal Reservoir Engineering, Stanford University, CA
  • Parker, L. M., C. H. Thurber, X. Zeng, N. E. Lord, D. O. Fratta, H. F. Wang, M. C. Robertson, A. M. Thomas, M. S. Karplus, A. Nayak, and K. L. Feigl (2018), Active-Source Seismic Tomography at the Brady Geothermal Field, Nevada, with Dense Nodal and Fiber-Optic Seismic Arrays, Seismological Research Letters, 89(5), 1629-1640

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

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