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Deep TVZ Resource Delineation

Combined MT, seismic, gravity and magnetics to identify heat sources, areas of possible deep-seated permeability and fluid flow, and potential targets for future deep drilling, and to understand time-spatial changes to geothermal fields.

Project Leader: Grant Caldwell

Task 1: Seismology (Task Leader: Stephen Bannister)

  • Earthquake seismic waveforms from geothermal reservoirs analysed to give high-resolution micro-earthquake locations, and to characterise the nature of the seismic sources
  • Shear-wave velocity image volume extended in the vicinity of potential deep drilling targets or other regions of interest
  • New seismic measurements acquired

 Task 2: Magnetotellurics (Task Leader: Ted Bertrand)

  • Aquisition of MT data and determination of the resistivity structure at Ohaaki
  • 3D inverse modelling for deep geothermal study area
  • Development of a joint MT-seismic rock property model at 3-7 km depth
  • Heterogeneities in 3D MT and seismic data interpreted with respect to deep drilling targets, and interpolation and qualitative comparison schemes developed
  • MT experiments to assess deep resistivity changes resulting from re-injection or production
  • Algorithms for improved 3D inversion of MT data
  • New MT measurements to expand coverage in the southern-central TVZ
  • Advanced geophysical techniques and combinations of geophysical techniques for identification of deep geothermal resources

 Task 3: Aeromagnetics & Gravity

  • Reinterpretation of TVZ basement structure using regional gravity and down-hole density data
  • Additional geophysical data obtained to help interpret structures identified in the MT and seismological surveys
  • Implications for deep geothermal resource prospectively in the southern-central TVZ