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@ARTICLE{Keskinen:836063,
      author       = {Keskinen, Johanna and Klotzsche, Anja and Looms, Majken C.
                      and Moreau, Julien and van der Kruk, Jan and Holliger, Klaus
                      and Stemmerik, Lars and Nielsen, Lars},
      title        = {{F}ull-waveform inversion of {C}rosshole {GPR} data:
                      {I}mplications for porosity estimation in chalk},
      journal      = {Journal of applied geophysics},
      volume       = {140},
      issn         = {0926-9851},
      address      = {Amsterdam [u.a.]},
      publisher    = {Elsevier Science},
      reportid     = {FZJ-2017-05187},
      pages        = {102 - 116},
      year         = {2017},
      abstract     = {The Maastrichtian-Danian chalk is a widely distributed
                      hydrocarbon and groundwater reservoir rock in north-western
                      Europe. Knowledge of lateral and vertical heterogeneity and
                      porosity variation in this type of rock is essential, since
                      they critically determine the reservoir properties. We have
                      collected a densely sampled crosshole ground-penetrating
                      radar (GPR) dataset from a highly heterogeneous section of
                      the chalk and inverted it with a full-waveform inversion
                      (FWI) approach. To date, successful crosshole FWI has only
                      been reported for a handful of GPR field data, none of which
                      include strongly heterogeneous environments like the one
                      considered in this study. Testing different starting models
                      shows that all FWI results converge to very similar
                      subsurface structures indicating that the results are robust
                      with regard to local variations in the permittivity starting
                      models and are not very sensitive to the conductivity
                      starting models. Compared to their ray-based counterparts,
                      the obtained FWI models show significantly higher resolution
                      and improved localization of fine-scale heterogeneity. The
                      final FWI permittivity tomogram was converted to a bulk
                      porosity model using the Complex Refractive Index Model
                      (CRIM) and comparisons with plug sample porosities and
                      televiewer image logs verify that variations in the obtained
                      permittivity are related to facies and lithology changes.
                      The inferred porosity varies from 30 to $54\%,$ which is
                      consistent with values in the chalk cores from the
                      investigated boreholes and in agreement with other studies
                      conducted in similar rocks onshore. Moreover, porosities
                      vary significantly over scales of less than a meter both
                      laterally and vertically. The FWI constrains porosity
                      variation with decimeter scale resolution in our 5 m
                      (horizontally) by 10 m (vertically) model section bridging
                      the gap between what is measured on the core sample scale
                      and the scale typical of hydrogeophysical field experiments
                      conducted to characterize fluid flow in the subsurface. The
                      results provide complementary knowledge to traditional chalk
                      reservoir characterization.},
      cin          = {IBG-3},
      ddc          = {620},
      cid          = {I:(DE-Juel1)IBG-3-20101118},
      pnm          = {255 - Terrestrial Systems: From Observation to Prediction
                      (POF3-255)},
      pid          = {G:(DE-HGF)POF3-255},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000401677100011},
      doi          = {10.1016/j.jappgeo.2017.01.001},
      url          = {https://juser.fz-juelich.de/record/836063},
}