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@ARTICLE{Moslemipour:644940,
      author       = {Moslemipour, Abolfazl and Sadeghnejad, Saeid and Enzmann,
                      Frieder and Khoozan, Davood and Schäfer, Thorsten and
                      Kersten, Michael},
      title        = {{E}fficient multi-scale image reconstruction of
                      heterogeneous rocks with unresolved porosity using octree
                      structures},
      journal      = {Computational geosciences},
      volume       = {29},
      number       = {3},
      issn         = {1420-0597},
      address      = {New York, NY [u.a.]},
      publisher    = {Springer Science + Business Media B.V.},
      reportid     = {PUBDB-2026-00483},
      pages        = {24},
      year         = {2025},
      abstract     = {Identifying rock properties at the pore scale plays a
                      crucial role in understanding larger-scale properties. For
                      this purpose, the digital rock physics technique is used to
                      model rock images at the pore scale. Achieving
                      high-resolution (HR) images with a large field of view (FoV)
                      is essential for pore-scale modeling of heterogeneous rock
                      samples, which presents significant challenges due to their
                      complex structures. However, because of the trade-off
                      between resolution and FoV, it is not possible to acquire
                      large HR images. Multi-scale image reconstruction methods
                      enable modeling images at different resolutions and FoVs.
                      Despite various approaches being introduced, a common
                      limitation is the high computational cost. In this study, a
                      novel approach based on Octree structures is introduced to
                      minimize computational cost while maintaining accuracy. A
                      Berea sandstone (BS) and an Edward Brown Carbonate (EBC)
                      sample were scanned at both HR and low resolution (LR) using
                      X-ray microtomography. Our method involves splitting the
                      unresolved porosity in rock images into smaller sections of
                      unresolved templates using the watershed algorithm and
                      considering the optimized parameters. We then applied a
                      cross-correlation based simulation technique to find the
                      best match of each unresolved template. The novelty of our
                      approach lies in the use of an Octree structure to perform
                      calculations on LR images, significantly reducing
                      computation time and memory consumption due to the fewer
                      number of pixels in Octree LR structures. The accuracy of
                      the images thus reconstructed using our approach was
                      compared with those from previous methods by evaluating
                      geometric properties and single- and two-phase flow
                      properties. The results were promising, demonstrating that
                      our approach achieved a permeability close to the real
                      value, while the previous method had an error of
                      approximately $4\%$ for both BS and EBC rocks. More
                      importantly, our approach was approximately three times
                      faster and reduced memory usage by 20 to 130 times. The
                      findings of this study facilitate dual- or multi-scale
                      modeling and evaluate heterogeneous rock images at a
                      significantly lower computational cost. In particular, for
                      heterogeneous rocks, where multi-scale image reconstruction
                      demands substantial memory and runtime, the use of the
                      Octree technique enables accurate reconstruction with lower
                      computational cost.},
      cin          = {DOOR ; HAS-User / Hereon},
      ddc          = {550},
      cid          = {I:(DE-H253)HAS-User-20120731 / I:(DE-H253)Hereon-20210428},
      pnm          = {6G3 - PETRA III (DESY) (POF4-6G3)},
      pid          = {G:(DE-HGF)POF4-6G3},
      experiment   = {EXP:(DE-H253)P-P05-20150101},
      typ          = {PUB:(DE-HGF)16},
      doi          = {10.1007/s10596-025-10362-w},
      url          = {https://bib-pubdb1.desy.de/record/644940},
}