Comparison of dfn modelled microfracture systems with petrophysical data in excavation damaged zone

Risto Kiuru*, Dorka Király, Gergely Dabi, Lars Jacobsson

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

2 Citations (Scopus)
35 Downloads (Pure)

Abstract

Physical and petrographic properties of drill core specimens were determined as a part of investigations into excavation damage in the dedicated study area in the ONKALO® research facility in Olkiluoto, Western Finland. Microfractures in 16 specimens from two drillholes were analysed and used as a basis for fractal geometry-based discrete fracture network (DFN) modelling. It was concluded that the difference in resistivity between pegmatoid granite (PGR) and veined gneiss (VGN) specimens of similar porosity was likely due to differences in the types of microfractures. This hypothesis was confirmed from microfracture analysis and simulation: fractures in gneiss were short and mostly in one preferred orientation, whereas the fractures in granite were longer and had two preferred orientations. This may be due to microstructure differences of the rock types or could suggests that gneiss and granite may suffer different types of excavation damage. No dependencies on depth from the excavated surface were observed in the geometric parameters of the microfractures. This suggests that the excavation damaged zone cannot be identified based on the changes in the parameters of the microfracture networks, and that the disturbed layer observed by geophysical methods may be caused by macro-scale fractures.

Original languageEnglish
Article number2899
Number of pages17
JournalApplied Sciences (Switzerland)
Volume11
Issue number7
DOIs
Publication statusPublished - 1 Apr 2021
MoE publication typeA1 Journal article-refereed

Keywords

  • Discrete fracture network model
  • Excavation damage
  • Laboratory testing
  • Percolation cluster
  • Petrophysics
  • Physical properties of rocks
  • Simulation

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