Anisotropy of permeability in faulted porous sandstones

N. J. C. Farrell, D. Healy, C. W. Taylor

Research output: Contribution to journalArticlepeer-review

119 Citations (Scopus)
9 Downloads (Pure)

Abstract

Studies of fault rock permeabilities advance the understanding of fluid migration patterns around faults and contribute to predictions of fault stability. In this study a new model is proposed combining brittle deformation structures formed during faulting, with fluid flow through pores. It assesses the impact of faulting on the permeability anisotropy of porous sandstone, hypothesising that the formation of fault related micro-scale deformation structures will alter the host rock porosity organisation and create new permeability pathways. Core plugs and thin sections were sampled around a normal fault and oriented with respect to the fault plane. Anisotropy of permeability was determined in three orientations to the fault plane at ambient and confining pressures. Results show that permeabilities measured parallel to fault dip were up to 10 times higher than along fault strike permeability. Analysis of corresponding thin sections shows elongate pores oriented at a low angle to the maximum principal palaeo-stress (σ1) and parallel to fault dip, indicating that permeability anisotropy is produced by grain scale deformation mechanisms associated with faulting. Using a soil mechanics ‘void cell model’ this study shows how elongate pores could be produced in faulted porous sandstone by compaction and reorganisation of grains through shearing and cataclasis.
Original languageEnglish
Pages (from-to)50-67
Number of pages18
JournalJournal of Structural Geology
Volume63
Early online date3 Mar 2014
DOIs
Publication statusPublished - Jun 2014

Bibliographical note

Thank you to Total E & P UK for funding the project, and especially Chris Wibberley, Claude Gout and Stephane Vignau for input. The author would also like to thank Zoe Shipton and Graham Yielding for their constructive reviews of the manuscript. Thanks also to Manuel Prieto for sharing his MSc pilot study written at the University of Aberdeen, Professor Martin Lee and Peter Chung at the University of Glasgow for SEM use and lastly thank you to Gavin Tennent for access to the Clashach Quarry and for samples.

Keywords

  • permeability
  • anisotropy
  • faulting
  • porous sandstone
  • cataclasis
  • confining pressure

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