Preprints
https://doi.org/10.5194/se-2020-178
https://doi.org/10.5194/se-2020-178

  17 Nov 2020

17 Nov 2020

Review status: this preprint was under review for the journal SE. A revision for further review has not been submitted.

Anisotropic transport and frictional properties of simulated clay-rich fault gouges

Elisenda Bakker1 and Johannes H. P. de Bresser2 Elisenda Bakker and Johannes H. P. de Bresser
  • 1Department of energy and environment, Royal HaskoningDHV, Laan 1914 35, 3818 EX Amersfoort, The Netherlands
  • 2Faculty of Geosciences, Utrecht University, Princetonlaan 4, 3584 CD Utrecht, The Netherlands

Abstract. We aimed to evaluate various factors that control the frictional and transport properties of gouge-filled faults cutting carbonate-bearing shales or claystone formations. The research experimentally determined the effect of shear displacement, dynamic shearing, static holding, and effective normal stress on fault gouge permeability, both parallel and perpendicular to the fault boundaries, as well as on frictional behaviour. The simulated gouge was prepared from crushed Opalinus Claystone (OPA), on which we performed direct shear experiments. The direct-shear experiments (σneff = 5–50 MPa, Pf = 2 MPa, and T ≈ 20 °C) showed ~1 order of magnitude decrease in permeability with shear displacement (up to ~6 mm), for both along- and across-fault fluid flow orientation. Moreover, our data showed an initial, pre-shear permeability anisotropy of up to ~1 order of magnitude, which decreased with increasing shear displacement (maturity) to ~0.5, with the along-fault permeability being consistently higher. Our results have important implications for calcite-rich claystones and shale formations, and in particular any pre-existing faults therein, that seal hydrocarbon reservoirs and potential CO2 storage reservoirs, as the current results point to a higher leakage potential of pre-existing faults compared to the intact caprock.

Elisenda Bakker and Johannes H. P. de Bresser

 
Status: closed (peer review stopped)
Status: closed (peer review stopped)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Status: closed (peer review stopped)
Status: closed (peer review stopped)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Elisenda Bakker and Johannes H. P. de Bresser

Elisenda Bakker and Johannes H. P. de Bresser

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Short summary
What is the effect of shearing, holding and effective normal stress on fault gouge permeability, parallel and perpendicular to fault boundaries, as well as on frictional behaviour? Experiments show a pre-shear permeability anisotropy, as well as a decrease in permeability with shear and eff. normal stress, for both fluid flow directions. The results have important implications for pre-existing faults in calcite-rich claystones that seal hydrocarbon reservoirs or potential CO2 storage reservoirs.