Microstructural controls on the pressure-dependent permeability of Whitby Mudstone

This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.1144/SP454.15. This is version 1 of this Preprint.


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Julian Mecklenburgh , Kevin G. Taylor, Ernie Rutter, Rosanne Mckernan


A combination of permeability and ultrasonic velocity measurements allied with image analysis is used to distinguish the primary microstructural controls on effective-pressure dependent permeability. Permeabilities of cylindrical samples of Whitby Mudstone were measured using the oscillating pore pressure method at confining pressures ranging between 30-95 MPa and pore pressures ranging between 1-80 MPa. The permeability-effective pressure relationship is empirically described using a modified effective pressure law in terms of confining pressure, pore pressure and a Klinkenberg effect. Measured permeability ranges between 3×10-21 m2 and 2 ×10-19 m2 (3 and 200 nd), and decreases by ~1 order of magnitude across the applied effective pressure range. Permeability is shown to be less sensitive to changes in pore pressure than changes in confining pressure, yielding permeability effective pressure coefficients (χ) between 0.42 and 0.97. Based on a pore-conductivity model which considers the measured changes in acoustic wave velocity and pore volume with pressure, the observed loss of permeability with increasing effective pressure is attributed dominantly to the progressive closure of bedding-parallel, crack-like pores associated with grain boundaries. Despite only constituting a fraction of the total porosity, these pores form an interconnected network that significantly enhances permeability at low effective pressures.




Earth Sciences, Geology, Physical Sciences and Mathematics


shale gas, permeability


Published: 2018-01-08 16:01


Academic Free License (AFL) 3.0

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