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TECHNICAL PAPER
SPE-168730-MS
ISBN 978-1-61399-302-6
A Nearly Complete Characterization of Permeability to
Hydrocarbon Gas and Liquid for Unconventional Reservoirs:
A Challenge to Conventional Thinking
Albert Cui (Trican Geological Solutions Ltd.), Raphael Wust (Trican Geological Solutions Ltd.), Brent Nassichuk (Trican Geological
Solutions Ltd.), Ken Glover (Trican Geological Solutions Ltd.), Ron Brezovski (Trican Geological Solutions Ltd.),
Cory Twemlow (Trican Geological Solutions Ltd.)
2013. Unconventional Resources Technology Conference
This paper was prepared for presentation at the Unconventional Resources Technology Conference held in Denver, Colorado, USA, 12-14 August 2013.
Abstract
In recent years interests in the North America oil/gas industry have shifted to and focused on tight/shale liquid-rich gas/oil reservoirs because
of the low price of natural gas. It is evident that, beside gas permeability, permeability to hydrocarbon liquids must be understood to properly
evaluate liquid production potentials. Previous studies have used gas to determine the intrinsically “true permeability” with the assumption that
the “true permeability” corrected from gas permeability is equivalent to the liquid permeability for shale or tight reservoirs with microporous
fabric. The microporous fabric with pores or pore-throats in the nanometer size range causes multiple co-existing gas transport mechanisms
(continuum/viscous flow, slip flow, transitional and Knudsen diffusion). Several studies have shown that the conventional Klinkenberg
correction to gas permeability is no longer appropriate for microporous medium, implying that the permeability to hydrocarbon liquid is likely
also different from the gas-based “true permeability”. We envision that for unconventional rocks with nano-scale pores or pore-throats, the
intrinsically “true permeability” from gas does not exist alone anymore because the permeability becomes a parameter that measures both the
effectiveness of pore-network connectivity and the strong interaction between the specific fluid and the pore structure.
In this study, the gas-based “true permeability” of multiple samples of the Montney Formation from the Western Canada Sedimentary Basin
were measured with different gases (including helium and argon) using different techniques. Permeability to hydrocarbon liquid (decane)
was also tested on duplicate samples. The results show that liquid permeability is significantly lower than the gas permeability, even with
Klinkenberg effect corrections. Gas and oil porosity, pore structure and lithology of the samples were also tested using pycnometry, highpressure mercury-injection porosimetry, scanning electron microscopy, and x-ray diffraction. Integration of the data provides a comprehensive
characterization of the permeability and porosity of the samples and sheds insights into our understanding of gas and liquid permeability of
unconventional rocks. The implications of the results, the importance of appropriately designed laboratory programs for permeability testing
and proper utilization of measured permeability data to evaluate the unconventional gas and oil production potentials are discussed.
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