Klinkenberg effect for gas permeability and its comparison to water permeability for porous sedimentary rocks

Abstract. The difference between gas and water permeabilities is significant not only for solving gas-water two-phase flow problems, but also for quick measurements of permeability using gas as pore fluid. We have measured intrinsic permeability of sedimentary rocks from the Western Foothills of Taiwan, using nitrogen gas and distilled water as pore fluids, during several effective-pressure cycling tests at room temperature. The observed difference in gas and water permeabilities has been analyzed in view of the Klinkenberg effect. This effect is due to slip flow of gas at pore walls which enhances gas flow when pore sizes are very small. Experimental results show (1) that gas permeability is larger than water permeability by several times to one order of magnitude, (2) that gas permeability increases with increasing pore pressure, and (3) that water permeability slightly increases with increasing pore-pressure gradient across the specimen. The results (1) and (2) can be explained by Klinkenberg effect quantitatively with an empirical power law for Klinkenberg constant. Thus water permeability can be estimated from gas permeability. The Klinkenberg effect is important when permeability is lower than 10−18 m2 and at low differential pore pressures, and its correction is essential for estimating water permeability from the measurement of gas permeability. A simple Bingham-flow model of pore water can explain the overall trend of the result (3) above. More sophisticated models with a pore-size distribution and with realistic rheology of water film is needed to account for the observed deviation from Darcy's law.

[1]  Peter Persoff,et al.  Hydrologic characterization of reservoir metagraywacke from shallow and deep levels of The Geysers vapor-dominated geothermal system, California, USA , 2001 .

[2]  James D. Byerlee,et al.  Friction, overpressure and fault normal compression , 1990 .

[3]  S. Uehara,et al.  Measurement of Gas-permeability of Rocks Using an Oscillating Pore Pressure Method and a Gas Flow Method: - An example of the Kakegawa Group Siltstone -@@@－ 掛川層群シルト岩の測定例 － , 2003 .

[4]  Adrian E. Scheidegger,et al.  The physics of flow through porous media , 1957 .

[5]  Louis S. Teng.  Geotectonic evolution of late Cenozoic arc-continent collision in Taiwan , 1990 .

[6]  L. Klinkenberg.  The Permeability Of Porous Media To Liquids And Gases , 2012 .

[7]  C. Wibberley,et al.  Earthquake slip weakening and asperities explained by thermal pressurization , 2005, Nature.

[8]  Hiroyuki Noda,et al.  Thermal Pressurization and Slip-Weakening Distance of a Fault: An Example of the Hanaore Fault, Southwest Japan , 2005 .

[9]  B. Massey,et al.  Mechanics of Fluids , 2018 .

[10]  David Jon Furbish,et al.  Fluid Physics in Geology: An Introduction to Fluid Motions on Earth's Surface and within Its Crust , 1996 .

[11]  S. C. Jones.  A Rapid Accurate Unsteady-State Klinkenberg Permeameter , 1972 .

[12]  J. B. Walsh,et al.  Permeability of granite under high pressure , 1968 .

[13]  D. Faulkner,et al.  Comparisons of water and argon permeability in natural clay‐bearing fault gouge under high pressure at 20°C , 2000 .

[14]  C. Wibberley.  Hydraulic diffusivity of fault gouge zones and implications for thermal pressurization during seismic slip , 2002 .

[15]  W. R. Gardner.  Physics of Flow through Porous Media , 1961 .