Permeability (materials science): Difference between revisions

Sometimes permeability to gases can be somewhat different than those for liquids in the same media. One difference is attributable to "slippage" of gas at the interface with the solid<ref>L. J. Klinkenberg, "The Permeability Of Porous Media To Liquids And Gases", Drilling and Production Practice, 41-200, 1941 [http://www.onepetro.org/mslib/servlet/onepetropreview?id=API-41-200&soc=API&speAppNameCookie=ONEPETRO (abstract)].</ref> when the gas [[mean free path]] is comparable to the pore size (about 0.01 to 0.1 μm at standard temperature and pressure). See also [[Knudsen diffusion]] and [[constrictivity]]. For example, measurement of permeability through sandstones and shales yielded values from 9.0×10⁻¹⁹ m² to 2.4×10⁻¹²&nbsp;m² for water and between 1.7×10⁻¹⁷&nbsp;m² to 2.6×10⁻¹²&nbsp;m² for nitrogen gas.<ref>J. P. Bloomfield and A. T. Williams, "An empirical liquid permeability-gas permeability correlation for use in aquifer properties studies". Quarterly Journal of Engineering Geology & Hydrogeology; November 1995; v. 28; no. Supplement 2; pp. S143–S150. [http://qjegh.geoscienceworld.org/cgi/content/abstract/28/Supplement_2/S143 (abstract)]</ref> Gas permeability of [[reservoir rock]] and [[source rock]] is important in [[petroleum engineering]], when considering the optimal extraction of gas from [[Unconventional (oil & gas) reservoir|unconventional]] sources such as [[shale gas]], [[tight gas]], or [[coalbed methane]].