Changes

===Gas permeability by unsteady-state method===

===Gas permeability by unsteady-state method===

Aronofsky<ref name=pt05r21>Aronofsky, J. S., 1954, Effect of gas slip on unsteady flow of gas through porous media: Journal of Applied Physics, v. 25, n. 1, p. 48–53., 10., 1063/1., 1721519</ref> has discussed the theory of transient permeability measurements, and the development of transient state permeameters has been discussed by Wallick and Aronofsky,<ref name=pt05r160>Wallick, G. C., Aronofsk, J. S., 1954, Effects of gas slip on unsteady flow of gas through porous media—experimental verification.: Transactions of the American Institute of Mining and Engineering, v. 201, p. 322–324.</ref>, [[Champlin (1962)]], Morris,<ref name=pt05r115>Morris, W. L., 1953, Assignor, Philips Petroleum Co. Portable Permeameter: U., S. Patent No. 2,633,015, March 23.</ref> and Jones.<ref name=pt05r85>Jones, S. C., 1972, Rapid accurate unsteady-state klinkenberg permeameter: Society of Petroleum Engineers Journal, v. 12, p. 383–397., 10., 2118/3535-PA</ref>

Aronofsky<ref name=pt05r21>Aronofsky, J. S., 1954, Effect of gas slip on unsteady flow of gas through porous media: Journal of Applied Physics, v. 25, n. 1, p. 48–53., 10., 1063/1., 1721519</ref> has discussed the theory of transient permeability measurements, and the development of transient state permeameters has been discussed by Wallick and Aronofsky,<ref name=pt05r160>Wallick, G. C., Aronofsk, J. S., 1954, Effects of gas slip on unsteady flow of gas through porous media—experimental verification.: Transactions of the American Institute of Mining and Engineering, v. 201, p. 322–324.</ref>, [[Champlin (1962)]]{{citation needed}}, Morris,<ref name=pt05r115>Morris, W. L., 1953, Assignor, Philips Petroleum Co. Portable Permeameter: U., S. Patent No. 2,633,015, March 23.</ref> and Jones.<ref name=pt05r85>Jones, S. C., 1972, Rapid accurate unsteady-state klinkenberg permeameter: Society of Petroleum Engineers Journal, v. 12, p. 383–397., 10., 2118/3535-PA</ref>

A schematic diagram of the unsteady-state Klinkenberg permeameter [[(Jones, 1990)]] is shown in [[:file:permeability_fig4.png|Figure 4b]]. The permeameter works on the principle of transient analysis of pressure pulse decay in which Klinkenberg permeability is determined as a function of gas (ideally helium) pressure decay. This equipment consists of a reference cell of known volume that charges the core sample with gas. A downstream valve vents the gas pressure, and pressure change as a function of time is recorded. A typical pressure drawdown plot [[(Jones, 1990)]] is shown in [[:file:permeability_fig5.png|Figure 5]]. Advantages of the unsteady-state method include the ability to determine simultaneously (from Figure 5) the Klinkenberg permeability (''k''_∞ helium slippage factor (β_He), and the inertial coefficient (β). A comparison of the steady-state method to the unsteady-state method is presented in Table 1.

A schematic diagram of the unsteady-state Klinkenberg permeameter [[(Jones, 1990)]]{{citation needed}} is shown in [[:file:permeability_fig4.png|Figure 4b]]. The permeameter works on the principle of transient analysis of pressure pulse decay in which Klinkenberg permeability is determined as a function of gas (ideally helium) pressure decay. This equipment consists of a reference cell of known volume that charges the core sample with gas. A downstream valve vents the gas pressure, and pressure change as a function of time is recorded. A typical pressure drawdown plot [[(Jones, 1990)]]{{citation needed}} is shown in [[:file:permeability_fig5.png|Figure 5]]. Advantages of the unsteady-state method include the ability to determine simultaneously (from Figure 5) the Klinkenberg permeability (''k''_∞ helium slippage factor (β_He), and the inertial coefficient (β). A comparison of the steady-state method to the unsteady-state method is presented in Table 1.

{| class = "wikitable"

{| class = "wikitable"