PETE311_06A_Class13_(Maggard)

PETE311_06A_Class13_(Maggard) - Factors Affecting...

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Factors Affecting Permeability Determination Non-Darcy Flow Some figures in this section are from “Fundamentals of Core Analysis,” Core Laboratories, 1989. Some slides in this section are from NExT PERF Short Course Notes, 1999. Some slides appear to have been obtained from unknown primary sources that were not cited by NExT. Note that some slides have a notes section.
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Air Permeability Measurement • Measurement of permeability in the laboratory is most commonly done with air – Convenient and inexpensive – Problem: low values of mean flowing pressure • downstream pressure, p atm • upstream pressure, just a few psi higher than p atm • At low mean flowing pressure, gas slippage occurs – Diameter of flow path through porous media approaches the “mean free path” of gas molecules • mean free path is a function of molecule size • mean free path is a function of gas density – Increasing mean flowing pressure results in less slippage •a s p mean →∞ , we obtain absolute (equivalent liquid) permeability
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Non-Darcy Flow - Gas Slippage • Liquid flow and gas flow at high mean flowing pressure is laminar – Darcy’s Law is valid – flow velocity at walls is zero • At low mean flowing pressure gas slippage occurs – Non-Darcy flow is observed – flow at walls is not zero • Klinkenberg developed a method to correct gas permeability measured at low mean flowing pressure to equivalent liquid permeability
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Non-Darcy Flow - Klinkenberg Effect •A s p mean →∞ , gas permeability approaches absolute permeability
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This note was uploaded on 12/03/2009 for the course PETE 311 taught by Professor Staff during the Spring '08 term at Texas A&M.

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PETE311_06A_Class13_(Maggard) - Factors Affecting...

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