The permeability is defined by Darcy's law:
"where q is the velocity of flow through the sample, k is permeability, ΔP is pressure drop along sample, m is the absolute viscosity and l is sample length."
Cleaned and dried plug is mounted in a Hassler core holder, and a confining pressure of 400 psi is applied to the sleeve. Nitrogen gas pressures of 3, 5 and 8 atm (0.3, 0.5, 0.8 MPa) (abs) are applied at the upstream end of the plug, and the downstream pressure is regulated until a suitable flow is obtained.
The differential pressure is kept approximately constant in order to maintain a similar flow regime during the 3 measurements. When a steady state is reached, the upstream pressure, the differential pressure across the plug and the flow reading are recorded.
A linear regression of permeability on inverse mean pressure is performed for the 3 measurements, and the intercept on the permeability axis is the Klinkenberg corrected gas permeability.
Technical Specs
- Measuring range: 1 mD to 1500 mD
- Quality parameter:
- Limit of detection: 1.14 mD (based on outcrop chalk)
- Limit of quantification: 3.42 mD (based on outcrop chalk)
- Precision: 5.71% (based on chalk)
- Sample matrix: All kinds of dry, clean, porous material can be measured
- Sample size: Our equipment allows samples of 2.5 cm diameter and below 7.0 cm length. Samples shorter than 3.0 cm may give unreliable results due to end effects
- Sample preparation: Samples must be drilled with a diamond drilling tool to fit the sample holder (Diameter = 2.5 cm and Maximum length = 7.0 cm)