Core sample may not be representative of the reservoir rock because of reservoir heterogeneity.There are several factors that could lead to some of error in determining reservoir permeability. For example injection of water to a sample with some amount of clay leads to decreasing permeability due to swelling of the clays. However liquids sometimes change the pore structure and therefore the permeability. Both liquids and gases have been used to measure permeability. The measured permeabilities on plugs that are drilled perpendicular to the bedding planes are referred to as vertical permeability ( K v).

These yield horizontal permeabilities ( K h). Routine core analysis is generally concerned with plug samples drilled parallel to bedding planes and, hence, parallel to the direction of flow in the reservoir. Permeability is reduced by overburden pressure, and this factor should be considered in estimating permeability of the reservoir rock in deep wells because permeability is an anisotropic property of the porous rock, that is, it is directional. The experiment can be arranged so as to have horizontal or vertical flow through the sample. Sometimes the permeability tests run on a whole core samples about 30-50 cm long. Cores are cylinders with approximately 3.81cm (1.5 inch) diameter and 5 cm (2 inch) length. Measurement of permeability in the case of isotropic media is usually performed on linear, mostly cylindrical shaped, “core” samples. The permeability of a porous medium can be determined from the samples extracted from the formation or by in place testing such as well logging and well testing. Fundamentals of Fluid Flow in Porous MediaĬhapter 2 Permeability: Measurement of Permeability

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