porosity and permeability determination

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porosity and permeability determination Porosity is measured from rock plugs in a porosimeter. The method involves the extraction of air from the pores in the rock by a vacuum, and measurement of the bulk volume of the rock. The porosity is calculated by the expression: % porosity = (volume of gas extracted/bulk volume of the rock sample) × 100. Permeability is measured in a permeameter, by determining the pressure drop (P1P2) from a fluid of known viscosity (μ) and flow rate (Q), across a rock sample of known cross-section (A) and length (L). Permeability (K) is then determined by Darcy's law: K = QμL/(P1P2)A.