Knowing the envelope and skeletal volumes of a core sample allows the total pore volume and percent porosity of the sample to be determined.
Since a core typically is a right circular cylinder, simple physical measurements of its diameter and length allow the envelope volume to be calculated.
A gas displacement pycnometer is a low-cost, non-destructive, non-hazardous technique for measuring the skeletal volume. The Porosimeter is a simple instrument using Boyle’s law for measurement of Grain Density. The system undergoes a 5 point Calibration routine against a set of calibrated discs.
A 4th degree polynomial equation is used to fit the data to generate the reference volume and the system dead volume.
The equation of the line is used to calculate the unknown grain volumes
Grain Density = Sample Weight / Measured Grain Volume
Knowing the Grain Volume, porosity can be calculated using various methods
Porosity = (Dimensional Bulk Volume – Measured Grain Volume) / Dimensional Bulk Volume