porosity

Porosity is a measure of the void spaces in a material, expressed as a fraction of the total volume. These voids can store fluids such as water, oil, gas, or air and may be connected or isolated. Porosity is a key property in geology, soil science, and materials engineering, influencing storage capacity and material behavior.

Porosity is commonly categorized as total porosity, effective (or connected) porosity, primary porosity, and secondary porosity. Primary porosity refers to the original pore spaces formed during deposition; secondary porosity develops after deposition, through processes such as fracturing or dissolution. Porosity can be open (connected to other pores or to the surface) or closed (isolated).

Porosity can be measured by laboratory methods such as gas or liquid intrusion porosimetry, helium porosimetry combined with density measurements, and non-destructive imaging like CT scanning or nuclear magnetic resonance. In the field, porosity is estimated from well logs (neutron and density logs) and from core samples. Porosity is usually reported as a dimensionless fraction or as a percentage of the total volume.

Porosity is closely related to permeability, but high porosity does not guarantee high fluid flow if pore spaces are poorly connected. Factors influencing porosity include mineralogy, grain size and sorting, cementation, compaction, diagenesis, fracturing, and dissolution. Porosity is a critical parameter for applications such as groundwater storage and transport, hydrocarbon reservoir characterization, soil water retention, and the design of ceramics and insulative materials.