Definition of porosity

i. The ratio, P, expressed as a percentage of the volume, Vp, of the pore space in a rock to the volume, Vr, of the rock, the latter volume including rock material plus the pore space; P = 100 Vp/Vr.

Ref: Holmes, 2

ii. The amount of void space in a reservoir usually expressed as percent voids per bulk volume. Absolute porosity refers to the total amount of pore space in a reservoir, regardless of whether or not that space is accessible to fluid penetration. Effective porosity refers to the amount of connected pore spaces; i.e., the space available to fluid penetration.

Synonym of: total porosity