Poisson's ratio — Oil & Gas Glossary
An elastic constant that is a measure of the compressibility of material perpendicular to applied stress, or the ratio of latitudinal to longitudinal strain. This elastic constant is named for Simeon Poisson (1781 to 1840), a French mathematician. Poisson's ratio can be expressed in terms of properties that can be measured in the field, including velocities of P-waves and S-waves
Detailed Explanation
as shown below.Note that if VS = 0, then Poisson's ratio equals 1/2, indicating either a fluid, because shear waves do not pass through fluids, or a material that maintains constant volume regardless of stress, also known as an ideal incompressible material. VS approaching zero is characteristic of a gas reservoir. Poisson's ratio for carbonate rocks is ~ 0.3, for sandstones ~0.2, and above 0.3 for shale. The Poisson's ratio of coal is ~ 0.4.