Sonic logging

Sonic logging shows a formation’s interval transit time, designated "Dt". It is a measure of a formation’s capacity to transmit sound waves. Geologically, this capacity varies with lithology and rock textures, notably porosity.

Quantitatively, the sonic log is used to evaluate porosity in liquid filled pores. The sonic tool is only capable of measuring travel time. Many relationships between travel time and porosity have been proposed, the most commonly accepted accepted is the Wyllie time average equation. The equation basically holds that the total travel time recorded on the log is the sum of the time the sonic wave spends traveling the solid part of the rock, called the rock matrix and the time spent traveling through the fluids in the pores.

Use in mineral exploration

Sonic logs are also used in mineral exploration, especially exploration for iron, hydrocarbons and potassium.