Sonic logging
Encyclopedia
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 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.
, hydrocarbons and potassium
.
Geologic formation
A formation or geological formation is the fundamental unit of lithostratigraphy. A formation consists of a certain number of rock strata that have a comparable lithology, facies or other similar properties...
interval transit time, designated Dt. It is a measure of a formation’s capacity to transmit sound waves. Geologically, this capacity varies with lithology
Petrology
Petrology is the branch of geology that studies rocks, and the conditions in which rocks form....
and rock textures, notably porosity
Porosity
Porosity or void fraction is a measure of the void spaces in a material, and is a fraction of the volume of voids over the total volume, between 0–1, or as a percentage between 0–100%...
.
Quantitatively, the sonic log is used to evaluate porosity
Porosity
Porosity or void fraction is a measure of the void spaces in a material, and is a fraction of the volume of voids over the total volume, between 0–1, or as a percentage between 0–100%...
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 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 ironIron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
, hydrocarbons and potassium
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...
.