Porosity log is a type of logging tool used to measure the ability of reservoir rocks to hold fluids. In other words, it measures the porosity of the formation to aid in determining the permeability of the formation. Porosity logs measure the total porosity of the formation, which is the volume of the pore space divided by the total volume of the rock. This logs are commonly used to evaluate sandstone and carbonate reservoirs prior to the extraction of hydrocarbons.
Porosity logs have been commonly used since the 1970s. In the older measuring devices, the core sample was taken from the formation and then analyzed in a laboratory. This analysis was time consuming and costly. With the introduction of new technologies, the measurements can now be taken directly from the drill hole. This makes the process of measuring porosity much faster and less costly.
In the porosity logging process, evaluation tools or logging tools are used to measure the properties of the formation. There are two types of tools; sonic tools and nuclear tools. Sonic tools emit sound waves or seismic waves through the surrounding formation and measure the return trip of the sound. Nuclear tools measure the emission of gamma rays or radiation through the surrounding formation.
The sonic tool is the most often used tool for porosity logging since it is used to measure the rock’s porosity, permeability and other physical properties such as grain size, composition, and lithology. Sonic tools analyze the propagation of waves through the formation and measure properties such as the velocity of the waves and the transmitted energy in a particular formation.
The nuclear tool measures the porosity of the formation by measuring the amount of gamma or other radiation emitted by the formation. Gamma ray log tools emit gamma rays into the formation and measure the amount of radiation that is absorbed. The absorbed radiation is inversely proportional to the porosity of the formation. The gamma ray log is used to measure the porosity of the formation and is especially useful for measuring tight or low-porosity formations.
Porosity log data can be used to determine the permeability of a formation. A formation is considered permeable if the porosity increases with depth. Permeability is important in hydrocarbon reservoir rocks because it determines the ability of the formation to transmit oil or gas. In other words, it is the ability of the formation to allow fluids to move through the formation.
In conclusion, porosity logs are used to measure the porosity of a formation. This is done by using sonic or nuclear tools which measure the propagation of sound waves or the emission of gamma rays through the formation. This data can then be used to determine the permeability of the formation. Porosity log data is essential in reservoir engineering so that the most productive formations can be identified and the most profitable oil and gas extraction techniques can be chosen.
