Definition - What does Sonic Logging mean?
Sonic Logging, also known as acoustic logging, is an electric log that records the acoustic characteristics of subsurface formations based on the travel time of sound waves through the reservoir rocks. The rate of travel of sonic waves depends on the composition, porosity and fluid content of the reservoir under test. The tool is considered to be in the category of well logging tools.
Petropedia explains Sonic Logging
Sonic logging is used in order to get the interval transit time of the formation which is measured by calculating the time taken by the sonic detectors and transmitters to transmit back the seismic/acoustic waves through the reservoir formation. The rock geology characteristics such as texture, composition, porosity, fluid content, etc., all affect the capacity of seismic wave transmission back to the seismic recorder and accordingly sonic logs are mapped.
An array of geophones is used to record the acoustic waves back by lowering them into the borehole. These waves are received from different depths within the reservoir and interval transit time is recorded accordingly.