Definition - What does Well Logging mean?
Well Logging is the practice of creating a detailed record (known as a well log) of the geological formation during the drilling of a borehole. A well log is prepared by either taking samples through visual inspections or with the aid of measuring instruments lowered into the borehole. Logs prepared using visual inspections are called geological logs whereas logs prepared with the help of inspection instruments are called geophysical Logs.
Petropedia explains Well Logging
Well Logging is generally carried out to evaluate hydrocarbon deposits. In order to perform this evaluation, testing of rock and fluid formations at different locations is conducted and the data is recorded on the logs. The device that is used to conduct well testing is called logging tool and it can be attached to a thin wire called wireline, which carries this tool to the necessary depth within the borehole to conduct testing on quantity and location of hydrocarbons beneath the earth’s surface. This tool gathers all data and sends it to the control room where the well logs are prepared.