Which logging tool is used to estimate formation properties by generating and detecting electromagnetic fields in the formation?

Which logging tool is used to estimate formation properties by generating and detecting electromagnetic fields in the formation?

• A. Induction log
• B. SP log
• C. Gamma Ray log
• D. Neutron log

Answer: (A)

Induction logging uses an alternating current in a transmitter to generate a changing magnetic field that penetrates the surrounding rock. This changing field induces electrical currents in the formation, and a receiver measures the resulting secondary magnetic field. The strength and decay of that signal depend on how conductive the formation is, which lets the tool estimate formation resistivity (and related properties) from EM response. In other logs, there is no generation and detection of EM fields in the formation: self-potential (SP) logs rely on natural electrochemical potentials, gamma-ray logs detect natural gamma radiation from minerals, and neutron logs probe hydrogen content through nuclear interactions.

Induction logging uses an alternating current in a transmitter to generate a changing magnetic field that penetrates the surrounding rock. This changing field induces electrical currents in the formation, and a receiver measures the resulting secondary magnetic field. The strength and decay of that signal depend on how conductive the formation is, which lets the tool estimate formation resistivity (and related properties) from EM response. In other logs, there is no generation and detection of EM fields in the formation: self-potential (SP) logs rely on natural electrochemical potentials, gamma-ray logs detect natural gamma radiation from minerals, and neutron logs probe hydrogen content through nuclear interactions.