Definition - What does Electromagnetic Thickness mean?
Electromagnetic thickness is the in situ measurement of thickness of tubing or casing string by the use electromagnetic techniques. The result of the measurement can be presented as the kind of casing inspection log that detects the corrosion and gives an estimate of metal loss. In the general method, a coil that is centered inside the casing produces an alternating magnetic field. It can be measured by using flux leakage measurement or casing potential profiles.
Petropedia explains Electromagnetic Thickness
Electromagnetic thickness is thickness measurement of the casing strings or the tubing strings with the use of various electromagnetic techniques. The phase shift that is introduced by the casing is measured by other tools which farther up the tool. This phase shift is based on the internal diameter and thickness of the casing wall, magnetic permeability and casing conductivity as well. The effects get changed at distinct frequencies and by differentiating the frequencies, the internal diameter and thickness can be determined uniquely.