A method can include energizing a tube with a longitudinally extending magnetic field generated inside the tube, using a magnetic field-detecting logging tool to generate magnetic flux signals generated inside the tube externally of the material of the tube wall resulting from such energizing at circumferential locations on the inner surface of the tube and at distances along the tube, iteratively using a model of the relationship between the generated magnetic flux signals and the thickness of the tube wall to derive a thickness profile of the tube wall by using (i) the magnetic permeability of the tube material deduced from the magnetic flux signals and (ii) a defect-free flux parameter representative of any non-linearity between the magnetic field strength and flux density in the tube, the iteration including using the model to calculate an initial approximate wall thickness profile using an initial estimate of the defect-free flux parameter.

Certain aspects and features relate to a system that includes a well tool configured to transmit an acoustic signal, detect a reflection signal, and transmit data representing the reflection signal. A processor analyzes the data to identify a pulse portion of the reflection signal, which is distinct from a reverberation portion. The processor determines a value for an attribute of the reflection signal, and executes a model to generate a first set of synthetic values for the attribute of the reflection signal and a second set of synthetic values for an impedance of a cement casing. The processor can then generate a lookup table that correlates the first set of synthetic values to the second set of synthetic values. By referencing the lookup table, processor can determine the impedance of the cement casing and alter a drilling plan or a completion plan based on the impedance of the cement casing.

A system may include an electromagnetic (EM) logging tool for inspecting downhole tubulars. The EM logging tool may include a mandrel, at least one low-frequency transmitter coil disposed on the mandrel, at least one-low frequency receiver coil disposed on the mandrel, and at least one-high frequency sensor configured to measure one or more electromagnetic properties of a tubular.

A system may include an electromagnetic (EM) logging tool for inspecting downhole tubulars. The EM logging tool may include a mandrel, at least one low-frequency transmitter coil disposed on the mandrel, at least one-low frequency receiver coil disposed on the mandrel, and at least one-high frequency sensor configured to measure one or more electromagnetic properties of a tubular.

A downhole tool for determining laterals in a borehole wall or a borehole casing, comprising a tool housing extending along a longitudinal axis and having a circumference perpendicular to the longitudinal axis and a plurality of sonic transceivers. Each sonic transceiver transmitting sonic signals from the housing and receiving sonic signals reflected from the borehole wall or borehole casing in a predefined angular segment. The sonic transceivers are arranged along the circumference of the tool housing having a mutual distance and are capable of transmitting sonic signals radially away from the tool housing in an entire central angle of 360 degrees towards the borehole wall or borehole casing. During a pulse time, one sonic transceiver transmits a sonic signal in the predefined angular segment of that sonic transmitter, and one sonic transceiver, during a subsequent echo time, receives a reflected sonic signal from the borehole wall or borehole casing.

A downhole tool for determining laterals in a borehole wall or a borehole casing, comprising a tool housing extending along a longitudinal axis and having a circumference perpendicular to the longitudinal axis and a plurality of sonic transceivers. Each sonic transceiver transmitting sonic signals from the housing and receiving sonic signals reflected from the borehole wall or borehole casing in a predefined angular segment. The sonic transceivers are arranged along the circumference of the tool housing having a mutual distance and are capable of transmitting sonic signals radially away from the tool housing in an entire central angle of 360 degrees towards the borehole wall or borehole casing. During a pulse time, one sonic transceiver transmits a sonic signal in the predefined angular segment of that sonic transmitter, and one sonic transceiver, during a subsequent echo time, receives a reflected sonic signal from the borehole wall or borehole casing.

A method for measuring the thickness of casing in a wellbore and/or analyzing the inner surface of the cased or non-cased wellbore. The method includes an positioning an untethered logging tool in a drill string, receiving the logging tool in a catcher positioned within the drill string, positioning a plurality ultrasonic transducers with the average distance between the outer surface of the plurality of transducers and an interior surface of the catcher sub being less than 0.8 mm, and moving the drill string and the logging tool toward a mouth of the borehole while transmitting acoustic waves through the catcher sub toward the wellbore casing and receiving acoustic waves back to the logging tool after the acoustic waves interact with the wellbore casing and reflect through the catcher.

A method for measuring the thickness of casing in a wellbore and/or analyzing the inner surface of the cased or non-cased wellbore. The method includes an positioning an untethered logging tool in a drill string, receiving the logging tool in a catcher positioned within the drill string, positioning a plurality ultrasonic transducers with the average distance between the outer surface of the plurality of transducers and an interior surface of the catcher sub being less than 0.8 mm, and moving the drill string and the logging tool toward a mouth of the borehole while transmitting acoustic waves through the catcher sub toward the wellbore casing and receiving acoustic waves back to the logging tool after the acoustic waves interact with the wellbore casing and reflect through the catcher.

A system may include an electromagnetic (EM) logging tool for inspecting downhole tubulars. The EM logging tool may include a mandrel, at least one low-frequency transmitter coil disposed on the mandrel, at least one-low frequency receiver coil disposed on the mandrel, and at least one-high frequency sensor configured to measure one or more electromagnetic properties of a tubular.

A system may include an electromagnetic (EM) logging tool for inspecting downhole tubulars. The EM logging tool may include a mandrel, at least one low-frequency transmitter coil disposed on the mandrel, at least one-low frequency receiver coil disposed on the mandrel, and at least one-high frequency sensor configured to measure one or more electromagnetic properties of a tubular.