Electronic sensing of discontinuities in a well casing

A method of sensing a discontinuity in a well casing, the method comprising:

• applying an AC voltage to an antenna mounted in or on a tubing string;
• monitoring a current generated in the antenna while the AC voltage is being applied to the antenna and while the tubing string is deployed within the well casing;
• sensing the discontinuity in the well casing by detecting a difference between the current generated in the antenna when the antenna is proximate to the discontinuity and the current generated in the antenna when the antenna is not proximate to the discontinuity;
• and
• providing at least a relative position indication based on sensing the discontinuity.

A system for sensing collar joints in a well casing, the system comprising:

• an antenna mountable in or on a tubing string;
• a driver module connectable to the antenna;
• a transmission line connectable to the driver module;
• and
• a controller connectable to the transmission line, the controller operable to:
• apply an AC voltage to the antenna;
• monitor a voltage drop across a sensing resistor connected to the antenna while the tubing string is deployed within the well casing;
• sense a collar joint in the well casing by detecting a difference between the voltage across the sensing resistor when the antenna is proximate to the collar joint and the voltage across the sensing resistor when the antenna is not proximate to the collar joint;
• and
• provide at least a relative position indication based on sensing the collar joint.