CASING COLLAR LOCATION USING ELECROMAGNETIC WAVE PHASE SHIFT MEASUREMENT

摘要

A method for locating casing collars in a cased wellbore includes moving a well logging instrument coupled within a drill string through the cased wellbore. The instrument includes at least one electromagnetic transmitter and at least two spaced apart electromagnetic receivers. The at least one electromagnetic transmitter is energized with alternating current. A phase difference between electromagnetic signals detected by each of the at least two electromagnetic receivers is measured. A position of at least one casing collar is determined when a change in the measured phase shift is detected.