The Cement Bond Logging tools have become the standard method of evaluating cement jobs. They indicate how good the cement bond is. A cement bond log (CBL) documents an evaluation of the integrity of cement job performed on an oil well. It is basically a sonic tool which is run on wireline. Similar to a ringing bell, when no cement is bonded to the casing, pipe is free to vibrate (loud sound). When the casing is bonded to hard cement, casing vibrations are attenuated proportionally to bonded surface.
CBL Measurement Principle:
The basic tool configuration of CBL-VDL log is composed by One Transmitter and Two Receivers: the first Receiver is located 3 ft. from the Transmitter and is used for CBL Measurement. The second Receiver is located 5 ft. from the Transmitter and is used for Variable Density Log (VDL).
NB: CBL-VDL logging tools MUST be centralized.
The following video explains the basics of Cement Bond Log:
NB: API 10TR-1 is an API standard for Cement Sheath Evaluation.