Principle of sonic logging
- Jan 24, 2019 -

A controlled acoustic wave source is placed in the well, and the sound waves emitted by the sound source cause vibration of the surrounding particles, and body waves, ie, longitudinal waves and transverse waves, are generated in the formation, and an induced interface wave is generated at the interface of the well wall and the pseudo-Rayleigh Wave and Stone Lapo. These waves, as carriers of the formation information, are received by the downhole receiver and sent to the ground for recording, which is sonic logging. The receiver and sound source are collectively referred to as the sound system. According to the arrangement and size of the sound system, the sonic logging tool can be divided into the compensation logging tool (BHC), the long source distance acoustic wave logging tool (LSS) and the array sonic logging tool. . Sound waves propagate in the well formation due to changes in the composition, structure, and fluid composition of the rock, and the speed, amplitude, and even frequency of the wave will change. A sound velocity log (AC) is recorded only for recording changes in acoustic velocity, and a sound amplitude log is recorded for recording changes in sound amplitude. In the sonic velocity logging, the short-source sound system only records the longitudinal wave (ie, the first wave) propagation time difference, and the long-source sound system can record the propagation time difference of various wave trains such as the longitudinal wave, the transverse wave, the pseudo Rayleigh wave, and the Stoneley wave. So it is also called full-wave sonic logging, and the array sonic instrument can record the longitudinal wave sound velocity due to the complex sound system, and can record the full-wave column sound velocity, and can also record the sound amplitude.


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