Design of an Acoustic Through-Casing Logging Tool.

Area of Science:

• Geophysics
• Petroleum Engineering
• Acoustic Technology

Background:

• Well logging is crucial for characterizing underground formations in oil and gas exploration.
• Cased-hole logging is vital in mature fields and for wells logged after casing due to borehole instability.
• Acoustic through-casing logging faces challenges from casing wave interference, particularly with poor casing-formation bonding.

Purpose of the Study:

• To develop and validate an acoustic logging tool capable of suppressing casing waves.
• To improve the quality and reliability of formation data obtained through casing.
• To enable commercial application of acoustic logging in cased wells.

Main Methods:

• Design of a novel acoustic tool featuring dual-source transmitters to actively cancel casing waves.
• Optimization of transducer spacing and development of a dual-source transmitting circuit with opposite polarity signals.
• Field testing of the tool in cased exploration wells.

Main Results:

• Successful suppression of approximately 90% of casing waves was achieved.
• The dual-source transmitter design effectively canceled interfering casing wave amplitudes.
• Demonstrated the capability to obtain trustworthy formation information in cased wells.

Conclusions:

• The developed dual-source acoustic logging tool significantly mitigates casing wave interference.
• This technology enhances the commercial viability of through-casing acoustic logging.
• Reliable formation evaluation is now possible even in wells with challenging casing-formation interfaces.