Research on attenuation rate correlation calibration method based on acoustic variable density logging.

Area of Science:

• Petroleum Engineering
• Geophysical Well Logging

Background:

• Traditional acoustic variable density logging faces challenges with free pipe calibration, including logistical issues and subjectivity.
• Existing methods struggle when a free pipe is unavailable for calibration, limiting accurate cementing quality assessment.

Purpose of the Study:

• To develop and validate an innovative attenuation rate calibration method for acoustic variable density logging.
• To address the limitations of free pipe calibration in cementing quality evaluation.
• To enhance the accuracy and applicability of acoustic variable density logging.

Main Methods:

• Laboratory calibration of acoustic wave probe response consistency and transmitting probe frequency using specialized devices.
• Derivation of acoustic wave attenuation rate using a calibration coefficient.
• Conversion of attenuation rate to relative sound amplitude for well scale calibration.
• Field testing in 18 oil wells to evaluate cementing quality.

Main Results:

• The attenuation rate correlation calibration method demonstrated results consistent with theoretical values, with a maximum deviation of 6.9%.
• Identified sources of deviation include annulus fluid, trace bubbles, and instrument centering.
• The method successfully replaced in-well free pipe calibration with indoor acoustic instrument calibration.

Conclusions:

• The attenuation rate correlation calibration method provides a viable and accurate alternative for acoustic variable density logging, especially when free pipe calibration is not feasible.
• This approach enhances the quantitative interpretation of acoustic variable density data for improved cementing quality assessment.
• The method offers greater accuracy and a wider application range compared to traditional techniques.