Study on the Annular Fluid Level IdentificationAlgorithmfor Ultra-Deep Wells Based on AcousticVelocityCorrection

The geological conditions and pressure system of ultra-deep oil and gas wells are complex, and formation leakage conditions are prone to occur. Accurately obtaining the annular liquid level depth during leakage is crucial for treatment decisions. In the high-temperature and high-pressure wellbore environment of ultra-deep wells, the sound velocity shows a nonuniform variation trend, which seriously affects the accuracy of annular liquid level identification. Therefore, it is of significance to carry out a study on the annular fluid level identification algorithm based on acoustic velocity correction. Based on establishing a calculation model for the annular temperature and pressure field, a sound velocity calculation model in the annular air section was constructed. By combining the actual sound velocity of the clear signal segment identified through the echo signal, the basic parameters in the sound velocity calculation model can be calibrated to obtain the calibrated wellbore sound velocity distribution. Finally, tests were conducted on simulated well sites and noisy production wells to verify the accuracy of the annular liquid level identification algorithm constructed in this study. The results showed that the identification algorithm had an error of less than 2%. All in all, this study can effectively meet the demand for dynamic annular liquid level data during the leakage conditions, which is of great significance for the treatment and decisionmaking in deep and ultra-deep wells.OPEN ACCESS Received: 30/07/2025 Accepted: 25/09/2025 Published: 23/01/2026