Low-Frequency Casing Guided Waves for Cement Bond Evaluation
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Solution Overview
Problem
Traditional methods for through tubing cement evaluation (TTCE) face challenges due to signal masking by metal pipe strings, which dominate acoustic signals and result in a poor signal-to-noise ratio, making it difficult to assess the bonding condition between the casing and cement in well installations.
Innovation Solution
An acoustic logging tool that uses a multi-firing multimode array processing system to transmit monopole, dipole, and quadrupole acoustic waves, recording these signals with an array of receivers and applying multimode dispersion analysis to separate casing-related modes, calculate the bonding index, and determine the bonding condition between the casing and cement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional acoustic signals (20 kHz or ultrasonic) are used for TTCE, then the logging operation can be performed, but the signal-to-noise ratio deteriorates because pipe string signals dominate and casing signals become weak
Solution Approach 1:
The patent changes the frequency parameter from traditional 20 kHz or ultrasonic frequencies to low frequencies (e.g., below 5 kHz). This parameter change allows acoustic signals to penetrate the pipe string more effectively and excite casing guided waves, improving the signal-to-noise ratio for cement bond evaluation while maintaining measurement reliability
Solution Approach 2:
The patent employs a dynamic signal processing approach using wavelet transforms and adaptive filtering to separate casing-related signals from pipe string signals in real-time. This dynamic processing adapts to varying signal conditions and enhances the weak casing signals while suppressing dominant pipe string noise
2Measurement precision
If high frequency acoustic signals are used, then better resolution is achieved, but the pipe string blocks most signals and casing-related signals become weak
Solution Approach 1:
The patent changes the frequency parameter from high frequencies to low frequencies (below 5 kHz). Low frequency signals have longer wavelengths that can penetrate the pipe string more effectively, reducing the blocking effect while still providing sufficient resolution for cement bond evaluation through advanced signal processing
Solution Approach 2:
The patent uses the pipe string itself as an intermediary medium by exciting and analyzing guided waves that propagate through the pipe string to reach the casing. Instead of treating the pipe string as a barrier, the method utilizes its wave-guiding properties to transmit acoustic energy to the casing and return bond evaluation signals
3Adaptability or versatility
If through tubing cement evaluation is performed, then cement bond assessment is possible with pipe string present, but traditional methods encounter serious signal-to-noise ratio issues
Solution Approach 1:
The patent changes multiple parameters including frequency (to low frequencies), wavelet scale (for multi-resolution analysis), and filtering parameters (for adaptive noise suppression). These parameter changes enable TTCE to function effectively in the presence of pipe strings while maintaining acceptable signal-to-noise ratios for reliable cement bond evaluation
Solution Approach 2:
The patent implements dynamic signal processing with adaptive filtering and wavelet transform that automatically adjusts processing parameters based on the measured signal characteristics. This dynamic approach enhances the weak casing signals while suppressing dominant pipe string noise, making TTCE viable with improved signal-to-noise ratio
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively separates and identifies casing-related modes from tubing-related waves, providing accurate bonding information by extracting dispersion and attenuation properties, thereby improving the reliability of cement evaluation in well installations.
Implementation Method 1
transmitting an acoustic wave from an acoustic source to generate a plurality of guided waves
Implementation Method 2
recording a plurality of acoustic signals with an array of receivers
Implementation Method 3
performing a multichannel multimode dispersion analysis of the one or more acoustic signals
Data Source
AI summary
A method and system for cement evaluation. The method may include disposing an acoustic logging tool into a pipe string that is disposed in a first casing of a wellbore, transmitting an acoustic wave at a first location within the wellbore from an acoustic source disposed on the acoustic logging tool, and recording one or more acoustic signals with one or more receivers on the acoustic logging tool at the first location. The method may further include performing a multichannel multimode dispersion analysis of the one or more acoustic signals, extracting one or more fluid modes propagating in the first casing from the dispersion analysis, extracting one or more pseudo-lamb waves propagating in the first casing from the dispersion analysis, extracting one or more pseudo-SH-plate waves propagating in the first casing from the dispersion analysis, and identifying a bonding condition between the first casing and a cement.