Acoustic Logging Tool Interface Noise Removal
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Solution Overview
Problem
Acoustic measurements in wellbores are complicated by the superposition of reflections from multiple interfaces, leading to inaccurate cement evaluation due to galaxy patterns and third interface echoes, which interfere with the assessment of cement quality and zonal isolation.
Innovation Solution
A method involving acoustic logging tools that normalize acoustic waves in the frequency domain, remove spectral noise, shape the spectrum around a resonance frequency, convert to the time domain, and subtract specular noise and second interface echoes to isolate third interface echo signals, thereby improving the accuracy of cement evaluation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If acoustic measurements are taken in wellbores with multiple interfaces, then cement evaluation data can be obtained, but the measurements are complicated by superposition of reflections from multiple interfaces leading to inaccurate cement evaluation
Solution Approach 1:
The acoustic signal processing is segmented into distinct frequency components using Fourier transformation. The spectrum is divided into regions of interest and noise regions, allowing selective processing of different frequency components to separate useful signal from harmful interface noise and galaxy patterns.
Solution Approach 2:
The harmful galaxy patterns and third interface echoes are extracted and removed from the acoustic signal through spectral filtering. By identifying and removing specific frequency components corresponding to noise outside the region of interest, the method isolates the useful acoustic information from the harmful reflections.
2Measurement precision
If spectral filtering is applied to remove noise, then measurement precision improves, but device complexity increases due to frequency domain processing
Solution Approach 1:
The mechanical signal processing approach is replaced with frequency domain processing using Fourier transformation. This substitution allows for more precise filtering and manipulation of acoustic signals by working with spectral components rather than time-domain waveforms, improving measurement precision while the processing is performed computationally.
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 enhances the precision of cement quality assessment by reducing galaxy patterns and third interface echoes, allowing for more accurate determination of cement installation and zonal isolation in wellbores.
Implementation Method 1
acoustic data comprising an acoustic wave reflected from the casing, the annular fill material, one or more interfaces between any of the mud, the casing, and the annular fill material
Implementation Method 2
normalizing the acoustic wave in a frequency domain, resulting in a specular spectrum
Implementation Method 3
shaping the specular spectrum around a resonance frequency
Data Source
AI summary
A method of determining properties of a wellbore in a formation includes obtaining from the acoustic logging tool, acoustic data comprising an acoustic wave reflected from the casing, the annular fill material, one or more interfaces between any of the mud, the casing, and the annular fill material, or combinations thereof. The method includes normalizing the acoustic wave in a frequency domain, resulting in a specular spectrum and removing spectral noise outside a region of interest in the specular spectrum. The method includes shaping the specular spectrum around a resonance frequency, converting the shaped specular spectrum into a time domain, resulting in a renormalized waveform, and subtracting from the renormalized waveform one or more of a specular noise, second interface echoes, resulting in a third interface echo signal.