Downhole Acoustic Waveform Filtering via Wavelet Transform
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Solution Overview
Problem
Processing acoustic signal data from downhole tools is challenging due to overlapping signals from different paths and materials, making it difficult to analyze and extract specific signal information effectively.
Innovation Solution
The method involves performing a direct complex continuous wavelet transform on acoustic data to generate wavelet maps, identifying and extracting the signal of interest using coherence data, and then filtering the data to remove unwanted components, such as casing arrival waves, to improve analysis of formation slownesses and other parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If acoustic signals are received through multiple paths and materials, then comprehensive formation information is obtained, but signal overlap and interference occur making analysis difficult
Solution Approach 1:
The patent transforms the acoustic signal analysis from the time domain to the time-frequency domain using wavelet transform. This dimensional change allows signals that overlap in time to be separated by their frequency characteristics, enabling differentiation of acoustic waves traveling through different paths and materials without increasing physical device complexity
Solution Approach 2:
The patent introduces wavelet transform as an intermediary mathematical tool between the raw acoustic signals and the formation analysis. This intermediary transformation enables the separation of overlapping signals by mapping them into a time-frequency representation where different signal components can be distinguished and analyzed independently
2Productivity
If traditional signal processing methods are used, then processing is simpler, but real-time processing capability is insufficient
Solution Approach 1:
The patent replaces traditional mechanical or sequential signal processing methods with a mathematical transformation approach using wavelet transform. This substitution enables parallel processing of signal components in the time-frequency domain, achieving real-time processing capability without the computational bottlenecks of traditional sequential methods
3Measurement precision
If acoustic receivers are distributed along the tool body, then spatial signal detection is improved, but signal overlap from different paths increases
Solution Approach 1:
The patent applies wavelet transform to convert the spatially distributed receiver signals from time domain to time-frequency domain. This transformation adds a frequency dimension that allows differentiation of signals arriving from different paths, even when they overlap in time, thereby maintaining the benefits of distributed receivers while eliminating signal interference
Data Source
AI summary
Methods and apparatus to filter acoustic waveforms in downhole environments are described. An example method involves receiving acoustic waveform data representing acoustic signals traversing at least a portion of a borehole adjacent a subterranean formation and performing a direct transform operation on the acoustic waveform data to generate wavelet map data. The wavelet map data comprises a time-frequency representation of the acoustic waveform data. The example method also involves identifying a waveform of interest via the wavelet map data, extracting data associated with the waveform of interest from the wavelet map data, generating filtered wavelet map data based on the extracted data, and performing an inverse transform operation on the filtered wavelet map data to generate filtered acoustic waveform data