Controlled Source Imbalance for Multipole Acoustic Logging Bandwidth
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Solution Overview
Problem
Traditional multipole acoustic logging tools face bandwidth limitations due to the use of matched sources, which reduces the effectiveness of measurements by introducing source-imbalance induced mode contamination.
Innovation Solution
The use of non-matched sources with controlled source imbalances and pairwise matched transmitters, where signal source pairs have a substantially equal and non-zero acoustic signature amplitude difference in the frequency domain, allows for increased bandwidth measurements by minimizing source imbalance induced mode contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If matched sources are used in traditional multipole acoustic logging tools, then source-imbalance induced mode contamination is reduced, but bandwidth limitations are imposed on measurements
Solution Approach 1:
The patent applies asymmetry by using non-matched sources with deliberately different acoustic signatures instead of traditional matched sources. Specifically, the sources are configured with different amplitudes or phases to create controlled asymmetry that enables broader bandwidth measurements while managing mode contamination through signal processing techniques
2Adaptability or versatility
If non-matched sources with controlled imbalances are used, then measurement bandwidth is increased, but source-imbalance induced mode contamination occurs
Solution Approach 1:
The patent converts the harmful effect of source imbalance into a beneficial feature by deliberately designing controlled imbalances in the sources. The different acoustic signatures of non-matched sources are used to excite a broader frequency range, and the resulting mode contamination is managed through signal processing to extract useful information across extended bandwidth
3Measurement precision
If pairwise matched transmitters are used, then signal-to-noise ratio is enhanced for specific modes, but frequency range of useful data is limited
Solution Approach 1:
The patent applies parameter changes by varying the acoustic signature parameters (amplitude, phase, frequency) of the sources in a controlled manner. Pairwise matched transmitters are configured with specific parameter relationships that enhance signal-to-noise ratio for desired modes while the overall system maintains extended frequency range through the use of non-matched source pairs
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 bandwidth and signal-to-noise ratio of acoustic measurements, particularly for Stoneley wave data, by selectively canceling out unwanted modes and increasing the frequency range of useful monopole data.
Implementation Method 1
Acoustic signals may be transmitted by the acoustic sources and received at the receivers as the tool is drawn through a borehole. Thus, the acoustic signal from each source may travel through the formation adjacent the borehole to the receiver array
Implementation Method 2
The use of non-matched sources with controlled source imbalances... selectively canceling out unwanted modes and increasing the frequency range of useful monopole data
Data Source
AI summary
In some embodiments, an apparatus and a system, as well as a method and an article, may include exciting a plurality of signal source pairs having a substantially equal and non-zero acoustic signature amplitude difference in a frequency domain to provide acoustic signal data, and acquiring the acoustic signal data along a selected azimuth. The plurality of signal source pairs may comprise acoustic bender plates, perhaps included in the outer wall of a downhole tool.