Downhole Acoustic Transducer Ringdown Noise Removal
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Solution Overview
Problem
Acoustic transducers in ultrasonic caliper tools face performance challenges due to ringdown noise, which affects signal quality and accuracy in borehole imaging, especially in oil-based muds, leading to poor signal-to-noise ratios and reduced instrument sensitivity.
Innovation Solution
The method involves estimating and subtracting ringdown noise from waveforms using the median of waveforms from previous tool firings, stored in memory or developed through laboratory testing, to improve signal accuracy and reliability, allowing for effective high-resolution borehole imaging in oil-based muds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If improved transducers are used to reduce ringdown noise, then signal quality and accuracy are improved, but device cost increases significantly
Solution Approach 1:
The patent extracts and removes the ringdown noise component from the received signal through signal processing techniques. By calculating the median of multiple waveforms to estimate ringdown characteristics and then subtracting this estimated ringdown from individual waveforms, the method separates and eliminates the harmful ringdown component without requiring expensive transducer modifications
Solution Approach 2:
The patent replaces the mechanical approach of using improved transducers with a signal processing approach. Instead of modifying the physical transducer to reduce ringdown, the invention uses digital signal processing (median calculation and subtraction) to achieve the same goal of improving signal quality, thereby avoiding increased device cost
2Reliability
If ringdown noise is not removed, then device complexity remains low, but signal-to-noise ratio deteriorates and measurement accuracy is reduced
Solution Approach 1:
The patent performs preliminary action by collecting multiple waveforms and calculating their median before processing individual waveforms. This pre-calculation of the median waveform (which represents the ringdown characteristics) is done in advance, allowing for efficient noise removal from subsequent waveforms without requiring complex real-time processing
Solution Approach 2:
The patent creates a copy of the ringdown noise characteristics by calculating the median of multiple waveforms. This median waveform serves as a template or copy of the ringdown pattern that can be subtracted from individual waveforms, simplifying the noise removal process while improving 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 enhances the accuracy and reliability of downhole tool performance by reducing ringdown noise, enabling the use of acoustic tools for high-resolution borehole imaging in oil-based muds, previously only feasible in water-based muds, and improves the signal-to-noise ratio.
Implementation Method 1
A transducer emits a high-frequency pulse that is reflected by the pipe or borehole wall back to the transducer
Implementation Method 2
The transducer emits a high-frequency pulse that is reflected by the pipe or borehole wall back to the transducer
Implementation Method 3
The diameter is determined from the time of flight of this echo and the fluid acoustic velocity
Implementation Method 4
the transducer's mechanical motion failing to instantly cease when a driver signal is removed. Due to the transmitted signal overlapping with a received signal, there is some residual motion and vibration which creates noise
Implementation Method 5
the "ringdown" phenomena due to the transducer's mechanical motion failing to instantly cease when a driver signal is removed
Data Source
AI summary
Ringdown noise can be estimated and removed from a waveform captured by a downhole tool. Ringdown may be estimated by calculating a median of waveforms from a number of tool firings. The estimated ringdown may then be subtracted from a waveform currently being processed. The resulting waveform contains a more accurate representation of a true echo signal reflected from the borehole wall or formation. In some embodiments, the acoustic transducer's deterministic waveform may be learned by statistical analysis of other waveforms near in time to the presently measured waveform. In other embodiments, the deterministic waveform may be learned via previously acquired waveforms now stored in memory, or through predictive waveforms developed in laboratory testing conditions similar to those experienced downhole.