Segmented Acoustic Transducer for Cement Bond Logging
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Solution Overview
Problem
Conventional cement bond logging tools face challenges such as limited frequency utility due to resonant frequency operation, interference from spurious vibrations, slow data processing, and the need for tedious calibration adjustments, which restrict their efficiency and accuracy in harsh downhole environments.
Innovation Solution
A longitudinally segmented acoustic transducer design using thin-walled piezoelectric cylinders divided into band-like rings separated by resilient spacers, operating in an anti-resonant mode, combined with high-speed digital signal processing and real-time normalization, enhances data clarity and reduces noise, allowing for faster data acquisition and improved calibration efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional piezoelectric crystals are operated at their resonant frequency, then the transducer operates efficiently with predictable behavior, but the utility is limited to a single frequency and spurious vibrations cause interference
Solution Approach 1:
The patent divides a single piezoelectric crystal into multiple segments along the acoustic axis. Each segment can be independently excited at different frequencies, enabling the transducer to operate at multiple frequencies rather than being limited to a single resonant frequency. This segmentation resolves the contradiction by maintaining reliable operation through controlled excitation while expanding frequency utility across multiple bands.
Solution Approach 2:
The patent implements dynamic frequency selection by allowing the transducer to be excited at different frequencies based on operational requirements. The system can dynamically switch between fundamental resonant frequencies and higher harmonic frequencies, providing adaptability while maintaining reliable operation through controlled excitation patterns that prevent spurious vibrations.
2Productivity
If conventional cement bond logging tools are used, then data can be acquired, but the data processing is slow and calibration requires tedious adjustments
Solution Approach 1:
The patent performs calibration measurements and signal processing operations in advance during the logging run. By preprocessing the acoustic signals and performing normalization operations before final interpretation, the system reduces the time required for post-processing and eliminates the need for tedious field calibration adjustments. This preliminary action resolves the contradiction by accelerating data acquisition while minimizing calibration time loss.
3Reliability
If conventional transducers are used in harsh downhole environments, then operation is possible, but spurious vibrations interfere with signal accuracy
Solution Approach 1:
The patent segments the piezoelectric crystal into multiple independent elements that can be excited in a controlled sequence. This segmentation allows the system to maintain reliable operation in harsh downhole environments while improving measurement precision by preventing spurious vibrations through controlled excitation patterns and selective frequency operation.
Solution Approach 2:
The patent implements signal processing techniques that use feedback from the received acoustic signals to improve measurement accuracy. By analyzing the received signals and applying normalization operations based on calibration data, the system compensates for environmental interference and spurious vibrations, maintaining high measurement precision despite harsh operating conditions.
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
The segmented transducer design and digital signal processing enable faster data transmission, improved signal-to-noise ratio, and reduced calibration time, resulting in more accurate and efficient cement bond logging with enhanced operational speed and reliability in extreme conditions.
Implementation Method 1
The crystal may be caused to vibrate at its resonant frequency by application of a suitable excitation signal applied to the two electrodes
Implementation Method 2
the crystal may vibrate in the presence of an acoustic disturbance or wave and generate an alternating electric voltage between the two electrodes
Implementation Method 3
The acoustic energy sensed by the receiving transducer is conveyed by the acoustic waveform as it is modified by attenuation, reflection, refraction and interference that may be encountered by the signal along the particular path between the transmitter and the receiver
Data Source
AI summary
A longitudinally segmented acoustic transducer for a cement bond logging (CBL) tool having a plurality of adjoining PZT ring-like segments driven synchronously in parallel by one or more pulses and caused to vibrate in an anti-resonant mode, substantially below the resonant frequency of an individual segment when used in a transmitting application. When used in a receiving application, each of the plurality of transducer rings are caused to vibrate by acoustic signals detected by the transducer array, also in an anti-resonant mode. High speed digital signal processing enables on-depth, high quality data for all azimuths at each depth to be obtained, processed, normalized and either sent to the surface in real time for each 20 Hz firing cycle, as the CBL tool is pulled toward the surface, or stored in a memory module in digital form for later retrieval. Built-in calibration factors used for normalizing the output signals to the operating conditions of use may be accessed at any time.