Ultrasonic Wellbore Tool Harmonic Casing Thickness Logging
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Solution Overview
Problem
Accurately measuring the thickness and integrity of wellbore casings with thick walls is challenging due to limitations in existing measurement methods, particularly with piezoelectric (PZT) sensors, which struggle to manufacture and implement sensors for higher frequencies generated by thicker casings.
Innovation Solution
The use of ultrasonic wellbore tools (UWTs) that select acoustic sensors based on casing thickness, measuring harmonics of the resonant frequency instead of the fundamental frequency, allowing for accurate logging of casings up to 2 inches thick by employing high, medium, or low frequency sensors depending on the casing thickness, and adjusting measurements accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard piezoelectric (PZT) sensors are used for measuring casing thickness, then manufacturing and implementation is straightforward, but measurement precision deteriorates for thick-walled casings due to inability to generate higher frequencies
Solution Approach 1:
The patent changes the measurement parameter from fundamental frequency to harmonic frequencies (2nd, 3rd, 4th harmonics). By measuring harmonic frequencies and multiplying by appropriate factors (2, 3, 4 respectively), the system achieves accurate thickness measurements for thick casings without requiring custom high-frequency sensors, thus maintaining ease of manufacture while improving measurement precision.
2Measurement precision
If higher frequency sensors are manufactured to measure thick casing walls, then measurement precision improves, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent makes standard PZT sensors universal by enabling them to measure both thin and thick casings through harmonic frequency analysis. The same sensor can measure fundamental frequencies for thin casings and harmonic frequencies for thick casings, eliminating the need for multiple specialized sensors with different frequency ranges.
3Adaptability or versatility
If fundamental frequency measurement is used, then the measurement method is simple, but adaptability to different casing thicknesses deteriorates
Solution Approach 1:
The patent introduces dynamic adaptability by automatically selecting which harmonic frequency to measure based on the casing thickness. The system can switch between measuring fundamental frequency, 2nd harmonic, 3rd harmonic, or 4th harmonic depending on the casing thickness, making the measurement method adaptable to various casing thicknesses without increasing operational complexity.
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
Enables accurate measurement of casing thickness and cement bond quality for wellbores with thick casings, overcoming the limitations of standard PZT sensors by using harmonic frequencies, thus improving the assessment of casing integrity and cement quality.
Implementation Method 1
generate an acoustic signal having a frequency that will stimulate resonance vibration of the casing
Implementation Method 2
receive the return signals
Data Source
AI summary
Methods and systems for logging a wellbore having a casing are described. Acoustic energy, typically ultrasonic acoustic energy, is used to stimulate reverberation of the casing at a harmonic (for example, the second or third harmonic) of the resonance frequency of the casing. One or more acoustic sensors are used to measure acoustic signals generated by the casing reverberation. Parameters of the casing are calculated based on the measured acoustic signals adjusted by an adjustment factor determined by the particular harmonic. The use of harmonics instead of the fundamental resonance frequency allows wellbores with casings having walls thicker than 0.625 inches to be logged.