Ultrasonic Pulse-Echo Wellbore Characterization
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Solution Overview
Problem
Current methods for inspecting and characterizing wellbores, particularly those with casing or cement, are limited in their ability to accurately discriminate between echoes from inside and outside the casing/liner, leading to incomplete or inaccurate data for wellbore analysis.
Innovation Solution
A downhole tool equipped with processor-executable instructions is used to carry out a method that involves emitting ultrasound signals and processing the received echoes to differentiate between internal and external echoes, utilizing a combination of time and frequency spectrum analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional echo inspection methods are used in cased wellbores, then the inspection can be performed, but the ability to accurately discriminate between echoes from inside and outside the casing is limited
Solution Approach 1:
The patent divides the echo signal analysis into distinct frequency segments (first frequency range for internal echoes, second frequency range for external echoes). By segmenting the frequency spectrum and applying different processing techniques to each segment, the system can separately identify and characterize internal and external echoes that would otherwise be indistinguishable in the full bandwidth signal.
Solution Approach 2:
The patent transforms the echo discrimination problem from the time domain to the frequency domain by applying spectral analysis. This dimensional transformation allows separation of overlapping echoes in the frequency spectrum, where internal and external echoes occupy different frequency ranges, enabling accurate discrimination that is not possible in the time domain alone.
2Measurement precision
If a single frequency ultrasound signal is used, then the equipment is simpler, but the discrimination between internal and external echoes is insufficient
Solution Approach 1:
The patent segments the frequency spectrum into multiple ranges and applies different processing strategies to each segment. This segmentation allows the system to achieve high-precision echo source identification by analyzing specific frequency characteristics in each segment, rather than attempting to discriminate all echoes using a single complex processing method across the entire spectrum.
Solution Approach 2:
The patent changes the frequency parameter of the ultrasound signal to differentiate between internal and external echoes. By transmitting signals at multiple frequencies and analyzing the frequency-dependent response characteristics, the system can identify echo sources based on their frequency signatures, improving discrimination accuracy without requiring overly complex equipment.
3Loss of information
If wide-band excitation is used to improve signal characterization, then more echo information is obtained, but the discrimination between internal and external echoes becomes more difficult
Solution Approach 1:
The patent resolves the contradiction between using wide-band excitation and achieving accurate discrimination by segmenting the received wide-band signal into multiple frequency ranges. Each segment is then processed independently with appropriate filtering and analysis techniques, allowing the system to retain all the information from wide-band excitation while systematically separating internal from external echoes based on their frequency-dependent characteristics.
Solution Approach 2:
The patent applies frequency domain transformation to the wide-band echo signals, converting the time-domain mixed signal into the frequency domain where internal and external echoes can be separated. This dimensional change from time to frequency domain enables the system to fully utilize the information content of wide-band excitation while achieving precise echo source discrimination through frequency-selective processing.
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 enables more accurate discrimination between internal and external wellbore echoes, providing improved data for wellbore characterization, such as casing inner radius, thickness, and cement thickness, thereby enhancing the precision of wellbore analysis and operations.
Implementation Method 1
An ultrasonic transducer may be disposed within a drill collar of a drill string to emit ultrasound signals
Implementation Method 2
The transducer can be configured to receive echoes of the ultrasound signals
Implementation Method 3
Received echoes are from inside and outside the casing/liner. Discrimination between these echoes may use a combination of time and frequency spectrum.
Data Source
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AI summary
A method can include, using a downhole tool, acquiring ultrasonic echo data of a borehole, where the ultrasonic echo data include echoes representative of material and borehole geometry responsive to reflection of ultrasonic energy that has a wide-band frequency range; filtering the ultrasonic echo data using at least one selected filter for multi-band frequency filtering corresponding to different frequency ranges of the wide-band frequency range to generate filtered data; and processing the filtered data to generate attribute values representative of physical characteristics the material, the borehole geometry, or the material and the borehole geometry.