Higher Order SH Mode Casing Thickness Detection
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Solution Overview
Problem
Current methods for evaluating the thickness and integrity of downhole tubulars, such as casing in oil and gas wells, face challenges in accurately measuring thickness beyond 0.4 inches due to dispersion and interference from multiple wave modes, particularly with conventional acoustic techniques and EMAT-based shear horizontal (SH) wave measurements.
Innovation Solution
The method involves inducing and measuring higher order SH waves, specifically SH1 and SH2 modes, using electromagnetic acoustic transducers (EMATs) to estimate tubular thickness independently of the fundamental SH0 mode, employing cross-correlation and Fast Fourier Transform (FFT) to determine group velocity and frequency, and using empirical relationships to calculate thickness without requiring prior knowledge of casing shear velocity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional acoustic techniques and EMAT-based fundamental SH0 mode measurements are used, then the measurement method is simple, but the measurement precision deteriorates for tubulars with thickness beyond 0.4 inches due to dispersion and interference from multiple wave modes
Solution Approach 1:
The patent extracts and isolates the higher order SH1 and SH2 mode signals from the complex wave field, separating them from the fundamental SH0 mode and other interfering modes. This extraction allows precise thickness measurement by focusing only on the useful higher order mode signals that are less susceptible to dispersion effects.
Solution Approach 2:
The patent changes the measurement parameter from fundamental mode (SH0) to higher order modes (SH1, SH2). By measuring at different mode frequencies and utilizing the dispersive characteristics of higher order modes, the method achieves accurate thickness measurements for thicker tubulars where fundamental mode measurements fail.
2Measurement precision
If higher order SH modes are used for thickness measurement, then the measurement precision improves for thicker casings, but the device complexity increases due to the need for advanced signal processing
Solution Approach 1:
The patent employs iterative signal processing where the measured group velocity and frequency information from higher order modes is fed back into the thickness calculation model. This feedback mechanism allows the system to refine thickness estimates and compensate for measurement uncertainties, achieving high precision despite the complexity of processing higher order mode signals.
Solution Approach 2:
The patent replaces complex mechanical wave mode separation with signal processing techniques. Instead of using physical filters or mechanical means to isolate modes, the invention uses digital signal processing methods including Fourier transforms and correlation analysis to separate and identify higher order mode signals from the composite wave field.
3Measurement precision
If cross-correlation and FFT methods are employed to determine group velocity and frequency, then the measurement accuracy improves, but the processing time increases
Solution Approach 1:
The patent performs preliminary signal conditioning and pre-processing of the received wave signals before applying the computationally intensive cross-correlation and FFT operations. By preparing the signals in advance (filtering, windowing, and organizing), the subsequent processing requires fewer computational iterations, reducing overall processing time while maintaining high accuracy in group velocity and frequency determination.
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 provides accurate thickness measurements for tubulars with a range of 0.318 to 0.53 inches, improving over existing plate models, especially in thicker casings, and does not necessitate prior measurements of the fundamental SH0 mode, offering enhanced precision and consistency.
Implementation Method 1
inducing with a transmitter a horizontal shear (SH) wave
Implementation Method 2
identifying higher order SH mode signals received at a plurality of offset receivers
Implementation Method 3
estimating a group velocity for the higher order SH mode from the higher order SH mode signals by estimating a time delay between a first receiver of the plurality and a second receiver of the plurality
Implementation Method 4
Estimating the dominant frequency may comprise performing a Fast Fourier Transform (FFT) of a portion of the higher order SH mode signals received at the second receiver to generate a FFT spectrum
Data Source
AI summary
Methods, systems, devices, and products for hydrocarbon tubular evaluation. Methods comprise conveying the logging tool in the tubular with a carrier; inducing with a transmitter a horizontal shear (SH) wave; identifying higher order SH mode signals received at a plurality of offset receivers responsive to a higher order SH mode engendered by the horizontal shear (SH) wave; estimating a dominant frequency for higher order SH mode from the higher order SH mode signals; estimating a group velocity for the higher order SH mode from the higher order SH mode signals; and estimating a tubular parameter using the dominant frequency and the group velocity. The tubular parameter may be at least tubular thickness. The method includes estimating the tubular parameter independent of the fundamental horizontal shear wave mode (SH0).