Casing Thickness Evaluation Using Shear Wave Dispersion
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Solution Overview
Problem
Existing methods for evaluating the thickness and quality of cement bonds in hydrocarbon wellbores are inadequate, leading to potential contamination and failure due to defective cement isolation, which is not effectively addressed by current casing analysis devices.
Innovation Solution
A method utilizing an electromagnetic acoustic transducer (EMAT) to induce shear waves in tubulars, measuring group velocities, and estimating tubular thickness through calibrated shear wave wavelengths, allowing for non-contact evaluation of cement bond quality and thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electromagnetic acoustic transducer (EMAT) is used to induce shear waves for non-contact evaluation, then measurement precision of tubular thickness is improved, but device complexity increases
Solution Approach 1:
The patent replaces traditional contact-based mechanical measurement systems with an electromagnetic acoustic transducer (EMAT) that uses electromagnetic fields to induce shear waves in the tubular. This substitution eliminates the need for physical contact and complex mechanical coupling, achieving non-contact measurement while maintaining high precision through wave propagation analysis.
Solution Approach 2:
The patent utilizes changes in shear wave propagation parameters (velocity, frequency, mode conversion) to determine tubular thickness. By measuring the group velocity of different shear wave modes (SH0, SH1) and analyzing their frequency-dependent behavior, the system extracts thickness information without direct mechanical contact, resolving the contradiction between precision and device complexity.
2Measurement precision
If multiple shear wave modes (SH0 and SH1) are measured to evaluate thickness, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent employs periodic excitation of the tubular at multiple frequencies to generate and measure different shear wave modes (SH0 and SH1). By using frequency-swept or multi-frequency periodic excitation, the system efficiently captures velocity-dispersion characteristics of multiple modes in a single measurement sequence, improving thickness precision without excessive time penalty.
Solution Approach 2:
The patent continuously monitors shear wave propagation through the tubular wall by maintaining continuous wave excitation and real-time velocity measurement. This continuous action allows simultaneous extraction of multiple mode velocities (SH0 group velocity, SH1 group velocity) from the same measurement window, eliminating the need for separate measurements and reducing total measurement time while maintaining high precision.
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 method provides accurate and non-destructive evaluation of tubular thickness and cement bond quality, enhancing the detection of potential failures and preventing contamination by effectively assessing the cement bond between the casing and formation.
Implementation Method 1
energizing the EMAT to induce a shear wave in the tubular
Implementation Method 2
measuring the SH0 mode group velocity, measuring the SH1 mode group velocity (Vg)
Data Source
AI summary
Evaluating casing thickness by inducing SH0 and SH1 modes of a shear wave in the casing. The SH0 group velocity and SH1 mode group velocity (Vg) are measured and the measured SH0 mode group velocity is assigned as the tubular material shear velocity (Vs). A shear wave wavelength λ from the ratio of SH0 mode frequency (fo) and the measured SH0 group velocity is estimated. The tubular thickness (d) is estimated from the estimated shear wave wavelength λ. The transmitter can be calibrated to operate at an optimum frequency.