Cement Bond Evaluation Using Shear and Lamb Waves
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current downhole tools for evaluating the integrity of cement bonds between wellbore casing and formation face challenges in accurately distinguishing between fluid and lightweight cement, leading to reduced attenuation of acoustic waves and diminished detection of poor cement bonds.
Innovation Solution
The method involves inducing and monitoring shear waves and Lamb waves to determine the integrity of casing bonds, including the presence of micro-annulus and free pipe conditions, using piezoelectric devices or other transducers to assess bond characteristics such as shear, compressional properties, and cement density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If P-SV acoustic waves are used for cement bond evaluation, then the attenuation can be measured, but the ability to distinguish between fluid and lightweight cement is reduced due to diminished attenuation
Solution Approach 1:
The patent segments the acoustic wave analysis into multiple wave types (P-SV waves and P-PG waves) with different polarization characteristics. By dividing the evaluation into separate wave mode analyses, the system can distinguish between fluid and lightweight cement that would otherwise appear similar in a single wave type analysis.
Solution Approach 2:
The patent changes the polarization parameter of the acoustic waves from vertical (P-SV) to horizontal (P-PG). This parameter change allows the waves to interact differently with the cement bond, producing distinct attenuation patterns that enable differentiation between fluid and lightweight cement.
2Measurement precision
If single wave type (P-SV) analysis is used, then the device complexity is low, but the detection precision of bond integrity is diminished
Solution Approach 1:
The patent makes the acoustic wave generation system multi-functional by enabling it to generate both P-SV and P-PG waves using the same transducer assembly. This universality allows comprehensive bond evaluation without requiring separate dedicated devices for each wave type.
Solution Approach 2:
The patent adds a dimensional aspect to the analysis by incorporating horizontal polarization (P-PG waves) in addition to vertical polarization (P-SV waves). This dimensional expansion provides additional information about bond integrity without proportionally increasing device complexity.
3Reliability
If lightweight cement is used to maintain shear coupling, then the cement bond integrity is improved, but the acoustic wave attenuation is reduced making detection difficult
Solution Approach 1:
The patent uses P-PG waves as an intermediary measurement approach. These horizontally polarized waves provide an alternative attenuation mechanism that remains effective for detecting lightweight cement bonds, where traditional P-SV wave attenuation becomes insufficient.
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 enhances the accuracy and precision of cement bond evaluation by providing detailed information on bond quality, type, and thickness, effectively differentiating between fluid, lightweight cement, and regular cement bonds, improving the detection of bond integrity and reducing contamination risks.
Implementation Method 1
using piezoelectric devices or other transducers to assess bond characteristics
Implementation Method 2
transducers 18 are disposed on the outer surface of the tool 8 capable of emitting acoustic waves into the casing 4 and recording the attenuation of the acoustic waves as they travel, or propagate, across the surface of the casing 4
Implementation Method 3
By analyzing the propagation velocity and attenuation of the received acoustic wave, the efficacy and integrity of the cement bond can be evaluated
Data Source
AI summary
A method and apparatus useful to determine the integrity of a cement bond log disposed in the annular space between a casing and a wellbore. The method and apparatus produce a transversely polarized shear wave and emit the wave through the casing and into the wellbore. The transversely polarized shear wave attenuates upon passage through the cement bond log. The integrity of the cement bond log can be determined through an analysis and evaluation of the attenuation results.