Oilfield Casing Thickness Analysis Using Apparent Thickness Approach
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Solution Overview
Problem
Existing casing inspection methods using remote field eddy current (RFEC) measurements often suffer from 'double-indication' or 'ghosting' artifacts due to non-collocation of tool receivers and transmitters, which complicates the detection of casing anomalies and corrosion defects, and fail to accurately measure individual casing thicknesses within nested casings.
Innovation Solution
The method employs an apparent thickness approach using induction instruments with transmitters and receivers operating at multiple frequencies, generating apparent thickness transforms for measured attenuation and phase responses, and removes double-indications and casing collar artifacts by assuming proportional changes in casing thickness, allowing for accurate determination of individual casing characteristics like thickness, eccentering, and material properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If RFEC measurements are used with non-collocated transmitters and receivers, then overall casing thickness can be measured, but double-indication artifacts and ghosting occur that complicate anomaly detection
Solution Approach 1:
The patent introduces an apparent thickness calculation as an intermediary parameter that mediates between the raw RFEC measurements and the final thickness determination. By calculating apparent thickness from multiple measurements at different transmitter-receiver spacings, the system eliminates double-indication artifacts while preserving accurate thickness information. The apparent thickness serves as a mediator that filters out the harmful ghosting effects.
Solution Approach 2:
The patent moves from one-dimensional thickness measurement to a multi-dimensional approach by incorporating multiple transmitter-receiver spacings and calculating apparent thickness values for each spacing. This dimensional expansion allows the system to distinguish between true casing features and artifact signals, resolving the double-indication problem through spatial differentiation.
2Reliability
If total thickness measurement of nested casings is performed, then overall integrity can be assessed, but individual casing thicknesses cannot be determined
Solution Approach 1:
The patent applies segmentation by dividing the total thickness measurement into individual casing contributions. By performing apparent thickness calculations at multiple transmitter-receiver spacings and using the known relationship between spacing and penetration depth, the system separates the combined signal into individual casing thickness measurements, enabling both overall and individual assessment.
Solution Approach 2:
The patent uses excessive action by taking measurements at multiple transmitter-receiver spacings beyond the single spacing that would provide total thickness. This redundant measurement approach provides additional information that can be processed to extract individual casing thicknesses while maintaining reliable overall integrity assessment.
3Ease of manufacture
If standard RFEC interpretation is used, then processing is simple, but accuracy of individual casing characteristics is insufficient
Solution Approach 1:
The patent changes the interpretation parameter from direct RFEC signal analysis to apparent thickness calculation. By transforming the raw measurements into apparent thickness values and then into individual casing characteristics, the system maintains processing simplicity while dramatically improving measurement precision for individual casing properties.
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 effectively corrects RFEC measurements, removes artifacts, and provides accurate individual casing thickness and integrity analysis, improving the precision of casing inspection by accounting for eccentering and material properties, leading to more reliable well integrity assessments.
Implementation Method 1
a transmitter of the field-testing probe produces an electromagnetic field that interacts with the casing
Implementation Method 2
remote field eddy current (RFEC)
Data Source
AI summary
Embodiments included herein are directed towards a system and method for analyzing an oilfield casing using an apparent thickness approach. Embodiments may include providing an induction instrument having at least one of a transmitter and a receiver configured to operate at one or more frequencies. Embodiments may further include generating, using data acquired by the induction instrument, one or more apparent thickness transforms for at least one of a measured attenuation and a phase response associated with an oilfield casing, wherein generating includes assuming a proportionate increase in all casing thicknesses.