Nested Casing Thickness Evaluation via Induction Inversion
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Solution Overview
Problem
Current remote field eddy current (RFEC) measurements in well logging primarily assess overall thickness and corrosion of nested casings rather than individual casings, failing to provide accurate thickness evaluation of each casing.
Innovation Solution
A system comprising an electromagnetic logging tool with transmitters and receivers, coupled with a data processing system that performs induction, multi-spacing, multi-frequency measurements, inverts these measurements for characteristics like thickness, and calibrates them using simulated responses to determine individual casing thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If RFEC measurements are used to evaluate nested casings, then overall thickness assessment is achieved, but individual casing thickness differentiation is lost
Solution Approach 1:
The patent applies segmentation by dividing the measurement problem into separate evaluations for each individual casing within the nested structure. The electromagnetic logging tool and inversion process separate the combined response into discrete contributions from each casing, enabling individual thickness assessment rather than only overall thickness measurement.
Solution Approach 2:
The patent utilizes parameter changes by employing multi-frequency measurements and inversion techniques that transform the electromagnetic response data into distinct casing characteristics. By varying frequency parameters and applying mathematical inversion, the system differentiates individual casing properties from the combined nested structure response.
2Measurement precision
If conventional RFEC measurements are performed, then measurement simplicity is maintained, but measurement precision for individual casings deteriorates
Solution Approach 1:
The electromagnetic logging tool is designed with multi-functionality, serving both as a simple measurement device and as part of a complex inversion system. The same tool that performs basic electromagnetic measurements also enables sophisticated individual casing evaluation when combined with the inversion process, achieving high precision without requiring multiple specialized devices.
3Measurement precision
If calibration using simulated responses is implemented, then measurement accuracy for individual casings is improved, but processing time and computational complexity increase
Solution Approach 1:
The patent applies preliminary action by pre-calculating simulated electromagnetic responses for various casing configurations and storing them for reference. During actual measurements, the system compares field data against these pre-computed models, significantly reducing the computational time required for inversion and individual casing characterization compared to real-time full-scale simulations.
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
Enables precise determination of individual casing thickness and characteristics, such as magnetic permeability and electrical conductivity, by accurately differentiating between measured and simulated responses, thereby overcoming the limitations of RFEC in assessing nested casings.
Implementation Method 1
A transmitter of the field-testing probe induces an electromagnetic field that interacts with the casing. The electromagnetic field varies depending on thickness and/or corrosion in the casing.
Implementation Method 2
In well logging via electromagnetic field testing, such as remote field eddy current (RFEC), a field-testing probe is slid within an interior diameter of a conductive tubular or casing. Receivers may detect these variations in the electromagnetic field
Data Source
AI summary
A method includes obtaining, with a plurality of receivers of a logging tool, a set of induction, multi-spacing, multi-frequency measurements of a plurality of nested casings. The method also includes inverting, with a processor, the set of measurements for magnetic permeability or electrical conductivity. The method further includes calibrating, with the processor, the set of measurements using differences between measured responses of the logging tool, and simulated responses of the logging tool resulting from inverting the set of measurements for the magnetic permeability or electrical conductivity of the plurality of nested casings, to determine a calibrated set of measurements. The method also includes inverting, with the processor, the calibrated set of measurements for thickness of individual casings of the plurality of nested casings, to determine the thickness of the individual casings.