Deconvolved EM Measurements for Downhole Corrosion Detection
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Solution Overview
Problem
Corrosion detection in multi-tubular downhole metal pipes using electromagnetic (EM) logging tools is challenging due to the 'ghost effect,' where a single defect appears as multiple features in measurements, complicating the interpretation of EM field data and reducing resolution in corrosion monitoring.
Innovation Solution
The use of deconvolved raw measurements from EM defect detection tools, which involve deconvolution with an impulse response obtained from defect simulation or known defects, followed by filtering and scaling, to enhance the resolution of defect detection in downhole tubular strings, allowing for accurate determination of thickness changes and EM properties indicative of corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If EM logging tools are used to detect corrosion in multi-tubular downhole pipes, then corrosion monitoring capability is provided, but the ghost effect causes a single defect to appear as multiple features, reducing measurement precision and complicating interpretation
Solution Approach 1:
The patent introduces an impulse response function as an intermediary element that characterizes the EM tool's measurement behavior. By convolving this impulse response with the actual defect distribution, the method creates a forward model that predicts measurements. The deconvolution process then uses this same intermediary to reverse the measurement process, effectively separating the tool's influence from the actual defect signal and resolving the ghost effect.
Solution Approach 2:
The patent applies inversion by reversing the conventional measurement interpretation approach. Instead of directly interpreting raw EM measurements, the method inverts the measurement process by deconvolving the measured data with the impulse response. This inversion transforms the blurred, ghost-effect-prone measurements into a resolved defect distribution that accurately represents the actual corrosion locations.
2Measurement precision
If deconvolution processing is applied to raw EM measurements, then defect detection resolution is improved, but processing complexity and computational requirements increase
Solution Approach 1:
The patent applies preliminary action by pre-computing and storing the impulse response function before actual defect detection occurs. The impulse response, which characterizes the EM tool's measurement behavior, is determined in advance through calibration measurements or theoretical modeling. This pre-computed intermediary is then reused during actual defect detection, avoiding the need to recalculate complex forward models during real-time processing.
Solution Approach 2:
The patent uses copying by creating a simplified representation of the measurement process through the impulse response function. This impulse response serves as a copy or model of how the EM tool interacts with defects, allowing the complex physical measurement process to be represented and reversed through a manageable mathematical function that can be efficiently stored and applied during processing.
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 improves the accuracy of defect detection by aligning deconvolved measurements with actual defects, enabling precise identification of corrosion and other deformations in multi-tubular scenarios, facilitating better well management and intervention operations.
Implementation Method 1
an EM logging tool may collect EM log data, where the EM log data can be interpreted to correlate a level of flux leakage or EM induction with metal loss indicating corrosion
Data Source
AI summary
A method includes deploying an electromagnetic (EM) defect detection tool in a downhole environment having a plurality of tubular strings with different diameters. The method also includes receiving raw measurements collected by the EM defect detection tool. The method also includes deconvolving the raw measurements with another input to obtain deconvolved raw measurements. The method also includes using the deconvolved raw measurements to determine a defect in at least one of the plurality of tubular strings. The method also includes performing, by a device, an operation in response to the determined defect.