Nested Tubular EM Logging Ghosting Reduction
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Solution Overview
Problem
EM logging tools in well logging often produce 'ghost' readings due to defects in tubulars, leading to inaccurate thickness measurements and defect identification, as the same defect is recorded multiple times in the data log.
Innovation Solution
The use of multiple EM receivers and deghosting techniques to determine apparent cumulative thicknesses, removing double-indications of defects and collars by taking the minimum and maximum of receiver measurements, and identifying collar-free sections to adjust thickness values, thereby reducing ghosting effects and improving defect detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single EM receiver is used to measure tubular thickness, then the device complexity is reduced, but ghosting effects cause measurement precision to deteriorate due to multiple recordings of the same defect
Solution Approach 1:
The patent divides the measurement function across multiple EM receivers positioned at different locations within the logging tool. Each receiver independently measures the EM field at its specific position, allowing the system to segment the detection of defects along the tubular. By comparing measurements from multiple receivers, the system can identify and eliminate ghosting effects where the same defect appears multiple times in the data log.
2Reliability
If multiple EM receivers are deployed to eliminate ghosting effects, then measurement precision improves, but device complexity increases due to additional receivers and processing requirements
Solution Approach 1:
The patent merges the data from multiple EM receivers through a coordinated processing approach. The system combines measurements from different receivers and applies algorithms to identify patterns characteristic of ghosting effects. By merging the information and comparing the data sets, the system can distinguish between actual defects and ghosting artifacts, thereby improving reliability while managing the complexity through integrated processing.
Solution Approach 2:
The patent implements feedback mechanisms where the system continuously compares measurements from multiple receivers and uses this comparison to identify and correct ghosting effects. The processing system analyzes the consistency of defect detections across different receiver positions and adjusts the interpretation of measurements accordingly, creating a feedback loop that improves defect detection accuracy by eliminating false positives from ghosting.
3Difficulty of detecting and measuring
If EM logging tool physical design is used to detect defects, then defect detection capability is provided, but ghosting effects cause loss of information by creating false multiple indications of the same defect
Solution Approach 1:
The patent introduces an intermediary processing layer that acts as a mediator between the raw EM measurements and the final defect identification. This intermediary system compares measurements from multiple receivers and uses logical algorithms to determine whether a detected anomaly represents a true defect or a ghosting effect. The intermediary processing prevents false information from being recorded by filtering out duplicate defect indications that arise from ghosting.
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 of tubular thickness measurements and defect detection by minimizing ghosting effects, allowing for precise identification of actual defects and reducing false readings, thereby improving the reliability of EM logging data.
Implementation Method 1
A transmitter of the EM logging tool creates an EM field that interacts with the tubular
Implementation Method 2
One or more receivers of the EM logging tool may be used to measure and generate a data log illustrating variations in one or more resulting and returning EM fields
Data Source
AI summary
Methods and apparatus for analyzing nested tubulars via electromagnetic (EM) logging. An example method includes operating an EM logging tool within tubulars nested within a wellbore. The EM logging tool includes an EM transmitter and multiple EM receivers. Data obtained via the EM receivers is utilized to estimate an individual thickness of each tubular at each of multiple depths within the wellbore. The estimated individual thicknesses are utilized to estimate a cumulative thickness of the tubulars at each depth. Local variations of the estimated cumulative thicknesses are utilized to distinguish between actual and spurious indications of differences between the estimated individual thicknesses at neighboring depths.