Multi-String EM Logging for High-Resolution Corrosion Measurement
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Solution Overview
Problem
Managing corrosion detection and data interpretation in multi-string well installations is challenging, particularly when multiple tubing strings are employed, as existing EM logging tools struggle to accurately differentiate and monitor corrosion in each string efficiently.
Innovation Solution
An electromagnetic (EM) logging tool with distinct sensor arrays and processing methods is employed to collect and process EM log data for each tubing string, allowing for the derivation of attributes like diameter, wall thickness, and conductivity, and correlating them with corrosion indices, with separate calibration and characterization steps for improved accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single EM logging tool is used to monitor multiple tubing strings, then device complexity is reduced, but measurement precision and ability to differentiate between strings deteriorates
Solution Approach 1:
The EM logging tool is divided into multiple independent sensor arrays, with each array dedicated to measuring a specific tubing string. This segmentation allows the tool to maintain simple overall structure while achieving precise differentiation between multiple strings through spatial separation of measurement functions.
Solution Approach 2:
Each sensor array is locally optimized for its specific tubing string with appropriate transmitter-receiver spacing and configuration. This local quality approach enables high measurement precision for each string while the modular design keeps overall device complexity manageable.
2Length of stationary object
If transmitter-receiver spacing is increased to penetrate outer tubing strings, then penetration depth improves, but resolution for inner tubing strings deteriorates
Solution Approach 1:
The tool uses separate sensor arrays with different transmitter-receiver spacings for inner and outer tubing strings. Inner string measurement uses smaller spacing for high resolution, while outer string measurement uses larger spacing for deep penetration, eliminating the trade-off between these two requirements.
Solution Approach 2:
Each sensor array is locally configured with optimal transmitter-receiver spacing for its target tubing string. The inner string array uses tight spacing for resolution, while the outer string array uses extended spacing for penetration, allowing both requirements to be satisfied simultaneously.
3Measurement precision
If multiple sensor arrays with different configurations are used, then measurement precision for different strings improves, but device complexity increases
Solution Approach 1:
Multiple sensor arrays share common components including the same basic transmitter-receiver unit design, signal processing electronics, and data acquisition system. This universality enables high measurement precision for different strings while minimizing the increase in overall device complexity through component reuse.
Solution Approach 2:
The sensor arrays are nested within the same tool body structure, with each array occupying a dedicated radial position. This nested arrangement allows multiple measurement functions to coexist in a compact configuration, improving string differentiation without proportionally increasing overall device complexity.
4Measurement precision
If separate calibration is performed for each tubing string, then measurement precision improves, but measurement time increases
Solution Approach 1:
Calibration is performed in advance using known reference structures or undamaged tubing sections before actual corrosion measurement. This preliminary calibration establishes baseline data for each string, allowing rapid and accurate corrosion index calculation during production monitoring without time-consuming on-site calibration.
Solution Approach 2:
The tool uses the tubing strings themselves as calibration references when possible, utilizing their known geometric dimensions and material properties. This self-service approach eliminates the need for external calibration artifacts, improving precision while minimizing calibration time through utilization of the target object's inherent characteristics.
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
The tool enables precise monitoring of corrosion in multiple tubing strings, facilitating timely corrective actions and enhancing the integrity of well installations, leading to improved production processes and financial benefits.
Implementation Method 1
One type of corrosion detection tool uses electromagnetic (EM) fields to estimate tubing wall thickness or other corrosion indicators. As an example, 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 corrosion.
Implementation Method 2
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 corrosion
Data Source
AI summary
A multi-string monitoring system that includes a processor. The processor obtains electromagnetic (EM) log measurements of a well having at least one inner tubing string and at least one outer tubing string, the measurements including first channel measurements for higher resolution and second channel measurements for deeper penetration. The processor inverts the first channel measurements over a characterization region of the well and the second channel measurements over the characterization region of the well, to obtain an attribute of the at least one outer tubing string and an attribute of the at least one inner tubing string, based, at least in part, on a first plurality of calibration coefficients and a second plurality of calibration coefficients. The processor stores the attribute of the at least one outer tubing string and the attribute of the at least one inner tubing string as a function of position along the well.