Multi-String Casing Thickness Estimation Using EM Inversion
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Solution Overview
Problem
Existing EM logging tools struggle to accurately determine the thickness of multiple nested casing strings due to complex signal interactions, making it difficult to manage corrosion detection effectively in multi-string well installations.
Innovation Solution
An EM logging tool and inversion method that utilizes a forward model and iterative algorithms to estimate the thickness of each pipe by comparing modeled and measured signals, accounting for nonlinear signal combinations and pipe properties, allowing for precise identification of metal loss and gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If EM logging tools are used to measure pipe thickness in multi-string configurations, then corrosion detection capability is provided, but signal interpretation complexity increases due to nonlinear signal combinations from multiple nested pipes
Solution Approach 1:
The patent segments the complex multi-pipe measurement problem into individual pipe thickness estimation problems. By using an inversion scheme that processes each pipe string separately and accounts for their nested relationships, the method divides the complex signal interpretation into manageable components, reducing overall interpretation complexity while maintaining corrosion detection reliability
Solution Approach 2:
The patent introduces a forward model as an intermediary between the measured EM signals and the pipe thickness parameters. This forward model simulates the expected signals based on assumed pipe configurations and serves as a mediator that enables systematic inversion to retrieve actual thickness values, thereby simplifying the interpretation process
2Ease of operation
If conventional EM logging interpretation methods are used on multi-string configurations, then measurement process is simplified, but measurement precision deteriorates due to inability to account for complex signal interactions
Solution Approach 1:
The patent implements an iterative inversion scheme that uses feedback from the forward model comparisons to progressively refine thickness estimates. The method continuously adjusts the estimated parameters based on the difference between modeled and measured signals, achieving high measurement precision while maintaining operational simplicity through automated iteration
Solution Approach 2:
The patent systematically varies pipe thickness parameters in the forward model during the inversion process to match measured signals. By changing these parameters iteratively and observing the effect on signal matching, the method achieves precise thickness estimation without requiring complex manual interpretation procedures
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 accurate estimation of individual pipe thickness and detection of corrosion in multi-string configurations, facilitating informed well intervention decisions.
Implementation Method 1
EM logging tools may measure eddy currents to determine metal loss
Implementation Method 2
magnetic cores at the transmitters
Data Source
AI summary
A method for estimating metal thickness on a plurality of casing strings in a cased hole may comprise obtaining a multi-channel induction measurement using a casing inspection tool, constructing a forward numerical model of the multi-channel induction measurement, using the forward numerical model in an initial guess estimation algorithm to estimate a first set of metal thicknesses of the plurality of casing strings, wherein the initial guess estimation algorithm places bounds on the metal thicknesses, using the forward numerical model in an inversion scheme to estimate a final set of metal thicknesses, wherein the first set of metal thicknesses are one or more initial guesses for the inversion scheme and the inversion scheme places no bounds on the metal thicknesses. A system may comprise an electromagnetic logging tool and a conveyance. The EM logging tool may further comprise a transmitter and a receiver.