Bayesian Inversion for Pipe Thickness Measurement
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Solution Overview
Problem
Current methods for detecting metal loss due to corrosion in oil and gas wells are time-consuming and not suited for time-sensitive operations, as they involve iterative inversion processes that require multiple iterations to achieve convergence.
Innovation Solution
A Bayesian framework is employed to prioritize inversion depth points based on expected information gain, allowing for parallel processing of data batches and providing intermediate results with uncertainty levels, which can be used to adjust inversion parameters and terminate the process when desired accuracy is reached.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If iterative inversion process is used to determine pipe thickness from EM measurements, then measurement precision is improved, but processing time increases significantly
Solution Approach 1:
The patent pre-calculates and stores a lookup table of synthetic EM responses for various pipe thickness values before actual measurement processing. During inversion, instead of running the full forward model iteratively, the system queries this pre-computed table to obtain synthetic responses, dramatically reducing computation time while maintaining measurement precision
Solution Approach 2:
The patent creates a simplified copy of the forward model in the form of a pre-computed lookup table that captures the essential relationship between pipe thickness and EM measurements. This copy allows rapid retrieval of synthetic responses without executing the complex iterative forward model, resolving the contradiction between precision and speed
2Manufacturing precision
If inversion is repeated for each depth point to achieve accurate thickness profiles, then manufacturing precision is improved, but productivity decreases
Solution Approach 1:
The patent segments the inversion process by applying it only to selected depth points rather than every depth point. The lookup table approach enables efficient inversion at key locations, and the results can be interpolated to reconstruct the full thickness profile, maintaining accuracy while improving productivity
Solution Approach 2:
The patent performs inversion at a subset of depth points rather than all depth points. By strategically selecting depth points where inversion is most needed and using interpolation for intermediate points, the system achieves sufficient thickness profile accuracy with reduced computational effort, thereby improving processing throughput
3Measurement precision
If multiple inversion iterations are performed with parameter adjustments, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The lookup table is pre-computed to include synthetic responses for a comprehensive range of pipe thickness values and measurement conditions. This preliminary action ensures that during actual inversion, the system can find accurate matches without needing multiple iterative forward model executions, reducing time while maintaining precision
Solution Approach 2:
The patent implements an efficient feedback mechanism where the inversion process queries the pre-computed lookup table to obtain synthetic responses, compares them with actual measurements, and adjusts parameters based on this feedback. The lookup table structure enables rapid feedback cycles without the computational burden of repeated full forward model executions
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 significantly reduces the time required for processing data, allowing for faster detection of metal loss and enabling more timely decision-making in oil and gas field operations, while also providing a more efficient use of resources.
Implementation Method 1
transmitting an electromagnetic field from the transmitter into one or more tubulars to energize the one or more tubulars with the electromagnetic field thereby producing an eddy current in the one or more tubulars
Implementation Method 2
measuring the electromagnetic field generated by the eddy current in the one or more tubulars with the receiver on at least one channel to obtain a plurality of measurements
Data Source
AI summary
A method for estimating a thickness for each of a plurality of nested tubulars may include disposing an electromagnetic (EM) logging tool in a wellbore, transmitting an electromagnetic field from the transmitter into one or more tubulars to energize the one or more tubulars with the electromagnetic field thereby producing an eddy current, and measuring the electromagnetic field generated by the eddy current. Additionally, the method may include defining a prior distribution of at least one pipe thickness log based on the plurality of measurements, processing a first set of measurement depth points to estimate one or more tubulars at one or more depths in the wellbore, computing a posterior distribution of the thickness log based at least in part on the prior distribution and the one or more thicknesses, and determining a second set of measurement depth points to process based on the posterior distribution.