Estimating Worst Case Corrosion in a Pipeline
First Claim
1. A method of estimating the integrity of a pipeline, comprising the steps of:
- receiving sampled measurement data of pipeline wall thickness loss for the pipeline, the measurement data obtained at a plurality of sample locations along the pipeline;
calculating sample statistics of the sampled measurement data;
applying the calculated sample statistics to a discriminant function, the discriminant function arranged to identify one of a plurality of candidate statistical distributions for accuracy in estimating an extreme value of pipeline wall thickness loss, each of the plurality of candidate statistical distributions based on wall thickness loss measurements of a corresponding one of a plurality of reference pipelines; and
evaluating an extreme value quantile of the identified candidate statistical distributions as fit to the sampled measurement data to obtain an estimate of an extreme value of pipeline wall thickness loss for the pipeline.
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Abstract
A method and system for estimating the worst case corrosion in a pipeline for which pipeline wall thickness measurements are limited to sampled ultrasonic or radiography (UT/RT) measurements. A data library contains distributions of in-line inspection (IL) measurements for other pipelines, calibrated to correspond to UT/RT measurements as needed. These ILI datasets are randomly sampled multiple times, to obtain multiple sample sets from each ILI dataset. Candidate statistical distributions are evaluated for each sample set to determine which of the candidate statistical distributions most accurately estimates the worst case corrosion measured by ILI. A discriminant function is then derived from sample statistics and pipeline descriptors associated with the sample sets, along with the best candidate statistical distribution for that sample set. Sample statistics and pipeline descriptors for the pipeline with sampled UT/RT measurements are then applied to the discriminant function to determine the best one of the candidate statistical distributions for extreme value estimation, and the worst case corrosion is then determined using that best statistical distribution.
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Citations
24 Claims
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1. A method of estimating the integrity of a pipeline, comprising the steps of:
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receiving sampled measurement data of pipeline wall thickness loss for the pipeline, the measurement data obtained at a plurality of sample locations along the pipeline; calculating sample statistics of the sampled measurement data; applying the calculated sample statistics to a discriminant function, the discriminant function arranged to identify one of a plurality of candidate statistical distributions for accuracy in estimating an extreme value of pipeline wall thickness loss, each of the plurality of candidate statistical distributions based on wall thickness loss measurements of a corresponding one of a plurality of reference pipelines; and evaluating an extreme value quantile of the identified candidate statistical distributions as fit to the sampled measurement data to obtain an estimate of an extreme value of pipeline wall thickness loss for the pipeline. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 20)
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9. An evaluation system for evaluating measurements of pipeline wall thicknesses, comprising:
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a memory resource for storing a data library; one or more central processing units for executing program instructions; and program memory, coupled to the central processing unit, for storing a computer program including program instructions that, when executed by the one or more central processing units, is capable of causing the computer system to perform a sequence of operations for estimating the integrity of a pipeline, the sequence of operations comprising; receiving sampled measurement data of pipeline wall thickness loss for the pipeline, the measurement data obtained at a plurality of sample locations along the pipeline, calculating sample statistics of the sampled measurement data; retrieving a discriminant function from the data library; applying the sample statistics to a discriminant function, the discriminant function arranged to identify one of a plurality of candidate statistical distributions for accuracy in estimating an extreme value of pipeline wall thickness loss, each of the plurality of candidate statistical distributions based on wall thickness loss measurements of a corresponding one of a plurality of reference pipelines; and evaluating an extreme value quantile of the identified candidate statistical distributions as fit to the sampled measurement data to obtain an estimate of an extreme value of pipeline wall thickness loss for the pipeline. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A computer-readable medium storing a computer program that, when executed on a computer system, causes the computer system to perform a sequence of operations for estimating the integrity of a pipeline, the sequence of operations comprising:
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receiving sampled measurement data of pipeline wall thickness loss for the pipeline, the measurement data obtained at a plurality of sample locations along the pipeline; calculating sample statistics of the sampled measurement data; applying the sample statistics to a discriminant function, the discriminant function arranged to identify one of a plurality of candidate statistical distributions for accuracy in estimating an extreme value of pipeline wall thickness loss, each of the plurality of candidate statistical distributions based on wall thickness loss measurements of a corresponding one of a plurality of reference pipelines; and evaluating an extreme value quantile of the identified candidate statistical distributions as fit to the sampled measurement data to obtain an estimate of an extreme value of pipeline wall thickness loss for the pipeline. - View Dependent Claims (21, 22, 23, 24)
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Specification