Evaluation of Well Casing Integrity Management for Underground Storage Wells

Overview

Main Objective

Provide the industry a better understanding of the current state of the storage well logging tool technologies and their performance, factors affecting the tool response, and the suitability of available methods to calculate remaining casing strength. This understanding will reduce uncertainty in the evaluation of storage well casing integrity through accurate assessment of reliability, leading to improved decisions regarding well interventions and allowable operating parameters.

Public Abstract

This project will provide an improved understanding of the methodologies used to predict the remaining casing burst capacity for underground natural gas storage wells, including casing logging technologies and burst capacity prediction models. Various logging tools will be used to characterize both natural and machined defects in representative well casing configurations, and these ILI tool outputs will be used in existing models to predict the burst capacity of the pipe specimens. Selected specimens from the logged pipes will be burst tested to supplement existing test results from previous testing and the public literature to benchmark the burst models. A reliability based casing strength assessment framework will be outlined to quantitatively address various uncertainties that may exist in measurement, load conditions and model accuracy. The outcome of this study is expected to improve confidence in the evaluation of storage well casing integrity, leading to improved decisions regarding well interventions and operating parameters.

PRCI Catalog No. PR-244-18702-R01

Summary and Conclusions

Commercial tools based on ultrasonic testing (UT) and magnetic flux leakage (MFL) generally have the capability to conduct high-resolution inspection of isolated casing corrosion features. The prototype tools based on the magnetic eddy current (MEC) technology tested in this project also demonstrated good performance that is comparable to commercial logging tools. The multi-finger caliper (MFC) tool can physically measure the casing inner-wall profile, which may be used to diagnose the casing deformation and metal loss due to internal corrosion. Tools based on electromagnetic (EM) technologies can conduct through-tubing corrosion logging. Finite element analysis (FEA) prediction using the actual material stress-strain relationship and the metal loss profile was found to achieve fairly good agreement with the physical burst test results. A reliability-based assessment framework is described that addresses issues of key importance with respect to casing corrosion integrity management based on high-resolution integrity logs.

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