A Simple Classification of Wellbore Integrity Problems Related to Fluids Migration


This work classifies in a simple form the wellbore integrity problems that cause fluids migration in oil and gas wells. This paper updates the categorization provided by Santos (Technology focus: well integrity. Society of Petroleum Engineers, 2015. https://doi.org/10.2118/0115-0100-JPT), which classifies the wellbore integrity problems based on the time of manifestation. Santos (Technology focus: well integrity. Society of Petroleum Engineers, 2015. https://doi.org/10.2118/0115-0100-JPT; Wilkins and Free A new approach to the prediction of gas flow after cementing. Society of Petroleum Engineers, 1989. https://doi.org/10.2118/18622-MS; Bois et al. How to prevent loss of zonal isolation through a comprehensive analysis of microannulus formation. Society of Petroleum Engineers, 2011. https://doi.org/10.2118/124719-P), and other researchers categorized the problems related to wellbore integrity similarly. These categorizations are found in multiple publications and are representative of most cements’ failures that may lead to fluids migration. However, the majority of these categorizations are too broad and do not clearly state and describe the wellbore failures. In addition, categorizing the failures based on the time of their appearance may not be enough to realize, recognize, and understand how connected the failures are. Well-integrity failures are continuously occurring and represent major issues in the oil and gas wells. Therefore, a new and simple classification that accounts for the potential locations of each failure, the causes of the failures, and methods to stop the failures is necessary. This paper aims to classify the failures that may occur in the wellbore into four main failures: (1) micro-annuli that form between the cement and its surroundings, (2) channels that create pathways through the body of the cement, (3) fractures/cracks in the cement sheath, and (4) cement chemical and mechanical degradation. Definition of these problems, causes of these problems, and solutions for those failures are summarized in this paper to clarify, understand, and provide a guideline to prevent and avoid such problems. Along with the classification, general considerations for the cement-testing methodologies against these failures are listed. This work also provides the oil and gas industry with some of the technologies that have been used to avoid oil cements failures.


Geosciences and Geological and Petroleum Engineering

Keywords and Phrases

Cement failure; Gas migration; Simple classification; Well integrity

International Standard Serial Number (ISSN)

2193-567X; 2191-4281

Document Type

Article - Journal

Document Version


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© 2021 The Authors, All rights reserved.

Publication Date

01 Jul 2021