The failure law of the cement plug-casing interface for direct plugging in the casing of old wells for salt cavern gas storage

Abstract

The old salt hole wells cannot be directly converted into gas storage, injection and production wells, so the old wells must be plugged to ensure the effectiveness of plugging. Aiming at the plugging problem of old wells in salt cavern gas storage, a finite element model of the formation-cement sheath-casing-cement plug assembly suitable for direct plugging in the casing of salt cavern gas storage is established to simulate the fracture stripping process of the cement plug-casing interface. The results show that under the pressure of the gas storage, the cement plug casing bonding interface will undergo shear deformation, and after stacking to a certain extent, peeling phenomenon will occur. As the simulation time increases, the peel failure length gradually increases and tends to stabilize, reaching the limit of peel failure length. In the process of research, the factors and laws affecting the peeling failure length are also analyzed. It is found that the peeling failure length of the cement-casing interface is related to the maximum operating pressure of the gas storage, the length of the cement plug, the diameter of the cement plug, the elastic modulus, Poisson’s ratio. The research results are helpful to judge whether the plugging length in the casing is sufficient, and provide theoretical guidance to ensure the long-term safe operation of the gas storage.

Keywords:

• Salt cavern gas storage
• stripping failure length
• cohesive element method
• integrity of seal

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Correction

Acknowledgments

This paper is significantly different from the published paper ‘Study on simulation of cement plug-formation interface stripping failure and main influencing factors’. First, the research object is different. The research object of this article is the cement plug-casing interface, and the finite element model established is the cement plug-casing-cement sheath-formation. Although the research methods used are similar, there are differences in the research objects, parameter settings, and laws obtained. In addition, this paper is aimed at another new technology—direct plugging in casing for plugging old wells in gas storage, and the research conclusions of the published papers cannot provide clear guidance for the implementation of this technology.

It should also be noted that because the research methods are similar, the two papers are similar or consistent in some basic formulas and basic schematic diagrams.

Disclosure statement

The authors declare no conflict of interest.

Correction Statement

This article was originally published with errors, which have now been corrected in the online version. Please see Correction (https://doi.org/10.1080/01694243.2023.2245662).

Additional information

Funding

This research is supported by the Project of China National Petroleum Corporation (CNPC) (2021DJ5402), the Research Foundation of Changzhou University (ZMF22020060), and the Basic Science (Natural Science) Research Project of Jiangsu Higher Education (22KJD430001).