Hydrogen-assisted Cracking Models of Steel for the Oil and Gas Industry

(De Gruyter) – Oil and gas reservoirs that had reached up to 20% H2S content were considered non-profitable but are now being reconsidered due to global energy demands.

Unfortunatley the steels used in the oil and gas industry can suffer from different forms of hydrogen embrittlement (HE), including blistering, hydrogen-induced cracking (HIC)/stress-oriented hydrogen induced cracking (SOHIC), sulfide stress cracking (SSC), and stress corrosion cracking (SCC). These types of damages can be triggered at relatively low stress levels and pose serious threat to structural integrity.

Predicative modeling of hydrogen-assisted cracking (HAC) of metals is necessary to prevent failure due to the increased H2S content oils.

By modeling the transport of hydrogen in the steels and subsequent subcritical cracking multiple benefits can be achieved throughout the life chain of the metallic component; (1) during alloy manufacturing stage, (2) at the steel selection stage, and finally, (3) during normal operation for component integrity assessments.

The authors review the established hydrogen degradation theories, which are at the basis of the HAC models. Existing micromechanical models for HAC are proposed, with comparison of their capabilities and highlights on technical gaps. Multiscale modeling of HAC is discussed and the last section summarizes issues and challenges for transferability of existing models to industry and their integration into large-scale component integrity analysis tools.

The authors indicate that modeling schemes performed in the continuum domain dealing with hydrogen embrittlement could be used for integrity assessment and prediction of remaining life of oil and gas steel equipment, provided as follows:

  • Databases exist on hydrogen influence on steels used in oil and gas industry and in various testing conditions, e.g. different hydrogen charging conditions, testing arrangements and measured parameters, correlation of measured parameters to hydrogen content in the steel, etc. These databases should be correlated with microstructures as well as with the grade of steels and have relevance with the field measurements. These databases will be used to calibrate the existing models, which should be used for integrity assessment.
  • Improve crack detection and crack size measurement through NDT
  • Training of personnel in using the modeling schemes. There is a need for high-skilled engineers in integrity assessment where modeling for hydrogen degradation is concerned.

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Edited for Content and Length by Dr. Matthew A. Hood.

The  full article can be found at De Gruyter in the journal of Corrosion Reviews.

2017 IMPACT FACOR 1.66

DOI: 10.1515/corrrev-2017-0079

 

 

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