Hydrogen-assisted damage develops in various forms and causes serious problems to the structural integrity of oil and gas plants. Its assessment remains a challenge as it starts at micro-scale and only propagates at macro-scale, which in turn poses difficulties to scientists in predicting this damage through comprehensive modelling tools.
By Mustapha Jouiad
With the increasing sourness of oil and gas reservoirs, the inherent hydrogen-related damages of metallic equipment, used in oil and gas processing facilities, have become a major concern. These damages are triggered by various forms of hydrogen embrittlement, among blistering, hydrogen-induced cracking (HIC), stress-oriented hydrogen-induced cracking (SOHIC), stress corrosion cracking (SCC) and sulfide stress cracking (SSC), appearing at relatively low stress levels and posing serious problems to the metallic structural integrity.
Even though hydrogen-assisted cracking (HAC) is a well-known phenomenon in the oil and gas industry, reliable numerical models predicting the lifetime of the assets suffering from HAC remain scarce. A current review, published in the journal Corrosion Reviews, therefore attempts to describe and compare the existing continuum models and mechanisms of HAC, with a special focus on their potential implementation to oil and gas integrity assessment and fitness for service tools.
Hydrogen-assisted cracking is a complex problem involving hydrogen transport, accumulation at the fracture process zone, hydrogen embrittlement and failure. Most hydrogen modeling schemes are based on continuum mechanics and material constitutive modelling, whereas the damage often impinges at the nano/micro-scale. Bridging between these scales up to the macro continuum domain is therefore said to be the correct pathway to be followed to consistently describe the damage.
The review investigates the effects of hydrogen on the nano- and micro-scales, such as hydrogen transport and binding energies, with relevant parameters extracted to mechanistically feed the constitutive continuum material models. Although several efforts have been made towards realising this goal, the use of multi-scale modelling remains a challenge due to the gap between the micro- and macro-scales. According to the researchers, “Current integrity assessment needs reliable models and methods, such as better crack detection and sizing tools, as well as highly trained engineers who can assess the hydrogen-related problems.”
Read the original article here:
Abderrazak Traidia, Elias Chatzidouros, Mustapha Jouiad: Review of hydrogen-assisted cracking models for application to service lifetime prediction and challenges in the oil and gas industry, 13.02.2018.