MATTRAN - Work Package 5

WORK PACKAGE 5: INTERNAL STRESS CORROSION CRACKING INVESTIGATION

LEADERS: DR E. CHARLES, DR J. RACE

Internal stress corrosion cracking (SCC) is a phenomenon which can occur in pipeline steels in an H₂S environment. In the oil and gas industry, this phenomenon of sour cracking is well researched and limits imposed on the H2S levels to prevent sour cracking. Although the removal of free water is a better option for controlling both corrosion and sour cracking, further work needs to be conducted to understand whether the same compositional limits on H₂S apply in a CO₂ environment and whether sour cracking could be an issue under conditions when free water may accidentally enter the pipeline. This phenomenon will be investigated in this work package together with any other potential cracking environments relevant to the materials in the pipeline or compressor train indicated by the work in WP1.

The work proposed in this work package compliments the corrosion testing of stressed specimens in WP4 as it allows the conditions of stress applied to the specimens to be accurately determined and monitored. Two experimental techniques will be utilised; slow strain rate testing and static load testing. The slow strain rate tests are selected as they allow results to be obtained in relatively short timescales, however, the static load tests will confirm whether strain rate effects are important. In addition, control tests will be conducted in non-cracking atmospheres. The effect of surface oxides will be investigated by pre-exposure of specimens in the corrosion atmospheres in WP4.

Newcastle University has an extensive track record in conducting tests of this type to investigate SCC for a range of materials and environments, including pipeline steels.

Work Package 1	WORK PACKAGE 5: INTERNAL STRESS CORROSION CRACKING INVESTIGATION LEADERS: DR E. CHARLES, DR J. RACE Internal stress corrosion cracking (SCC) is a phenomenon which can occur in pipeline steels in an H₂S environment. In the oil and gas industry, this phenomenon of sour cracking is well researched and limits imposed on the H2S levels to prevent sour cracking. Although the removal of free water is a better option for controlling both corrosion and sour cracking, further work needs to be conducted to understand whether the same compositional limits on H₂S apply in a CO₂ environment and whether sour cracking could be an issue under conditions when free water may accidentally enter the pipeline. This phenomenon will be investigated in this work package together with any other potential cracking environments relevant to the materials in the pipeline or compressor train indicated by the work in WP1. The work proposed in this work package compliments the corrosion testing of stressed specimens in WP4 as it allows the conditions of stress applied to the specimens to be accurately determined and monitored. Two experimental techniques will be utilised; slow strain rate testing and static load testing. The slow strain rate tests are selected as they allow results to be obtained in relatively short timescales, however, the static load tests will confirm whether strain rate effects are important. In addition, control tests will be conducted in non-cracking atmospheres. The effect of surface oxides will be investigated by pre-exposure of specimens in the corrosion atmospheres in WP4. Newcastle University has an extensive track record in conducting tests of this type to investigate SCC for a range of materials and environments, including pipeline steels.
Work Package 2
Work Package 3
Work Package 4
Work Package 5
Work Package 6
Work Package 7