Inner Defect Induced Crack Growth Analysis and Fatigue Life Prediction for Anthropogenic CO2 Pipelines

One approach to limiting CO2 emissions from oxidation of carbon-based fuels is to capture the CO2 and store it, possibly in onshore or offshore subsurface geologic formations. From the CO2 transportation structure perspective, a critical component of this approach is the pipeline transportation of supercritical or dense CO2. In CCS, the pipelines undertaking a CO2 transportation task suffer various loads, the effects of which is easily aggravated due to the existence of a high working pressure (above 7.4MPa) and inner corrosion. For the application of anthropogenic CO2 pipe transportation technique, this paper will address a LEFM-based finite element method which can evaluate fatigue life for a CO2 transmission pipeline containing a semicircle inner defect. Specifically, a portion of welded round steel pipeline is selected as the object of our analysis. Under the inner pressure fluctuation scenarios, an FRANC2D finite element procedure is generated to simulate mode-I crack extension from a given inner edge crack, which initiates from the half circle defect,and the corresponding stress intension factors(SIFs), , and its increment, , varied with different cracking depths, are calculated and compared. Afterwards, the fatigue lives for the pipeline with the defects of different sizes are obtained by using a modified Paris formula which can analyze the influence of crack closure and stress ratio. Thus, the relation between the fatigue life of CO2 pipelines and the dimension of the inner defect can be determined by performing the proposed fatigue crack growth analysis.