Failure Analysis of the Under-Deposit Corrosion on Shale Gas Field Pipeline

Abstract The elbow of a newly developed shale gas field pipeline fails for severe internal corrosion. Large amount of deposit is found around the holes. On the basis of chemical composition analysis, metallographic analysis, product micromorphology analysis and XRD results, this study purposes that CO2 contributes to the electrochemical reaction, while sands erode off the FeCO3 corrosion scale and settle down to the wall providing condition for localized corrosion. In order to uncover the law of the erosion and settling process of the sands transported through the shale gas field pipeline, this study carries out numerical simulations. The result shows that, at the elbow, the larger the flow rate is, the greater the sand-carrying capacity and the more intense the erosion. On the other hand, sands tend go reversely and finally settle at the elbow when the flow rate is small, which is the same with the deposition in this case.