Objective  A corrosion failure prediction model considering axial spatial variability is proposed for the internal corrosion of shale gas gathering pipelines.

Method  Indoor tests were carried out on A^# and B^# gathering pipelines in a shale gas field in Sichuan, and the main influencing factors of shale gas gathering pipeline corrosion were investigated through the identification of corrosion morphology, indoor corrosion orthogonal experiments, and the comparison of corrosion rates. According to the experimental results, a corrosion failure probability model considering the axial spatial variability of parameters was established. The model was applied to predict the corrosion behavior of A^# and B^# pipelines, and its accuracy was verified through field excavation of the pipelines.

Result  The results show that the bacteria in the produced fluid of shale gas gathering pipelines are mainly sulfate-reducing bacteria (SRB), and the main elements of its corrosion products are C, O, Fe and a small amount of S; the main factors affecting the corrosion are the flow rate, the liquid holdup, SRB number the inclination of the pipeline, the corrosion inhibitor, and a variety of anions and cations; the model predicts that the corrosion of pipeline concentrates on the area of the pipeline at 5-7 o'clock and it mainly occurs in the pipeline sections with water deposition at the low-lying places. The engineering example showed that the model accurately predicted the corrosion morphology of A ^# and B ^# pipelines in a shale gas field in Sichuan. The main corrosion pattern of 7 out of 11 pipe sections of A^# pipeline is pitting corrosion, and the main corrosion pattern of 8 out of 12 pipe sections of B^# pipeline is uniform corrosion, which is consistent with the excavation results.

Conclusion The research results can provide a theoretical basis and practical reference for predicting the corrosion behavior inside shale gas pipelines.