CO₂-O₂-SRB-Cl⁻ Multifactor Synergistic Corrosion in Shale Gas Pipelines at a Low Liquid Flow Rate

The corrosive environment in the gathering pipelines of shale gas fields is very harsh. Through an analysis of the gas and water quality of a shale gas field, six important factors in the corrosion environment of gathering pipelines are determined. Under the synergistic effect of CO₂-O₂-SRB-Cl⁻, low liquid phase flow rate and appropriate temperature, the gathering pipelines perforate quickly, causing serious economic losses. Eighteen groups of orthogonal experiments with six factors and three levels in high-pressure reactor are completed, with the maximum local corrosion rate reaching 3.5523 mm/a. Through a combination of range analysis and variance analysis, the main control factors of general corrosion and local corrosion are clarified. The most significant factors responsible for general corrosion are dissolved oxygen and temperature, while the most significant factors responsible for local corrosion are dissolved oxygen, temperature, and liquid velocity. The morphology and composition of the corrosion products are characterized by SEM, EDS, and XPS, and the corrosion mechanism of CO₂-O₂-SRB-Cl⁻ at a low liquid flow rate is determined.