Causes of Corrosion of BG110SS Steel Tubing in High Sulfur Oil and Gas Field

Corrosion occurred on BG110SS steel tubing with two sizes after one year of service in a high sulfur oil and gas field in northeastern Sichuan. The causes of corrosion of tubing were analyzed by means of macroscopic observation, chemical composition analysis, phase analysis, scanning electron microscopy and energy spectrum analysis. The results showed that homogeneous corrosion was dominant on the outer wall of BG110SS steel tubing, and severe local pitting corrosion was dominant on the inner wall. The corrosion degree of the tubing with size of φ88.90 mm was more serious than that of the tubing with size of φ73.02 mm. Pitting corrosion was mainly caused by S^2-, HS^- and CO₂ permeating to substrate surface under the combined action of high sulfur environment, Cl^- enrichment and oxygen absorption corrosion, which aggravated the substrate corrosion. Under the coupling action of environment, load and other factors, corrosion gradually expanded on the tubing.