Analysis of corrosion failure causes of the heat-insulated tubing joint in a thermal recovery well for heavy oil

The analysis of the corrosion failure of the heat-insulated tubing joint in a heavy oil thermal recovery well was conducted using a variety of methods, including macroscopic morphology observation, physicochemical property testing, chemical composition analysis, microstructural examination, scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDS) analysis, as well as sulfate-reducing bacteria (SRB) microbial culture experiments on the produced water. The research revealed that the produced water contained a significant concentration of SRB. The primary causes of the joint’s corrosion failure were SRB, SO 4 2- , HCO 3- , and oxygen corrosion, which led to localized pitting corrosion. High-temperature sulfur and sulfide corrosion, coupled with cavitation corrosion, further exacerbated the surface corrosion at the middle section of the joint, resulting in a honeycomb-like corrosion morphology and, eventually, corrosion perforation. These phenomena severely impacted the reliability and service life of the tubing. The research findings have great significance for guiding material selection, formulating corrosion prevention measures, and extending the service life of tubing in oilfield production.