Erosion-Corrosion Effect in the Low-Temperature Heavy Oil Annular Flow Transportation

Abstract

Abstract. According to statistical data, proven heavy oil reserves account for approximately 70% of the world's remaining crude oil resources. As an important alternative energy resource, technologies for the pipeline transportation of high-viscosity heavy oil have developed rapidly. Among the available methods, water-loop transportation, characterized by its low cost and operational simplicity, has emerged as the most promising approach. However, the exceptionally high viscosity of heavy oil intensifies the entrainment of sand particles in the wellbore, significantly reducing sand removal efficiency. Furthermore, erosion of the pipe wall caused by sand particles, combined with the electrochemical corrosion environment created by the water annulus, poses serious threats to pipeline integrity. To investigate the evolution of erosion and corrosion rates during heavy oil–water-loop transportation, an optimized multifactor erosion rate model was developed and coupled with heat transfer and multiphase flow models for numerical simulation. In addition, CO2 corrosion experiments were conducted under actual engineering conditions to account for key influencing factors, including sand particle size, water content, flow velocity, and the thermal effects of heavy oil. The results indicate that erosion in straight pipeline sections during heavy oil annular transportation is negligible, and pipeline damage is primarily caused by CO2-induced corrosion in the aqueous phase. Increases in flow velocity, temperature, and CO2 partial pressure accelerate the corrosion process. Under stable annular flow conditions, erosion is mainly observed in elbows when the water content is low (below 9%), and the lower the water content, the more significant the erosive effect of large particles. When the water content exceeds 9%, no observable erosion occurs in the elbows.