Corrosion Inhibitor Distribution and Injection Cycle Prediction in a High Water-Cut Oil Well: A Numerical Simulation Study

Abstract

The wellbore downhole strings corrosion has attracted extensive interest as most of the oilfields in China enter the high water-cut period. Injection of corrosion inhibitors, one of the most effective corrosion protection methods, is employed to mitigate the wellbore corrosion. Nevertheless, its wider application suffers from insufficient knowledge regarding the distribution of corrosion inhibitors inside the tubing, particularly with different inhibitor injection cycles. Thus, in this study, the computational fluid dynamics (CFD) method was first attempted to investigate the hydrodynamics in a tubing and the interactions between the corrosion inhibitor and produced fluid with high water-cut. Key factors including the time, wellbore heights, injection rates, oil phase velocities and corrosion inhibitor viscosities were discussed in detail as regards how they affect the corrosion inhibitor distribution inside the tubing. Feasible formulas were established for predicting the volume fraction of the corrosion inhibitor at different wellbore heights, which showed good agreement with the simulation results. It is noted that the determination of the corrosion inhibitor injection rate depends on both the film quality of the corrosion inhibitor and the stability of the annular flow. Based on the interphase diffusion effect, a new method for determining the intermittent injection cycle of corrosion inhibitor was proposed to maintain the integrity of corrosion inhibitor film at the tubing inner wall.