Study of Cathodic Protection System for Oil Well Casings Based on Pulse Current

Abstract

Impressed Current Cathodic Protection(ICCP) is the most effective method for mitigating corrosion on oil well casings. ICCP systems are commonly based on direct current(DC) power supply, DC power supply determine the protective effect. However, traditional DC protection exist some problems, such as protect depth is not enough, uneven distribution of current and potential. In this study, a kind of cathodic protection system for oil well casing based on pulse current is designed. Pulse current is used as the polarization current required for cathodic polarization of oil wells. When electrons flow through the formation to the surface of the casing, electronic will not react with the surrounding corrosive substances at the same time. Electrons will gather at the surface of the casing, Potential direction of the casing surface is shifted to the negative direction, and Produce cathodic polarization. The effect of pulse current and direct current under simulated conditions for the well casing cathodic protection was investigated. The results indicate that under the simulated casing condition, Pulse Current Cathodic Protection(PCCP) system has better protection effect than Direct Current Cathodic Protection(DCCP) system under the same power output condition, and consumption of current is less than DCCP system. In addition, the influence of middle range of the duty ratio and frequency on the cathodic protection effect is determined.