Wellhead Corrosion Mechanism and Optimization Under Alternating Injection Condition of Liquid CO2 and Fracturing Fluid

Abstract

With the continuous exploitation of conventional oil and gas resources, their recoverable reserves are decreasing day by day. Unconventional oil and gas resources have attracted much attention, and CO2-enhanced fracturing technology is gradually taking the lead. During the implementation of this technology, the electrochemical corrosion of CO2 on the inner wall of pipelines will have a significant impact on the exploitation efficiency and equipment service life. To elucidate the corrosion mechanism of wellhead components under alternating CO2 and fracturing fluid injection conditions, and to identify the key controlling factors influencing corrosion within actual engineering parameters while investigating their corrosion patterns, this study employs a finite element numerical simulation approach. The research takes into account the structural characteristics and spatial distribution of erosion pits formed in the pipeline following fracturing fluid injection, subsequently conducting a comprehensive analysis of the electrochemical corrosion processes during the CO2 injection phase. The results indicate that injection displacement, pressure, and temperature are the main factors influencing pipeline corrosion, with decreasing degrees of influence. Optimization analysis reveals that the optimal parameter combination is: injection displacement of 3 m3/min, injection pressure of 42 MPa, and injection temperature of −14 °C. Under these conditions, the corrosion on the inner wall of the pipeline is minimized. Specifically, increasing the injection displacement significantly reduces corrosion, increasing the injection pressure makes corrosion more severe while increasing the injection temperature slightly alleviates corrosion.