Study on the Corrosion Law of Coiled Tubing in High CO₂ Gas Field Environment in Sichuan

Abstract

Aiming at the serious corrosion problem of coiled tubing operation in the gas field with high CO2 content in Sichuan，a high-temperature and high-pressure autoclave was used to simulate the working conditions of coiled tubing，and the corrosion rate of CT80 and 2205DSS tubing steel in CO2 environment was measured by weight loss method.In addition，the surface morphology and element composition of coiled tubing were analyzed by surface analysis techniques such as scanning electron microscopy (SEM)， X-ray diffraction analysis (XRD).Results showed that in the CO2-dominated corrosive environment， with the increase of temperature and pressure， the corrosion rate of CT80 in the gas phase environment gradually increased， the corrosion rate of 2205DSS had little change and was lower than that of CT80.The corrosion rate of CT80 in the liquid phase environment increased with the increase of temperature and pressure and then decreased， and the corrosion rate of 2205DSS was very low and changed little.Moreover， microscopic analysis of corrosion products found that the corrosion products of CT80 liquid-phase corrosion specimens mainly were FeCO3 and Fe2O3，and the product films were loose and porous，indicating that the corrosion was more serious.Comparably， the corrosion product of 2205DSS liquid-phase corrosion specimens were mainly Cr2O3，and the product film was denser，indicating that the corrosion was slighter.Overall， 2205DSS coiled tubing had good corrosion resistance and was suitable for use in high CO2 gas fields.

Keywords

• ct80 steel； 2205dss； coiled tubing； co2 corrosion； sichuan gas field