Anti-corrosion study of tungsten alloy coating on tube column under high CO2 partial pressure

Abstract

In order to address the low-cost corrosion prevention of wellbore tubing in high-temperature and high-pressure gas injection development environments, tungsten alloy-coated tubing specimens were selected for corrosion experiments. Microscopic characterization techniques such as SEM/EDS were used to analyze the corrosion product composition, phase structure, and three-dimensional morphology of the specimens. Uniform corrosion rates and localized pitting corrosion rates of the specimens were tested separately. Based on the uniform corrosion rate, residual strength verification and service life prediction of the tubing after corrosion were conducted. The study revealed that in a simulated gas injection development corrosion environment at a high temperature of 190 °C, as the CO2 partial pressure increased, both the uniform corrosion rate and pitting corrosion rate of the tungsten alloy-coated specimens gradually increased. When the CO2 content reached 100%, the uniform corrosion rate was 0.4300 mm/a, and the pitting corrosion rate was 0.4684 mm/a. The main substances causing material corrosion were O, Cl, and S in the environment. Furthermore, with the increasing CO2 partial pressure, the damage to the tungsten alloy coating on the specimen's surface deepened. By verifying the residual strength of the tubing after corrosion, it was found that at a temperature of 190 °C and a CO2 content of 38%, the tensile safety factor of the production tubing exceeded the critical value in the 10th year, and the casing's tensile safety factor exceeded the critical value in the 36th year. This research can provide reference insights for the selection of tungsten alloy coatings for corrosion prevention in gas injection wellbore tubing.