Influence of temperature on corrosion behavior of VM110SS casing steel in sour environment

The influence of temperature on corrosion behavior of VM110SS casing steel in sour environment was studied in high temperature and high pressure autoclave by simulating the downhole environment of a gas field in Sichuan. The partial pressure of CO₂, partial pressure of H₂S and total pressure are 0.54 MPa, 0.41 MPa and 18 MPa respectively. The test temperature is from 30℃ to 150℃. The relation between temperature and corrosion rate of the VM110SS steel can be obtained. The compositions and appearance of corrosion products were analyzed by SEM and EDS. The results showed that the corrosion rate of VM110SS increased firstly then decreased with the increase of test temperature. The maximum value appeared at 90℃. The corrosion rate in gas phase was 0.838 mm/a, and the corrosion rate in liquid phase was 1.130 mm/a, which showed a extremely severe corrosion. Uniform corrosion characteristic was presented to specimens at all test temperatures and corrosion product was composed mainly of iron sulfides. The paper provides theoretical basis for casing corrosion mechanism at different temperature and guidance for casing steel selection.