Study on the Corrosion Behavior of Oil Casing String in Annular Protection Fluid Environment of Kunteyi Block

Abstract

Aiming at clarifying the corrosion behavior of oil casing materials in high salinity and high temperature annulus protection fluid environment, the corrosion damage sensitivity of oil casing materials under non-stressed and stressed conditions in the simulated oilfield annulus protection fluid environment was evaluated by high temperature and high pressure (HPHT) test system. The micromorphology, cross section characteristics and chemical composition of the product film on the surface of the material were analyzed and characterized by scanning electron microscope and energy dispersive spectrometer. Results showed that the corrosion of the material was relatively worse in the annulus protection liquid without deoxygenation treatment. The corrosion product film was cracked and partially detached, and the cracking of the bottom film layer could be seen at the shedding place. Moreover, the average corrosion rate of P110 material was up to 3.83 mm/a. Observing the cross section could find the cracking on the surface of the double film layer was limited to the corrosion product film, and the substate material was not involved. The material was uniformly corroded and thinned. Furthermore, after deoxygenation treatment, the erosion of the annulus protection fluid decreased significantly, and the corrosion rate of P110 material decreased by 80%. Generally, P110 and P110SS were insensitive to stress corrosion cracking under the synergistic effect of high temperature and high pressure annulus protection fluid without deoxygenation treatment environment and loading stress, and corrosion thinning was the main corrosion damage mode of P110 oil casing material.

Keywords

• p110/p110ss oil casing|annulus protection fluid|corrosion|stress corrosion cracking