Corrosion Of Typical Anion/cation On Tubing Steel In Oilfield Water

The corrosion problem of the complex composition of the oil field water and formation water on the tubing steels caused extensive attention.The study of synergistic corrosion problems for multiple ion coexistence(eg,HCO3-/Cl-/S2-coexistence)was reported little,and previous studies had focused on corrosion behavior of single/two ions,such as Cl-corrosion and C-1/HCO3-coordinated corrosion.Therefore it has important practical significance to study the corrosion behavior of P110 casing steel and 2205 stainless steel in the simulating formation water for the Gas Field in East Sichuan.The synergistic effect of typical anions on the corrosion of P110 casing steel and 2205 stainless steel was studied by the weight loss measurement and electrochemical test.Similarly,the same tests were used to study the synergistic effect between typical anions and cations.The results showed that the studied anions had synergistic effect of promotion first and then inhibition on P110 casing steel while they had synergistic effect of promotion on 2205 stainless steel in HCO3-1Cl-/S2-coexistence system.In particular,under the S2-synergistic effect,the corrosion rate of P110 casing steel increased mostly in 0.16g/LHCO3--20g/LCl-simulated solution.However,for the 2205 stainless steel,the corrosion rate increased mostly under the Cl-synergistic effect in the 0.16 g/L HCO3--0.03g/LS2-simulated solution.Ca2+ and Mg2+promoted the corrosion behavior of Cl-and S2-on the studied steels,while the inhibited the corrosion behavior of HCO3-,particularly,the corrosion rate of P110 casing steel was increased mostly in 0.09g/L S2-solution under the action of Ca2+,and the corrosion rate decreased to 0.19mm/a under the action of Mg2+.The difference is that the corrosion rate of 2205 stainless steel increases mostly in the 60g/LCl-solution under Ca2+ synergistic effect,and the corrosion rate varied similarly in 0.48g/L HCO3-solution.Furthermore,the water-soluble imidazoline inhibitor was suitable for the studied water corrosion system of the oilfield.And when the dosage was 200mg/L,the corrosion inhibition effect was 90%.The morphology and composition of the corrosion products were analyzed by SEM,EDS and XRD.The results showed that the hydrolysis of FeCO3 or protective film layers on P110 casing steel surface made the corrosion rate increased and then reduce.The final corrosion products were Fe2O3,FeOOH and other oxides on the HCO3-,Cl-synergistic effect,when there were FeS,Fe3S4 on the S2-synergistic effect.the passivation film of 2205 stainless steel were damaged,the strong penetration of studied anion,and generating holes,they lead corrosion reaction intensified,and corrosion products were a small amount of Fe2O3,FeOOH and chromium oxide passivation film.A large number of regular blocks of CaCO3 and flaky MgCO3 were stacking orderly on the sheet,so the protective effect was better,and they compensated for the destruction of HCO3-chromium oxide passivation film,thereby inhibitd the corrosion of HCO3-on the studied oil casing.