Study On The Corrosion Of Su-qiao-wen-an Oilfield Injection-production String And Anticorrosion Technology Of Inhibitors

In this paper, the influence law of various corrosion factors such as flow rate, temperature, CO₂ partial pressure and Cl-concentration on the column corrosion are Studied under Su-Qiao-Wen-An oilfield water-injection well casing corrosion environment by using orthogonal test method. Corrosion morphology is observed by SEM,the elemental composition and phase composition of corrosion products are analized With EDS and XRD,and the Corrosion mechanism of Su-Qiao-Wen-An oilfield water-injection tube is obtained. The results shows that, in Su-Qiao-Wen-An oilfield water-injection well corrosion conditions, the string corrosion rate is in the range of 0.6521¹.6104mm/a; corrosion degrees vary with the corrosion factors, The most and minimal impact on corrosion rate are the variation of flow velocity and Cl-concentration respectively. The effect of various factors on corrosion rate from large to small are listed as follows: flow velocity>temperature>CO₂ partial pressure>Cl-concentration. According to the analysis to corrosion reason and corrosion mechanism, four inhibitors of BTA（benzotriazole）, benzimidazole,bis-imidazoline and Oleic imidazoline are selected. The corrosion inhibition efficiency of inhibitor with different concentration is calculated by indoor simulation experiments, and the effect of the concentration of inhibitor on corrosion pattern of metal surface is observed,which indicates that the order of corrosion efficiency form high to low can be listed as: bis-imidazoline >Oleic imidazoline >BTA（benzotriazole）>benzimidazole. Corrosion efficiency of bis-imidazoline can reach 92.05% when the concentration is 100 ppm. To conduct further researches of inhibition mechanism of inhibitor, the inhibitor films made by BTA（ benzotriazole）, benzimidazole,bis-imidazoline and Oleic imidazoline is studied from the angle of molecular for their absorption of iron surface. The dispersal behavior of H₂ O and Cl- in BTA（ benzotriazole）, benzimidazole, bis-imidazoline and Oleic imidazoline is also researched. The dispersal behavior of Corrosion particles in the above four inhibitor films is analyzed and discussed with respect to the interaction of Corrosion particles and inhibitor film, factional free volume of inhibitor film and self-diffusion of Corrosion inhibitor molecules. The results of simulated calculation is consistent with that of experiments. The research provide Su-Qiao-Wen-An oilfield with reliable rot-proof method from both experimental and theoretical aspects. The ideas given in the paper can be borrowed to other oilfields with similar corrosion problems.