Influence of produced water with high salinity and corrosion inhibitors on the corrosion of water injection pipe in Tuha oil field

• The structure of corrosion products are analyzed in the water injection pipe.
• The reasons of corrosion are discussed in the water injection pipe.
• The static and dynamic coupon corrosion experiments are carried out.
• The scale inhibition has a good synergistic effect to the corrosion inhibitors.

In order to study the corrosion of water injection pipe and the performance of new corrosion inhibitors, the characteristics of corrosion products in pipe were observed by using energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). Under the static or dynamic condition, the corrosion rate of coupons in produced water was investigated through the weight loss test. The effect of new corrosion inhibitors was evaluated under the dynamic condition. The microscopic corrosion morphology of coupons was observed by using scanning electron microscope (SEM). The results suggest that in the water injection pipe, the main corrosion product is FeOOH, while the corrosion scales are mainly composed of CaCO3 and Mg6Al2CO3⋅(OH)16⋅4H2O. Furthermore, the pipe corrosion was mainly resulted from the dissolved oxygen, Ca2+ and other inorganic salt in produced water. A good inhibition effect was obtained due to the synergistic effect of corrosion inhibitors, meanwhile HZ-2 inhibitor was the best among all kinds of corrosion inhibitors prepared by the proportion of oleic acid imidazoline and phosphonic acid salt of 2:1. A high corrosion inhibition rate (89.78%) was obtained when HZ-2 inhibitor dosage and temperature were 350 mg/L and 35 °C, respectively. According to the microscopic corrosion morphology of coupons, it is clear that the corrosion rate could be significantly slowed down by the HZ-2 inhibitor.

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