Extend The Corrosion And Corrosion Inhibitor Of N80 Steel Produced By Typical Oil Well Produced Oil Fields

The corrosion of oil tube has become a major troble which restrcited the development of oil and gas fields,and the corrosion caused by produced water has always been concerned.Because of the diffenrence of composition of produced water,its corrosion research was different.The serious corrosion of oil tube was discovery at an oil production plant of YanChang Oilfield.And the corrsoive wells are in the late stages of development,its water content ratio was over 90 percent.The study on corrosion of its produced water and corresponding anti-corrosion measures was necessary.4 produced water of corrsoive wells were slected as the research object.First,the composition of these water was analyzed.Then the effect of temperature,dissolved oxygen and velocity on corrosion of N80 steel was discussed by weightlessness experiment.And the corrosion products were analyzed by energy spectrum.The effects of temperature,dissolved oxygen,soaking time and rust on the corrosion behavior of N80 steel were studied by electrochemical method.The solubility,stability and anti-corrosive ability of imidazoline quaternary ammonium salt(DN5-4),imidazolinium amide(DTC),fatty acid imidazoline(CI-2)were studied by experiments,and the optimum concentration of corrosion inhibitor was tested.The anodic desorption behavior and the post-effect of the corrosion inhibitor was also studied.Uropropine,thiourea,ascorbic acid,peregal O,sodium dodecyl-benzene sulfonate(SDBS)were respectively mixed with CI-2 in water2 and water4,its synergistic effect were studied.The ratio of complex,anodic desorption and post-effect was discussed.Finally,the corrosion inhibition of the corrosion inhibitor was investigated by dynamic weightlessness experiment.The results showed that:the corrosion of N80 steel was mainly affected by dissolved oxygen and the velocity,the tempetature followed.The corrosion products are mainly iron oxides and FeCO3.The rise of temperature didn't change the corrosion mechanism,it just sped up the corrosion reaction.Dissolved oxygen has participated in the corrosion reaction,and the oxygen concentration diffusion was the reaction control step.After Soaked 17 d,the charge transfer resistance in waterl,water3 and water4 increased a little,and due to its higher charge transfer resistance in water2,the corrosion was not serious.The rusted specimen had an accelerated corrosion effect on the non-rusted sample near it,higher temperature lead to more acceleration.The anti-corrosive ability of CI-2 in waterl and water3 was good,the anode reaction was inhibited,and the best concentration was 1000 ppm,the corrosion inhibition rate under dynamic weightlessness test was higher than 90%overall.Anode desorption occured when the overpotential was above 0.52 V wihle 1000 ppm CI-2 in waterl,while it didn't happen in water3.And post-effect of CI-2 in waterl and water3 was excellent.It showed a synergistic effect when CI-2 and peregal O mixed with 1:1 in water2,the co-ordination coefficient was 1.26,and the best ratio was 3:1.Anode desorption occured when the overpotential was above 0.37 V.It still had good corrosion inhibition after immersed 8 d,while CI-2 and peregal O mixed with 3:1 in water2.The corrosion inhibition rate,except 0.8 m/s,tested by weightlessness experiment was between 92%and 98%.It showed synergistic effect when CI-2 mixed respectively with thiourea,urotropine,ascorbic acid at 1:1 in water4,the co-ordination coefficient was 2.24,4.97,1.53 respectively,and the best ratio was 4:1 for these complex systems.Anode desorption occured when the overpotential was above 0.36 V,while CI-2 and ascorbic acid mixed with 4:1 in water4.Anodic desorption didn't happen while CI-2 and thiourea mixed with 4:1 in water4.However,severe anodic desorption occured when overpotential was above 0.5 V,while CI-2 and urotropine mixed with 4:1 in water4.The impedance value of CI-2 and thiourea or urotropine complex has been large,its post-effet was good.While CI-2 and ascorbic acid comlex has smaller impedance value after immersed 7 days,indicated that the anti-corrosive ability was worse.The corrosion rate of 3 kinds of complex methods in water4 was above 90%genernally.However,severe localized corrosion may be caused when CI-2 mixed with thiourea and urotropine,while corrosion type belong to general corrosion when CI-2 mixed with ascorbic acid.So,CI-2 and ascorbic acid mixed with 4:1 was more appropriate in water4.