| With the deepening of gas field exploitation,the production of water in gas field is increasing.It is one of the commonly mean in Chinese land gas fields to make a large number of gas field production effluent treated by surface water treatment system for two mining.The corrosion and perforation of the process pipelines in the water treatment system can be caused by the microorganism in the effluent,in which the sulfate reducing bacterium(SRB)has a significant impact on the pipeline steel.Therefore,the research on the corrosion behavior and influencing factors of SRB in the process pipeline is carried out in laboratory,and the protection measures applied in the field can provide some theoretical basis for the corrosion and protection of the pipeline,which has positive practical significance.According to the general situation and operation period of the process pipeline engineering of KLML gas field,the corrosion test specimen material,corrosive medium and main experimental method are determined.Based on the weight loss Experiment(static immersion experiment,dynamic reaction kettle Experiment),electrochemical system(Tafel polarization curve/EIS),analytical test method(SEM,EDS,XRD),the corrosion behavior of SRB in the shutdown and operation of process pipeline is studied,as well as the influence of pipeline temperature,Cl-concentration.Finally,the protection of bactericide is studied and the protective effect is evaluated for the SRB corrosion of the process pipeline.And the main conclusions obtained are as follows:(1)The static corrosion experiment shows that:the average corrosion rates of sterilizing group,blank group and SRB group were 0.0463mm/a,0.0633mm/a and 0.124mm/a respectively after immersion 49d.The surface of the SRB group has obvious corrosion pit,the maximum diameter is about 20 ?m.SRB accelerates the corrosion rate of carbon steel,and also induces the formation of pitting pit,which threatens the corrosion and perforation of the pipeline.(2)The results of EDS and XRD show that there is no S element in the corrosion products of the sterilization group,while the S element content of the blank group and SRB Group is 11.12%and the 12.61%separately.The S element comes from the sulfide produced by SRB metabolism.At the same time,Ca2Fe2S2O3 was detected in the metabolites of SRB group,the results showed that the sample was mixed with oxygen during the soaking process,and the sulfide was oxidized to thiosulfate.(3)The increase of the flow velocity in the bacteria solution can promote the rapid diffusion of H and H2O to the surface of the electrode,promoting the cathodic polarization and increasing the corrosion rate of the specimen.When the velocity of flow to 1.4m/s,the corrosion rate of carbon steel drops sharply to 0.0152 mm/a,which indicates that the high velocity of flow rate increases the scour effect of the biofilm,the growth of the biofilm is inhibited and the corrosion rate is reduced.(4)The corrosion of carbon steel is the most serious at the temperature of 35 ?.At this time the highest activity of SRB,the metabolic products and corrosion products continue to accumulate more and more,the structure of the biofilm becomes loose and uneven,and the oxygen concentration difference between the films increases the corrosion rate of the metal.(5)under low C1-concentration,Cl-and SRB have synergistic action to induce pitting of metal.When the concentration of Cl-is 20g/L,the SRB adsorbed on the surface of the metal specimen is very few,but the corrosion rate of the sample is still increasing.It shows that the high salinity can inhibit the microbial growth and no obvious microbial corrosion.But when the Cl-exceeds a certain concentration,it will induce the corrosion of the matrix and aggravate the corrosion of the metal.(6)The glutaraldehyde with a concentration of 60 mg/L is suitable for the protection of the field pipeline,and the protective effect is best when the flow rate is 0.45 m/s. |
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