Study On Microbiologically Influenced Corrosion Mechanism And Influencing Factors In Symbiotic Oil And Gas Fields

Microorganisms are widely distributed in seawater,fresh water and soil environment.The microbiologically influenced corrosion induced by them will cause the corrosion and damage of a variety of materials,including carbon steel,stainless steel,copper,magnesium alloy,and even concrete materials,causing serious economic harm.In this paper,taking sulfate reducing bacteria,iron oxidizing bacteria,total general bacteria and specific shewanella bacteria enriched and cultured in the produced water of an oil field as the research object.Carry out corrosion experiment and electrochemical experiment to explore the difference of corrosion law between single bacteria and multi bacteria,as well as the inhibitory effect of bactericides and corresponding corrosion inhibitors on microbial corrosion.The main research results are as follows:1.Among SZ36 water samples,the pitting corrosion caused by IOB is the most serious,and the maximum pitting depth can reach 19.5μm。The pitting corrosion caused by SRB in WHPH water sample is the most serious,and the maximum pitting depth can reach 12.2μm。The pitting corrosion during symbiosis is not as serious as that caused by the corresponding IOB or SRB,but it can be seen from the pitting scatter diagram that it tends to be between the experimental groups of single bacteria.In terms of general corrosion,the results of the two water samples have the same trend,which is IOB>MIX>SRB>TGB,and the general corrosion rate of symbiosis experiment is closer to the IOB experimental group with the largest rate.2.According to the corrosion law of SRB bacteria in WHPH water sample,referring to the blasting equation given in ASME-B31G standard and the relevant parameters of L245 pipeline in the literature,the service time of pipeline failure can be calculated.The L245 pipeline in the target literature will fail due to microbial corrosion caused by SRB after about 4 years and 1 month.3.The bactericide shows a significant reduction effect on the pitting caused by microbial corrosion,which reduced the maximum pitting depth by 46.1%to 56.5%,and the addition of corrosion inhibitor has no obvious enhancement or reduction effect.The results show that the corrosion inhibitor can not effectively inhibit the metal corrosion caused by microorganisms.It is worth noting that H₂S inhibitor has a slight mitigation effect on the pitting corrosion caused by SRB.On the one hand,it shows that H2S produced by SRB metabolism also has a certain corrosion effect on the metal matrix.On the other hand,it shows that the corrosion of SRB on carbon steel is the superposition effect of electron transfer process and metabolite corrosion,and it is mainly caused by electron transfer process,that is,the so-called EET-MIC.Metabolite corrosion,that is,the effect of M-MIC is very light.4.In the symbiosis experiments of shiwanella with SRB and IOB,present different symbiosis situations.When SA and IOB coexist,IOB can use the electron carrier produced by SA.The electron acquisition ability of symbiotic colonies to the base metal is strengthened,which is manifested in the enhancement of local corrosion and the weakening of uniform corrosion.When SA and SRB coexist,due to the hydrogen sulfide produced by the metabolism of SRB,the acidity of the liquid environment in which the symbiotic colonies are located is enhanced,which is not suitable for SA to survive,and the local corrosion and uniform corrosion are weakened.