Research On Corrosion Behavior And Corrosion Inhibitor Screening In SL Gas Field Gathering Pipeline

During the development of oil and gas fields,H₂S and CO₂ are relatively common Corrosive medium.Dry H₂S and CO₂ are generally non-corrosive,but in pipelines where water is present,it causes severe corrosion of the pipes,causing leakage and explosion,resulting in economic loss and causing casualties.The H₂S content in the S-L field is 3.0%to 16.49%,and the CO₂ content is 5.44%to 10.41%.The gas field contains condensate oil and belongs to a condensate gas reservoir.At present,there are many studies on the corrosion of H₂S and CO₂,but there are few researches on the corrosion rules and control methods of the pipe under the condition of S-L gas field.Therefore,in this paper,through the combination of indoor corrosion experiment and corrosion simulation software,the internal corrosion behavior of the gas gathering pipeline is studied and the corrosion inhibitor for the gas field is selected.Based on the investigation of corrosion behavior under the existence of H₂S and CO₂ at home and abroad,combined with the production requirements of the gas field,a dynamic and static indoor high temperature autoclave experiment was carried out under the typical working conditions of the wet gas transmission pipe section.The experimental material is L245NCS.Based on the static corrosion test method,the influence of vapor phase and condensate oil severity on the corrosion rate was analyzed.Based on the dynamic corrosion experiment method,the influence of flow rate and temperature on the corrosion rate was analyzed,and microscopic characterization techniques such as SEM,XRD,and EDS were used for corrosion Product analysis.Based on investigations of CO₂ corrosion software and corrosion models at home and abroad,the corrosion rate simulation was performed using the ECE-5 software under laboratory conditions.The experimental results were compared with the software simulation results to confirm the effectiveness of the corrosion simulation software.Then,using ECE-5 software to further study the effect of temperature,flow rate,water content,and condensate severity on its corrosion rate under different partial pressures of CO₂ and H₂S,and use the gray correlation method to screen out the main factors of corrosion.Finally,based on the standard SY/T 5405-2001 "Test methods and evaluation indicators for corrosion inhibitor performance for acidification",inhibitors for this gas field were screened out.Through the above research work,the following results were obtained:Based on the results of indoor corrosion experiments,it was found that the gas phase corrosion rate was greater than the liquid phase corrosion rate,the corrosion product was mainly FeS and the corrosion was mainly controlled by the H₂S partial pressure.Comparing the software simulation results based on indoor experimental conditions with the results of indoor corrosion experiments,it was found that the software simulation results are large with a maximum deviation of about+30%,which is within the allowable deviation range of the software.According to the software simulation results of the actual operating conditions of the S-L gas field,the temperature change has the greatest influence on the corrosion rate when the temperature is between 70? and 100?;and the corrosion rate changes quickly when the flow rate is between 5 m/s and 10 m/s;When the condensate weight is between 40 and 50,the corrosion rate changes the most,and the maximum corrosion rate reaches 11.07 mm/a;When the flow rate is 12 m/s,the temperature is 75?,and the condensate oil is 35,the change of water content has the greatest effect on the corrosion rate.Through the screening results of corrosion inhibitors,A5-09263 corrosion inhibitor can be used for pipe sections with more condensate and water,C3-217 corrosion inhibitor can be used for pipe sections with lower water content,and its corrosion inhibition effect is more obvious.C1-215 corrosion inhibitor is used pipe sections with higher water cuts have better corrosion inhibition.