Research On Corrosion Mechanism And Corrosion Resistance Layer Of Oil Field Gathering &Transportation Pipelines

In the exploitation of gas&petroleum,the corrosion of mining equipment is most common problem that companies suffer,which has incurred some serious damage.Especially in the middle and final stage of oil development,the problem from CO₂,H₂S,in combination with the existence of bacteria,minerals in crude oil,account for a more serious and more complicated corrosion problem.So a detail knowledge of corrosion mechanism and an elaborated method are needed.In this dissertation,a detailed investigation of the corrosion situation on the oil pipelines of oil field was conducted.Through to pipeline's corrosion gas,water salinity condition investigation and study,bacteria culture and scale under corrosion simulation experiment in the laboratory,using the weight loss test,potentiodynamic polarization curves,wire beam electrode,electrochemical noise test technology combining with the corrosion morphology observation,it was found that the corrosion types of CO₂/H₂S corrosion under the mixed control types of sediments,the corrosion besides affected by salinity,corrosive gases,still under the influence of pipeline elevation difference.The causation of corrosion of single well pipeline in oil field was studied by statistical analysis,and it was found that brine sweeping process was the causation of corrosion of single well pipeline,which was affected by the dual action of corrosion under sediment and dissolved oxygen.The corrosion of long distance pipelines was evaluated by pipeline current mapper?PCM?,current infeed experiment,probing test.Result shows that the anti-corrosion layer suffered from partial failure local corrosion.The Fourier-transform infrared spectroscopy?FTIR?,SEM and the analysis of soil morphology demonstrates that the epoxy layer has some defects.The combined effect of the microdefection of corrosion resistance layer,water immersion as well as temperature,leads to the failure of the epoxy layer.A mathematic model was constructed for the failure of epoxy layer.The early warning and repair Suggestions for the service life of the long line of parts of instrument were put forward.A self-healing liquid paint was designed to solve the failure problem of the epoxy layer on gathering&transportation pipelines.The test of adhesion strength,contact angle,and the XPS result show that the addition of active resin into the epoxy promotes the binding strength of the protection layer,majorly due to the strong chemical bond between the resin and the hydroxyl on the steel.The tensile test,adhesion test,water absorption test,and the contact angle test demonstrates that the dispersity of additive was significantly improved in the modified epoxy layer.The salt spray test and the electrochemical impedance spectroscopy?EIS?both demonstrates that the compatibility of the boundary between the additive and resin was improved,which leads to the inhibition of diffusion of corrosion products.A chemical bond?with a binding energy of 10²to 10³KJ mol-l?was formed,instead of the previous physical bond?with a binding energy of 2 to 40 KJ mol-l?.This also leads to a better adhesion between the nonorganic-organic,which solves the critical problem regarding the strength of boundary,and leads to a better corrosion protection of epoxy layer to the pipelines.