Experimental Study On Influencing Factors Of Composite Passivation Film Of Oil Pipe

Due to the limitation of nitrogen production process in oil fields,the nitrogen injected into the formation contains 2% ~ 5% oxygen,which leads to corrosion of pipeline.Because of the systematic and comprehensive understanding of the factors affecting the formation of the composite passivation film,the popularization and application of the related technologies have been limited.Therefore,the experimental study on the factors affecting the formation of the composite passivation film is helpful to optimize the formulation of the composite passivation film and determine the film formation conditions,which is conducive to the efficient and economic development of the oil and gas.In this paper,we studied the formation of composite passivation of oil tube,scanning electron microscopy(SEM)and electron scattering spectroscopy(EDS)and other advanced observation techniques and test methods are introduced,combined with copper sulfate experiment and dynamic(static)state of corrosion evaluation,the innovative research on the influence of tube compound passivation film factors,microstructure,corrosion resistance and film forming law research,lay the foundation for the field application.The research results are as follows.(1)By changing the filming temperature,concentration and film forming time,visual observation and copper sulfate experiment on tubing composite passivation film formed by the formation of different membrane forming conditions of tubing composite passivation film effect,which is pre-filming temperature> volume ratio of methanol to water> solidify temperature> pre-filming time> mass of silane coupling agent> solidify time> the value of pH.At the same time,Based on level-experiment of three factors of alcohol water ratio,methane addition and pH value,combined with the results of orthogonal test,the composite passivation film was determined,volume ratio of methanol to water is 30:70,mass of silane coupling agent is 15 g,and the value of pH is 4.(2)Scanning electron microscopy(SEM)was used to obtain the microscopic morphology of the composite passivation film under different film formation conditions,and the main components and the mass fraction of the surface of the composite passivation film and the non coated steel test piece were obtained by electron scattering spectroscopy(EDS),the optimum film forming conditions was determined,which is the pre-filming temperature is 90?,the solidifying temperature is about 120?,the pre-filming time is 10 min,and the solidifying time is 90 min.(3)The corrosion resistance of composite passivation film,composite passivation film and compound corrosion inhibitor was analyzed systematically by the method of salt water immersion test,neutral salt spray test and dynamic(static)state corrosion evaluation combining.The corresponding compounding process is obtained that the metal with film covering under optimal film forming condition,dip into CHKH-5 compound corrosion inhibitor with concentration of 1000mg/L,in 90?.The corrosion resistance was strongest in 72 h ~ 96 h after dosing,and replenishment of corrosion resistance should be based on the actual needs when 96 hours later.(4)Result of field application shows that the combined process,compound passivation technology and compound corrosion inhibitor CHKH-5,can effectively improve the corrosion resistance.The total number of workover wells of two test wells all decreased apparently.The research results include the formula of compound passivation and the passivation process,the feasibility of composite passivation process in pipeline corrosion prevention is proved,and it lays a foundation for the wide application and research of oil pipe composite passivation technology in the future.