Study Of Corrosion Mechanism Of Different Phase In Crude Oil Storage Tanks And Anti-corrosion Technology Of Gas Phase

With the gradual development of exploration,the crude oil content of moisture and corrosive medium crude oil increase in the exploitation of a domestic oil field.The quality of crude oil is inferior step by step,which has a large impact on the safety of oil storage in storage tank.Therefore,it is of great significance to study the corrosion mechanism and protective measures of crude oil storage tank.In this paper,storage tank internal complex environment can be divided into silt phase,oil-water interface,water phase and oil phase,oil-gas interface and gas phase from the bottom to top.Three storage tanks of different joint stations were selected,and the corrosion mechanism was analyzed by situ coupon testing using the hangers in each phase.In addition,the survey found that pitting corrosion of the tank deck is more serious.A vapor phase corrosion inhibitor corrosion control method is purposed to effectively control the corrosion of the gas phase area,and the filling process is studied through laboratory coupon testing.The following conclusions are obtained:The corrosion mechanism of each phase was analyzed by the analysis of the corrosion morphology,the composition of the corrosion products and the composition of gas,oil,water and mud.The severe local corrosion of gas phase corrosion is caused by O₂?CO₂?H₂S dissolved in condensed water.The corrosion of oil phase is mainly caused by acid,sulfide and water content in crude oil.The corrosion of water phase is more complex and the degree of pitting is relatively serious.The corrosion factors mainly includes dissolved oxygen,dissolved salts(Cl^-,Ca²⁺,Mg²⁺,etc.)and its resulting scale,bacteria,etc.The corrosion of mud phase is mainly caused by sulfate-reducing bacteria?SRB?,where the pitting corrosion is the most serious.In addition to the corrosion of two adjacent single phases,the concentration cell corrosion can also have an important effect on the interface corrosion.Comprehensively,the order of corrosion rate is water,mud>gas,oil-gas interface>oil-water interface,oil and the corrosion of sedimentation tank is more serious than oil removal tank.The optimal volatile corrosion inhibitor injection process was obtained through the screening of the aerosol technology and the volatile corrosion inhibitor as well as its injection technology.and the gas phase corrosion inhibitor in the gas phase was formed.A well protection effect was obtained.The particle size,safety,construction difficulty and maintenance of fog droplet are taken into account,and the ultrasonic nebulizer has minimal particle size and is convenient for field installation and maintenance.In addition,the results of electrochemical experiment and coupon testing show that favourable anticorrosion performance is achieved in the form of spray upon the addition of Dicyclohexylamine nitrite,a volatile corrosion inhibitor with well-rounded technology.Taking the economy and anticorrosion performance into consideration,the optimal spraying inhibitor concentration and spraying time interval are set to200 mg/L and 24 h,respectively,under which the corrosion inhibition efficiency of 92.71%are accomplished.