Study On Corrosion And Influencing Factors Of LD Heavy Oil Mixed With Water Transmission Pipeline

The colloid and asphaltene content of heavy oil is relatively high,and the viscosity is relatively high,so heavy oil is difficult to transport.LD oilfield uses the method of mixing heavy oil with water to reduce transportation viscosity.Since the mixed water often contains a large amount of soluble ions,it has a certain degree of corrosion which affects the safety of pipelines.In order to ensure the operation safety of pipelines and guide the site to make targeted anti-corrosion measures,and the study on the corrosion behavior and main influencing factors of heavy oil mixed water transmission pipelines in LD oilfields has strong practical significance.In view of the influencing factors of corrosion of oil-water mixed-transport pipelines,the commonly used pipe steel——X52 steel is the study object.The main research results are as follows:(1)Orthogonal experimental methods were used to design two groups of experiments to study the three environmental factors such as temperature,pH value,and salinity,and five different ions such as Cl-,HCO3-,Mg2+,SO42-and Ca2+,which have major effects on corrosion in the produced water.The effect of salinity on the corrosion of X52 steel was found to be greatest in environmental factors such as temperature,pH and salinity of the produced water,followed by pH value and temperature.Among Cl-,HCO3-,Mg2+,SO42-and Ca2+ ions,Cl-has the greatest effect on the corrosion of X52 steel,followed by Mg2+,SO42-and HCO3-,and the Ca2+ affects least respectively.(2)Applying the dynamic weight loss method to study the influence of the flow rate of produced water and the moisture content of crude oil on the corrosion rate of X52 steel,it is found that the liquid flow has a certain flushing effect in addition to the corrosion of X52 steel,and the flow rate has a great influence on the corrosion rate.With the increase of flow rate,the corrosion rate of X52 steel increases,and the corrosion rate reaches a maximum of 3.53 mm/a at a flow rate of 0.8 m/s.When the flow rate exceeds 0.8 m/s,the corrosion rate decreases.The corrosion of X52 steel pipeline is mainly affected by the produced water.The influence of corrosion by crude oil can be ignored.When the crude oil contains no water,the corrosion rate of X52 steel is very low.With the increase of water content,the corrosion rate of X52 steel increases,and the corrosion rate of X52 steel reaches 2.85 mm/a when the water content is 65%.(3)The influence of temperature,pH value,salinity,and ion species on the corrosion rate and corrosion behavior of X52 steel was investigated by means of static weight loss method.At the same time,electrochemical experiments were used to study these factors' corrosion.The electrochemical corrosion behavior of steel was cross-validated with the static weight loss test,and the SEM test was used to test and analyze the corrosion of several conditions of X52 steel.It was found that the corrosion rate of X52 steel increases with temperature increases.The polarization curve showed that the passivation film appeared on the surface of X52 steel after 60?,but the passivation was obvious.The influence of the membrane is less than the influence of the mass transfer process of the corrosive medium;the corrosion rate of the X52 steel in the alkaline environment is significantly less than that in the acidic environment,and the corrosion rate is the lowest at the pH value of 8 and the passivation film of the X52 steel electrode surface appears at the pH values of 8 and 9;with the increase of salinity,the corrosion rate increases first and then decreases.At 20.00 g/L,the corrosion rate of X52 steel reaches a maximum of 2.04 mm/a,and it reaches a minimum at 60.00 g/L.When the salinity changes,the corrosion rate of X52 steel changes but the reaction mechanism does not change.The effect of Cl-on the corrosion of steel is greatest.The corrosion rate of X52 steel reaches 1.56 mm/a when the Cl-concentration is 20.00 g/L.(4)According to the influence factors of corrosion of X52 steel in oil and water mixed transportation and on-site working conditions,anticorrosion measures are proposed.The advantages and disadvantages of various anti-corrosion measures are compared from economic applicability,etc.It is found that adding corrosion inhibitor method costs low and has good applicability.It is recommended to use it.Corrosion inhibitors are preserved,but further research on the selection and formulation of inhibitors is needed.