Study On Corrosion Law Of X80 Pipeline Steel In Produced Liquid Of Complex Formation

In this paper,the orthogonal simulation method and the single factor control variable method are used to carry out the dynamic simulation test using the high temperature autoclave.The weight loss method was used to study the corrosion law of X80 pipeline steel in simulating different crude oil moisture content,salinity,CO₂ partial pressure,total pressure,temperature and flow rate in Changqing Oilfield,and the application research of X80 pipeline steel in gathering pipeline laid a certain theoretical foundation.The results of orthogonal test show that the influence degree of each factor on the corrosion rate of X80 steel is:temperature,crude oil moisture content,CO₂ partial pressure,total pressure,salinity and flow rate;and temperature,crude oil moisture content and CO₂partial pressure are all highly significant factors.The results of single factor test showed that when the water content of the crude oil is in the range of 20 to 80%,with the increase of water content,the average corrosion rate of X80pipeline steel increased linearly,the surface corrosion of the sample increased,the product film thickened,and the corrosion morphology showed local corrosion-uniform corrosion.When the salinity is between 5000 and 100000mg/L,with the increase of salinity,the average corrosion rate of X80 pipeline steel first increases and then decreases,and at the critical value of 60000mg/L,the average corrosion rate reaches the maximum within the test range.With the increase of salinity,the density of the product film increases first and then decreases,and the corrosion pattern shows the trend of uniform corrosion-local corrosion.When the partial pressure of CO₂ is between 0.5 and 3.5 MPa,as the partial pressure of CO₂ increases,the average corrosion rate of X80 pipeline steel increases.After the partial pressure of CO₂ is more than 2.5 MPa,the production of dense product film causes the corrosion rate to decrease rapidly and corrosion.The morphology changes from localized to uniform corrosion with increasing CO₂ partial pressure.When the temperature is between 40 and 100?,the average corrosion rate of X80pipeline steel decreases first and then increases with the increase of temperature.At 80°C,the corrosion rate reaches the minimum.As the temperature increases,the thickness of the product film also decreases,and the density first increases and then decreases.The corrosion morphology changes from uniform corrosion to local corrosion.When the total pressure is between 4⁸MPa,the change of total pressure has little effect on the corrosion rate of X80 pipeline steel.The increase of total pressure makes the corrosion rate increase slightly,but the corrosion degree is basically the same;when the pressure is more than 8MPa,the corrosion rate is drastically reduced,and the corrosion pattern shows a trend of uniform corrosion-local corrosion.When the flow rate is between 0.5 and 2m/s,the average corrosion rate of X80 pipeline steel increases first and then decreases with the increase of flow rate.When the flow rate is1.0m/s,the corrosion rate reaches the maximum.The change of corrosion pattern with increasing flow rate is uniform corrosion-local corrosion.