Construction and Corrosion Mechanism of Erosion-corrosion Prediction Model for P110 Steel
As a common oil well pipe material in the oil and gas industry,P110 steel is prone to erosion corrosion at high temperature,high pressure,and high salinity flowing media,which threatens the safety of oil and gas development.In this paper,P110 steel was taken as the research object,and a high temperature and pressure erosion corrosion experiment was carried out by electrochemical workstation and high temperature and pressure reactor. The microstructure,chemical composition and phase composition of the material before and after erosion corrosion were characterized by metallographic microscope,scanning electron microscope (SEM) and X-ray diffractometer (XRD). The erosion corrosion behavior and mechanism of materials under different erosion speeds and angles in a high temperature and pressure environment were investigated. In addition,the corrosion prediction model of P110 steel was constructed based on the random forest (RF) algorithm,through the investigation of literature data. Then the prediction accuracy and corrosion influencing factors were analyzed.The results showed that the corrosion current density (Jcorr) decreased with the increase of erosion angle from 2.19×10-4 A/cm2 at 30° to 1.44×10-4 A/cm2 at 90° at the erosion speed of 3 m/s. At the erosion angle of 30°,the Jcorr increased from 6.30×10-5 A/cm2 at 0 m/s to 2.19×10-4 A/cm2 at 3 m/s. This was because the mass transfer time decreased with the increase of erosion speed and the decrease of angle,and the synergistic effect of tangential and normal stress enhanced as the increase of erosion speed and the decrease of erosion angle. Thus,the integrity and thickness of the corrosion product film were reduced,accelerating the corrosion.The HCO3-and CO32-,produced by CO2 dissolution,and the presence of Cl-in the solution greatly increased the reaction activity of the P110 steel interface and decreased the pH of the solution,forming a corrosion product film dominated by FeCO3. Due to the diffusion of Fe2+from the surface of P110 steel and the consumption of H+caused by cathodic hydrogen evolution reaction,the pH value of the solution at the interface between P110 steel and corrosive medium was significantly higher than that of the whole solution. The local high pH was beneficial to the formation of Fe(OH)2 between FeCO3 and P110 steel substrate. It was then oxidized and dehydrated in air form Fe2O3. A double-layer corrosion product film structure was formed on the surface of the substrate,with Fe2O3 as the inner layer and FeCO3 as the outer layer.In addition,the results of the corrosion prediction model showed that the temperature had the most significant effect on the corrosion behavior,followed by CO2 and erosion speed. The accuracy of the corrosion prediction model reaches 89％,which can be used to guide the corrosion prediction of oil and gas field materials.
P110 steelerosion corrosionhigh temperature and pressuremachine learningrandom forest
万方数据
维普
