Study On The Corrosion Characteristics Of Thermal Production String In The Environment Of Chloride Ion And Acid Gas

During the exploitation of heavy oil gas reservoir by injecting multiple thermal fluids,the produced medium usually contains O₂,CO₂ or Ca²⁺,Mg²⁺,HCO₃^-,Cl^-.The presence of these gases and ions will change the pH value of the liquid and produce a strong electrolyte solution,resulting in safety problems such as wall thickness thinning,strength reduction and deformation of the thermal production string due to electrochemical corrosion.In order to study the corrosion damage of the thermal production well string in the process of multi-element thermal fluid injection,the high temperature and high pressure reactor was used to stir the liquid in the laboratory test,and the medium flow environment was simulated.The corrosion law of K55 and J55 oil well pipe in different temperature and gas concentration was measured by weight-loss method,and the corrosion law and cause of formation were analyzed by combining the results of SEM,EDS and XRD.Through experiments and theoretical analysis,the main results are as follows:?1?In the hot fluid system containing O₂,environmental factors affect the corrosion rate of pipe steel by changing the diffusion rate of oxygen;?2?In the system of hot fluid containing CO₂ corrosion,temperature affects the physical properties of the corrosion product film on the surface of the material,and then affects the corrosion rate of carbon dioxide of the oil well pipe material;?3?Cl^-affects the corrosion process of the test material in acid gas environment by changing the solubility of acid gas in the produced liquid and the performance of passivation film.The results show that rc-3 is better than triethanolamine phosphate,and it is the best corrosion inhibitor for multicomponent gas co-existence in multi-component hot fluid wells.