Corrosion Behavior Of High Grade Acid-resistant Oil Casing Steel In Simulated H₂S/CO₂ Environments

In this paper,high grade acid-resistant oil casing C110 and Q125S was used as experiment materials.The uniform corrosion and local corrosion performance of the C110 and Q125S was investigated by high temperature and high pressure corrosion testing,which stimulated the downhole corrosion environments.Additionally,SEM,XRD and XPS analysis were performed to characterize the corrosion product film.The NACE TM 0177-2005 standard method D was used to evaluate the SSC resistance performance of the materials.The result of corrosion rate test shows that in all simulation conditions,H₂S corrosion is the main role.With the increase of temperature,the uniform corrosion rates of C110 and Q125S decrease firstly,and then increase.The minimum corrosion rate occurs about 110?.When the partial pressure of H₂S increases,the uniform corrosion rates of the both materials decrease.But if the pressure of H₂S is above 12 MPa,the corrosion rate of the both materials increases significantly.Corrosions of the both materials are uniform at the partial pressure of H₂S less than 9MPa,while local corrosion is serious when the partial pressure of H₂S is more than 10 MPa.With the increase of the elemental sulfur content,the corrosion rates of the both materials increase,but the local corrosion are slight.When the flow rate of the corrosion medium increase,the corrosion product films of both materials become sparse,uniform corrosion rates increase,and local corrosion become apparent.The results of SSC resistance performance testing show that the C110 has excellent SSC resistance.But the SSC threshold value of Q125S is obviously low because of the high strength and hardness.