1.Dissolved oxygen: Dissolved oxygen in drilling fluid is the main cause of drill pipe corrosion, forming iron hydroxide precipitation. It has two accelerated corrosion mechanisms, one is the depolarization of oxygen; the other is oxygen directly attacks the metal at the anode.
2. Hydrogen sulfide: In an environment where sulfide exists, hydrogen atoms enter the steel and cause hydrogen embrittlement. Maintaining the pH value of drilling fluid above 8 is an effective method to control hydrogen sulfide corrosion. In addition, sulfide stress cracking of steel is closely related to temperature, external stress or residual stress, and the metallographic structure and chemical composition of the steel itself.
3. Carbon dioxide: When dissolved in water, carbonic acid is formed, and the corrosion characteristic is pit corrosion. The intensity of corrosion depends on the partial pressure of carbon dioxide and the pH value.
4. SRB: Bacterial corrosion, especially sulfate-reducing Bacteria (SRB), is a major corrosive bacteria causing corrosion of oil casings.
