Analysis of the causes of tubing corrosion in shale gas wells and research on countermeasures

To study the causes of tubing corrosion in a shale gas well, XRD, SEM and EDS are used to analyze the composition of corrosion products, surface morphology and elemental composition on the surface of the riser tubing. The results show that there is scale/corrosion product adhering to the outer wall of this oil pipe, and the deeper the depth, the more serious the scale/corrosion product. No obvious pitting corrosion/local corrosion is found on the outer surface of the oil pipe after removing the scale/corrosion product. The male buckle of the oil pipe is corroded and incomplete, while the female buckle is basically not corroded. The results of SEM/EDS and XRD detection show that the elements of the corrosion products on the outer surface of the oil pipe are almost all O and Fe, with a small amount of C and Cl. The proportion of Fe₃O₄ is the highest, ranging from 60% to 70%, the content of Fe₂O₃ is about 15%, and Al₂O₃, SiO₂ and FeCO₃ are relatively small, each accounting for approximately 2-3%. It is determined that the main cause of the tubing corrosion in this shale gas well is oxygen corrosion based on the experimental test results, along with slight carbon dioxide corrosion. For the current corrosion on the outer wall of the oil pipe, it is recommended to adopt corrosion protection measures such as controlling the oxygen content, optimizing the types of corrosion inhibitors, and applying coating protection.