Study on Fracture Failure Behavior of Super 13Cr Tubing Caused by Deposited Corrosion

Abstract

Fracture failure of super 13Cr can occur in complex and harsh environments such as high temperature, high pressure, and corrosive gas wells, which damages the economic benefit of oil and gas development and also poses a great threat to wellbore integrity. Therefore, it is urgent to study the corrosion mechanism of super 13Cr tubing in oil and gas wells, and this study performed an on-site experimental analysis on failed super 13Cr tubing, employing the microarea electrochemical scanning Kelvin probe (SKP) method to investigate the causes of corrosion of super 13Cr material. In addition, the thermodynamics of the mechanism by which pits turn into cracks was examined in light of the experimental findings on the nucleation and development of pitting corrosion. The findings reveal scale and clear pits on the surface of the failed super 13Cr tubing and that CaCO3 as well as FeCO3 are the scale’s primary constituents. According to the SKP scan results, the super 13Cr tubing has a risk of pitting under wells, and the galvanic cell with microcorrosion is the primary cause of pitting corrosion, which also shows that the potential difference between the anode area and the cathode area of the super 13Cr material gradually increases with the increase in immersion time. Under the autocatalytic effect of the occlusive corrosion cell and the applied load, the corrosion pits and cracks of super 13Cr tubing propagate, eventually leading to tubing breaks and failure.