Study on Corrosion of Gas Injection Well with Oxygen-Reduced Air Flooding in Gasikule E31 Reservoir

E31 reservoir in Gaskule Oilfield in the Qaidam Basin has entered the high water cut stage. In order to further increase the recovery rate, an oxygen-reduced air gravity flooding development test has been attempted since 2019. Affected by high temperature, high pressure, and high salinity conditions in the reservoir, the corrosion evaluation and prevention of gas injection pipe string has become a key factor affecting whether the oxygen-reduced air gravity drive can be carried out successfully. In this paper, the characteristics of oxygen corrosion of J55, N80, P110 and 13Cr steels in Gasikule E31 reservoir conditions and 0–21% oxygen concentration were studied by weight loss method combined with scanning electron microscope; Analysis of Corrosion Products of Gas Injection String Using XRD Method; Evaluate the mine field corrosion behavior according to the corrosion failure of the gas injection pipe string. The results show that: under the conditions of 126 ℃, 30 MPa, and reservoir flood water conditions, the 13Cr material tubing can meet the anti-corrosion requirements (annual corrosion rate ≤0.076 mm/a) when the oxygen content is less than 1%, and other materials cannot meet the requirements. When the oxygen concentration exceeds 3%, the corrosion rate of each material increases rapidly. The current corrosion types in the test area include oxygen corrosion, CO2 corrosion, H2S corrosion and under-deposit corrosion, mainly oxygen corrosion. The pipe string above the packer is combined with the existing anti-corrosion measures, and the corrosion is controllable. The corrosion of the pipe string below the packer is more complicated, and the prevention and control methods are limited, and further research is needed.