Research and Application of Shell Changbei Gas Well Corrosion Monitoring Technology

Abstract

Effective corrosion monitoring technology is an important basis for accurately evaluating the corrosion resistance of gas wellbore string materials, exploring the corrosion mechanism and formulating anti-corrosion measures. In this study, two kinds of corrosion specimens, N80 and P110, carried by downhole electronic fishing device, were put into the depth of 955 and 1498 m target wells for 8760 h dynamic corrosion weightlessness test, and the fluid characteristics in gas wells were analyzed. At the end of the experiment, the specimens were taken back and the corrosion rate was calculated. The corrosion morphology was observed by SEM, EDS, XRD and other materials characterization techniques. The element composition and phase composition of the corrosion products were determined. The results show that the experimental wells are mainly hydrogen depolarization electrochemical corrosion caused by the dissolution of CO2 corrosive gas associated with natural gas in a small amount of condensate water and uniformly adsorbed on the surface of carbon steel in the form of water film. The main corrosion products are typical cubic crystal FeCO3. The corrosion products of N80 and P110 specimens at 1498 m are uniformly and compactly adhered to the surface of carbon steel, and the corrosion rate is less than 0.01 mm/a, which can effectively prevent the penetration of corrosion media. However, the corrosion products of 995 m/P110 specimens are loose and easy to fall off, and the grain is sparse. The corrosion tendency of 995 m/N80 specimens is local, and the corrosion of the tubular column will be accelerated with the increase of water production in the later mining process. This technology provides technical support and theoretical basis for the implementation of anti-corrosion measures for gas wellbore string.