A Technology of FBG Rapid Corrosion Monitoring in Injection and Production CO2-Flooding-Wells

According to the principle of corrosion monitoring with fiber Bragg grating (FBG), which means corrosion rate can be obtained through FBG from the metal part where tiny strain change can be recorded if it is corroded to be thinner in a sensor, an FBG instrument for rapid downhole corrosion monitoring was developed, including a sensor and a modem. Changes of the metal C-type ring in the sensor before and after corrosion were numerically simulated, using ANSYS. The result showed that strain was big in the inner wall of the C-type ring, and the change value of the strain before and after corrosion was big, too. The strain was distributed on the overall cambered surface before corrosion and mainly focused within the corroded area after corrosion. A pilot field trial was then taken, using the instrument. The result showed the corrosion rate was 0.015 mm/a, obtained by weight loss method in 6 months, while the rate was 0.012 mm/a, done by the FBG instrument at the same position only in several hours, which testified the technology was feasible, fast, and effective. Therefore, it is of great significance for rapid downhole corrosion monitoring in CO2-flooding-wells, even for that in natural gas wells.