An Improved FBG Rapid Corrosion Monitoring Technology and Application

In recent years, Fiber Bragg Grating (FBG) corrosion monitoring technology has gradually become a research hotspot in the field of oilfield corrosion monitoring. In previous studies, an FBG downhole rapid corrosion monitor was developed, in which the sensor was a C-shaped ring structure, and the minimum diameter after encapsulation could only reach 26 mm. In the pilot field test, it was found that due to the influence of the tubing collars in the eccentric annulus between tubing and casing, during fishing process, there often existed some problems such as tool string jamming, wear and deformation, which sometimes even led to sensor damage. Aiming at the above problems, based on the principle of FBG corrosion monitoring, the sensor structure was redesigned and optimized, and a new integrated sensor with a diameter of 22 mm and a pressure bearing capacity of 35 MPa was developed, of which the impact resistance was increased. A 120 °C high temperature resistant adhesive was also developed to encapsulate the integrated sensor successfully. In addition, a noise reduction circuit was developed to enhance the anti-interference ability of the demodulator and ensure a stable signal output. Using the improved monitor, up to now, five well field tests have been completed in the CO2-flooding production wells. The results show that the tool string fishing is smooth and safe, and the integrated sensor has high reliability and smaller size, which can work continuously for a long time in high temperature, high pressure and strong corrosion downhole environments. The improved technology has high application value for CO2-flooding injection and production wells and natural gas wells downhole and surface gathering and transportation rapid corrosion monitoring.