This operating well is an injection-production well in a gas storage reservoir. The well uses a three-string drilling design, with a maximum inclination angle of 21.4°, and the final drilled depth is 2586 meters.

During the second gas injection cycle of the well, all three annular spaces (A, B, and C) were pressurized.

Our company employed a steel wire operation method to lower the optical fiber to the target layer, performing pressure relief and pressure recovery tests on each annular space. We collected temperature and vibration data from the downhole distributed system under eleven different working conditions. Based on these data, we carried out interpretation of the distributed fiber optic sensing data and identified the categories of well integrity and the depth intervals at which well integrity issues occurred under the condition of pressurized annular spaces in the single well. The well has multiple well integrity issues, with gas injection along the annular space due to failure of the cement seal at the casing shoe being the source of the energy for the pressurization in the annular spaces.

With the high-precision distributed fiber optic temperature monitoring system (DFA) and vibration monitoring system (DAS), we achieved precise detection of the wellbore technical condition during the gas injection process in the gas storage reservoir. The monitoring system identified the location of losses and external annular migration, further determining the cause of the pressurized annular spaces. This provided a basis for later evaluating the casing column and wellbore sealing conditions, as well as for adjusting well integrity.