Analysis on the corrosion laws of the tubing and casing in the wells of Dazhangtuo Underground Gas Storage

In order to detect and evaluate the technical situations and actual tubing and casing corrosion situations of the injection and production wells in Dazhangtuo Underground Gas Storage, defect detection was carried out on the tubing and casing of injection and production wells by means of the electromagnetic inspection technology of multi-layer pipe string, and accordingly the wall thickness of tubing and casing were obtained. In addition, statistical analysis was further performed on the residual wall thickness and corrosion rate of tubing and casing. The research results show that the corrosion rate of tubing and casing are more different from the laboratory experimental data before the design of injection and production well and the coupon monitoring test data in the process of the production. What’s more, the actual corrosion of tubing and casing increase with the increase of well depth and the corrosion near the annulus protection fluid and the cement sheath interface and at the wellhead section increases greatly. When the tubing and casing of injection and production wells for gas storage are designed, it is recommended to set the surplus much higher than that of conventional oil and gas wells, especially the ones at the wellhead 200 m section and the lower part. And the reference wall thickness of tubing and casing of injection and production wells for gas storage shall be detected when the well is completed or its service period is within 5 a.