Research Article
Experimental Study on Sealing Failure Mechanism of Injection-Production String in Underground Gas Storage under Cyclic Loading
Table 4
Methods of thread connection assessment specified by the ISO 13679 standard [
20,
21].
| Connection assessment level | Number of the test piecea | Strictness degree | Test load | Loading mode | Test temperature (°C) | Dura-tions (h) | Limit load test area | Application | Pressurized medium |
| CAL IV | 8 | The strictest | Internal and external pressure, tension, compression, and bending at ambient temperature and high temperature | Cyclic loading | 180 | 50 | Four quadrants of the axial pressure load diagram | Tubing and casing for gas injection and production | Gas |
| CAL III | 6 | Strict | Internal and external pressure, tension, compression, and bending at ambient temperature and high temperature (optional) | Cyclic loading | 135 | 5 | Four quadrants of the axial pressure load diagram | Tubing and casing for gas and liquid injection | Gas |
| CAL II | 4 | Less strict | Internal pressure, tension, compression, and bending at ambient temperature and high temperature (optional) | Cyclic loading | 135 | 5 | Under internal pressure and axial load | Tubing, casing, and protective casing for partial injection and production of gas and liquid | Gas |
| CAL I | 3 | Generally strict | Internal pressure, tension, compression, and bending at ambient temperature (optional) | Cyclic loading | Ambient temperature | — | Tow quadrants of the axial pressure load diagram | Tubing and casing for liquid injection and production | Liquid |
|
|