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 levelNumber of the test pieceaStrictness degreeTest loadLoading modeTest temperature (°C)Dura-tions (h)Limit load test areaApplicationPressurized medium

CAL IV8The strictestInternal and external pressure, tension, compression, and bending at ambient temperature and high temperatureCyclic loading18050Four quadrants of the axial pressure load diagramTubing and casing for gas injection and productionGas

CAL III6StrictInternal and external pressure, tension, compression, and bending at ambient temperature and high temperature (optional)Cyclic loading1355Four quadrants of the axial pressure load diagramTubing and casing for gas and liquid injectionGas

CAL II4Less strictInternal pressure, tension, compression, and bending at ambient temperature and high temperature (optional)Cyclic loading1355Under internal pressure and axial loadTubing, casing, and protective casing for partial injection and production of gas and liquidGas

CAL I3Generally strictInternal pressure, tension, compression, and bending at ambient temperature (optional)Cyclic loadingAmbient temperatureTow quadrants of the axial pressure load diagramTubing and casing for liquid injection and productionLiquid