Analysis Fatigue Life on Casing Subjected to Cyclic Steam Injection

Casing may experiences failure during its life on specific project. Failure of casing varies from buckling, collapse, leak, and fatigue. Steam injection is one of the causes casing failure due to its thermal expansion, especially in cyclic steam injection. The heating and cooling process from steam injection may results tension and strain in casing interval. The analysis of Stress-Strain & fatigue life on 7” L-80 casing for cyclic steam injection well is presented on this study. A finite element analysis (FEA) is carried out to evaluate the stress-strain and fatigue life of the casing. With given temperature range of 30°-350°C of steam injection, stress-strain is analysed on this study. The subjected casing becomes hot-yielded as the axial compressive stress developed during the injection phase and becomes tensile when the temperature decrease on the soak period or cooling phase. The stresses generated from the thermal expansion load of steam determine the equivalent total strain of the casing and fatigue life of casing is determined using empirical equation. From the results of the analysis, it is obtained 7” L-80 production casing will fail after 811 cycles of heating-cooling process. Moreover, for the steam injection well higher material ultimate strength and ductility shall be taken into consideration in order to get a better and longer fatigue life.