Safety analysis of casing with considering strength degradation in steam-injection well

摘要

Casing damage is a very severe problem in steam-injection well due to thermal stress. In this paper, the computational model of casing-cement-formation coupling system is established. Considering strength degradation of casing, the temperature field and stress field are coupled to calculate casing stress. Related factors, such as concentric casing, cement thickness, casing specification and internal pressure, are considered to analyze casing safety. The results show that yield strength of N80 casing reduces as a linear function with temperature variation. There is little effect of cement thickness and casing specification on the thermal stress. Von Mises stress decreases with increase of steam injection pressure in wellbore as the casing doesn't yield. Based on the results, some measures against casing damage are presented.