因稠油热采井周期性蒸汽吞吐,井筒面临循环高温服役工况,造成水泥石力学性能损伤、下降,引发水泥石完整性失效。基于此,模拟井下实际工况,提出了超高温热循环作用下水泥石力学损伤行为的特色测试方法,建立了全尺寸“生产套管—水泥石—技术套管”组合体实验装置,结合取芯技术,开展了30~300 ℃、30~350 ℃和30~400 ℃热循环作用下普通和热采水泥石力学性能测试,对比了普通和热采水泥石力学行为差异,定量获得了热循环作用下普通和热采水泥石损伤因子,揭示了超高温热循环作用下水泥石力学损伤机理。结果表明,热采水泥石在热循环作用前后的力学性能均优于普通水泥石力学性能,这主要与热采体系固有的耐高温能力和三轴状态下的延性有关,热采水泥体系的延性可有效降低热循环作用引发的疲劳损伤,使损伤程度远低于普通水泥损伤程度。此外,超高温热循环作用下普通和热采水泥体系均不可避免地发生强度衰退,损伤来源包括了化学损伤、疲劳损伤和附加疲劳损伤。研究结果可为水泥石损伤力学理论研究提供参数和依据。

The wellbore undergoes cyclic high-temperature service conditions in heavy oil thermal recovery wells due to periodic steam huff-and-puff operations, leading to mechanical property degradation and damage in the cement stone, ultimately causing its integrity failure. In response, a novel test method was developed to characterize the mechanical damage behavior of cement stone under ultra-high-temperature thermal cycling by simulating actual downhole conditions. A full-scale experimental device for the “production casing—cement stone—technical casing” assembly is developed. Using coring technology, mechanical property tests are conducted on both conventional and thermal recovery cement stones after typical thermal cycling at 30~300 ℃,30~350 ℃, and 30~400 ℃. The differences in mechanical properties between the two cement systems are compared, the damage factors of common and thermal recovery cement stones under thermal cycling are quantitatively determined, revealing the cement stone mechanical damage mechanisms under ultra-high-temperature conditions. The results indicate that the mechanical properties of the thermal recovery cement stone exhibits superior mechanical performance compared to conventional cement stone before and after thermal cycling, primarily due to its inherent high-temperature resistance and ductility under triaxial stress conditions. The ductility of the thermal recovery cement system can effectively mitigate the fatigue damage caused by thermal cycling, resulting in a significantly lower damage than in conventional cement. However, both cement systems experience unavoidable strength degradation under ultra-high-temperature thermal cycling, with damage stemming from chemical degradation, fatigue, and additional fatigue-related effects. The research findings can provide parameters and basis for the theoretical study on cement stone damage mechanics.