Research on the Variation Law of C-ring Sealing Performance of the Steam Injection and Soak Period in Heavy Oil Recovery

Abstract The heavy oil resources in the Bohai Lvda (LD) Oilfield have the characteristics of high viscosity and poor fluidity, therefore, it is necessary to inject steam for efficient development. According to specific regulations, heavy oil thermal recovery wells must be equipped with a high-temperature resistant Surface Controlled Sub-Surface Safety Valve (SCSSV). However, observations in 2022 revealed several instances of hydraulic leakage in these valves, primarily due to severe deformation of the internal C-rings. To investigate this issue, this study employed the Abaqus software to simulate the stress state of C-rings within SCSSV throughout the entire steam injection and soak period, with a special focus on the sealing performance variation of metal C-rings at various contact interfaces. The findings highlight that the primary causes of diminished sealing performance are localized plastic deformation of the metal C-rings induced by heating and subsequent shrinkage upon cooling. Furthermore, the movement of the piston within the safety valve significantly impacts the stress magnitude at some C-ring part sealing performance. Additional investigations reveal that different installation methods of C-rings lead to varying patterns in sealing performance. Notably, excessive interference between the C-ring and piston should be avoided, as it results in more severe plastic deformation upon cooling, further diminishing the sealing performance of the C-rings post-cooling. The insights gained from this study are of paramount importance for the improvement and design optimization of C-rings in SCSSV used in thermal recovery wells of heavy oil. Offering significant value in enhancing the safety and efficiency of offshore heavy oil Recovery. Moreover, this research provides new theoretical support and practical guidance for related engineering practices and academic inquiries.