Mechanical analysis on cement sheath integrity under asymmetric load

Abstract In large-scale multi-section hydraulic fracturing, the stress environment of wellbore is extreme complex, often causing unbalanced distribution around wellbore. That poses great challenges to integrity sheath. this paper, firstly, triaxial compression test and cyclic are carried out at 130 °C study deformation characteristics cement under high temperature. Then based on that, an appropriate plastic mechanics model established. Finally, shakedown theory applied analyze acquires a maximum loading asymmetric stress. The result shows that (1) well cement, with increase load, flow can be regarded as ideal elastic–plastic material (2) During unloading process, "hysteresis loop" becomes denser, which indicates accumulation rate continuously declining. main strain appears in phase first loading. (3) external pressure P z plays positive role control With growth , max will also increase. (4) Asymmetric significantly affect bearing capacity If difference coefficient λ = 0.3, tends decrease nearly by 50%. λ, negative influence asymmetry reduces gradually. High beneficial reduce impact asymmetry. benefit enhance. (5) engineering practice, if geology wellhole showcases strong (the value large), some steps need adopted concentration.