Theoretical Analysis of the Micro Annulus of an Oil-Well Cement Sheath Formed via Cooling under Acid-Fracturing Conditions

The plastic deformation and interface micro annulus of oil-well cement during acid fracturing are key reasons for the failure wellbore seal sustained casing pressure. However, most existing research ignores influence cooling effect fracturing, owing to which, design conditions in theoretical analysis may be inconsistent with those actual wellbore, calculation results biased. In this study, a novel elastoplastic mechanical model sheath was established. This can analyze yield state under three-dimensional principal stress consider differential temperature on debonding from beginning end fracturing. Moreover, generation mechanism development law were clarified. findings indicated that intermediate cannot ignored; otherwise, conservative. During casing–cement is influenced by stress, debonded; however, not generated. sheath–formation occurs only when completely plastic. After likely generated at interface, presence increase formation risk annulus. provide guidance prediction seals acid-fracturing conditions.