The Analytical Model for Elastic Deformation of Cement Sheath in Well Cementing

During oil and gas extraction, alternating wellbore pressures can induce cyclic loading, which can potentially lead to structural damage of the casing cement sheath, posing safety risks.An analytical model for the elastic deformation stage of the cement sheath was developed to investigate its mechanical response and failure modes during well operations.A casing-cement sheath-formation system model and thick-walled cylinder theory were utilized.Analytical expressions for the elastic deformation stage were derived.These expressions were validated through finite element analysis.Results show that, the cement sheath primarily fails in either tensile or compressive modes.As the elastic modulus increases, a transition from compressive to tensile failure modes occurs.When the elastic modulus exceeds 40 GPa, the effect on radial stress stabilizes.Moreover, when the casing pressure reaches 60 MPa, the cement sheath expands outward, transitioning from a compressive state to a tensile state in the circumferential direction.This study provides valuable insights for analysing mechanical response parameters and evaluating the safety of the casing cement sheath during operations.