Contact stress analysis of a packer based on shape memory polymers using finite element method

Shape memory polymers (SMPs) possess multiple advantages as a sealing element for a packer. The contact stress between the SMP rubber and a casing (or the formation) is an essential indicator in evaluating the sealability of packers. This work conducts a finite element simulation based on the generalized Maxwell viscoelastic model and the time-temperature equivalence (TTE) principle to analyze the contact stress during the setting. The proposed model simulates the mechanical response of the polymer, including the stretch at a high temperature, cooling with a fixed shape, unloading at a low temperature, the shape recovery with reheating, and the stress relaxation. The results show that the contact stress distribution in the middle section of the packer is relatively uniform. The average contact stress is over 7.5 MPa and meets sealing needs. More significant stresses occur at the shoulders of the packer due to stress concentration. Both the shape recovery and the stress relaxation finish fast that it needs about 228.7 s to obtain stable contact stress after shape recovery. This study provides a method to evaluate the performance of the packer based on SMPs.