Abstract:Dengying Formation stratum has become an important stratum for Sinopec to increase natural gas storage and production in Sichuan Basin and improve national energy security. Due to unclear understanding of the mechanical properties of dolomite in the ultra-deep high-temperature Dengying Formation， it often leads to instability of the dolomite wellbore. By conducting uniaxial compressive strength experiments of dolomite at 25℃ （room temperature）， 100℃， 150℃， 180℃， 200℃， and 220℃， the uniaxial mechanical strength and deformation characteristics of dolomite were revealed. The dolomite in the Dengying Formation will exhibit significant brittleness enhancement with increasing temperature within a certain temperature range （100~220℃）， which is believed to be the reason why the peak strength of the dolomite in the Dengying Formation decreases with increasing temperature. Based on the strain Equivalence principle， the damage deformation constitutive model of dolomite in Dengying Formation after high temperature is established. The comparative study shows that：（1）The stress-strain curve drawn by the constitutive model is in good agreement with the experimental curve， and the model can fully reflect the damage process of dolomite in Dengying Formation at different temperatures； （2）This model can accurately characterize the strength and deformation parameters of dolomite at different temperatures， providing a more scientific and rigorous model for wellbore stability analysis， and improving the geological understanding of ultra-deep to ultra-deep complex formations in key areas and the ability to prevent and control complex faults during drilling and completion.