Abstarct: Over the past decades, numerical methods have been used as an effective tool for predicting rock mass engineering behavior. The ability to simulate simple continuous environments to environments with complex, ductile, hydraulic, and creep conditions with high speed and precision as well as the ability to consider changes in material behavior over time in different aspects of mechanical, thermal and Hydraulics have increased the tendency to use these methods in solving geomechanical problems. The casing collapse of the oil wells influenced by ductile formations time-dependent behaviors, is one of the challenges faced by the oil industry in the country. In order to investigate the effect of creep as a ductile formation time dependent behaviors on casing collapse of oil wells, one of the Kupal Oil wells has been modeled by using the finite difference numerical method and FLAC3D software because of the special conditions of the Kopal oil field in terms of the presence of salt formations under High-stress conditions. Field data such as in situ stresses and mechanical properties of the formation around the well at the desired depth should be carefully applied in the model since the numerical modeling response is highly dependent to the input data. In this research, in order to establish a basic model and confirm the results of modeling, a similar study in the area was conducted due to the inability to access geomechanical data. A three-dimensional model of formation surrounding well in the FLAC3D software was built after selecting the numerical software according problem conditions. At the first initial and boundary conditions have been applied in 3D model. Then different stages of drilling, applying Mud pressure, casing instalation and cement injection have been modeled. Finally analysis the long-term stresses, the amount and pattern of the deformations of the casing in various geomechanical and operational conditions have been investigated regardless of the effect of temperature. It is availible to examine both possible types of damage to the interstitial casing, namely, the local shear at the salt laxyer and the adjacent laxyers interfac, and also the examination of the casing in the vicinity of the salt formations which have visco-plastic behavior because of modeling attribute of the formation around the wells. baxsed on the results, the creep behavior of the salt laxyer in addition to time is a function of the stress distribution and the geometric properties of the salt formation. The shear deformation pattern of the casing is more likely than reduction diameters deformation to occur in the cases of diffrantial stresses distribution around the well. On the other hand, the study of the role of well completion parameters in preventing damage to the casing shows the major role of the elastic modulus of cement sheath in the first degree and the casing grade in the second degree. It should be noted that the parameters such as the thickness of the cement sheath, the diameter/the wall thickness ratio and the cohesion strength of the cement sheath are of relative importance.