The objective of this paper is to develop a better understanding of the performance of the casing -cement bond under HPHT well conditions, leading to a model to predict well life. An analytical model of wellbore stresses based on wellbore parameters was developed. The new model considers the casing as a thin wall cylinder, while cement and formation are modeled using a thick wall cylinder theory. Also the equivalent stress is calculated using different failure criteria that allow the user to simulate all possible load conditions on the casing-cement-formation system. The results were confirmed by finite element simulations. The new model that was implemented in an easy to use calculation sheet will give production engineers a simple tool to estimate the well integrity under various downhole conditions.