Asmari formation in Mansuri oil field is a complex geological environment. Variation in proportion of different lithologies (sandstone, limestone, and dolomite) in this formation poses serious challenges to drilling and production management, and makes it difficult to evaluate lithological and geomechanical characteristics of reservoir formation.Wellbore instability and formation damage could substantially decrease drilling and production efficiency. Drilling of Asmari formation is almost always accompanied with mud loss causing damage to the reservoir formation. With developing a consistent mechanical earth model, an appropriate mud weight window is suggested based on formation strength and induced stress along the wellbore. Choosing an optimum mud weight would prevent fracturing the reservoir and losing mud into formation. Hence, drilling time and production rate of Asmari formation would improve considerably.In this paper, laboratory testing on cores such as triaxial compressive test and ultrasonic test under confining pressure of reservoir provides experimental data to establish precise correlation between compressional and shear velocity and calibrate dynamic elastic properties resulting from sonic and density log. In addition, static elastic properties and mud logging data is used to assess induced stresses due to drilling of the formation. As a result, an accurate geomechanical model is constructed in minimum error since a complete set of data required to perform a proper evaluation is available. In addition, numerical modeling as well as analytical one is employed to analyze stresses and strains around the wellbore, especially in complex, heterogeneous areas. Suggested mechanical earth model helps petroleum engineers evaluate geomechanical characteristics of reservoir formation in spite of its natural heterogeneity, make field development and well construction decisions accurately, and overcome the challenges of this complex area throughout the life of the field.