The present dissertation describes a correlation between the bit performance and the state of stress acting upon the rock formation located immediately beneath the bottom of the wellbore. Bit performance data from 6 wells drilled offshore Brazil were collected and anlyzed. In order to reduce the empiricism associated with this type of data analysis, a study is being put forward that considers the geomechanical log along the drilled wellbore. The geomechanical log of a given rock formation is composed of its mechanical properties (Young's modulus, Poisson's Ratio, unconfined compressive strength, internal friction angle, etc.) as well as formation fluid pressure and in situ total stresses. The dissertation shows the metodology to evaluate the stresses at the bottom of the wellbore through a 3D finite element program. Trough these stresses it is possible to define an index of plastification ahead of the drill bit, and bit performance is rated taking this index into account. Some of the wells analyzed were drilled in deep water locations, and the initial results obtained herein, showed a great potential for better understanding for the good and bad performances, regarding the rate of penetration of the drill bit evaluation will be put forward with the great potential for drilling cost savings.