92 страниц. 2013 год. LAP Lambert Academic Publishing In this research, a new equation for Mechanical Specific Energy was formulated by incorporating an effective torque equation from a torque-and-drag model among other downhole drilling parameters to estimate energy transferred to the bit. This new MSE equation considered wellbore trajectory for directional wells. This new MSE equation was tested with actual field data. The result shows a high level of accuracy when compared with MSE measurement from a downhole measuring instrument.