Systems and Methods for Determining and/or Using Estimate of Drilling Efficiency

A system comprising:

• a borehole assembly comprising a drill bit configured to drill into a geological formation as a weight-on-bit and a torque-on-bit is applied, wherein the drill bit wears down as the drill bit drills through depths of the geological formation to a greater extent through parts of the geological formation having a greater intrinsic energy;
• a measuring assembly for obtaining a plurality of measurements of weight-on-bit and torque-on-bit, at least during a period in which weight-on-bit and torque-on-bit are non-steady-state;
• and
• a data processing system configured to use the plurality of measurements of weight-on-bit and torque-on-bit to estimate one or more drilling efficiency parameters relating to the drilling of the geological formation during the period.