A general rock-bit interaction model was developed to determine the bit walk-rate and the best estimate of the lead angle required while kicking off a directional well.

The model was used by a computer program and was validated using the data from 15 directional wells drilled in the offshore Campos Basin area in Brazil. The results showed that the bit walk predictions were good for most of the well trajectories. Due to lack of the appropriate geological information on the history wells, additional field examples are necessary to further validate the model. The results on the lead angle computations showed that it is possible, sometimes, to avoid direction corrections through the appropriate prediction of this angle.