A method of determining 'walk rate' of a rotary drag-type drill bit.

摘要

A prediction method for use with drill bits of the kind where the leading face of the bit body 10 is formed with a central depression or cone 16, comprises the steps of: calculating the cone volume VSBcone/SB of the bit, calculating the percentage TSBcone/SB/TSBbit/SB of the total torque generated by the cutters 15 on the bit which is attributable to those cutters which are mounted in said cone; calculating a Walk Factor, FF = VSBcone/SB x TSBcone/SB/TSBbit/SB/F ; and then determining the predicted walk rate W of the bit from a graph (eg figure 3), or other database, relating previously established values of F for other drill bits to the respective walk rates W for those drill bits.