Patent ID: 8678111

Claim:
A method of varying a cutting rate of a bit used during drilling a well, the bit having a bit body, at least one fixed blade cutter depending downwardly from the bit body, at least one frustoconical rolling cutter mounted for rotation on a bit leg depending downwardly from the bit body, a plurality of cutting elements arranged on a leading edge of the at least one fixed blade cutter and wherein the plurality of cutting elements are disposed in parallel with at least one row of back-up cutters arranged between the leading edge of the at least one fixed blade cutter and a trailing edge of the at least one fixed blade cutter, wherein at least one of the plurality of cutting elements on the leading edge of the fixed blade is located at or within about 0.040 inch of a central axis of rotation of the bit body, and a plurality of cutting elements arranged on the at least one frustoconical rolling cutter, the method comprising: defining an aggressiveness of the bit as a function of penetration rate of the bit during drilling to weight-on-bit during drilling; and adjusting the aggressiveness of the bit by one or more methods selected from the group consisting of: adjusting the angular distance between each frustoconical rolling cutter and each fixed blade cutter; adjusting the effective projection between at least two adjacent cutting elements on a frustoconical rolling cutter, wherein the frustoconical rolling cutter is truncated in length; arranging the cutting elements of the at least one fixed-blade cutter and the cutting elements of the at least one frustoconical rolling-cutter so that one of the rolling-cutter and the fixed blade cutter leads the other; and arranging the cutting elements of the at least one fixed-blade cutter and the cutting elements of the at least one frustoconical rolling-cutter on an opposing rolling cutter and fixed blade cutter so that the cutting elements of the at least one fixed-blade cutter and cutting elements of the at least one frustoconical rolling-cutter fall in the same kerf during drilling operations, wherein the cutting elements of the frustoconical rolling cutter are arranged to lead the cutting elements on the fixed blade cutter which is angularly spaced apart from the rolling cutter approximately 180 degrees; wherein the aggressiveness is further defined by the position of the at least one row of back-up cutters with respect to the leading edge of the at least one fixed blade cutter.