High shear roller cone drill bits

摘要

A drill bit includes a bit body comprising at its upper end a connection adapted to connect to a drill string and at its lower end a plurality of journals extending downwardly and radially outward from a longitudinal axis of the bit. A plurality of roller cones are rotatably mounted on the plurality of journals and at least three rows of cutting elements are disposed on each of the plurality of roller cones. The outermost row of the at least three rows of cutting elements has an extension height to diameter ratio greater than a mid row, and the mid row has an extension height to diameter ratio greater than an innermost row.