WELLBORE MILL HAVING SHEAR CUTTERS AND GOUGING CUTTERS

摘要

A mill includes a mill body defining a plurality of blades extending in a direction from a center or rotation of the mill body to a gauge surface. The blades define a cutting profile having a minimum diameter at a longitudinal endmost position. The minimum diameter is smaller than a diameter of a drop ball. The cutting profile has an intermediate diameter at most equal to the diameter of the drop ball at a longitudinal distance from the endmost position greater than the diameter of the drop ball. Shear cutters (16) are mounted on at least one of the plurality of blades, mounted such that at least one shear cutter is mounted closer to a center of rotation of the mill body with respect to other cutters mounted to the blades. Gouging inserts (18) are mounted rotationally ahead of the shear cutters.