Combination coring bit and drill bit using fixed cutter PDC cutters

摘要

A drill bit having fixed Polycrystalline Diamond Compact cutters is used to drill a borehole having a core stump therein. A plurality of additional fixed Polycrystalline Diamond Compact cutters are disposed in the dome of the bit and are usable to concentrate stresses in the top end of the core stump to facilitate the cutting down of the core stump.

主权项

1. A fixed cutter, polycrystalline diamond compact drill bit for drilling oil and gas wells, comprising:
a carbide matrix bit body having a male threaded end and blades at a second end of said bit body, each of said blades having a first plurality of polycrystalline diamond compact cutters mounted therein, said blades being spaced from each other such that the rotation of the drill bit causes a cutout into the earth formation while leaving a core stump in the center of a drilled borehole, a second plurality of polycrystalline diamond compact cutters attached to said blades in a recessed region above the first plurality of polycrystalline diamond compact cutters, wherein each of said blades is separated from an adjacent blade by a space therebetween, wherein the space radially extends through the entire radial width of the blades adjacent the first plurality of polycrystalline diamond compact cutters, wherein the space radially extends through the entire radial width of the blades adjacent the second plurality of polycrystalline diamond compact cutters, wherein each of said blades further comprises an inner gauge relief for enabling freestanding of the core stump unsupported by said blades, and wherein the second plurality of polycrystalline diamond compact cutters contact a top surface of the core stump to thereby increase stress concentrations in the periphery of the core stump and thereby rupture and facilitate the drilling of the core stump.