| 摘要 |
Drill bit with multiple stages of durability and ROP characteristics is disclosed. The drill bit has multiple layers of cutters established by deploying the cutters on blades of different heights or maintaining the blades at the same height and deploying the cutters to have different heights on one or more blades. Each layer provides independent bottom hole coverage and has independent stabilization, ROP, and durability characteristics so as to effectively drill through different subsurface formations. Cutters deployed on the different layers have their respective centers at substantially different radial positions. Due to the different radial positions, cutters in different layers cut different swaths in the subsurface formation. Cutters in different layers may also have different initial peripheral portions or shear lengths, resulting in different impact resistance characteristics for the different layers. This changes the wear and/or cutter deterioration processes for the different layers, resulting in different and/or improved toughness characteristics.
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