A New Theory on Cutter Layout for Improving PDC-Bit Performance in Hard-and Transit-Formation Drilling

This paper presents a theory on layout PDC cutters in force-balanced groups. A group of cutters consists of two or three single-set cutters, which is able to efficiently remove a ring of rock. By carefully selecting the order of layout cutter groups, a new feature of a PDC bit is obtained: any three or four consecutive cutters on a bit profile may form a force-balanced cutter group, which ensures the efficient removal of any ring of rock. The concepts are verified by a core PDC bit and by a fullscale PDC bit in laboratory tests. Two field applications are provided in the paper to further validate the theory.