| 摘要 |
Downhole drilling tools designed and manufactured to reduce bit axial force and torque and enhance drilling efficiency comprising laying out some cutters in one spiral direction of rotation about a bit rotational axis and other cutters in an opposite spiral direction of rotation; evaluating forces acting on cutters during simulated engagement with a downhole formation (straight and transitional drilling); and modifying cutter layout with respect to a spiral direction of rotation. Some embodiments further comprise, prior to simulation, placing cutters in cutter groups/sets at respective locations to obtain a level of force balance. Multilevel force balanced downhole drilling tools may be designed using five respective simulations: cutter group level, neighbor cutter group level, cutter set level, group of N (N=3 or N=4) consecutive cutters level and all cutters level. Cutter layout procedures and algorithms to minimize respective bit forces and in some embodiments to obtain force balance are described. |
