The parallel track scraping principle of conventional PDC bits largely limits the cutting efficiency and working life in deep formations. Cross-cutting polycrystalline diamond compact (PDC) bit may be an efficient drilling tool that increases the rock-breaking efficiency through both cross-cutting and alternate-cutting modes of the PDC cutter. The motion track equation of the cross-cutting PDC bit was derived by using the compound coordinate system, and the motion track was analyzed. Meanwhile, through the unit experiment and discrete element simulation, the cutting force, volume-specific load, and crack propagation were analyzed under different cutting modes. Through establishing a nonlinear dynamic model of the bit-rock system, the speed-up mechanism of the novel bit was analyzed based on rock damage, rock stress state, and motion characteristic of the bit during the rock-breaking process. Compared with unidirectional cutting, cross-cutting produces less cutting force, more brittle fracture, and a greater decrease of formation strength. The novel PDC bit can put more rock elements into a tensile stress condition than a conventional PDC bit, and the plastic energy dissipation ratio of the cross-cutting PDC bit is lower while the damage energy consumption ratio is higher than they are for conventional bits, which is beneficial to increasing the ratio of fracture failure and improving rock-breaking efficiency. Laboratory drilling tests show that the cross-cutting PDC bit can create mesh-like bottom-hole features. Drilling contrast experiments show that a mesh-like bottom-hole pattern can be obtained by using the cross-cutting PDC bit, of which the ROP is obviously higher than that of the conventional bit when drilling in sandstone or limestone formation. Meanwhile, the influence of deviation angle, weight on bit, and rock properties on cutting efficiency of the cross-cutting PDC bit are studied.

中文翻译：

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交叉切割多晶金刚石紧凑钻头钻削效率的研究

常规PDC钻头的平行履带刮擦原理在很大程度上限制了深层地层的切割效率和工作寿命。横切多晶金刚石复合片（PDC）钻头可能是一种有效的钻探工具，可通过PDC切刀的横切和交替切割方式提高破岩效率。利用复合坐标系推导了横切PDC钻头的运动轨迹方程，并对运动轨迹进行了分析。同时，通过单元实验和离散元模拟，分析了不同切削方式下的切削力，体积比载荷和裂纹扩展。通过建立钻头-岩石系统的非线性动力学模型，基于岩石的破坏，岩石的应力状态，对新型钻头的提速机理进行了分析，破岩过程中钻头的运动特性。与单向切割相比，横向切割产生的切割力更小，脆性断裂更大，并且成形强度降低更大。与传统PDC钻头相比，新型PDC钻头可将更多的岩石元素置于张应力条件下，横切PDC钻头的塑性能量耗散率更低，而破坏能量消耗率则高于常规PDC钻头。有利于提高断裂破坏率，提高破岩效率。实验室钻探测试表明，横切PDC钻头可产生类似网眼的井底特征。钻探对比实验表明，使用横切PDC钻头可以获得网状的井底图案，其中在砂岩或石灰岩地层中钻探时，ROP明显高于常规钻头。同时，研究了偏角，重量对钻头和岩石特性的影响对横切PDC钻头的切削效率的影响。