Abstract: PDC bits are generally inadaptable for drilling hard formation,especially for the gravel layer with high compressive strength and abrasion.Under such extreme conditions,the impact abrasion will severely decrease the durability of PDC cutters.A fully embedded back-up cutter technology for design of a new PDC bit can remarkably enhance its durability.The new technology can provide successive back-up cutting structure added on the ordinary cutters.The back-up cutters were placed beneath the primary cutters and fully embedded into the matrix body in conjunction with primary cutters to form a complex cutting structure capable of penetrating rocks successively.The embedded cutters start to work only after the primary cutters overhead worn out.Therefore,the life of PDC bit can be longer.The patented technology was applied successfully in drilling basal conglomerate formation of LD Oilfield in Bohai Bay of China,which greatly improved the drilling efficiency and reduced drilling cost.

Key words: PDC bit, embedded back-up cutter, hard formation, drilling tool, cutting structure, cutting capability

摘要： PDC钻头不适宜钻硬地层,尤其是高强度、高研磨性的砾石层,因为在极其恶劣的工作条件下,PDC齿的冲击破损严重,热磨损及磨料磨损往往同时存在,齿的磨损速度快,钻头的工作寿命急剧缩短.研究了一种新的PDC钻头技术--内镶式二级齿技术,可以使PDC钻头在极限应用条件下的持续破岩能力显著增强.内镶式二级齿是在常规的切削结构基础上增加的后备PDC切削结构,二级齿位于主切削齿的上方,除金刚石表面外,齿的其他部分全部隐藏在胎体内部,为负出露切削齿.主切削齿和二级齿相组合,构成了可连续接替切削岩石的复合切削结构.在主切削齿的切削破岩能力丧失或接近丧失时,二级齿开始工作,显著增加了钻头的工作寿命.新技术应用于渤海LD油田钻底砾岩,提高了钻井时效,降低了钻井成本.

关键词: PDC钻头, 内镶式二级齿, 硬地层, 钻井工具, 切削结构, 破岩能力