适用于砾石夹层钻进的PDC钻头

Research on PDC bit for drilling in gravel interlayer.

PDC钻头在砾石夹层中钻进时钻头不平稳、PDC复合片崩裂、磨损消耗快、机械钻速低,针对这些问题,采取了两方面的措施:一是创造条件使PDC钻头工作平稳,即减少或分散PDC钻头所承受的冲击载荷;二是减少钻头上PDC复合片在工作中的崩裂与磨损。具体的设计方案是:通过优化设计PDC钻头结构,主要采取外抛内锥带辅助切削齿的形式结构;研制与选取PDC复合片,主要采用双向多条直槽非平面结合方式,提高了复合片质量,使其热稳定性为750℃,耐磨性为2.9×105,抗冲击性大于600 J。按此方案设计与生产了3只钻头,分别在3口中井试用,直接钻穿砾石夹层馆陶组地层井段,相比之下,研制的新型PDC钻头,钻井效率提高26%,较大幅度地提高了钻井速度,突破了砾石夹层钻进不能使用PDC钻头的禁区,具有推广价值。

Abnormal conditions like instability of drilling,breakage of PDC,high wear of bit crown,low penetration rate and service life etc.will often occur when PDC bits were used to drill gravel interlayer formation,In order to relieve these conditions,the following two measures had been adopted in designing and manufacturing PDC bits:(1) to improve the working conditions of PDC bit,namely reduce or distribute the impact load acted on PDC bit which is related to designation of PDC bit structure.(2) to select proper PDC to reduce the conditions of its break or wear.Based on above two considerations,a kind of bit combination structure of bit crown with outside parabola-inside cone features and aided cutting edges has been adopted and PDC with non-plane multi groove binding is selected.The selected PDC can reach 750 ℃ in thermal stability,2.9×10~5 in wear resistance and more than 600 J in impact toughness.3 bits were produced according to the ideas and tried to drill in 3 exploration wells.All the three bits drill through the specified gravel interlayer and Guantao formations,while in the same formations in the nearby wells the drilling method using tri-cone bit first and then PDC bit.Had made a breakthrough in drilling the gravel interlayer formation which was not allowed to drill with PDC drill bits.These data show that drilling efficiency is improved by 26%,the new type of PDC bit has advantages in drilling gravel interlayer formation.