非平面PDC切削齿破岩有限元仿真及试验

The Finite Element Simulation and Test of Rock Breaking by Non-Planar PDC Cutting Cutter

  • 摘要: 为了指导PDC钻头设计,对三棱形和斧形PDC切削齿、常规平面PDC切削齿的破岩性能进行了研究。利用有限元软件建立了PDC切削齿直线切削岩石和垂直压入岩石的三维有限元模型,模拟了相同布齿角度下、不同形状PDC切削齿垂直压入岩石和不同切削深度直线切削均质岩石及非均质岩石的过程,发现不同形状PDC切削齿的破岩过程存在明显差异。与常规平面PDC切削齿相比,三棱形PDC切削齿更易压入地层形成破碎坑;三棱形和斧形PDC切削齿破碎均质砂岩时所需的切削力较小,岩石产生的预破碎区域更大,破碎非均质岩石时的切向力波动幅度小,更易破碎岩石。根据模拟结果,设计研制了三棱形切削齿PDC钻头,并在钻进混合花岗岩地层时获得较好的效果。研究结果表明,有限元模拟可为PDC钻头设计提供参考。

     

    Abstract: In order to provide references for PDC bit design, the rock breaking performance of triangular prism, axe-shaped and the conventional planar PDC cutting cutter was studied. 3D finite element models of vertical press-in and linear cutting into rocks were established by using finite element software, which simulated the processes of vertical press-in by cutters with the same tooth arrangement angle, and linear cutting of homogeneous/heterogeneous rocks with different cutting depths. It is found that there are significant differences in rock breaking, depending of the shape of the cutters, which can be quite different shapes. Compared with the conventional planar PDC cutters, triangular prism PDC cutters are more easily pressed into the formation to form a crushed pit. When breaking homogeneous sandstone, triangular prism and axe-shaped PDC cutters require less cutting force, and they establish a uniform contact with the rock, resulting in creating a larger pre-crushing area of the rock. For breaking heterogeneous rocks, the tangential force fluctuation of the triangular prism and axe-shaped PDC cutters is small, and it is more easily to break the rocks. According to the simulation results, the test of mixed granite stratum drilling with PDC bit with triangular prism cutters was conducted, and the test results showed that the finite element simulation could provide references for the design of a PDC bit.

     

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