钻头选型中的因素分析(Fahd).ppt

Bit Design Considerations – Rake Angles Cont.钻头设计因素——倾角（续） Side rake is a measure of cutter skew relative to a line normal to the direction of travel. 侧倾角指刀具与钻头行进方向标准直线之间的倾斜度。 Negative side rake positions the cutter face towards the bits central axes and results in cuttings being urged inward, instead of towards the junk slots. 若侧倾角为负角，则刀具的位置为表面朝向钻头中心轴，这样就会将钻屑推入钻头内部而非垃圾槽中。 Positive side rake positions the cutter face towards the outside diameter and produces the opposite effect. 若侧倾角为正角，则刀具的位置为表面朝向外直径，并能产生与上述相反的效果。 Different companies have experimented extremely high side rake angles, both positive and negative, but no advantages were seen. As side rake increases, the effective operating width of the cutter decreases, necessitating more cutters to obtain the same coverage. 个别公司尝试过使用极其大的侧倾角（包括正角和负角），但并未无任何优势。因为侧倾角增大，刀具的有效操作宽度则减小，这样则需使用更多的刀具才能完成相同范围内的工作。 In light of the above many bit companies currently orients all PDC cutting elements with zero side rake. 鉴于上述原因，许多钻头公司目前都将所有PDC切削元件的侧倾角设定为零。 Bit Design Considerations – Bit Length钻头设计因素——钻头长度 We suppose that the distance from the face where bit touches the drive shaft to the bit cutting face may vary from 1 to 2 of nominal bit diameter. 我们假设钻头接触驱动轴的表面与钻头切削表面之间的距离可有1至2个公称钻头直径的差异。 The overall bit length is important from a steer-ability perspective. Shorter bits are more steerable, as they reduce the radius of the possible turn. 就导向能力而言，钻头的整体长度非常重要。钻头越短则越容易被操纵，因为它们能减少可能转动的半径。 The length of a PDC bit is governed by the length of the bit gauge desired for the application, the blade height and the bit cutting profile. PDC钻头的长度取决于应用中理想钻头保径的长度、刀片高度和钻头的切削剖面。 Bit Design Considerations – Bit Gauge钻头设计因素——钻头保径 Gauge Protection Maintaining the full gauge diameter of the hole being drilled is crucial. If the bit loses gauge and begins to drill an undersized hole, a variety of problems can follow, including the bottom hole assembly becoming stuck in the well. 保径保护——维持钻孔的全尺寸直径至关重要。若钻头为安全保径而开始钻尺寸过小的孔，各种问题将会接踵而至，包括井底钻具组合陷在井内。