砾石层异型齿PDC钻头的设计及现场试验

Design and Field Test of Special-Shaped Cutter PDC Bit in Gravel Layer

塔里木盆地库车山前盐上砾石层发育,砾石含量高、粒径大、抗压强度高,地层可钻性差,钻速慢,井下复杂多。为此,文章针对山前盐上大段砾石层进行了地层砾石层特征和钻头失效模式分析,并在此基础上进行了PDC钻头的异型齿结构设计、优化布齿及冠部形状等设计,形成抗冲击、强攻击性的异型齿PDC钻头设计方案,从而提高了PDC钻头的抗冲击、抗涡动及破岩效率,有效扩大钻头在砾石层中的适用范围。钻头在山前高含砾地层进行了现场试验,取得了优异的应用效果,单只钻头平均进尺达到530 m,平均机械钻速达到4.28 m/h,同比邻井在该地层钻井效果最好的10只PDC钻头的单只钻头进尺提高了42%,平均机械钻速提高了52%,成功解决了塔里木盆地库车山前盐上砾石层钻井的低机械钻速及短进尺的问题。

The gravel layer of Kuqa Piedstone in Tarim Basin is developed,with high gravel content,large particle size,high compressive strength and poor drillability in Bozi block,which are the key factors resulting in low drilling efficiency and complex drilling accidents.In this paper,the formation lithology characteristics,drilling characteristics and failure mode analysis of the large gravel layer in the fore-salt section are carried out,and on the basis of this,the special-shaped cutter structure design of the PDC bit,the optimization of cutters layout and rock breaking efficiency are studied,and the design scheme of the special-shaped tooth PDC bit with strong impact resistance and aggression is formed.The design scheme not only improves the anti-impact but also improves anti-eddy performance and the rock breaking efficiency of PDC special cutter bit,which effectively expands the application range of PDC special-cutter bit in gravel layer.This bit has been tested in the high gravel layer of Kuqa Piedstone and achieved excellent application results.The single bit footage reaches 545 m,the average ROP is 4.72 m/h,compared with the PDC bit used for this formation in the same adjacent well,the single bit footage increased by 35%,the average ROP by 55%,it successfully solved the problems of low ROP and short footage of single bit in Kuqa formation and other formations.