Study on Mechanical Properties and Rock Breaking Effect of Ridge-Shaped Cutters
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摘要: 以地层特性为依据,有针对性的选择异形齿可以减少PDC齿失效的概率,并且提高机械钻速和进尺。为了综合对比脊形PDC齿的机械性能和破岩效果,对三种脊形PDC齿(165斧形、135斧形、三刃)首先进行了耐磨性和抗冲击性研究,然后选择花岗岩进行3个吃入深度的单齿切削实验和不同压力下的全尺寸钻头模拟钻进试验,并与圆形齿进行对比。研究结果表明:①脊形PDC齿的耐磨性均优于圆形齿;②165斧形与三刃齿的抗冲击性优于圆形齿,135斧形由于冲击点缺少支撑,其抗冲击性能较差;③相同吃入深度下,脊形齿的切向力与法向力均低于圆形齿,并且脊角越小切削力越小;④135斧形的机械钻速最快,并且适合高钻压,与165斧形相比,三刃齿在低钻压区间(小于20 kN)机械钻速更快,高钻压区间(大于20 kN)钻速较慢,圆形齿机械钻速最慢,所适合的钻压也较低。实验结果表明脊角变化时,其冲击点支撑材料也发生改变,进而影响其抗冲击性能,同时脊角变化会改变前方的岩石内部的应力集中,进而改变其破岩效果。本文的研究结果可以为脊形齿设计优化设计、钻头布齿和钻井参数优选提供参考。Abstract: Based on the formation characteristics, the targeted selection of shaped cutters can reduce the probability of PDC cutters failure and increase the rate of penetration (ROP) and footage. In order to comprehensively compare the mechanical properties and rock-breaking effect of ridge-shaped PDC cutters, three kinds of ridge-shaped PDC cutters (165-axe, 135-axe, and triple-edged) were firstly studied for wear resistance and impact resistance, and then granite was selected to conduct single-cutter cutting experiments at three depths of cut (DOC), and simulated drilling experiments of full-size bits under different weight of bit, and compared with round cutter. The results show that: ① The wear resistance of ridge-shaped PDC cutter is better than that of round cutter. ② The impact resistance of 165-axe and three-edged cutter is better than that of round cutter, and 135-axe has poorer impact resistance due to the lack of support at the point of impact. ③ At the same DOC, the tangential force and normal force of ridge cutter are lower than that of round cutter, and the smaller the angle of the ridge is, the smaller the cutting force is. ④ The 135 axe shape has the fastest ROP and is suitable for high WOB, the triple-edged cutter have a faster ROP in the low drilling pressure range (less than 20 kN) and a slower ROP in the high drilling pressure range (more than 20 kN) compared to the 165-axe. The rounded cutter have the slowest ROP and are suitable for lower WOB. The experimental results show that when the ridge angle changes, the support material at the impact point also changes, which affects its impact resistance, and at the same time, the change of the ridge angle will change the stress concentration inside the rock in front of it, which will change the effect of rock breaking. The results of this paper can provide a reference for the optimal design of ridge cutter design, bit cutter placement and drilling parameter selection.
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Key words:
- PDC Bit /
- Shaped cutter /
- Ridge-shaped cutter /
- Mechanical property /
- Rock breaking effect
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