西南石油大学学报(自然科学版)

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Study of the PDC Single-tooth Cutting Model About the Bit Balling on Its#br# Cutting Efficiency

Chen Xiuping*, Zou Deyong   

  1. School of Petroleum Engineering,China University of Petroleum(East China),Qingdao,Shandong 266580,China
  • Online:2015-12-01 Published:2015-12-01

Abstract:

Bit balling is a common phenomenon in shale drilling when using PDC bit,which results in seriously reduced ROP.
The change of drill bit performances fundamentally comes from the cutter-rock interaction,but the single cutter-rock interaction
models built by researchers at present didn′t take all the factors into consideration which were not available to the situation of
balling. In this paper,two new PDC single cutter-rock interaction models are built which can be applied to the cases of cutter
balling and global balling separately. The models consider comprehensive factors including confining pressure,forces exerted
on cutter chamfer,the back of the cutter and the build-up edge of cuttings. The results of the models are validated by example
calculation and reference to predecessors′ laboratory data. At last,the effect of bit balling on cutting efficiency is analyeed
quantitatively by using the models,and the results show that both cutter balling and global balling affect the cutting efficiency
seriously,and the latter influences more seriously. In the case of cutter balling,the confining pressure and the length of“cutter
ball”are the two main factors affecting cutting efficiency,which decreases as they increase. In the case of global balling,the
area of balling affects and cutting efficiency greatly,cutting efficiency decreases as the area increases.

Key words: PDC bit, balling, single cutter-rock interaction model, cutting efficiency, shale

CLC Number: