泥包对破岩效率影响的PDC 单齿切削模型研究

PDC 钻头泥页岩地层钻进易发生泥包，严重影响机械钻速。钻进性能的变化归根结底源于切削齿与地层的相互作用，但是目前建立的单齿切削模型考虑的因素不全面，并不适用于钻头发生泥包的情况。建立了PDC 钻头分别发生切削齿泥包和钻头整体泥包时的单齿切削模型，模型全面考虑了围压、切削齿倒角面、切削齿后底面、岩屑破碎带等因素，通过实例计算、利用前人实验数据验证了模型计算结果的可靠性。最后利用模型量化分析了泥包对破岩效率的影响规律，结果发现切削齿泥包和钻头泥包均严重影响破岩效率，且后者影响程度更大；切削齿泥包中，围压和“泥包团”长度对破岩效率影响显著，破岩效率均随两者的增大而减小；钻头泥包中，泥包面积对破岩效率影响显著，破岩效率随泥包面积的增大而减小。

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

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 interactionmodels built by researchers at present didn′t take all the factors into consideration which were not available to the situation ofballing. In this paper，two new PDC single cutter-rock interaction models are built which can be applied to the cases of cutterballing and global balling separately. The models consider comprehensive factors including confining pressure，forces exertedon cutter chamfer，the back of the cutter and the build-up edge of cuttings. The results of the models are validated by examplecalculation and reference to predecessors′ laboratory data. At last，the effect of bit balling on cutting efficiency is analyeedquantitatively by using the models，and the results show that both cutter balling and global balling affect the cutting efficiencyseriously，and the latter influences more seriously. In the case of cutter balling，the confining pressure and the length of“cutterball”are the two main factors affecting cutting efficiency，which decreases as they increase. In the case of global balling，thearea of balling affects and cutting efficiency greatly，cutting efficiency decreases as the area increases.