Simulation on Microscopic Damage of PDC Cutter During Conglomerate Cutting
Conglomerate generally has complex pore structures and severe heterogeneity.Drilling by PDC bit in conglomerate usually exhibits low rock-breaking efficiency,and the rock-breaking process of PDC cutter can hardly be investigated through laboratory experiment.A numerical model for conglomerate cutting by PDC cutter was built by using the discrete element software PFC2D to analyze the conglomerate breaking form and process under different cutting depths,rake angles and rock heterogeneities,and the rock-breaking specific energy was used to e-valuate the rock-breaking efficiency in the conglomerate cutting process.The results show that when the cutting depth is increased within a certain range,the shear cracks are initiated faster inside conglomerate,the proportion of shear cracks is significantly increased,and the main crack propagates around the gravel along the free surface di-rection and cutting direction.When the heterogeneity of conglomerate is increased,the plastic failure of rock is gradually transformed to brittle failure,and too high heterogeneity would increase the overall strength of conglomer-ate and the impact breaking frequency on PDC cutter,which is not favorable for rock-breaking.When the con-glomerate is cut by PDC cutter at 1 mm cutting depth and 5° rake angle,the maximum rock-breaking efficiency is obtained.The study results provide theoretical support for the design of PDC cutter and the selection of cutting pa-rameters.
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万方数据
维普
