Experiment and Numerical Simulation on Shale Cutting and Breaking of Special-shaped Cutter
In order to solve the problems of low rock-breaking efficiency and short service life of PDC bit in drilling shale gas wells,a study was made on the shale cutting and breaking mechanism of special-shaped cutter.Based on typical special-shaped cutters such as concave cutter,axe-shaped cutter and triangular cutter,experiment was performed on shale cutting process and cutting load,and numerical simulation was conducted to analyze the rock damage during the cutting process.The experimental results show that in the shale cutting process,hard plas-tic features such as mirror surface and"curling chips"occur,and the cutting load and rock-breaking specific ener-gy of concave cutter are smaller than those of other types of cutters.As the rake angle increases,the cutting load of planar cutter and triangular cutter shows an increasing trend.Concave cutter and axe-shaped cutter are not sensi-tive to changes in rake angle,and concave cutter has the best rock-breaking performance at a rake angle of 10°.Under the same conditions,concave cutter forms the largest cuttings,which is favorable for the improvement of rock-breaking efficiency.The numerical simulation results show that in the cutting process,the concave cutter breaks the rock in a"backing-off cutting"manner,and the ridges of the triangular cutter and axe-shaped cutter have an obvious compression on the rock,the triangular cutter divides the cuttings along the ridge and discharge them to both sides,while the axe-shaped cutter forms obvious plastic deformation in the middle part of the mass cut-tings.The study results provide basic support for ROP improving and efficiency enhancing of shale gas well drilling.
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NSTL
万方数据
维普
