不同冲击钻井方式PDC切削齿侵彻深度及破岩机制研究

Study on Penetration Depth and Rock Breaking Mechanism of PDC Cutter in Different Per⁃cussion Drilling Methods

基于常规钻井和冲击钻井工程应用实际,考虑岩石动力学材料参数及本构模型,建立了聚晶金刚石复合片(PDC)钻头切削齿破岩数值模型,对比分析了不同冲击钻井方式下PDC切削齿侵彻深度、损伤区域、岩屑颗粒大小以及破岩体积。研究结果表明:数值模拟结果与室内单齿切削物理实验模型相比,岩石切削形态上具有较好的一致性。旋冲钻井、扭冲钻井和复合冲击钻井相比常规钻井的单齿侵彻深度分别提升了19.8%、6.6%、26.9%,复合冲击钻井在机械钻速提升方面效果最明显。冲击钻井过程中存在轴向冲击载荷时(如复合冲击钻井或旋冲钻井)会导致切削面以下岩石产生较为明显破损,有利于钻齿转过360°后的“二次切削”,但容易产生较大尺寸的岩屑颗粒,需要优化钻井液参数以保持井眼清洁。扭冲钻井钻齿侵彻深度的波动幅度较小,表明该方式有利于降低钻头粘滑风险,且产生的岩屑颗粒较小、利于井筒清洁。研究结果对于选择不同冲击类型钻具和优化钻具参数具有重要的借鉴意义。

Based on actual engineering applications of conventional drilling and percussion drilling,and considering the material pa-rameters and intrinsic model of rock dynamic mechanics,a numerical model of rock breaking of the cutters of Polycrystalline Diamond Composite(PDC)bit was established.The penetration depth,damage area,size of rock debris particles and rock breaking volume of PDC cutters under different percussive drilling models were compared and analyzed.The results show that the rock cutting pattern is very similar between the numerical simulation results and the laboratory physical experimental model of single-cutter.The penetration depth of single tooth of rotary,torsional,and combined percussive drilling increased by 19.8%,6.6%and 26.9%respectively compared with that of conventional drilling,and the combined percussive drilling saw the most significant increase in rate of penetration.When there is axial impact load during percussive drilling(such as combined percussive drilling or rotary percussive drilling),it will cause visible damage to the rocks below the cutting surface,which facilitates the“second cutting”after the drilling cutters turn 360°,but large rock debris particles can be produced,so it is necessary to optimize the drilling fluid parameters to keep the wellbore clean.The fluctuation range of penetration depth of the cutter in torsional percussive drilling is small,which indicates that this method helps reduce the risk of bit stick-slip,and the rock debris particles produced are small which makes it easy to keep the wellbore clean.The research results are of great significance for the selection of different types of percussion drilling tools and tool parameters optimization.