高压水射流-PDC单刀翼联合破岩与携岩研究

Study on combined rock-breaking and rock carrying by high-pressure water jet and PDC single blade

摘要:

高压水射流在对井底进行清理的同时可显著提高钻进速度，使钻井效率得到大幅提高。然而当前高压水射流与PDC钻头联合破岩的研究主要集中于以PDC齿为基本切削单元进行分析，无法完整反映高压水射流对整个PDC钻头工作时的影响。因此本文以PDC钻头单刀翼整体作为基本切削单元，并基于SPH-FEM（Smoothed Particle Hydrodynamics-Finite Element Method）方法建立了高压水射流-PDC单刀翼联合破岩与携岩数值模型，通过切削力和射流破碎坑尺寸验证了模型的可靠性，模型与实验误差仅为9.29%。此外，基于该数值模型，通过切削力、岩石应力场、岩石应变场和井底流场对高压水射流-PDC单刀翼联合破岩与携岩机理进行了分析。该方法基本能够反映高压水射流对整个PDC钻头的影响，验证了高压水射流对PDC钻头破岩与携岩能力的增强。

Abstract:

High-pressure water jet can not only clean the bottom of wells but also significantly enhance the drilling speed， thus substantially improving the drilling efficiency. At present， however， the research on the combined rock-breaking of high-pressure water jet and PDC （Polycrystalline Diamond Compact） bits mainly centers on analyzing with PDC cutters as the basic cutting unit. This approach fails to comprehensively reflect the impact of high-pressure water jet on operation of the overall PDC bit. Therefore， in this study， the entire PDC single blade is regarded as the basic cutting unit. A numerical model for the combined rock-breaking of high-pressure water jet and PDC single blade is established using the SPH-FEM（Smooth Particle Hydrodynamics-Finite Element Method）. The reliability of the model was verified by the cutting force and the size of the water jet fracture pit， and the error between the model and the experiment was only 9.29%. Furthermore， based on this numerical model， the rock-breaking and rock-carrying mechanism of the high-pressure water jet and PDC single blade was analyzed through cutting force， rock stress field， rock strain field and bottom hole flow field. This method can basically reflect the influence of high-pressure water jet on the entire PDC bit， and verify the enhancement of the rock-breaking and rock-carrying capacity of the PDC bit by high-pressure water jet.