基于岩石动态本构的轴扭复合冲击作用下PDC单齿破岩机理研究

Aimed at the problems of low drilling efficiency in deep formation, a number of researchers have investigated the rock mechanism of impact drilling. The axial-torsional composite impact (ATCI) drilling is a new technique used for improving the rate of penetration for which axial impacts and torsional impacts are applied onto a polycrystalline diamond compact (PDC) drill bit. Although the impact drilling has been extensively studied, little concentration has been focused on the ATCI drilling and the rock breaking mechanism of the ATCI drilling is still unclear. In addition, the parameters obtained through quasi-static tests are used to describe the constitutive relationship of rock in most of the existing studies, in which the dependence of strain rate on constitutive relationship of rock is not included. In this study, a damaged plasticity model is selected to define the dynamic constitutive relationship, which is followed by carrying out quasi-static compression tests, quasi-static tensile tests, and dynamic compression tests of the rock samples. After determining the parameters of the damaged plasticity model, finite element models of PDC tooth breaking rock smaple are established. In the models, the PDC tooth encounters ACTI loads. Then, the rock breaking processes are simulated and parameter sensitivity analyses are conducted. Based on the simulation results, rock mechanical responses and PDC tooth dynamics can be obtained, by which the effects of different parameters (for example impact parameters and drilling parameters) on rock breaking as well as the relationship between each two parameters are revealed. This study can be of scientific basis for the design of ACTI drilling tools and the application of ACTI drilling technique.

针对深部地层钻进效率较低的问题，国内外学者开展了冲击破岩技术研究。轴扭复合冲击破岩，即同时施加轴向冲击和扭转冲击用于辅助钻头破岩，是近年来新发展的钻井提速技术。尽管目前已有大量关于冲击破岩的基础研究，但对轴扭复合冲击破岩的研究较少，轴扭复合冲击作用下PDC钻头破岩机理尚不明确。此外，现有冲击破岩研究中，普遍使用准静态下的岩石力学参数描述岩石本构而较少考虑应变率对岩石本构的影响。本项目选取损伤塑性模型描述岩石的动态本构，开展岩样的准静态压缩、准静态劈裂拉伸和动态压缩等实验，在获取各参数并确定岩石动态本构模型的基础上，建立基于岩石动态本构的轴扭复合冲击作用下的PDC单齿破岩仿真模型并开展不同参数下的破岩仿真分析，基于仿真结果得到轴扭复合冲击破岩时的岩石力学响应、钻齿动力特性、参数敏感性及各参数间的交互影响机制。研究成果可为轴扭复合冲击钻井工具的设计及轴扭复合冲击破岩技术的应用提供科学依据。

本项目针对深部地层钻进效率低的问题开展轴扭复合冲击作用下的破岩机理研究。完成的研究内容包括：（1）使用MTS和SHPB等装置开展岩样的准静态压缩、准静态劈裂拉伸和动态压缩等实验；（2）在获取各参数并确定岩石动态本构模型的基础上，以损伤塑性本构模型为基础，建立基于岩石动态本构的轴扭复合冲击作用下的PDC单齿破岩有限元模型；（3）开展不同参数下的破岩有限元分析，基于仿真结果得到轴扭复合冲击破岩时的岩石力学响应、钻齿动力特性、参数敏感性及各参数间的交互影响机制。项目研究成果发表学术论文4篇，其中SCI论文3篇，授权发明专利1项实用新型专利1项。