页岩钻进界面动态放热特性及其对刀具失效影响机理

The heat release in shale drilling process directly affects the service life of tool and the efficiency and safety of shale gas exploration. But the drilling heat of shale has not been clarified at home and abroad, there is no available calculation model about interface temperature could be used in shale drilling process, and no foreign and domestic report on the relationship between tool failure and shale drilling heat so far. Theoretical analysis and experimental study are combined to research the project, and the heat source model of the shale drilling process will be established by the method of infrared thermography and optical fiber collection. The influence factors of dynamic heat transfer characteristics of the interface would be studied, and the calculation model of heat absorption ratio between shale and tool would be presented. The dynamic time and space characteristics of the interface temperature will be studied, and the average and flash temperature calculation model of the interface would be presented. The calculating formulas of the macro and micro thermal stress are derived to study the influence of the interface temperature on the working performance of the tool, and the thermal fracture and thermal wear mechanism of the tool in shale drilling process are revealed according by the microstructure and composition analysis. The computational models between interface temperature and tool life of fracture and wear will be established. The optimization design method of reducing the tool heat failure and improving the shale drilling efficiency would be established.

页岩钻进过程产生的热效应对钻进刀具寿命、钻进工程效率及生产安全有重要影响。但是目前相关研究还很不完善，既没有页岩钻进界面温度计算模型，更缺乏页岩钻进热效应与刀具失效间的相互作用机制。本课题利用红外热像与光纤温度采集方法, 结合岩石力学、热物性能实验，研究页岩钻进过程能量转化释放机理与变化规律，建立页岩钻进热源模型；分析钻进界面热量分配的影响因素，建立页岩与刀具吸热比率计算模型；研究界面温度时空动态演变特性，建立界面平均温度及闪温计算模型；阐明页岩钻进过程热应力影响因素和变化规律，建立页岩与刀具宏观和微观热应力计算模型；结合微观形貌与成分分析，研究界面温度对刀具工作性能的具体影响机制，揭示页岩钻进过程的刀具热断裂和热磨损机理；研究界面温度与刀具断裂及磨损寿命间数量关系，建立减小刀具热失效提高钻进效率的钻进优化设计理论与方法，成果为保证页岩气勘探开发工程的高效安全实施提供理论基础。

页岩钻进过程中界面复杂的放热及温度变化规律，对刀具寿命、工作性能以及钻进安全及效率产生不可忽视的影响，是页岩油气资源开发工程中必须面对的科学问题。本项目采用理论分析和实验、数值模拟研究相结合的方法，对页岩钻进界面热效应产生机理、动态演变规律及刀具失效机理开展深入研究，取得了一定的研究成果。（1）在页岩钻进、力学性能及热物性能实验基础上，结合温度测试与岩屑颗粒度测试，研究了钻进过程热量释放来源与变化规律，建立了钻进过程中温度场计算模型，揭示了钻进界面温度场动态演变机理，为钻进放热及温度场问题理论研究提供了有效的参考依据。（2）在温度模型和实验数据的基础上，结合数值方法模拟钻进过程，系统研究了页岩钻进过程刀具应力的影响因素和变化规律，发现了钻进刀具表面周期性应力波动引起局部塑性应变的现象，深入分析揭示钻进界面热效应及机械作用的非均匀动态变化是导致刀具失效的根本原因。进一步研究了钻进刀具应力与磨损失效之间的联系，结合刀具表面形貌测试，揭示了刀具失效的微观机理和影响机制。（3）综合研究了不同工作条件下的钻进温度场及钻具应力的变化规律，揭示了钻进参数、颗粒输运、刀具构形及破岩方式等多种因素对钻进性能的影响规律，初步建立起减小钻进热效应、提高钻进效率的页岩优化钻进设计理论与方法。研究成果为保证页岩油气勘探开发工程的高效安全实施提供了理论基础，对于地质资源安全开采等重大工程问题有着重要的参考依据和应用价值。