页岩钻进过程破碎颗粒结构演化特征及其对输运特性影响

The structure characteristics of broken shale particles have an important influence on the efficiency of shale drilling. However, the current researches are far from completed, and the structure evolution rules of shale particle under different drilling conditions have not been mastered. There is also a lack of the influence of particle structure on the flow performance of debris. This project is studied by the experiments and theories of rock mechanics, fluid mechanics and tribology, combined with the laser particle size test and microstructure extraction technology. The dynamic model of broken shale particle will be established. The relationship between drilling parameters and broken particle size is studied, and the calculation model of granularity will be deduced. The influence of drilling parameters on particle morphology is studied, the temporal and spatial evolution rules of particle morphology and structure are mastered, and the structure model of particle morphology is established. The effects of the particle structure on the internal friction between particles and the viscosity of the drilling fluid under different drilling parameters will be researched. The specific influence mechanism of the shale particle size distribution and morphology structure on the flow performance of the debris will be revealed. The key particle structure parameters to control the flow performance of debris are determined, and the optimized control method for the flow performance of drilled shale particles is established. This study will further reveal the particle breakage mechanism and related impacts to shale drilling. It will be an improvement to efficient shale drilling theory and high efficiency development of unconventional oil and gas resources.

页岩钻进过程颗粒破碎结构特征对页岩钻进效率产生重要影响。但目前相关研究还很不完善，没有掌握不同钻进条件下页岩颗粒结构的具体演变规律，更缺乏页岩钻进颗粒结构变化对岩屑输运特性的影响规律。本课题利用激光颗粒度测试和微观形貌提取分析技术，结合岩石力学、摩擦学与流体力学实验与理论分析，建立页岩破碎颗粒动力学模型，研究页岩破碎颗粒粒径与钻进参数间关系，建立页岩钻进破碎颗粒度计算模型；研究钻进参数对颗粒形貌的影响，掌握页岩钻进颗粒形貌结构的时空演化规律，建立页岩颗粒形貌结构特征模型；研究不同钻进参数下页岩颗粒结构对颗粒间内摩擦力和钻液粘度影响规律，揭示页岩粒径分布和形貌结构对岩屑输运特性的具体影响机制，确定控制岩屑流动性能的关键颗粒结构参数，建立页岩颗粒输运特性优化调控方法。研究将深入揭示页岩钻进颗粒破碎机理及相关影响规律，为完善页岩高效钻进理论提供基础，也对非常规油气资源高效开发研究具有参考意义。

页岩钻进颗粒的粒度结构和形貌特征不仅是破岩效果的直接体现，也是影响岩屑运移状态与输运效率的关键因素，对页岩油气资源开发工程的钻井能耗、效率以及油气开采的整体效能产生至关重要的影响。本项目针对页岩钻进颗粒产生与输运过程中的关键力学问题，采用理论分析和实验、数值模拟研究相结合的方法，对页岩钻进颗粒产生机理、颗粒形态结构演变规律及岩屑输运机制开展了深入研究，全面完成了预期目标，取得了一定的研究成果：（1）结合岩石钻进实验与岩石破碎学理论，揭示了钻进过程中页岩延性与脆性破碎模式下颗粒产生机制，建立了考虑压缩与剪切破碎的岩石切削力学模型，提出了切削作用下岩屑应力计算方法，基于岩石分形破碎理论，建立了考虑颗粒形态结构的岩石钻进破碎比能预测模型。（2）通过岩石钻进颗粒形态测试分析，研究获得了钻进颗粒的粒径分布、形状及表面形貌等特征，采用分形理论定量刻画了钻进颗粒的粒度结构特征，阐明了岩石组成结构与钻进参数对钻进颗粒形态特征的具体影响规律，获得了岩屑密相输运过程中的颗粒运动规律，发现颗粒间磨损效应是增大输运能耗的重要原因，建立了岩屑密相输运负载计算模型。（3）采用颗粒离散元与计算流体力学相结合方法开展了钻井液-岩屑两相输运的流固耦合模拟，掌握了页岩颗粒粒度结构、形状特征等因素对流场特性和输运效果的影响规律，构建了岩屑颗粒形状参数与输运特性之间联系，初步建立调控岩屑输运性能的页岩钻进优化设计理论与方法。研究成果为保证页岩钻井工程的高效安全实施提供了理论基础，对于页岩油气等深部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。