基于随钻及多尺度方法的页岩力学性质实验与理论研究

The mechanical properties of shale are one of the important foundations for shale oil and gas development. Macro measurements have many problems such as sample preparation, discontinuous profile of mechanical behavior, and low-quality logging result, because of the special properties of shale such as heterogeneity and anisotropy. This study proposes to analyze the scale composition characteristics of shale using outcrop and drill cutting. Furthermore, the experiment and theory study on mechanical behaviors of shale can be carried out based on drilling and multi-scale method. According to the research objectives, the major characterization method and basic theory research are as follows. Multi-scale model of shale will be established, based on the analysis of composition and microstructure. A large number of the nano/micro-indentation test will be carried out so as to establish the multi-scale mechanical test method of shale, based on component-mechanical coupling analysis. According to configurational homogenization and dimension analysis, the multi-scale homogenization model of shale will be established. Therefore, the macroscopic mechanical behaviors such as elasticity modulus and strength can be predicted. The mechanism response of shale micromechanical fracture will be analyzed by microscopic fracture indentation experiment so as to propose an evaluation method for the mesoscopic fracture toughness of type Ι. The configuration force and conservation integral model will be established to evaluate the influence factors on mechanical behavior based on the analysis of configuration defects. The prediction models are verified by comparing the calculated results and the analysis of the macro test dada. Finally, shale cuttings will be used to measure the mechanical properties during the drilling process. The present work provides a new idea and method to cognize mechanical properties of shale. The study also provides a reliable scientific basis for the development of shale oil and gas.

页岩力学性质是页岩油气开发的重要基础之一，由于页岩的非均质和各向异性，常规宏观力学测量方法存在制样困难、力学解释参数不连续、精度偏低等问题。本项目拟采用页岩露头和随钻钻屑评价页岩的尺度组成特征，开展基于随钻及多尺度方法的页岩力学性质实验与理论研究：构建页岩多尺度组分模型，通过纳/微米力学测试评价页岩弹性模量和压入硬度，建立组成-力学耦合的页岩多尺度力学测试方法；基于点构型均匀化、多参数量纲分析等方法，建立页岩多尺度均匀化表征模型，进行页岩多尺度弹性模量和强度预测；通过显微断裂压入实验分析页岩细观断裂响应机理，建立页岩细观Ι型断裂韧度评价方法，通过页岩构型缺陷的分析建立构型力与守恒积分模型，描述微缺陷发育对页岩力学性质的影响；采用宏观力学表征方法验证本研究的合理性，并开展页岩钻屑的力学随钻测量。本项目研究形成页岩力学表征新体系，为有效解决页岩油气开发提供可靠的科学依据。

针对页岩油气安全、高效开发过程中存在的岩石力学问题，开展了基于多尺度力学理论的页岩组成、力学评价，页岩多尺度均匀化表征、细观断裂和损伤分析。主要的研究工作和成果包括：开展了页岩矿物组成和孔隙分布特征评价，并以此构建页岩多尺度组成模型，进行页岩微/细观力学测试的理论研究，明确了测试岩样的制备、测试流程和测试参数，研究微/细观测试对弹性模量和压入硬度的影响机制，进行了微观多孔黏土力学参数随组成变化的分布评价，建立了页岩多尺度力学测试方法。采用耗散能原理和均匀化理论，研究了页岩的应变能、非线性差值函数，建立了微/细观尺度下的均匀化刚度张量和∏函数模型，采用量纲分析方法建立了硬度与强度的量纲关联模型，基于页岩微观力学测试结果数据，开展微/细观压入测试的有限元模拟，评估硬度与强度参数的内在联系。基于仪器化压入表征技术，分析细观断裂韧度的实验测试，描述断裂韧度与弹性模量和硬度的关系，明确了细观断裂韧度的测试影响机理；基于构型力学理论，描述页岩内部缺陷的构型改变规律，明确页岩损伤程度与组成关系，建立页岩的损伤准则及演化方程。通过宏观力学实验的比对分析，验证了多尺度力学求解的合理性，为页岩力学表征和井壁稳定研究提供更为可靠的科学依据。.通过以上问题的分析研究，建立基于组成的页岩多尺度力学测试方法，弥补了宏观力学测量的不足，为页岩力学测量问题的深入研究和进一步解决提供新思路和方法；提出运用多尺度均匀化理论和量纲分析相结合的方法，建立基于组成的页岩多尺度力学均匀化模型，为页岩组成与弹性和强度耦合分析以及宏观力学预测提供新的认知；提出运用仪器化断裂测试技术和构型力学理论，有效揭示页岩细观微断裂和缺陷损伤的形成机理，为页岩井壁稳定预测提供更为科学的依据。