页岩跨尺度力学特性的实验表征及基础理论研究

The mechanical property of shale rock is a key factor for the effective development of shale oil and gas. However, shale rock is a kind of multi-phase, multi-scale and nonhomogeneous material, whose multi-scale mechanical behavior is very difficult to be described by continuum mechanics. Furthermore, the acquisitions of the mechanical parameters of shale reservoirs are usually difficult in realistic engineering operation. The present work aims to investigate the multi-scale mechanical natures of shale rock, and to study the characterization method and basic theory for the multi-scale mechanical characteristics of shale rock by using the downhole cuttings, micro/nano-indentation techniques and multi-scale mechanics. The influencing factors of the micro/nano-indentation will be investigated by experimental studies, and then the testing parameters can be optimized; thereby, recommended methods for the micro/nano-indentation testing will be established. The mesoscopic representative elementary volume (REV) and its mechanical performance will be investigated by experimental studies as well, based on which a homogenization constitutive model will be proposed between mesoscopic and macroscopic scales by using the finite element method and the asymptotic homogenization method; therefore, the multi-scale correlation from mesoscopic to macroscopic scale, and the macroscopic mechanical parameters such as modulus and strength can be predicted. To verify the validity and applicability of the multi-scale mechanical characterization, the predicted results will be compared with the logging and experimental results. The present work can not only enrich the characterization methods of shale rock mechanics, but also promote the application and development of multi-scale mechanics theory. The proposed work will play a very important practical role in the effective development of shale oil and gas.

页岩力学特性是影响页岩油气高效开发的关键因素，但页岩是一种多相、多尺度的非均质材料，采用连续介质力学难以描述页岩的多尺度力学行为，而且工程中获取页岩储层力学参数往往较难。本项目针对页岩的跨尺度力学属性，拟采用井下岩屑、微/纳米压痕技术和多尺度力学方法，研究页岩跨尺度力学特征的表征方法及基础理论。实验研究页岩微/纳米力学测试影响因素，优化微/纳米压痕测试参数，建立页岩微/纳米压痕测试推荐方法；实验研究页岩细观特征单元体及其力学性能，采用有限元和渐近均匀化方法，建立细观-宏观间的均匀化本构，明确细观-宏观之间的跨尺度关联关系，预测页岩弹性模量、强度等宏观力学参数；通过对比宏观力学实验、测井及预测结果，检验跨尺度表征方法的正确性和实用性。本项目研究不仅丰富了页岩力学特征表征方法，也推动了多尺度力学理论的应用与发展，对于页岩油气高效开发具有重要的现实作用和意义。

页岩力学性质是页岩油气高效开发的重要基础参数，但由于页岩的多相、多尺度特性导致其力学行为非常复杂。为此，采用井下岩屑、微/纳米压痕技术和多尺度力学方法，研究了页岩跨尺度力学特征的表征方法及基础理论。通过实验确定了页岩微/纳米压痕岩样制备要求，明确了实验影响因素及其影响规律，形成了页岩微/纳米压痕测试建议方法；实验测试了页岩细观尺度矿物、孔隙及结构特征，测试了页岩在纳米、微米尺度下的力学特征；采用有限元方法模拟了不同页岩性质下的压痕力学响应特征，基于自洽模型、微分等效介质模型及微观结构定量表征，建立了页岩力学性质跨尺度均匀化方法，揭示页岩的跨尺度力学行为，并进一步建立了宏观模量、强度、断裂韧性及脆性参数的预测方法。通过对比宏观力学实验及预测结果，检验了本项目方法的正确性和实用性。本项目研究不仅丰富了页岩力学特征表征方法，也推动了多尺度力学理论的应用与发展，对于页岩油气高效开发具有重要的现实作用和意义。