基于微米压痕实验研究页岩力学特性

The mechanical properties of shale based on micro-indentation test

针对页岩储集层力学特性较难获取的问题,提出基于微米力学测试技术的页岩细观力学特性定量评价方法;通过开展四川盆地长宁区块寒武系龙马溪组页岩露头的微米压痕实验,分析页岩的细观力学特性,评价宏观、细观尺度下页岩力学特性的关系。页岩微米压痕实验结果分析表明:细观弹性模量和压入硬度呈非均匀分布;宏观、细观实验对比分析显示弹性模量的细观实验统计平均值近似于宏观实验测量值。通过引入页岩组成参量——颗粒堆积密度,得到页岩组成与力学性质的关系:细观弹性模量和压入硬度随颗粒堆积密度的增加,呈非线性递增变化。基于硬度-颗粒堆积密度模型,逆向分析细观内聚力和内摩擦角,细观测量值的统计平均值略小于宏观值。微米力学测试技术可较好地表征页岩细观力学特性并有效预测宏观力学参量。

In view of the difficulty to get mechanical characteristics of shale reservoirs, a quantitative evaluation method based on micro-indentation test technology was proposed to research the meso-mechanical properties of shale. Through micro-indentation test of shale outcrop samples from the Cambrian Longmaxi Formation in the Changning area, Sichuan Basin, the meso-mechanical properties of shale were analyzed, and the relationship between the macro-scale and meso-scale shale mechanical properties was evaluated. The analysis results of micro-indentation tests show that the mesoscopic elastic modulus and indentation hardness are heterogeneous in distribution. The comparison of macro and meso experiments shows that the statistical mean value of meso-elastic modulus is approximate to the value of the macro-elastic modulus. The relationship between composition and mechanical properties of shale was obtained based on the packing density model theory. The result shows that mesoscopic elastic modulus and indentation hardness increase nonlinearly with the increase of the packing density. Based on the hardness-packing density model, the reverse analysis of cohesion and friction angles shows that the mesoscopic value is slightly smaller than the macroscopic value. The micro-indentation test technology can evaluate shale meso-mechanical properties and predict the macro-mechanical properties effectively.