EFFECTS OF THE MICRO FRACTURES ON THE SHALE MECHANICS BASED ON INDENTATION SIMULATION METHOD

Abstract

With methods of nanoindentation and dimensional analysis applied, mechanical properties can be determined and evaluated through small debris. In this paper, the results of dimensional analysis and mechanical parameters are presented based on the finite element method and mathematical statistics method. The indentation of shale is simulated to investigate the influence of the fracture within the sample on the mechanical parameter. Five different factors of fracture are researched in this paper. The investigation shows that the development of fracture and pore is correlated with the deviation of points to the theoretical curve based on dimensional analysis, corresponding to the experimental results of shale, i.e., the lager the deviation, the better the fractures within the sample develop. By analyzing the deviation, the difference values, which represent the influence of each factor, rank as follows in a descending manner: depth (0.01555), shape (0.00765), count (0.00757), eccentricity (0.00319 or 0.00238), angle (0.0044). It shows that the depth of the fracture exerts greater influence on rock mechanics than the eccentricity and the size of the fracture (count and shape), and the influence of the angle is minimum. This paper is of great significance for the shale in evaluating the micro-mechanics of shale and assessing fractures through dimensional analysis.