| Based on the analysis of different scales of fractures in rock outcrops, drilling cores and thin slices of the Lower Permian Shanxi Formation in southern Qinshui Basin, the developmental characteristics and dominant factors of fractures in tight sandstone were systematically studied. The statistical results show that the structural fractures account for more than 90%, which mainly contain tensile fractures, and followed by shear fractures and extrusion fractures. The main controlling factors of fracture development include structural location, faults, rock brittleness, single sand body thickness, anisotropy and diagenesis of rocks. For the regions with large gradient change of structural stress, and fracture development, as well as high brittleness, the degree of fracture development is higher. There is a good exponential negative correlation between the fracture linear density and the single sand body thickness. As for the influence on the degree of fracture development, the rock anisotropy is a stronger factor than geostress. The fracture is a dominant factor of the anisotropy of coal measure strata in Shanxi Formation. The minerals with unstable chemical properties, such as carbonate and feldspar cements, provide the favorable conditions for the formation and development of corroded fracture. |
