Abstract: To study the rupture evolution of the calcite vein-filled shale in the Niutitang Formation in northern Guizhou, this paper obtains the image of the shale interior by the CT scanning. The shale matrix and calcite veins are identified by using the threshold segmentation technique. The three-dimensional numerical model of the shale by combining with the numerical simulation software of RFPA-3D is established. The numerical simulations of the uniaxial compression tests on the calcite vein-filled shale with four angles are conducted. The test results show that the mechanical properties of the shale show obvious anisotropy with the inclination angle of the calcite veins, in which the compressive strength reaches the maximum of 45.05MPa when the calcite veins are 0°. The tensile strength reaches the minimum of 37.02MPa when the calcite veins are 60°. The calcite-filled shale samples show two damage modes under the uniaxial compression, which are the shear-slip damage along the calcite veins, composite damage and the “composite damage” veins and “V”-shaped tensile-shear composite damage. The research results have an important reference value for the prediction of the fracture initiation and the extension in calcite vein-filled shale reservoirs.

Key words: Shale, Calcite Veins, Anisotropy, Damage Evolution