<p>Limestone reservoir resources of the Taiyuan formation in the Ordos Basin have huge potential and its efficient development is of great significance for Chinese energy industry. But the well-developed and random distribution of natural fractures put a huge impact on rock mechanics and wellbore stress, leading to frequent drilling fluid leakage and significant differences of reservoir stimulation, which restricts the production. Therefore, this study uses SEM, CT imaging, mechanical tests and numerical simulation to analyze how fracture development affects rock mechanics and wellbore stress. Rock is mainly composed of calcite/dolomite and has high brittleness. Natural fractures with different scales are noticed, weakening rock integrity. Mechanical experiments show that rock strength increases with growing confining stress due to this radial constraint on fracture displacement. Also, because of the difference of fracture number and distribution, rock mechanical parameters are varying. Numerical simulation reveals that borehole fractures induce an asymmetric shift in wellbore stress distribution, with stress concentration prone to occur at fracture tips. This triggers fracture propagation and exacerbates leakage risk. Under fracture condition, the distribution of stress and rock strength are more complex. The fracture initiation points around the wellbore and the dominant position of fracture propagation are not completely controlled by in-situ stress, which easily leads to significant differences in the volume of hydraulic fracture network. Results in this paper are able to guide drilling design and fracturing optimization for fractured reservoirs.</p>