In this study a three-dimensional Distinct Element Methods (DEM) scheme was used for the simulation of initiation and propagation of the hydraulically induced fractures in a typical reservoir. Due to the fact that modeling the initiation of an induced fracture in DEM is difficult, a fictitious joint technique was introduced to simulate the process. The analysis results show that the success of the hydraulic fracturing process not only depends on controllable parameters such as fracture fluid properties and the injection rate, but also on the uncontrollable parameters such as stress regime, orientation of principal stress, and in-situ rock mass properties. Moreover, a sensitivity study of input variables was performed to examine the effect of different field conditions. These involved the orientation and magnitude of principal stress components, fracture fluid properties, injection rate and rock parameters. In addition, the results obtained from numerical modeling were compared with analytical solutions indicate that an obvious connection exists between them.