A computer-implemented method to assess the impact of existing fractures and faults for reservoir management, comprising: generating a geological and reservoir model employing information from seismic data, well log, and well production data; characterized by: defining one or more locations of one or more pre-existing geological faults or fractures or combination thereof; creating a numerical mesh that represents the generated geological model comprising delimitation associated with regions and layering of geology without constraining the numerical mesh to explicitly represent a fault or fracture; locating mesh elements from the numerical mesh that intersect the defined one or more locations; discretizing mesh elements of the numerical mesh that do not intersect the defined one or more locations of one or more pre-existing geological faults or fractures or combination thereof, according to a first numerical method; discretizing said located mesh elements that intersect the defined one or more locations of one or more pre-existing geological faults or fractures or combination thereof, according to a second numerical method; and populating the numerical mesh elements with mechanical and flow properties, said populated numerical mesh forming a geomechanical model employed for assessing the impact of existing fractures and faults. generating a geological and reservoir model employing information from seismic data, well log, and well production data; characterized by: defining one or more locations of one or more pre-existing geological faults or fractures or combination thereof; creating a numerical mesh that represents the generated geological model comprising delimitation associated with regions and layering of geology without constraining the numerical mesh to explicitly represent a fault or fracture; locating mesh elements from the numerical mesh that intersect the defined one or more locations; discretizing mesh elements of the numerical mesh that do not intersect the defined one or more locations of one or more pre-existing geological faults or fractures or combination thereof, according to a first numerical method; discretizing said located mesh elements that intersect the defined one or more locations of one or more pre-existing geological faults or fractures or combination thereof, according to a second numerical method; and populating the numerical mesh elements with mechanical and flow properties, said populated numerical mesh forming a geomechanical model employed for assessing the impact of existing fractures and faults. defining one or more locations of one or more pre-existing geological faults or fractures or combination thereof; creating a numerical mesh that represents the generated geological model comprising delimitation associated with regions and layering of geology without constraining the numerical mesh to explicitly represent a fault or fracture; locating mesh elements from the numerical mesh that intersect the defined one or more locations; discretizing mesh elements of the numerical mesh that do not intersect the defined one or more locations of one or more pre-existing geological faults or fractures or combination thereof, according to a first numerical method; discretizing said located mesh elements that intersect the defined one or more locations of one or more pre-existing geological faults or fractures or combination thereof, according to a second numerical method; and populating the numerical mesh elements with mechanical and flow properties, said populated numerical mesh forming a geomechanical model employed for assessing the impact of existing fractures and faults.