The fluid flow simulation in porous media has been used in oil industry to characterize the reservoir. However, the analysis has been carried out with conventional assumptions that must be taken back in reservoirs with complexities that were not considered before. At present it has been found that those reservoirs are not as ideal as was thought and petrophysical properties change with stress; this is the basis of fluid flow coupled to geomechanics. The fluid flow equation is for a naturally fractured reservoir with single fluid and coupled with the equations of deformation. These are solved by using finite differences technique and a Picard type iterative method. The result is a numerical simulator for well tests interpretation taking into account the permeability changes with stress by using the permeability module.