Water production in the oil industry has become so common that colloquial expressions such as “oil companies no longer produce oil, but water” have been unconsciously accepted in this industry. Nevertheless, water production is a serious issue in heavy oil fields with strong aquifers or fields under waterflooding for two reasons: It increases the costs affecting the economic viability of a project, and it has a serious environmental impact due to increasing energy consumption and CO2emissions. The root cause behind this problem is a phenomenon called Viscous Fingering, which appears mainly by the viscosity ratio between the phases. This study aims to understand better the Viscous Fingering phenomenon associated with a horizontal well in 3D. For the first time, a scaled horizontal well in a numerical constructed porous media was studied using a full 3D Computational Fluid Dynamics (CFD) model. The horizontal well was scaled using the Reynolds law of similarity from a real section of a horizontal well. While the porous media was made with the DEM physical model using spherical 7mmparticles, which allows reproducing rock properties such as permeability and porosity. This phenomenon was studied at three different scaled production rates, 1000, 1500, and 2000 bbl/d. Finally, three different oils were considered to study the influence of the viscosity ratio in the CFD modeling of the fingering. It was determined that CFD was capable of simulating Viscous Fingering for horizontal wells at the pore scale. Also, it could give information such as production and water cut-profiles, location and time of breakthrough, and specific locations of unrecoverable oil along the reservoir. The information given by the CFD approach could be useful for the development and improvement of completion and enhanced recovery techniques.