This document presents a mathematical model for simulating the diffusion of microbes injected during microbial enhanced oil recovery (MEOR) processes in porous media. The model is based on a diffusion equation that describes the transport and distribution of microbes over time. Computer simulations using the model produce 3D views showing higher microbial concentration in the center of the porous media that decreases towards the outer boundaries due to diffusion. The model and simulations indicate that microbial diffusion can effectively distribute microbes through the reservoir during MEOR, but an uncontrolled process risks permeability damage that would counter the intended effects.