The phenomenon of Co-current imbibition in a vertical download direction, coupled with the influence of heterogeneity and gravitational effects, is investigated through a comprehensive mathematical analysis in this research paper. Imbibition, the process of fluid penetration into porous media, plays a pivotal role in various natural and engineered processes. This study focuses on quantitatively understanding the behavior of Co-current imbibition and its interactions with heterogeneity and gravitational effects. The mathematical framework yields a non-linear partial differential equation (PDE) that describes the phenomenon. To solve this governing equation, the Variational Iteration Method is employed, along with appropriate initial and boundary conditions. The results are presented through numerical computations and graphical representations, facilitated by MATLAB.