This paper focuses on the diffusion process between two fully miscible liquids in fractured porous media and more specifically, the interaction between fluid in a fracture (solvent) and fluid in a porous matrix (solute). This type of process is encountered in many different applications including enhanced oil (or heavy-oil) recovery and groundwater contamination. Experiments were performed on vertical and horizontal orientations of 25 mm x 75 mm Hele-Shaw models with different boundary conditions. Oil recovery from a unit element reservoir by solvent injection was simulated on these models, mimicking solvent injection into fractured oil reservoirs. Despite tremendous efforts in injection controlled miscible displacement experiments (dispersion dominated), purely Fickian-diffusion controlled static experiments (no fluid injection) in Hele-Shaw models are very limited. This type of experimentation gives a clear understanding of the fluid-fluid interaction between oil in the rock matrix and solvent in the surrounding fracture. We first analyzed the interaction between oil saturated 2-D models and the hydrocarbon solvent surrounding it qualitatively. Also provided was an analysis of the high temperature water injection that followed this process to retrieve the solvent diffuse into the oil saturated model. We mainly explored the effects of the model (matrix) boundary conditions controlled by the aspect ratio and solvent oil interaction area on the process, using the images acquired during the experiments. Results were then analyzed quantitatively and two new dimensionless numbers were defined as functions of fluid properties and matrix boundary conditions. The work concluded that, under a fully static interaction between the solvent and oil, the process is strongly controlled by the boundary conditions that determined the relative contribution of the gravity and diffusion on the interaction process. (C) 2011 Elsevier B.V. All rights reserved.