The application of fracture mechanics is an increasingly important topic in fields including geophysics, geomechanics, materials engineering, structural mechanics and engineering design. The initiation and evolution of fractures in porous media often gives rise to discontinuous fields within computational problems. We compute the crack's aperture, or crack opening, by making use of the gradient of the phase-field in the damaged area. This is useful for determining the material's fluid-mechanical properties, such as the estimation of Poiseuille-type flow that occurs within a sufficiently damaged medium. Using this approach, it can be shown that the evolution of such fractures in a porous medium can contribute to the material's fluid flow characteristics, giving rise to a coupled model of fluid flow and damage within a porous solid. Using the Sierra Mechanics code suite at Sandia National Laboratories, a phase-field model of fracture is developed which will allow a loose, two-way coupling of these physics for future implementations. We find the model's ability to predict fractures initiated and propagated by introducing fluid mass to be consistent with analytical solutions. We also find that the crack openings calculated with this model will be helpful for implementing Poiseuille flow along fractures which is a valuable feature in geomechanics modeling.