Estimation of Water Film Thickness in Geological Media Associated with the Occurrence of Gas Entrapment

When water and entrapped gas co-exist in pore spaces of a geological medium, a water film is formed on grain surfaces, which potentially influences chemical reaction and mass transport. We developed a model to estimate the film thickness in a geological medium using a concept of disjoining pressure associated with the electric double layer repulsion force and van der Waals force. The model indicates that the thickness of the water film associated with the occurrence of gas entrapment is controlled by the diameter of pore (the diameter of meniscus), and that larger pores have thicker water films. Examples of the relationship between pore size distribution and film thickness are shown.