A Moving Boundary Approach for Determination of Molecular Diffusion Coefficient in a Propane/Bitumen System

Shauheen Etminan
Supervisors: Prof. John Chen, Prof. Brij Maini


The research on the molecular diffusion can be applied into improving the prediction of compositional reservoir simulators and designing solvent based-processes. For measurement of gas-Bitumen diffusion coefficient, there are direct methods and indirect methods. For the indirect methods measuring the change in one of the system parameters that varies because of the diffusion and correlating this property to composition, there is no need to determine the composition. The objective of this work is the estimation of propane-MacKay River Bitumen Molecular Diffusion.

Due to the moving of interface, a diffusion-induced convection term comes into the play, and only diffusion equation is not sufficient to model. A simplified moving boundary problem is solved by the heat integral method. And then formula for penetration depth and concentration profile is obtained. Experimental analysis is carried out to test the interface movement & velocity, gas dissolution amount, and prediction from interface velocity and amount of gas dissolved. Dispersion coefficient in VAPEX is studied experimentally, including the fluid characteristic measurement and fluid characteristics. It is concluded that the value of convective mixing in VAPEX is larger than the value of mixing in diffusion cell; in the diffusion cell, there is convective mixing which is due to the movement of interface; however, the value of mixing in VAPEX is still larger which could be due to enhancement of mixing in presence of porous medium.