Dispersion Determination in VAPEX: Experimental Design, Modelling and Simulation

The heavy oil and bitumen reservoirs of Canada are one of the largest hydrocarbon sources in the world. Vapor extraction of heavy oil, or VAPEX, has emerged as a very promising recovery process since its inception in 1991. The principal reason is the environmental friendliness of VAPEX together with its cost-effective nature vis à vis other recovery processes. In this work, a review has been done on various factors affecting VAPEX process. Also, a lab-scale VAPEX experimental setup is designed to determine the dispersion coefficients of solvent gases in heavy oil and bitumen. Further, a mathematical model is developed based on earlier reported rectangular physical model of homogenous porous medium saturated with heavy oil and bitumen. The developed mathematical model is simulated to determine gas dispersion along with solubility during the vapor extraction of live oil from a laboratory scale physical model. At a given temperature and pressure, the block is initially exposed on its side to a solvent gas, which diffuses into the medium and gets absorbed. The absorption of gas reduces the viscosity of heavy oil and bitumen causing it to drain under gravity. The low-viscosity “live oil” is produced at the bottom of the porous block. The production of live oil with time is accompanied by the shrinkage of block as well as its increased exposure to gas from top. These phenomena of VAPEX are described by the mathematical model, which is used to calculate live oil production with various values of gas solubility and dispersion. Their optimal values are determined for the vapor extraction of Cold Lake bitumen with butane by matching the calculated live oil production with its experimental values published earlier.