A new technique is developed to measure the diffusivity of gas in bitumen as a function of composition. Results are presented for a carbon dioxide-bitumen system, which is of considerable industrial relevance. The technique employs transient pressure data obtained from a nonintrusive pressure decay experiment at constant temperature and volume. The underlying theory is presented along with a computational algorithm to calculate diffusivity. Using experimental pressure decay data in the range 25-90 °C at 4 MPa, the diffusivity of carbon dioxide in bitumen is calculated. The results are compared with the limited data available in the literature. The approach is straightforward and can be easily applied to other nonvolatile liquid systems.

Experimental data for the diffusivity of carbon dioxide, methane, ethane and nitrogen in Athabasca bitumen are presented in the range 25–90°C at 4 and 8 MPa. The diffusivity of these gases has been determined as a function of gas concentration in bitumen using a non‐intrusive experim̀ental method. The diffusivity of gas in general is found to increase with temperature and pressure, and is a unimodal function of concentration. A correlation is provided for the average diffusivity of these gases as a function of temperature.

The vapor extraction of heavy oil and bitumen, or Vapex, has emerged as a very promising recovery process since its invention in 1991. The principal reason is the environmental friendliness of Vapex together with its cost-effective nature vis-a `-vis other recovery processes. This paper assimilates and presents the research and technological contributions made toward Vapex. The development and applicability of Vapex is brought up in context of the availability of oil from natural sources, challenges of oil recovery, environmental factors, and cost economics. Significant findings and salient features of several experimental and theoretical studies on Vapex are included. Various factors that influence the operation of Vapex are discussed. Important issues are identified that need further investigations for the continued enhancement of Vapex. It is expected that this paper will serve as a useful reference tool for the engineers and scientists interested in Vapex.

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