The injection of non-condensable gases (NCG's) with steam in SAGD is a concept that has been much discussed in the literature, and tested via laboratory studies, and in a small number of field pilots, the most comprehensive being the UTF Phase B. There has been considerable discussion, both positive and negative, regarding the behaviour of these gases in the steam chamber, and their impact on ultimate bitumen recovery. Benefits to SAGD productivity have been suggested by some, while other authors have projected impacts on bitumen recovery.

The authors have reviewed the results of methane injection in several projects, and used thermodynamic theory to develop a method to effectively model this behavior via simulation. While conventional simulators use the Peng-Robinson Equation of State, the effectiveness of EOS's become challenging at high temperature. In addition, the effects of recent developments in high temperature solution thermodynamics become significant with increasing temperature in SAGD.

AOSC has developed a method of modeling the effects of NCG in a steam zone, via the development of a new set of equilibrium values for methane exchange between the oil/gas phase, water/gas phase and oil/water phases. This paper will present the results of these simulations and predicted impact of methane injection on SAGD performance, as well as implications for other NCG's.

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