Non-Condensable Gasses (NCG) are gasses such as carbon dioxide, hydrogen sulphide, methane and nitrogen which can be present in a SAGD steam chamber but do not condense into the liquid phase to any large degree. Recent theoretical and laboratory work has shown that these gasses can enhance the thermal efficiency of SAGD without a significant reduction in productivity. There has been considerable discussion, both positive and negative, regarding the behavior of these gases in the steam chamber. Benefits to SAGD productivity have been suggested by some, while other authors have projected impacts on bitumen recovery.
This paper highlights how numerical simulation can be used as a tool to analyze the impact of NCG in SAGD through modification of K-value based on thermodynamic theory. As the simulated bitumen production rates were much less than those found in the field. It is necessary to adjust physical properties so as to make the gas more soluble, e.g. by artificially modifying the K values. The author has developed a method of modeling the effects of NCG in a steam zone using the new modified K value table. This paper will present the results of these simulations with and without modification of K-value and predict impact of NCG on SAGD performance.