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. In the laboratory, NCG has been shown to finger into the bitumen ahead of the main steam chamber, bringing with it heat and pressure.

This paper looks at temperature and pressure data from the world’s most mature SAGD pilot, Phase B of the Dover project, to determine whether naturally occurring NCG in the form of solution gas can be detected fingering ahead of the main steam front. The paper looks at the propagation of the steam chamber front by examining thermocouple data from observation wells drilled within and outside the SAGD pattern. The steam chamber propagation velocity, which also determines the velocity of the pressure front, is calculated. The pressure build-up profile is used to determine the pressure diffusivity constant, which in turn determines where the pressure front would be located without any NCG fingering.

The actual pressure front is compared to the predicted. In every case the actual pressure front travels between five and twelve meters ahead where one would expect it from the theory.

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