To combat the challenge of high water usage and environmental foot prints, Steam-Assisted Gravity Drainage (SAGD) operators are beginning to combine steam and non-condensable gas (NCG) injection, as described in Butler's Steam and Gas Push (SAGP) recovery process. Recent field reports have also shown significant reductions of the steam-to-oil ratio, a key performance indicator for SAGD. However, there is still a limited understanding of the interaction of the NCG and steam and how this affects fluid flow and heat transfer dynamics within the reservoir. This research examines the operation of the SAGD-SAGP hybrid as applied in the MEG Christina Lake reservoir with the aim of clarifying the underlying mechanisms that occur in the reservoir as the process evolves. The results demonstrate that replacement of steam with NCG lowers the amount of steam injected with consequent reduction of the saturation pressure, and thus, saturation temperature of the steam. Although this adversely impacts the amount of mobilized bitumen, its impact is relatively small and the reduction of injected steam improves the steamto-oil ratio. The interplay between NCG and steam at the edge of the chamber affects heat transfer leading to reduced heat transfer to the overburden and sides of the depletion chamber. (C) 2019 Elsevier Ltd. All rights reserved.