Spatial Variations of Latent and Other Forms of Heat in a SAGD Process

Abstract

Abstract Steam-assisted gravity drainage (SAGD) is characterized by the development and expansion of a steam chamber. It is generally assumed that all points within a steam chamber are at same temperature as the injected saturated steam. Hence, the view that the injected steam releases the full latent heat corresponding to its injection temperature. Leveraging on relationship between steam latent heat and temperature, as well as that between saturation temperature and pressure, this paper interrogates the general view that a constant amount of latent heat is released at all points within a steam chamber. We formulate and simulate a new mathematical model that reveals why and how the net specific latent heat released varies across a steam chamber. For completeness, a similar analysis is extended to examine the spatial variations of sensible and total heats in a SAGD. From parametric tests performed, spatial variations of the effective latent, sensible and total heats in a SAGD are quantified. The parametric tests show that the spatial variations of effective latent, sensible and total heats released are more sensitive to in-situ steam temperature than density contrast. For the range of density contrasts examined, simulation results suggest that the spatial variations are more pronounced at steam temperatures less than 150 °C. At higher temperatures, at which most SAGD and steam-based recovery processes are operated, spatial variations of the specific latent, sensible and total heats of steam are found to be negligible. These findings provide a technical basis not to operate SAGD and other steam-based recovery techniques below 150 °C.