There is a large amount of reserves associated with heavy oil worldwide and as a result SAGD is reaching technological maturity and its implications on the future of the petroleum industry are considerable. Most of the theory of SAGD was developed in idealized lab models and flow simulations without accounting for much heterogeneity as well as operational effects.
Currently there are a large number of wells in SAGD projects with available production, injection, and pressure data that needs to be analyzed. In addition, there are thousands of pressure and temperature measurements, 4D seismic surveys, and tiltmeter surveys. It is essential to examine all of this available data and explore important factors like areal coverage of the steam chamber, vertical sweep, and residual oil saturations within the steam chamber, as well as the role that heterogeneity plays in the development of the steam chamber. It is our opinion that some of the empirical field case observations cannot be easily explained by conventional reservoir engineering, or even by current thermal simulation techniques.
By closely examining available production, injection, pressure, seismic, temperature logs for two different SAGD projects, this paper will show that there is a good correlation between the volume of the steam chamber (Vstm) as calculated by vertical temperature observation well data and seismic data, compared to the steam chamber size as indicated by oil recovery. When we use seismic data for estimating areal coverage and vertical observation wells for vertical coverage or sweep, it appears that the oil saturation slowly decreases in the steam chamber and displacement efficiency is slowly increases with time. This paper attempts to use all the available seismic data and data from observation wells in not just a qualitative analysis of the steam chamber, but to develop a method to analytically determine quantitative estimates for volumes of the steam chamber, areal displacement efficiency of the steam chamber, and remaining oil saturation in the steam chamber over time. Invesitgating available data from different observation wells along SAGD well pairs will show that steam chamber shape is far from uniform.