Pore-level Investigation of Heavy Oil Recovery using Steam Assisted Gravity Drainage (SAGD) (2009)

1. Abstract Successful application of gravity drainage process, facilitated with steam injection, using horizontal wells in various field tests, especially within Canada, indicates that high recovery factor and also economical steam to oil ratios are achievable. Steam Assisted Gravity Drainage recovery scheme was theoretically developed, pilot tested and commercialized in Canada, however, there are still several technical challenges to be solved in this process. The pore-scale events of heavy oil recovery in SAGD process are not yet well understood to the extent of incorporating pore-level physics of the process into mathematical models. Investigation of the physics of fluid distribution and flow behavior in porous media for SAGD process at the porescale is expected to result in significant improvement in understanding the macroscopic phenomena observed in either laboratory or field scale. The main objective of this paper is to visually investigate and to document the pore-scale events of the SAGD process using glass micromodel type of porous media. SAGD experiments were carried out in micromodels of capillary networks etched on glass plates which were initially saturated with heavy oil. Experiments were conducted in a vacuum chamber in order to reduce the excessive heat loss to the surrounding environment. Initial results indicate that when the heavy oil-steam interface is established, gravity drainage process takes place through a layer of pores, with a thickness of 1 - 6 pores, in the direction perpendicular to the interface. The interplay between gravity and capillarity forces results in the drainage of mobilized oil. The visualization results demonstrate the phenomenon of water in oil emulsification at the interface due to the local steam condensation. The extent of emulsification depends directly to the temperature gradient between steam phase and cold bitumen. Other pore-scale phenomena such as film-flow drainage type of mobilized oil, localized entrapment of steam due to the capillarity followed by condensation, steam condensation at the interface due to temperature gradient, and snap-off of liquid films are also illustrated using glass micromodels in pore-level visualization experiments. 2. Introduction Heavy oil and bitumen are of great economic importance to Canada. The quantity of oil in place in the form of bitumen in Canada is as great as that of the conventional crude oil in the Middle East and it is a major Canadian technical challenge to utilize this vast resource efficiently and economically. A recent estimate of the recoverable volume represents only 12% of the volume of bitumen in place, based on the available economic conditions. However, there is considerable potential for this percentage to increase as advances are made in the recovery technologies. Recently, the reserves are estimated to be 28.3 billion cubic meters, made up of only 5.6 billion cubic meters in the surface-mineable areas and 22.7 billion cubic meters for the deeper areas. This total volume is sufficient to satisfy total Canadian demand for crude oil, at current rates, for approximately 250 years [1]. Thermal recovery techniques have been proved to be effective methods of utilizing heavy oil, extra heavy oil, and bitumen considering their in-situ upgrading potential as well as economic considerations. Among the vast spectrum of thermal recovery techniques, Steam Assisted Gravity Drainage (SAGD) seems a suitable recovery candidate especially for the Canadian and Venezuelan unconventional viscous hydrocarbon resources because of their unique unconsolidated lithology and its associated high vertical permeability.