Abstract
Chemical flooding has great potential for enhancing heavy oil recovery,
especially for reservoirs where thermal methods are not feasible. It has been
shown that the formation of emulsions during chemical flooding can effectively
improve sweep efficiency and, consequently, increase heavy oil recovery. The
mechanism of flow of oil-in-water (O/W) emulsion in porous media has been
extensively studied and simulated using the filtration theory. Few studies have
been done for the modelling of water-in-oil (W/O) emulsion flow in heavy oil
reservoirs. This study experimentally investigated the effective viscosity of
W/O emulsion in porous media. Alkaline flooding tests were performed in
channelled sandpacks to demonstrate the effectiveness of sweep efficiency
improvement by the in-situ produced W/O emulsions. High tertiary oil recoveries
were obtained for all these tests. The alkaline flooding process was simulated
by including the observed flow behaviour of extra resistance to water phase
flow caused by the formation of W/O emulsions, as well as the adsorption of
chemicals, interfacial tension reduction, and in-situ generation of W/O
emulsions. These laboratory results and the developed simulation technique are
proposed as an improvement to the simulation and design of the field-scale
projects of chemical flooding for heavy oil recovery.
Introduction
Many heavy oil reservoirs in Western Canada are not suitable for steam
injection techniques due to thin pay thickness. Both field and laboratory
results demonstrate that waterflooding of heavy oil reservoirs can only achieve
a very low oil recovery. The main causes for the poor sweep efficiency of
waterflooding for these heavy oil reservoirs are very adverse mobility ratio,
natural area and vertical reservoir heterogeneity and heterogeneity induced by
primary production(1,2). Therefore, improving mobility ratio and blocking water
flow through channels are essential for improving heavy oil recovery. The
in-situ formation of emulsions during alkaline flooding has been recognized as
one of the efficient methods to improve sweep efficiency for heavy oil
recovery(3,4,5).
The effectiveness of alkaline flooding for acidic crudes was recognized as
early as in the 1920s(6). Jennings et al.(3) proposed the mechanism of
emulsification and entrapment for alkaline flooding. They carried out caustic
flooding tests using a heavy oil. Their results showed that the in-situ
produced O/W emulsions tended to plug water fingering and channels, resulting
in improved sweep efficiency. Johnson(7) summarized possible mechanisms of
alkaline flooding to improve oil recovery: dispersion and entrainment,
wettability reversal, and emulsification and entrapment. The formation of W/O
emulsions was also observed as a mechanism of improving oil recovery(8,9).
© 2010. Society of Petroleum Engineers
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History
- Original manuscript received:
25 June 2008
- Meeting paper published:
17 June 2008
- Revised manuscript received:
8 January 2010
- Manuscript approved:
29 January 2010
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