Summary
In earlier work (Pathak et al. 2010, 2011), we presented the initial results
for heavy-oil and bitumen recovery using heated solvent vapors. The heavy-oil-
and bitumen-saturated sandpack samples of different heights were exposed to
heated vapors of butane or propane at a constant temperature and pressure for
an extended duration of time. The produced oil was analyzed for recovery,
asphaltene content, viscosity, composition, and refractive index. Recovery was
found to be very sensitive to temperature and pressure.
The current work was undertaken to better understand the physics of the
process and to explain the observations of the earlier experiments using
additional experiments on tighter samples of different sizes, numerical
simulation, and visualization experiments. The effects of temperature and
pressure on the recovery were studied using a commercial reservoir simulator.
Propane and butane were used as solvents. Asphaltene precipitation was also
modeled. A qualitative history match with the experiments on different
porous-media types was achieved by mainly considering the permeability
reduction caused by asphaltene precipitation; pore plugging; the extent of
interaction between the solvent and oil phases; and parameters such as model
height, vertical permeability, and gravity. The effect of asphaltene deposition
on models of varying permeabilities was also studied.
To investigate the phenomenon further, visualization experiments were
performed. 2D Hele-Shaw models of different dimensions were constructed by
joining two Plexiglass sheets from three sides, or in some experiments, from
all sides. The models were saturated with heavy oil and left open on one side
(or all sides) and were exposed to different types of solvents. The setup was
monitored continuously to observe fluid fronts and asphaltene
precipitation.
By use of this analysis, the mechanics of the process was clarified from the
effect of solvent type on the recovery process. The optimum operating
temperature for the hot-solvent process and the dominant mechanisms were
identified. The dynamics of the asphaltene deposition and its effect on oil
recovery were clarified through visual and numerical models.
© 2012. Society of Petroleum Engineers
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History
- Original manuscript received:
12 June 2011
- Meeting paper published:
8 May 2011
- Revised manuscript received:
3 October 2011
- Manuscript approved:
28 December 2011
- Published online:
30 March 2012
- Version of record:
3 April 2012
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