Seyed Ali Feizabadi, SPE, University of Calgary, Jalal Abedi, SPE,
University of Calgary, Zhangxin Chen, SPE, University of Calgary
SPE Improved Oil Recovery Symposium,
14-18 April 2012,
Tulsa, Oklahoma, USA
The injection of different solvents, such as propane and CO2, into bitumen,
has proven to be an effective method in the production of these kinds of
reservoirs. However, in some cases, the prediction of large solvent
requirements can make it uneconomical. The formation of a second liquid phase
has been observed when the solvent is propane or CO2, with the second liquid
phase mainly composed of the solvent itself.
The objective of this research is to understand the importance of this second
liquid phase and its effect on production. Also, a simulator that can allocate
an individual phase to this liquid phase would allow for prediction of the
amount of solvent that can be produced and recycled. This makes the cost
evaluation of solvent injection processes to be more realistic.
Depending on the reservoir fluid distribution, a three- or four-phase flow can
occur in the absence or presence of water. A compositional simulator based on
an equation of state is designed to simulate these multiphase situations. This
simulator has a four-phase flash and stability subroutine, which make it more
realistc compared to other compositional simulators. In fact, it can handle a
maximum of three hydrocarbon phases and one aqueous phase. Relative
permeability plays an important role in multiphase flow; numerical results
indicate that, by increasing the number of phases, there is an increase in
project life. It is valuable to mention that the results of this research can
be also used in CO2 sequestration.
Heavy Oil and Bitumen
Heavy oil and bitumen are viscous mixtures of hydrocarbons and other organic
compounds. In general, heavy oil and bitumen are classified according to API
and viscosity. Crude oils with API less than 20º and viscosity less than 10,000
cp are known as heavy oils while those with viscosities greater than 10,000 cp
are termed as extra heavy oil or bitumen (Das, 1995; Miller 1994).
Canada has huge heavy oil and bitumen resources. Original Oil In Place, OOIP is
estimated to be more than 400 billion m3 (approximately 2.5 trillion bbl) which
is approximately twice that of the total conventional oil reserves in the
Middle East (Dusseault, 2001; Farouq Ali, 2003).
These reserves exist in unconsolidated sand and carbonate sedimentary
formations of Athabasca, Cold Lake, Peace River and Wabasca regions in Alberta,
Saskachewan and British Columbia. Heavy oil and bitumen are becoming more and
more important considering the depletion of conventional oil reserves in the
world. However, production of heavy oil and bitumen is more challenging and
more expensive than that of conventional oils because of immobility of them in
reservoir conditions due to their high viscosity.
There are two methods for recovery of heavy oil and bitumen: open pit mining by
using large trucks and shovels and insitu recovery through wells. The first
method is very effective (more than 90% recovery). However, this is only
suitable for shallow reservoirs with overburden formation depth of less than
75m. In Canada, most of the reservoirs are deep enough not to be exploited by
open pit mining.
At present time cold heavy oil production (CHOP), cyclic steam stimulation
(CSS) and steam-assisted gravity drainage (SAGD) are the major in-situ recovery
methods used in Canada.