future in situ technology
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The evolution and future of in situ oilsands recovery technology
By Ian D. Gates and Jacky Wang Department of Chemical and Petroleum Engineering Schulich School of Engineering University of Calgary
e av y oi l and oilsands reservoirs
40–60 per cent for steam assisted
displayed in Figure 1. Typical original
making bitumen mobile within the res-
gravity drainage (SAGD).
reservoir temperatures range between
ervoir. After the bitumen is mobilized,
in Alberta, host
For cold producible reservoirs, in
7ºC and 13ºC for the majority of oil-
a drive mechanism must be available
approximately
general, the in situ viscosity of the live
sands reservoirs where the viscosity of
to move the mobilized oil to the pro-
1.7 trillion barrels
oil must be lower than approximately
the bitumen is over one million cP. By
duction wellbore. Thus, there are two
of heav y oil and
35,000 cP. With sufficient solution-
raising the temperature to greater than
requirements of technically success-
bitumen. This is a
gas drive, oil can be recovered, with
200ºC, the oil viscosity drops to about
ful oilsands recovery processes: first,
significant fraction of the global
or without sand, from these reservoirs
six cP. Thus, heating bitumen to lower
mobilize the oil, and second, deliver
estimated six trillion barrels of heavy
at economic rates. The majority of
its viscosity provides one means of
the mobilized oil to a production well.
oil and oilsands reserves. The key
unconventional oil in Alberta is con-
challenge faced by operators in
tained in oilsands reservoirs. The
producing heavy oil and oilsands
bitumen contained in these reser-
reservoirs is the viscosity of the
voirs often has very low solution-gas
oil. Permeabilities are relatively
content and, given its viscosity, it is
10,000,000
high, often being between one and
essentially immobile within the res-
eight darcys (D), but oil viscosities
ervoir with virtually no natural drive
1,000,000
range in the tens of thousands of
energy. Thus, to move bitumen to a
centipoise (cP) for heavy oil to the
production well in an oilsands res-
hundreds of thousands to millions
ervoir implies that first the oil must
of cP for bitumen. Consequently,
be mobilized. One key property of
oil recovery factors average at
bitumen is that its viscosity drops by
about 10 per cent for cold heavy oil
five to six orders of magnitude when
10
production, about 25–35 per cent
it is heated to over 200ºC. An exam-
1
for cyclic steam stimulation (CSS,
ple of the dependence of Athabasca
also referred to as huff’n’puff), and
bitumen viscosity on temperature is
56
Canadian heavy oil association
Figure 1: Dependence of Athabasca bitumen viscosity on temperature (Mehrotra and Svrcek, 1986).
VISCOSITY, cP
100,000 10,000 1,000 100
0
50
100
150
200
TEMPERATURE, deg. C
250
300