Ikelic - Alliance Digital Repository

OIL SANDS
was shown that the volumetric sweep efficiency
Increased from 59 percent for vertical wells to
70 percent for horizontal wells. The oil recovery
increased accordingly.
So far, horizontal wells-ln conjunction with an In
situ combustion process in the field-have been
drilled in two Canadian projects. In both cases
the horizontal wells were used as producers.
In the first project, Eyehill, Saskatchewan, three
horizontal wells with a horizontal leg of
1 ,000-1 ,2000 meters were drilled.
Of these three wells, the first one had a very
good production performance. This well
produced for a long time with oil rates of
55-60 cubic meters per day. The second horizon
tal well was situated on the other side of the first
horizontal well, too far from the project area and
probably it was screened by the first one. The
third horizontal well intercepted a portion of the
previously burned area and it had a mediocre per
formance.
In the second project, Battrum, Saskatchewan,
one horizontal well was drilled in conjunction with
the commercial wet combustion process which
has been in progress on this reservoir since
1964. This process takes place in a reservoir
having a relatively low oil viscosity. The horizon
tal well was drilled in December 1993 and it has a
horizontal leg of 610 meters. It was positioned
between the gas tongue and the water tongue in
an exploitation using the patterns system. The
performance of this well was very good as the oil
rate increased by 5-10 times (from 3 to 15 cubic
meters per day for a vertical well, to 35 to
75 cubic meters per day for the horizontal well).
So far, horizontal wells have been used only as
producers. However, the utilization of horizontal
wells could be extremely useful as injectors in
low injectivity reservoirs where they can open the
door for the application of wet combustion in
more cases. It is expected that horizontal well in
jectors will be used first in the reservoirs where
spontaneous ignition is easily achieved.
3-26
Possible Improvement of the Process
For ISC projects applied to heavy oil reservoirs
the volumetric sweep efficiency usually is poor,
less than 25-35 percent.
Given the ability of foams to achieve high resis
tance factors in oil-free rocks it appears that ac
tually the foam could have high efficiency when
applied with ISC processes. In this case the
other positive element for the foam use is that
after 6-7 months from the beginning of the
process, the temperature around the air
(air/water) injector is low, close to the reservoir
temperature. This creates favorable conditions
for foam application. Injected in the combustion
wells, the foam can significantly decrease gas
channelings.
The first foam field testing in the Karajanbas field
gave promising results.
It is expected that the greatest future progress in
application of ISC will be due to the use of
horizontal wells. The only
problem which still
remains when using a horizontal well as a
producer is that the combustion front can inter
sect the horizontal leg close to the heel and can
damage the whole horizontal portion
prematurely
of the well.
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VENEZUELA IN SITU COMBUSTION
PROJECTS REVIEWED
At the Symposium on In Situ Combustion Prac
tices held in Tulsa, Oklahoma last year, a paper
by
M. Villalba et al. of INTEVEP presented a litera
ture review of four In Situ Combustion (ISC)
projects: in Miga, Tia Juana, Melones and
Morichal fields in Venezuela.
The behavior of the four field tests can be sum
marized as follows:
THE SYNTHETIC FUELS REPORT, JANUARY 1995