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OIL SANDS
- The
- The
- For
The problems most often encountered
were corrosion and high temperature
producing wells.
direction in which the burning front
moved was guided essentially by reser
voir characteristics.
produced oil was upgraded by
about 4API, and viscosity was substan
tially reduced.
Morichal and Miga fields, the
analyses indicated that the process had
been successful in the affected region.
In Venezuela, the first ISC projects started at the
beginning
of the 1960s. Their impact was over
shadowed, at that time, by operation problems
(oil emulsification, corrosion of well equipment,
etc.) and the discovery of the cyclic steam injec
tion process. Cyclic steam has since become
the most successful and economic technique
used in Venezuela heavy oil fields. In spite of all
the disadvantages of the in situ combustion tech
nique, the authors believe it still has a high poten
tial for application to tar sand and heavy oil reser
voirs. Among its advantages are high thermal ef
ficiency, low impact on the environment, and it
uses less fuel than cyclic steam injection.
Morichal Test
The Morichal field test was located in Monagas
State in Eastern Venezuela, approximately
150 kilometers south of the City of Maturin (see
Figure 1).
An ISC pilot test was conducted in 1960 in an
unconsolidated reservoir to investigate the pos
sibility of recovering heavy (9
to 12
API)
oil at a
depth of 3,500-4,000 feet. Primary recovery from
these flat reservoirs is low (2-7 percent), and oil
viscosities range from 400-1,850 centipoise at
reservoir temperature.
An Isolated two-spot pattern with 329-foot spac
ing
was selected for this test. Air injection began
on June 8, 1960, and the pressure stabilized at
3-27
1,425 psi. Air injection was terminated on
May 17, 1962. Injection production history after
air injection termination can be followed in
Figure 2. The oil production rate rose gradually,
peaking at 365 barrels of oil per day in July 1963,
and thereafter declining to 100 barrels of oil per
day in June 1964 when the test was terminated.
Miga Test
The Miga field test was located approximately
25 kilometers south of San Tome, Anzoategui
State in the Northeastern part of Venezuela (see
Figure 1). From 1964 to 1985 a fireflood project
was carried out in the P2-3 sand reservoir in the
Miga field to stimulate production of 13
14
API heavy oil.
The original-oil-in-place was estimated at
22 million barrels. Only 1 .2 million, or 5 percent,
was expected to be produced by primary deple
tion. Up to April 1983, about 5 million barrels of
oil or 25 percent of the original-oil-in-place were
recovered by the use of the in situ combustion
process, and about 50 billion standard cubic feet
of air had been injected. The air/oil ratio
averaged 12 thousand cubic feet per barrel.
Based on this air/oil ratio, the project was con
sidered to be a technical and economic success.
Melones Field Test
A single injection well pilot test was carried out in
2.06 acres of the Melones field from 1977 to
1978. The purpose of the test was to evaluate
the combination of forward combustion and
water injection in an Orinoco heavy oil reservoir.
Figure 1 shows the location of the Melones field
in the Northeastern part of Venezuela.
The pattern consisted of an inverted five-spot pat
tern with a well spacing of 212 feet and two obser
vation wells.
This project encountered many difficulties in the
oil production wells. Plugging of the wellbore by
sand caused the productivity to decrease, and
workovers were necessary in August 1977.
During this period, the loss of large amounts of
THE SYNTHETIC FUELS REPORT, JANUARY 1995
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