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FIPVYQIJlE
April 9, 1963
R. 0. WEST ETAL
3,684,743
SECONDARY RECOVERY OF PETROLEUM
Filed Sept. 16. 1958
QUE
mm
m
N1.
9:
m_21
‘in
Robert C. West
Gerald D. HRH
Donald M Bee on
Inventors
By
Attorney
'ilnited States atent O?hce
1
3,084,743
Patented Apr. 9, 1963
2
3,084,743
SECONDARY RECOVERY OF PETROLEUM
Robert C. West, Geraid D. ()rllotf, and Donald M. Bee
son, Tulsa, Okla, assignors to. Jersey Production Re
search Company, a corporation of Delaware
Filed Sept.- 16, 1958, Ser. No. 761,313
5 Claims. (Cl. 166—9)
crude oil. Speci?cally, this invention provides an im
proved secondary recovery process using carbon dioxide
wherein a bank of ?uid comprising carbon dioxide is in
jected into a partially dcpletcd reservoir to establish a
pressure of at least 1000 p.s.i. and preferably one in the
range of 1000 to 4000 psi. Thereafter, an aqueous
medium is injected into the reservoir to cause the carbon
dioxide in contact with oil contained therein to pass
through said reservoir while the above pressure is main
tained on the reservoir. Finally, as an integral step in
ularly to an improved process for recovering oil which 10 the novel process which has been discovered, injection of
involves the injection of a ?uid comprising gaseous or
the aqueous medium is ceased and the reservoir is depres~
liqui?ed carbon dioxide into an oil reservoir from which
sured to atmospheric pressure by pumping down the pro
production by conventional methods has decreased to a
duction well.
stage where further recovery by such methods is no
In a preferred embodiment of the present invention, an
15
, longer pro?table.
oil-bearing reservoir to be treated in accordance with the
In normal oil production techniques during a ?rst or
novel process is ?rst brought under substantially hydraulic
primary recovery period, natural earth pressures are relied
control and a static pressure of at least 1000 psi. is ex
upon to cause the production of oil. Primary recovery
erted upon water in ?uid communication with the oil
can be continued’ until the pressure existent in the re
20 bearing reservoir. In some instances a reservoir which
servoir is so depleted that economic oil recovery can no
previously has been watertlooded will be treated. Alter
This invention relates to the secondary recovery of
petroleum from subterranean formations and more partic
longer be obtained. In general, however, primary re
covery techniques can secure production of only twenty ,
to twenty-five percent of oil in a- reservoir. In order to
nately, it may be necessary to inject water until ?ll-up
occurs. After the reservoir has been put under substan
tially hydraulic control, the reservoir mean pressure is
increase recovery, a variety of secondary recovery proc_ 25 raised to 1000 psi. or above, and a limited bank of a
esses have been employed. Usually, a drive ?uid such
?uid comprising gaseous or liqui?ed carbon dioxide is
as water is injected into the reservoir through an injection
injected at a pressure which is at least 1000 p.s.i. There
well so as to drive oil through the oil-bearing strata to
after, an aqueous ?uid or simply more water is injected
a production well. The present invention, which is con
until economic limit to cause the bank of carbon dioxide
cerned with this general technique of employing a ?uid 80 to pass through the reservoir in contact with the oil con
, drive, provides an improved process which comprises the
tained therein and the reservoir is then depressured. In
injection of carbon dioxide to force oil from a hydrocar
an alternate embodiment, wherein an oil-bearing reservoir
bon bearing formation.
already contains water at a pressure in excess of 1000
While the general principles of secondary'recovery
p.s.i., the initial step of the process is the injection of the
1 processes have long been appreciated, practical ditl‘iculties 35 carbon dioxide containing gas.
exist which have seriously limited the value of known
In accordance with the present invention, the secondary
procedures. The principal problem has been that oil dis
recovery of oil from a depleted or partially depleted res
placement in a reservoir by a driving ?uid is normally in
ervoir is e?iciently carried out by injecting carbon dioxide
e?icient. For example, by the use of water, which has
into a reservoir under pressure. It has been observed
been the most common driving ?uid which has been em— 40 that when carbon dioxide and crude petroleum are placed
ployed in secondary recovery procedures, it usually has
been impossible to recover some ?fty percent of the oil
originally contained in a reservoir. More recently, oil
recovery has been increased by a method involving in
jection of air, natural gas, or other gaseous hydrocarbon 45
into some of the wells in a producing ?eld and the produc_ ~
tion of oil from adjacent wells.
Generally, where a gas drive is employed in a partially
depleted underground reservoir, the viscosity ratio of the
oil phase to the gaseous phase is of the order of from
about ?fty to one to several hundred to one.
This great
in equilibrium at high pressure and after a pressure of
about 1000 p.s.i. is exceeded, a point is reached where
additional carbon dioxide will not dissolve in the liquid
phase but instead a portion of the crude oil enters the
second and separate phase which is predominately carbon
dioxide. Thus, two immiscible phases are formed, one
mostly hydrocarbons with carbon dioxide dissolved there
in, and the other mostly carbon dioxide with hydrocar- _
bons dissolved therein. The present invention makes use
of this phenomenon for recovering additional oil from a
reservoir and in a preferred embodiment avoids both the
difference in viscosity between the driving gas and the oil
problem of having the gas bypass the oil in a partially de—
in the reservoir is ‘believed to cause a large proportion of
pleted reservoir, and the problem involved in the tedious
the gas to bypass the oil. The method also leads to ex
and costly pumping required to raise the pressure of a
cessive gas to oil ratios at the producing well and makes 55 compressible ?uid such as carbon dioxide to the exceed—
the conventional process ine?icient, since there must be
ingly high pressures required to obtain the unique prop
considerable recycling of the driving gas to effect ap
erties of carbon dioxide for oil recovery. The surprising
preciable recovery of oil. In an effort to overcome the
discovery has been that by means of the present process
above problems, various gases have been injected into a
it is possible to achieve a degree of oil recovery not here
well under pressure to establish a bank of gas at high
tofore available.
pressure or a bank of liquid into which some oil will
Broadly, this invention is directed to a novel method
dissolve. Heretofore, however, in order to build up a
for recovering oil from a partially depleted subterranean
high pressure bank of gas, or liqui?ed gas, continuous
oil-bearing strata having an injection well and a producing
pumping of the compressible ?uid for several days or even
well in comunication therewith, wherein gas comprising
for many months has been necessary.
carbon dioxide is injected into and swept through the
reservoir under conditions such that the amount of oil
The present invention relates to a novel secondary
recovered is in excess of that possible by any of the here
recovery technique ‘in which a gas comprising carbon
toforo known methods of primary and secondary recovery.
dioxide is employed in a unique manner thereby utilizing
In accordance with one embodiment of the invention an
70 oil-bearing stratum is ?ooded with water following which
static pressure in excess of 1000 psi. is exerted upon the
plicable to the recovery of both high- and ‘low-viscosity
Y the peculiar properties of carbon dioxide in the recovery
of oil from underground reservoirs. It is equally ap
water in ?uid communication with the oil-bearing stratum. .
3,084,743
3
Thereafter, carbon dioxide from a suitable source is in
troduced into compressor 16 and from there passes under
pressure through valves 17 and 19 into injection well 4.
The carbon dioxide bank is then driven by water through
In the range of 0.03 to 0.50 pore volume of a ?uid com
prising gascous or liquillcd carbon dioxide is then injected
through the injection well into the stratum at a pressure
in excess of 1000 p.s.i. and is caused to be passed through
the stratum in contact with the oil contained therein to
the oil producing stratum to producing well 5 from which
is removed a mixture of water, carbon dioxide and hy
force the oil from the reservoir in the manner described
hereinafter, preferably without decreasing substantially
drocarbons picked up by the carbon dioxide by virtue of
the reservoir pressure, but in any event without decreas
ing the reservoir pressure below 1000 p.s.i. Thereafter,
the phenomenon referred to'ahove. The mixture is con
ducted through valves 29 and 27 into separator 26 wherein
into the reservoir at a pressure in excess of 1000 p.s.i. and
preferably ‘at substantially the same pressure as the car
completed by the pumping down of the production well.
in conducting the improved method of oil recovery in
bon dioxide.
volving a combination of water?ooding, carbon dioxide '
the reservoir is dcpressured and oil forced from the 10 ‘a portion of the hydrocarbons is ‘removed by partially
reducing the pressure. Separated hydrocarbons are re
reservoir by the injected gas which is driven through
covered from separator 26 through line 22. The mixture
the formation by water?ooding is removed to the surface
of carbon dioxide and unseparated hydrocarbons is passed
of the earth through a producing well.
overhead from the separator through line 23 into stripping
Preferably, the inert gas comprising carbon dioxide
which is utilized in accordance with the present invention 15 tower 24 which may be of conventional design. Here
further separation ‘of hydrocarbons from the carbon di
contains in the range of 50 to 100 percent carbon dioxide.
oxide occurs. Carbon dioxide leaving stripper 24 through
Where the supply of carbon dioxide is limited, and a pure
line 25 can be injected into other injection wells, not
gas is not employed, nitrogen, flue gas; air or a hydrocar
shown. Hydrocarbons recovered in stripping tower 24
bon gas can be mixed with the available carbon dioxide
and an injection gas containing in the range of 50 to 100 20 are removed through line 28.
At all times when either carbon dioxide or aqueous driv
percent carbon dioxide can be employed in accordance
ing ?uid such as water is being injected into the reservoir,
with the invention.
the reservoir at the production well is maintained prefer
Further, in accordance with the present process, operat
ably at a pressure of the same order of'magnitude as at
ing pressures must be at least 1000 p.s.i. The upper pres~
sure limit is restricted by the operating pressure readily 25 the injection well but su?iciently below the injection pres
sure so as to permit oil to flow through the reservoir. The
obtainable by use of conventional equipment and of
oil caused to ?ow through the reservoir by the injected gas
course ultimately by the formation breakdown pressure.
is removed to the surface of the earth through the pro
Preferably,.pressures in the range of 1000 to 4000 p.s.i.
ducing well. Injection of aqueous ?uid is continued until
are employed. The injection of a carbon dioxide cou
oil and carbon dioxide no longer ?ow from the reservoir
taining-gas is continued only until va predetermined volume
in substantial quantities. At that time, injection of
which preferably is in the range of 0.05 to 0.25 pore
aqueous ?uid is ceased and the back pressure is released
volume has been introduced into the reservoir. At that
through valve 29 to produce additional oil as the reservoir
vtime injection of carbon dioxide containing gas is discon
approaches atmospheric pressure and recovery of oil
tinued and injection'of an aqueous driving ?uid is com
in accordance with this embodiment of the invention is
vmenced. This aqueous driving ?uid likewise is injected
I
injection, water?ooding, and depressuring in accordance
Advantageously, a driving ?uid which is a low solubility
?uid, comprising essentially water, is employed to cause 40 with the present invention, carbon dioxide is introduced
into injection well 4 as previously described while the
the bank or slug of carbon dioxide to pass through the
pressure at producing well 5 is maintained at least 1000
reservoir. In some instances, however, it may be desirable
p.s.i. Preferably, ?uid production from the reservoir is
to add a viscosity increasing agent to at least the initial
restricted during the injection of the carbon dioxide con
portion of the driving fluid to thereby adjust the viscosity
taining gas so that the pressure in the reservoir can be
so as to be of the order of or greater than that of the oil
I to be recovered.
maintained at least 1000 p.s.i. Following the injection
Conventional surface active agents and x
emulsi?ers can also be employed. The aqueous driving
of the limited bank of carbon dioxide, water or an aqueous
- ?uid functions to drive or force the carbon dioxide through
As a ?nal step in the process of the present invention, ad
ditional oil is recovered at the end of the carbon dioxide
medium is injected and continued until the ratio of water
to oil ?owing from the separator has reached an economic
limit, such as for example, 25 barrels per barrel.
By pore volume as used herein, is meant the pore
volume in that portion of the reservoir through which the
?ood by releasing the back pressure and depressuring the
reservoir by pumping down the production well.
Further objects and features of the invention and the
injected carbon dioxide passes in ?owing from injection
well to the producing well. The pore volume can be
determined with sufficient accuracy for the purpose of
preferred manner in which it is to be performed will
this invention in accordance with the procedures well
known in the industry from certain information obtained
by established investigating methods. Such procedures
the reservoir in contact'with the oil contained therein
without substantially decreasing the reservoir pressure.
be more readily apparent from the accompanying descrip
tion in connection with the drawing in which the single
FIGURE shows schematically the method of injecting an
are so well known in the art that a description thereof is
unnecessary.
The most advantageous volume of carbon dioxide to be
aqueous fluid and then carbon dioxide into an injection
' well and recovering oil swept from the strata through at
producing well.
introduced into the reservoir can be ascertained by labora
With particular reference to the drawing, a partially
depleted subterranean oil-bearing stratum lvis depicted
isolated by impervious strata 2 and 3. At least two wells,
an injection well 4 and a producing well 5, have been
drilled into the producing stratum. Initially, ‘water. is
introduced into the formation through injection well 4
tory experiments on a core under conditions simulating
- recovery of oil from a subterranean oil reservoir in ac;
cordance with conventional procedures. It is to be under
stood that the quantity of carbon dioxide required is in
?uenced by various factors, such as for example, com
and the reservoir ?ooded in the conventional manner un
til water ?ll-up occurs. Water is introduced under suit
able pressure indicated on gauge 11 from line 12 through
position of injection gas and reservoir oil, injection pres
sure, and the composition of the aqueous driving ?uid.
The volume required for conditions normally encountered
valves 18 and 19 until the pressure at both injection well
4 and producing well 5 reaches at least 1000 pounds per
square inch. A suitable back pressure indicated on pres
sure gauge 21 is maintained at the production well 5. 75
determined in the conventional manner in the laboratory
using an arti?cial reservoir. In accordance with the
present invention, in the range of 0.05 to 0.25 pore volume
in the ?eld is from 0.03 to 0.5 pore volume and can be
3,084,743
.
6
5v
of the gas comprising carbon dioxide is most advantage
and by infra red analysis con?rmed the accuracy of the
In accordance with the present discovery, when carbon
dioxide is injected into and driven through 'a watertloodcd
results.
A summary of experimental results obtained on Loudon
crude oil—-Wciler sandstone systems is shown in Table l.
Loudon crude oil has a viscosity of approximately 6 up.
ously employed.
oil reservoir upon which there is exerted a static pressure
of 1000 p.s.i. or above, there is an unexpected increase in
at 70° F. and an AP] gravity of 38°.
the amount of oil that can be recovered over that recover
The Wciler sand
stone possessed a porosity of approximately 20 percent
and a permeability in the range of 50 to 150 md. All
test cores used inthis example initially contained about
able by heretofore known methods of oil production,
with a corresponding decrease in the residual oil in the
reservoir. Further, additional oil can be recovered at
26% pore volume (PV) of connate water and 74% PV
the end of the carbon dioxide ?ood when the reservoir is
o? Loudon crude oil. Table I illustrates oil recovery ob
blown down or depressured. The above has been demon
tained with the process oi the present invention (Experi
strated by experiments carried out on linear laboratory
ment D), compared with that obtained by primary recov
models under conditions simulating a subterranean oil
ery alone (Experiment A), and by a water?ooding sec
reservoir in accordance with conventional laboratory 15 ondary process (Experiment B). Oil recovery obtain
practice. The following example illustrates the amount
able by driving a 0.20 PV bank of carbon dioxide at 1000
of oil that can be recovered from a reservoir by means
psi. through a test core with watertlooding wherein the
of the present invention.
core has not previously been water pressurized to 1000
psi. is shown in Experiment C.
EXAMPLE 1
20
Table 1
In a series of tests, crude oil was displaced from sand
stone models by the process of the present invention. The
Total Oil
models were cylinders two inches in diameter having a
length in the range of from ‘1 to 18 feet. _ The sandstone
cylinder-s were centered in steel tubes of 2% inch LD. and '
Experiment
Recovery
(percent)
Process
(based on oil
initially in
the annular space between the sandstone and the tube wall
was ?lled with a low-melting point alloy which expands
place)
on freezing. A tight seal was thus obtained at the sur
A _________ __
(Simulated Primary
41
face of the cylinder. Fluid inlets and outlets were located
B _________ __ Secondary Witter Flooding (Rcpressurcd
49
at opposite ends of the model.
>
30
Recovery).
to 1,000
s.i.)
C _________ ._ 0.20 l‘\-‘ carbon dioxide at 1,000 p.s.l. lol-
The flooding experiments were carried out at a pres
sure level of approximately 1000 psi. at room temper
taure with pressures maintained by the use of regulators
60
lowed by \vutcrllood.
D _________ ..
at'the producing outlets. Initially, the sandstone “reser
Present l’roecss (0.20 I’V carbon dioxide)..
71
From the above. it is clearly seen that the present proc
ess comprising exerting static pressure of at least 1000
psi upon an aqueous medium in fluid communication
- voirs” were saturated with crude oil and connate or “inter
stitial” water.
Gas Drive alone
The injection system was a motor-driven
direct-reading, constant-rate hydraulic pump, which dis
with an oil bearing reservoir. then injecting in the range
placed iluid from a high-pressure container into the model.
of 0.05 to 0.25 pore volume of carbon dioxide, thereafter
Commercial carbon dioxide of greater than 99% purity
driving the bank of gas with an aqueous medium to sweep
employed in liquid state was maintained at 80° F. during 4.0 oil through the reservoir and ?nally depressuring the reser
the tests. '
voir to atmospheric pressure, results in recovery substan
After the desired volume of water had been injected,
tially in excess of that recovered by water?ood. By this
in the range of 0.05 to 0.25 pore volume of carbon dioxide
novel sequence of operations, approximately 71 percent
was‘ injected into the sandstone reservoirs. Thereafter,
of the oil in place was produced.
the‘carbondioxide container was replaced by a cell con 45
EXAMPLE 2
taining water, and water injection was started again at
linear rates of ?uid advance until the producing water-oil
Further data on other systems in which the present in
ratio reached a value of 20. At that point, water injec
vention was tested in the manner of Example 1 are given
tion was discontinued and the back pressure on the model
below. The experimental studies dealt with the recovery
outlets was released. The produced ?uids were dis
of both'high-viscosity and low viscosity crude oil. In the
charged through the pressure regulator into a liquidgas
heavy oil tests, Ada crude oil was displaced from Torpedo
separator and the quantity of oil, water, and gas produced
sandstone models. This sandstone is a mildly water-wet
was measured. Overall material balance checks made
material having porosity in the range of 20 to 28 percent
on the oil production data by extracting residual oil from" ' ' and permeability in the range of 500 to 1500 md.
Ada
the models and determining residual oil by distillation 55 crude oil is an aromatic base crude, high in asphaltenes.
Table II
_ LINEAR MODEL EXPERIMENTS-ADA CRUDE OIL-TORPEDO SANDS'I‘ONE
Experl-
'
,/ "W" '
Initial Connate
Approx.
011
Water
_
_
Oil Recovery.
Fraction of Oil
Initially in Place
ment
Length
k air
is’,
Sutn.
Sam.
Experiment Description
Number
(FL)
(md.)
Fez'ceut
(l’cr-
(Per-
cent
cent
By
PV)
PV)
Flood
Percent:
Increase
Over
Reference
By
Blmv-
Wutcrfloud
Total
Recovery
Down
15
500
20.1
75.0
25.0
\‘\'uter?0od__......
0.29
1B
500
20.4
72.8
27.2
Water-driven 0.17 PV liquid
carbon dioxide bank.
0.52
1
1,500
27.0
82.4
17.0
\\"ntcrllood__._....__.......___
0.39
17
1,500
26.8
80.3
19.7
Water-driven 0.09 P\' liquid
carbon dioxide bank.
0. 59
1
1,500
27.0
75.5
24.5
Watcrilood of 180 ep. oil to
0 42 ...... ..
0.42 __________ __
17
1, 500
26. 8
79. 2
20.8
simulate watt-rllood of Ada
crude at 100° F.
Water-driven 0.08 PV gaseous
0. 50
0.61
carhogn
dioxide bank at
100
.
‘ Porosity.
...... ..
0.13
...... __
0.14
0. 11
0.29
__________ __
0.05
125
0.30
__________ __
0.73
87
45
8
Its viscosity at 70° F. is approximately 400 cp. The data
of Tables II and III further illustrate the amount of oil
injecting water into a subsurface oil-bearing reservoir
that can be recovered from a reservoir by means of the
pressure of at least 1000 psi. is attained, injecting a bank
present invention.
of from about 0.03 to about 0.5 pore volume, based on
through at least one injection well until a mean reservoir
'
Table III
LINEAR MODEL EXPERIMENTS-LOUDON CRUDE OIL-‘VEILER SANDSTONE
Model Description
Oil Recovery. Fract ion oi‘ Oll
Initially in Place
.
Experiment
Number
Length
(FL)
Approx.
k air
¢ (Pen
(mdi)
cent)
Initial Connato
Oil
Water
Satn
(l’or~
Over
By
By
Water- Iniec-
Satn.
(l’er'
cent)
Percent
Increase
Displacement Type
?ood
tion
By
Blow-
Total
down
Relercnce
Waterllood
Recovery
cent
PV)
M’)
10 _______ __
16
75
20.0
74.0
26.0
Watcrllood __________ ..
11 _______ ._
16
75
20.0
74.0
26.0
Present Process02 PV ______ ._
0. 42
______ __ ______._
0.57
0.14
0.42
__________ __
0.71
69
0011 Bank.
reservoir conditions, of normally gaseous ?uid compris~
ing carbon dioxide into said reservoir through said injec
The above results clearly show that in the water-driven
carbon dioxide process a considerable quantity of oil is
produced by depressuring the reservoir after ?ooding has .
been stopped at a high water-oil ratio. This recovery is
referred to as “blow-down” recovery.
tion well at a pressure in excess of] 1000 p.s.i., injecting
an aqueous medium into said reservoir through said in~
jection well to displace said bank of ?uid toward at least
It can be seen that
oil produced during blow-down represents a surprising
one production well, withdrawing produced ?uids from
part of the total recovery.
said production well while maintaining a mean reservoir
A thorough experimental investigation of the blow~
pressure of at least 1000 p.s.i.; discontinuing the injection
of said aqueous medium when the producing?uids no
down recovery was made. The results of these experi
ments, as described below, clearly show that the oil re 30 longer contain substantial quantities of oil and carbon
covery by blow-down is not merely a laboratory phenom
dioxide, and thereafter depressuring said reservoir by
pumping down said production well and recovering addi
enon, but would ‘contribute to oil production during a ?eld
tional oil from said production well.
operation. i
It was ?rst considered that at least part of the blow
2.- A process as de?ned by claim 1 wherein said bank
down recovery might be the result of a capillary end effect
of normally gaseous ?uid is a bank of gaseous carbon
prevailing during the ?ood, causing a severe pile-up of oil
dioxide.
'
of carbon dioxide, the ?ooding rate .was increased sharply
3. An improved oil recovery process which comprises
injecting water into a subsurface oil-bearing reservoir
during the ?nal stages of ?ooding.
through at least one injection well until a mean reservoir
near the model outlets.
In subsequent tests with banks
In no case was any
change in the producing water-oil ratio observed. These 40 pressure of at least 1000 p.s.i. is attained, injecting a bank
results preclude the possibility of an end e?ect due to
of from about 0.03 to about 0.5 pore volume, based on
capillary forces.
reservoir conditions, of carbon dioxide into said reservoir
Further observations indicated that the length'o? the
through said injection well at a pressure in excess of' 1000
model‘ and the rate of blow-down had no signi?cant effect
p.s.i., injecting water into said reservoir through said
on the blow-down oil recovery. The recoveries of Ada 45 injection well to displace said bank of carbon dioxide to
crude oil obtained with water-driven banks of carbon
ward at least one production well, withdrawing produced
dioxide over a range of model lengths and blow-down
?uid-s from said production well while maintaining a mean
rates are presented in Table IV.
reservoir pressure of at least 1000 p.s.i., discontinuing the
Table IV
EFFECT OF RATE OF BLOW-DOWN AND MODEL LENGTH ON OIL RECOVERY-LINEAR
' TORPEDO MODELS-ADA CRUDE OIL VVATER~DRIVEN 0.17 PV CO: BANK FLOODS
Model Description
Oil Recovery.
.
Expertmum
N 0.
.
_ ‘
Fraction of Oil
Blow-Down Rate
at
Approx.
Initial
Oil
Connate
Water
(Time Required to
Complete lBlow
Length
(Per-
It air
Satn.
Satu.
Down) ,
(FL)
cent)
(1nd.)-
(Per-
(Per-
can t;
can t;
PV)
PV)
>
1
18
18
20. 3
20. 4
20. 4.
500
500
500
79. 6
72. 8
70.8
20. 4
27. 2
29.2
Initially in Place
By
Flood
By
Blow-
Total
Down
Fast (3 hours) _____ __
Fast (1% days)- __
Slow (60 days) ____ _.
While in the foregoing there has been shown and de
scribed the preferred embodiment of this invention, it
0.505
0. 525
0. 520
0.127
0. l24
0. I22
0. an
0. 649
0. 642
injection of water at said injection well after the produc
ing ?uids at said production well reach a high water-to-oil
is to be understood that minor changes in details of con
ratio; thereafter reducing the reservoir pressure to a level
struction, combination and arrangement of parts may be
below 1,000 p.s.i. by pumping down said production well,
resorted to without departing from the spirit and scope 701 and recovering ?uids having a reduced water-to-oil ratio.
of the invention as claimed. For example, whereas only
4. A process as de?ned by claim 3 wherein a bank of
a single injection and production well are depicted herein,
from about 0.05 to about 0.25 pore volume, based on
two or more such wells may be utilized as desired.
What is claimed is:
1. An improved oil recovery process which comprises 751
reservoir conditions, of carbon dioxide is injected into
said reservoir.
5. A process as de?ned by claim 3 wherein the injec—
9
3,084,743
10
tion of water to displace said carbon dioxide is discon
tinued after the water-to~oil ratio of the producing ?uids
at said production well reaches about 25:1.
References Cited in the ?le of this patent
UNITED STATES PATENTS
1,511,067
2,623,596
2,669,307
2,875,831
2,875,832
"1
2,875,833
2,878,874
Martin _______________ .._ Mar. 3, 1959
Allen _______________ __ Mar. 24, 1959
‘669,2 l 6
Great Britain _________ __ Mar. 26, 1952
Great Britain _________ __ Sept. 2, 1953
FOREIGN PATENTS
5
696,524
Russell ______________ __ Oct. 7, 1924
Whorton et al __________ __ Dec. 30, 1952
OTHER REFERENCES
Mulholland et a1 _______ __ Feb. 16, 1954
Uren:
Petroleum
Production Engineering, Exploita
Martin et a1. _________ __ Mar. 3, 1959 10
tion, 2nd Edition, published by McGraw-Hill Book Com
Martin et a1. _________ __ Mar. 3,,1959
pany of New York, 1939, pages 423 to 426.
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