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Патент USA US3055433

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Sept. 25, ‘1962
Filed May 4, 1959
2 Sheets-Sheet 1
25 24
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‘Sept 25, 1962
Filed May 4, 1959
2 Sheets-Sheet 2
FIG. 3
United States Patent hire
Patented Sept. 25, 1962
Harry W. Par-her, Eartiesviiie, (Eda, assignor to Phillips
Petroleum Company, a corporation of Delaware
Filed May 4, 1959, Ser. No. 810,919
22 Claims. (Cl. 166-41)
ess for the production of hydrocarbons from carbonaceous
strata by controlled thermal drive. Another object is
to provide a thermal drive process which is controllable
‘as to direction and pattern. A further object is to pro
vide a process for producing hydrocarbons from a can
bonac-eou-s stratum around a single well therein by ther
mal drive thru a substantial section of the stratum. Other
objects of the invention will become apparent to one
skilled in the art upon consideration of the accompany
This invention relates to the production of hydro carbons 10 ing disclosure.
by thermal drive. A speci?c aspect of the invention is
A broad aspect of the invention comprises plugging a
concerned with selective plugging of the carbonaceous
selected area of ‘a permeable stratum so as to control the
stratum while producing same by thermal drive.
pattern of a thermal drive process ‘by heating the ‘area
In situ combustion in the recovery of hydrocarbons
to be plugged to ‘a high temperature and injecting into
from underground strata containing carbonaceous mate 15 the hot stratum a concentrated ‘aqueous solution of a
rial is becoming more prevalent in the petroleum indus
solid compound so as to vaporize water tfnom the solu
try. In this technique of production, combustion is ini
tion ‘and deposit the compound in the pores of the stra
tiated in the carbonaceous stratum and the resulting com
tum until plugging is effected. Any highly soluble com
bustion zone is caused to move thru the stratum by either
pound not readily decomposable or volatilizable by heat
inverse or direct air drive whereby the heat of combus
tion of a substantial proportion of the hydrocarbon in the
stratum drives out and usually upgrades a substantial
pro-portion of the unburned hydrocarbon material.
is operable in the process.
Preferred compounds are the
relatively cheap and highly soluble salts of sodium and
calcium such as sodium chloride and calcium chloride.
Calcium chloride is preferred because of its greater solu
The ignition of carbonaceous material in a stratum
bility and hence its greater efficiency in the process. It
around a borehole therein followed by injection of air 25 has been 'found that the ‘addition of a small quantity of
thru the ignition borehole and recovery of product hydro
carbons and combustion gas thru another borehole in
[the stratum is a direct iair drive process ‘for effecting in
glycerin in the solution greatly raids in rendering the re
sulting plug impermeable after cooling. A concentra
tion of glycerin in the range of about V1 to 4 volume
situ combustion ‘and recovery of hydrocarbons vfrom the
percent of the solution is re?ective in aiding the plugging
stratum. In this type of operation the stratum usually 30 and rendering the plug impermeable.
plugs in front of the combustion zone because a heavy
A more complete understanding of the invention may
viscous liquid bank of hydrocarbon collects in the stratum
be had by reference to the accompanying schematic draw
in advance of the combustion zone which prevents move
ing of which FIGURE 11 is an elevation in partial section
ment of air to the combustion process. To overcome this
thru a carbonaceous stratum; FIGURE 2 is a similar ele
difficulty and to permit the continued progress of the com
vation showing another embodiment of the invention;
bustion zone thru the stratum, inverse air injection has
FIGURE 3 is a similar elevation showing a third em.
been resorted to. By this technique, a combustion zone
bodiment of the invention; and FIGURE 4 is a plan View
is established around an ignition borehole by any suitable
of 1an arrangement of wells nor production by in situ
means and air is fed thru the stratum to the combustion
combustion illustrating another embodiment of the in
40 vention.
zone from one or more surrounding boreholes.
in situ combustion techniques are being applied to
Referring to FIGURE 1, a stratum ‘10 is penetrated by
tar sands, shale, Athabasca sand and other strata in vir
a well 12, which is provided with casing 14- extending doWn
gin state, to coal veins by fracturing, ‘and to strata par
approximately to the stratum 10 and capped by a well
tially depleted by primary and even secondary and ter
head. Within casing 14 are concentric conduits 16‘, I8,
tiary recovery method-s.
20, and 22, extending to successively lower levels of the
Strata containing hydrocarbon material in the form of
stratum. Packers 24, 25, 26 and 27 pack o? spaces ad
solid and semi-solid and heavy viscous oil are often di?i
jacent the ends of each of conduits 16, 18 and 20‘, respec
cult to produce because of their low permeability. Such
tively, for injection of brine in the upper and lower spaces
strata include shales, heavy tar sands, and those contain
and water in the intermediate space, all of these spaces
ing semisolid hydrocarbons and/‘0r highly viscous oils.
being at an intermediate level of stratum 10. Line 30
In producing hydrocarbons ‘from such strata around a Well
connects with tubing 22 for injection of air or hot gas
therein by passing hot gas along the Wall of the well
for effecting the thermal drive. Line 32 connects with con
within the stratum, very little production can be e?ected
duit 20 for introducing brine to the lowermost packed oif
because of the di?iculty in ?owing the hot gas into the
space and line 34 connects with conduit 16 for introducing
stratum. After producing hydrocarbons from a relatively 55 brine to the uppermost packed off space at the end of con
thin annulus around the well, the hot gases used in heating
duit 16. Line 36 connects with conduit 18 for introduc
the stratum merely flow along the wall of the Well Without
ing water into the intermediate packed oif space at the
end of conduit v18. Line 38 connects with casing 14 and
contacting the deeper solid, semi-solid, and viscous hydro
carbon material.
provides an e?luent line for produced gases collecting in
the outer annulus of the well.
When producing hydnocarbons irom carbonaceous stra
ta by thermal drive such as by in situ combustion where
When the arrangement of FIGURE 1 is utilized for
in the stratum 1to be produced is ignited ‘and the resulting
production by in situ combustion, a combustion front 40
is driven thru the stratum axially away from Well ‘12.
combustion zone is driven thru the stratum, burning a
portion of the hydrocarbon material and producing most
Numerals 42 and 44 designate salt blocks at the upper and
of the balance as product, it is desirable in many instances 65 lower levels of the plugged o?? area.
to control the direction of the movement of the combus
Referring to FIGURE 2, a stratum 10, which may be
a shale or heavy tar sand, is penetrated by a borehole or
tion front. Heretofore, no reliable method has been
avail-able tor such control.
well ‘12 which is provided with a casing 14 and a tubing
This invention is concerned with selective plugging of
string 22 extending to adjacent the bottom of the hole.
strata containing hydrocarbon material during a thermal 70 A conduit '46 extends from the well head to an interme
drive process ‘for producing the strata. Accordingly, it
diate level of stratum 10 and the well is ?lled with sand
is ‘an object 'of the invention to provide an improved proc
48 up to the top of stratum 10.
A production line 50
connects with tubing 22 at the well head for removal of
produced gases. Hot gases and/or air are introduced
thru line 52 to casing 14 and the outer annulus of the
well. A line 54 is connected with conduit 46 for introduc
ing brine to the inner annulus. Numeral 56' designates a
fracture formed around well 12, while numeral 58‘ desig
nates a salt block in the stratum adjacent the fracture
water is controlled in response to the hydrocarbon content
both above and below same.
air injection rate and the pressure on the injected liquids,
the movement of the salt block and the combustion zone
In FIGURE 3 stratum 10 is penetrated by a pair of
of the produced gases. When the hydrocarbon concentra
tion in the produced gases decreases below a normal pro
duction level, it is an indication that the brine and water
are not being forced rapidly enough into the stratum to
force the hot gases or combustion front farther into the
stratum at a reasonable rate. By properly regulating the
spaced apart wells 12 and 13 each of which is provided 10 thru the stratum can be controlled so as to drive the com
bustion front deep into the stratum from the ignition well
with a casing 14- extending to about the level of the top
and produce hydrocarbons from the section of stratum
of stratum 10, and with tubing strings 22 and 23, respec
above and below the salt block. At any time during the
tively. An air line 30 connects with tubing string 23 and
process, upon termination of the injection of brine and
a production line 50 connects with tubing string 22. A
water, the combustion zone may be driven around the end
brine injection line 60 connects with the annulus of well
of the salt block and back to the well above the salt block.
12 thru the well head. Packers 62 and 64 are positioned
Of course, it is to be understood that the combustion zone
around tubing strings 22 and 23, respectively, at a se
may be driven from the well Wall above the salt block
lected intermediate level of stratum 10. A ?re front 66
thru the stratum and back to the well wall below the salt
is shown intermediate wells 12 and 13, below the level of
block by injecting air thin line 38 and recovering produc
packers ‘62 and 64, moving toward well 13 countercur
tion thru line 30. Indirect drive of the combustion front
rently to air injected thru well 13 below packer 64. A
by inverse air injection is not operable in the embodiment
salt block 58 is shown extending from well 12 toward
of the invention shown in FIGURE 1 because it is neces
well 13 as far as the approximate location of the ?re
sary to drive the hot gases around the end of the injected
In FIGURE 4, air injection wells 13 are positioned in a 25 brine and Water layers in order to open up the stratum to
flow of gases and liquids.
ring around production well 12 with a flame front ‘66 being
The lower limit of the injection pressure on the brine
driven thru stratum 10 by inverse air injection thru wells
is limited by the concentration of hydrocarbons in the
13. Production is recovered thru well 12. Brine injec
produced gases. The block should be advanced at a rate
tion wells ‘15 are positioned intermediate air injection
wells 13 and production well 12 outside the ?re front in 30 su?icient to cause the hot gases bypassing the block to
retort hydrocarbons from the area in front of the advanc
a selected location designed to block the movement of the
ing salt block rapidly enough to render the process eco
?re front and seal off a selected section of the stratum
nomically feasible. However, advancing the salt block
to ?ow of gases.
at any appreciable rate makes the process operable. The
‘In producing hydrocarbons from shale, heavy tars, and
upper limit of brine pressure and rate of injection is deter
other bituminous strata of little or no permeability around
mined and limited by the air compressors and permissible
a single well, as illustrated in FIGURE 1, air or fuel gas
air injection pressures at the depth of the stratum being
air mixtures are injected thru tubing 22 to establish in
situ combustion in the stratum around the Wall of the well.
In operating the embodiment of the invention illustrated
Of course, it is to be understood that hot gases such as
in FIGURE 2, the wall of well '12 is ?rst produced by
steam, CO2, combustion gases, nitrogen, etc., may be
retorting hydrocarbons therefrom with hot gases injected
utilized to retort hydrocarbons from the stratum adjacent
thru line 52 and with production being recovered thru
the well. Without the use of the invention, it is possible to
tubing 22 and line 50. Brine is then injected thru line
retort hydrocarbons from only a very thin annulus of the
54 and conduit 46 where it flows into the hot sand ad
wellbore because of the dif?culty of forcing the gases
jacent the end of conduit 46 and into the permeable stra
and/ or the combustion front deeper into the stratum and
tum opposite the end of the conduit. The evaporation of
because heat transfer laterally thru the stratum is exceed
water from the salt solution by the heat in the hot sand
ingly slow. Naturally, unless some means is provided
to force the air or other hot gas into the stratum, the same
merely passes up the unobstructed borehole without pene
trating the stratum to any appreciable depth. In the em
bodiment of the invention shown in FIGURE 1, two layers
of brine are injected into the stratum together with an
intermediate layer of water after the preliminary retorting
and opening of the stratum around the wall of the well
as deep as is possible in the open borehole. After this
preliminary retorting, injection of air or hot gas is ter
minated to permit setting of the packers and conduits
preparatory to injecting brine and water. Thereafter, the
combustion zone is re-established below packer 27 by
and rock forms a salt block at levels below and above the
end of conduit 46 and in the stratum between these levels.
The introduction of a salt block into the stratum opposite
the end of conduit 46 forces the hot gases to ?ow deeper
into the stratum in order to bypass the salt block and
thereby produces more tar and hydrocarbon material from
the stratum. The resulting salt block eventually blocks
the injection of brine and, in order to overcome this
difliculty, the brine injection pressure is increased until a
horizontal fracture 56 is produced around well 12. This
permits the brine to flow into the stratum thru the fracture
but the ?ow of hot gases around the salt block and the
injected brine produces more of the stratum in advance
conventional means and injection of brine and water is
initiated so as to commence plugging of the stratum at 60 of the injected brine thereby rendering the same perme
able and increasing the depth to which the brine can pene
the upper level of the upper brine layer and lower level
trate the stratum. The salt block can therefore be con~
of the lower brine layer. The hot ‘gases and hot rock in
tinually extended into the formation along the fracture and
the area of injection of the brine evaporate water from the
the fracture can be increased in radial depth as the in
brine and leave in the pores of the rock or sand a solid
salt block which forces the produced gases and combustion 65 jection process is continued, resulting in the production
of more tar and other hydrocarbons from the stratum in
gas deeper into the stratum to bypass the salt block.
front of the advancing fracture and salt block. It is feasi
The function of the water is to prevent plugging across
ble to either continually inject brine or to inject a large
the advancing face or edge of the injected brine layers
quantity of brine only when the injected gas-to hydro
by continued evaporation of water from the brine. The
carbon ratio becomes too high.
injection of clear water dissolves any salt block which
The embodiment illustrated in FIGURE 2 is similar to
[might tend to form in the path of the advancing injected
that illustrated in FIGURE 1 in all respects except the
brine, thereby allowing forward movement of the brine
manner in which the continued injection of brine is as
into the stratum so as to continue forcing the produced
sured. The injection of hot gases, including steam, is
hot gases deeper into the stratum.
The pressure applied to the injection of the brine and 75 illustrated but it is also feasible to initiate combustion
either above or below the salt block and drive the com
bustion front thru the stratum as in the embodiment illus
When cooled, salt blocks formed in this manner tended
to leak a small amount of brine. The injected brine was
trated in FIGURE 1. It is also feasible to utilize in the
not saturated therefore it dissolved the salt block. This
plugging step any liquid solution or slurry from which
‘difficulty was avoided by the addition of glycerine (2
evaporation leaves a plugging or blocking residue. To
ml./10? in solution) to a calcium chloride solution (75
illustrate, in FIGURE 2, the stratum may be fractured by
gr./ 100 ml. water). The block formed by 24 hours of
any suitable means and a slurry of time clay particles may
attempting to ?ow this solution into the hot sand remained
be used to plug the stratum adjacent the fracture and the
after cooling of the apparatus.
sand adjacent the end of conduit 46.
In other tests the power to the heater was cut off when
The embodiment of the invention illustrated in FIG 10 brine ?ow was started. In [these cases due ‘to the high
URE 3 comprises initiating combustion in a selected selec
heat losses and small thickness of sand through which
tion of the stratum 10 such as below the level of packers
the solution ?owed no stable permeability block formed.
62 and 64, driving the combustion front thru the stratum
Tests showed the superiority of a calcium chloride solu
from well 12 to well 13 and injecting the solution effective
tion (75 gr./ 100 ml.) over a sodium chloride solution
in plugging thru line 60 to the annulus above packer 62 15 (30 1g./ 100 ml.) to form permeability blocks under ad
so that a salt plug 58 is formed along the upper boundary
verse conditions. This is ‘due to (the higher solubility of
of the burned out area which progresses thru the stratum
calcium chloride, and the higher viscosity of the result
adjacent the combustion zone as the latter moves thru the
ing solution.
stratum. This embodiment of the invention is applicable
Various modi?cations of the invention will occur to one
only to strata which are sufficiently permeable to allow 20 skilled in the art. For example, it is feasible rto use as
the passage of gases from well to well. It is to be under
the plugging medium :a liquid which decomposes to a solid
stood that well 12 may represent a central well with a ring
product when it reaches the hot zone, such as a solution
of wells 13 surrounding same, or wells 12 and 13‘ may
of water glass (sodium silicate).
simply represent wells in a line of production and a line
Certain modi?cations or‘ the invention will become
of injection wells, respectively. A combustion front 66 25 apparent in those skilled in rthe art and the illustrative
is moved thru the stratum by inverse air injection thru
‘details disclosed are not to be construed as imposing un
line 3t} and tubing 23, while production is recovered thru
necessary limitations on the invention.
tubing 22 and line 50‘.
I claim:
In the embodiment illustrated in FIGURE 4, a stratum
1. A process for plugging 1a selected disc-like area of
10 is being produced by inverse air injection in a ring
a permeable stratum around a well penetrating said stra
pattern of injection wells 13 around a central production
tum which comprises heating the area to be plugged to
well 12. It may be desirable to block the movement of
\a temperature substantially vabove the boiling point of the
the combustion front 66 in a given direction, such as along
hereinafter described solution at stratum pressure; and
the edge of a cliff, to prevent escape of produced gases
injecting thru said well a concentrated aqueous solution
or air, or along the boundary of a ?eld. Brine injection
of a compound, solid and stable at said temperature, un
wells 15 are positioned in the vicinity of the desired block
der pressure, radially into the hot area so as to iorce
ing area and brine is injected so that the injected air and
solution into the pores of said stratum, vaporize water
brine pressure force the brine into the combustion zone
therefrom, and precipitate said compound in the pores
and the hot rock adjacent same whereby evaporation of
of said stratum in said disc-like area until plugging is
the liquid from the brine deposits su?icient salt to effect 40 effected.
plugging. This technique may also be desirable in con
2. The process of claim v>1 wherein glycerin in {the range
verting a ring type combustion front to an in-line combus
of about 1 to 4 volume percent is incorporated in said
tion front. In the process illustrated, the ?re front in the
area of the injected brine may be smothered for lack of
3. The process of claim 1 wherein said compound is
oxygen, but there is su?icient heat in the hot stratum to
calcium chloride.
vaporize enough water to effect plugging by salt deposi
4, The process of claim 3 wherein glycerin in [the range
tion. Rough calculations show for typical conditions us
of about 1 to 4 volume percent is incorporated in said
ing sodium chloride in a given volume of rock after burn
ing that there is suf?cient heat to vaporize enough water
5. The process of claim 1 wherein said compound is
so that 20 percent of the pore space could be ?lled by
sodium chloride.
salt crystallizing from a saturated solution. The move
‘6. The process or" claim 5 wherein glycerin in the range
ment of the resulting slurry further into the hot zone
of about 1 to 4 volume percent is incorporated in said so
evaporates more water and thereby plugs the formation
completely. More highly soluble salts such as calcium
7. A process for plugging a selected area of la permeable
chloride are even more effective. It is also feasible to 55 stratum around a well penetrating same which comprises
inject a slug of brine followed by injection of clear water,
extending a conduit from ‘the Well head to the level or"
the brine quantity being su?icient to effect the blocking
said area; ?lling ithe annulus ‘around said conduit and the
and the water serving as the driving ?uid. In some in
well below same with sand; heating said sand ‘and said
stances, the slug of brine may be driven to the desired lo
stratum at the level of said area so a temperature substan
cation in the stratum by injecting gas.
60 tially ‘above the boiling point of the hereinafter described
To illustrate the invention a glass tube 9 inches long
solution at stratum pressure; and injecting thru said con
and %-inch inside diameter was packed with white sand
duit radially in a disc-like pattern into the hot sand and
which had a permeability of approximately 2.0 darcys. A
hot stratum ‘adjacent said level 1a concentrated aqueous
1/s-inch stainless steel tube was placed along the axis of
solution of a compound, solid and stable at said tempera
the glass tube so that a sliding thermocouple could be used 65 ture, so as to vaporize water therefrom and precipitate
to measure the temperature of the sand. The central 6
said compound in the interstices within said sand ‘and in
inches of the glass tube was wrapped with an electric heat
rthe pores of said stratum in said area until plugging is
ing tape and covered with approximately 3Ai-inch of glass
wool insulation. The sand was heated in this manner to
a maximum temperature of 900 F. After the sand had
been heated, brine was injected into the bottom of the
tube. When the brine reached a position about 3 inches
from the bottom of the tube su?icient water had been
evaporated to reduce the permeability IOGO-fold or more,
8. A process nor producing hydrocarbons from a car
70 bonaceous stratum penetrated by a well, which comprises
extending a ?rst conduit from the well head to a selected
intermediate level in said stratum; extending a second con
duit from the well head llJO‘ a lower level in said stratum;
?lling the annulus within said stratum between the well
and soon there was no further appreciable brine ?ow. 75 wall and said conduits with sand; passing hot gas along
the wall of said well within said stratum via said annulus
and said second conduit so as to ?uidize and drive hydro
and an area below said injection zones, whereby water
carbons from the well Wall thereby increasing the per
precipitated in the pores of said stratum to form solid
rings of said compound so as to torce said gas deeper
into said stratum; injecting water thru said water injection
meability of an annulus of said stratum and heating same
to a temperature substantially above the boiling point
is vaporized ‘from said solution and said compound is
of the hereinafter described solution at stratum. pressure;
zone so as to provide tor flow of said solution deeper
therea?ter, continuing the passing of said gas thru said
into said stratum while continuing the injection of said
solution and the passing of hot gas thru the expanding
annulus and While said stratum is at said temperature, in
annulus, thereby progressively extending said rings into
jecting thru said ?rst conduit radially in a disc-like pat
tern into the hot sand adjacent the lower end thereof 10 said stratum and producing hydrocarbons ‘from deeper in
said stratum; ‘and recovering the produced ?uids includ
and into the adjacent hot stratum a concentrated aqueous
ing hydrocarbons ‘from said well.
solution of a compound, solid and stable at said tempera
17. The process of claim 16 wherein said compound is
ture, whereby water vaporizes trom said solution and said
calcium chloride and glycerine in the range of 1 to 4
compound is precipitated in said sand and in said stra
Volume percent is incorporated in said solution.
tum above and below the level of the end of said ?rst
18. The process of claim 16 wherein said compound is
conduit so as to form a block to upward and downward
sodium chloride and iglycerine in the range of 1 to 4 vol
?ow of said solution; continuing the passing of said gas
nine percent is incorporated in said solution.
thru said ‘annulus and the injection of said solution deeper
19. The process of claim 16 wherein said hot gas is
into said stratum so as to force said gas deeper into said
stratum, thereby continuing the production of hydrocar 20 produced ‘by igniting an annulus of said stratum at a
level spaced substantially from said intermediate level
bons; ‘and recovering the produced ?uids including hydro
and passing combustion supporting ‘gas directly into the
carbons from said well.
ignited annulus ‘from said well so as to force resulting
9. The process of claim 8 wherein said hot gas is passed
hot gas thru said stratum ‘around said rings into said
thru said second conduit and hydrocarbons are recovered
25 well.
\tluu said annulus.
‘20. A ‘process vfor producing hydrocarbons trom a re
10. The process of claim 9 wherein said hot gas is pro
stricted horizontal section of a stratum containing hydro
duced by igniting said stratum below said intermediate
carbons .which comprises igniting a selected vertically
level and injecting combustion-supporting gas th-ru said
second conduit so as to effect in situ combustion.
restricted area of said stratum around an ignition well
11. The process of claim 8 wherein said compound is 30 therein; passing combustion-supporting gas to the ig
nited area so as to move the resulting combustion zone
calcium chloride.
thru said stratum toward at least one other well therein
‘12. The process of claim 11 wherein glycerin in the
and produce hydrocmbons trom said stratum; as said
range of about “1 to 4 volume percent is incorporated in
combustion zone is advanced radially outwardly from
said solution.
13. The process of claim 8 wherein said compound is 35 said ignition well injecting a concentrated aqueous solu
tion of a compound, solid and stable at combustion tem
sodium chloride.
perature, into said stratum adjacent the horizontal bound
14. The process of claim. 8 wherein said gas comprises
ary of said combustion zone so as to vaporize Water from
15. The process of claim 8 wherein said gas comprises
combustion gas.
16. A process for producing hydrocarbons from a car
bonaceous stratum penetrated by a Well, which comprises
establishing in said well at an intermediate level of said
said ‘solution along said boundary and deposit said com
pound thereby iiorming a solid layer of said compound
along said boundary; and recovery from one of said wells
produced ?uids including hydrocarbons.
21. The process of claim 20 wherein said compound is
calcium chloride.
stratum an upper solution injection zone, an intermediate
22. The process of claim 20 wherein said compound is
water injection zone, and a ‘lower solution injection zone, 45
sodium chloride.
each being separated and connected with a separate well
conduit; heating an annulus of said stratum immediately
References Cited in the ?le of this patent
surrounding said well to an elevated temperature substan
tially above the boiling temperature of the hereinafter de
scribed solution at stratum pressure by contacting same 50
‘with hot gas, thereby producing hydrocarbons from said
annulus; while said annulus is at said temperature, inject
ing a concentrated aqueous. solution of a compound, solid
and stable at said temperature, into said annulus tlu'u
said ‘upper and lower injection zones and simultaneously 55
passing hot gas thru said lannulus between an area above
Barton etal ___________ __ Dec. 11, 1945
Tadema _____________ __ Feb. 24, 1959
Morse ct a1 ___________ __ Apr. 14, 1959
Holbrook et al. _______ __ Sept. 8, 1959
Dew et al _____________ __ Sept. 27, 1960
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