Note: Descriptions are shown in the official language in which they were submitted.
CA 02644612 2008-10-10
SYSTEM, METHOD AND APPARATUS FOR HYDROGEN-OXYGEN BURNER IN
DOWNHOLE STEAM GENERATOR
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates in general to steam generators used downhole in
wells and,
in particular, to an improved system, method, and apparatus for a burner for a
downhole steam
generator.
2. Description of the Related Art
There are extensive viscous hydrocarbon reservoirs throughout the world. These
reservoirs contain a very viscous hydrocarbon, often called "tar," "heavy
oil," or "ultra heavy
oil," which typically has viscosities in the range from 3,000 to 1,000,000
centipoise when
measured at 100 degrees F. The high viscosity makes it difficult and expensive
to recover the
hydrocarbon. Strip mining is employed for shallow tar sands. For deeper
reservoirs, heating the
heavy oil in situ to lower the viscosity has been employed.
In one technique, partially-saturated steam is injected into a well from a
steam generator
at the surface. The heavy oil can be produced from the same well in which the
steam is injected
by allowing the reservoir to soak for a selected time after the steam
injection, then producing the
well. When production declines, the operator repeats the process. A downhole
pump may be
required to pump the heated heavy oil to the surface. If so, the pump has to
be pulled from the
well each time before the steam is injected, then re-run after the injection.
The heavy oil can also
be produced by means of a second well spaced apart from the injector well.
Another technique uses two horizontal wells, one a few feet above and parallel
to the
other. Each well has a slotted liner. Steam is injected continuously into the
upper well bore to
CA 02644612 2008-10-10
heat the heavy oil and cause it to flow into the lower well bore. Other
proposals involve
injecting steam continuously into vertical injection wells surrounded by
vertical producing wells.
U.S. patent 6,016,867 discloses the use of one or more injection and
production
boreholes. A mixture of reducing gases, oxidizing gases, and steam is fed to
downhole-
combustion devices located in the injection boreholes. Combustion of the
reducing-gas,
oxidizing-gas mixture is carried out to produce superheated steam and hot
gases for injection into
the formation to convert and upgrade the heavy crude or bitumen into lighter
hydrocarbons. The
temperature of the superheated steam is sufficiently high to cause pyrolysis
and/or
hydrovisbreaking when hydrogen is present, which increases the API gravity and
lowers the
viscosity of the hydrocarbon in situ. The '867 patent states that an
alternative reducing gas may
be comprised principally of hydrogen with lesser amounts of carbon monoxide,
carbon dioxide,
and hydrocarbon gases.
The '867 patent also discloses fracturing the formation prior to injection of
the steam.
The '867 patent discloses both a cyclic process, wherein the injection and
production occur in the
same well, and a continuous drive process involving pumping steam through
downhole burners
in wells surrounding the producing wells. In the continuous drive process, the
'867 patent
teaches to extend the fractured zones to adjacent wells. Although this and
other designs are
workable, an improved burner design for downhole steam generators would be
desirable.
SUMMARY OF THE INVENTION
Embodiments of a system, method, and apparatus for a downhole burner for a
steam
generator are disclosed. The downhole burner includes an injector and a
cooling liner. Fuel,
steam and oxidizer lines are connected to the injector. The burner is enclosed
within a burner
casing. The burner casing and burner form a steam channel that surround the
injector and
cooling liner. The steam enters the burner through holes in the cooling liner.
Combustion
occurring within the cooling liner heats the steam and increases its quality.
The heated, high-
-2-
CA 02644612 2008-10-10
quality steam and combustion products exit the burner and enter an oil-bearing
formation to
upgrade and improve the mobility of heavy crude oils held in the formation.
The injector includes a face plate having injection holes for the injection of
fuel and
oxidizer into the burner. The face plate also has an igniter for igniting fuel
and oxidizer injected
into the burner. Fuel and oxidizer holes are arranged in concentric rings in
the face plate to
produce a shower head stream pattern of fuel and oxidizer. The injector also
comprises a cover
plate having an oxidizer inlet, an oxidizer distribution manifold plate having
oxidizer holes, and
a fuel distribution manifold plate having fuel and oxidizer holes.
The injector is positioned at an upper end of the cooling liner. The inner
diameter of the
cooling liner is slightly larger than the diameter of the injector to allow
small amounts of steam
to leak past for additional cooling. The cooling liner includes an effusion
cooling section and an
effusion cooling and jet mixing section. The heated steam and combustion
products exit the
cooling liner through an outlet at its lower end. The effusion cooling section
includes effusion
holes for injecting small jets of steam along the surface of the cooling liner
to provide a layer of
cooler gases to protect the liner. The effusion cooling and jet mixing section
has both effusion
holes and mixing holes. The effusion holes cool the liner by directing steam
along the wall while
the mixing holes inject steam further toward central portions of the burner.
The foregoing and other objects and advantages of the present invention will
be apparent
to those skilled in the art, in view of the following detailed description of
the present invention,
taken in conjunction with the appended claims and the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
So that the manner in which the features and advantages of the present
invention, which
will become apparent, are attained and can be understood in more detail, more
particular
description of the invention briefly summarized above may be had by reference
to the
embodiments thereof that are illustrated in the appended drawings which form a
part of this
-3-
CA 02644612 2008-10-10
specification. It is to be noted, however, that the drawings illustrate only
some embodiments of
the invention and therefore are not to be considered limiting of its scope as
the invention may
admit to other equally effective embodiments.
FIG. 1 is a side view of one embodiment of a downhole burner positioned in a
well
having a casing and packer shown in sectional view taken along the
longitudinal axis of the
casing;
FIG. 2 is a bottom sectional view of the assembly of FIG. 1 taken along line 2-
-2 of FIG.
1 and is constructed in accordance with the invention;
FIG. 3 is a plan view of one embodiment of a cover plate constructed in
accordance with
the invention;
FIG. 4 is a plan view of one embodiment of an oxidizer distribution manifold
plate
constructed in accordance with the invention;
FIG. 5 is a plan view of one embodiment of a fuel distribution manifold plate
constructed
in accordance with the invention;
FIG. 6 is a plan view of one embodiment of an injector face plate constructed
in
accordance with the invention;
FIG. 7 is a lower isometric view of one embodiment of an injector constructed
in
accordance with the invention;
FIG. 8 is a side view of one embodiment of a cooling liner constructed in
accordance
with the invention;
-4-
CA 02644612 2008-10-10
FIG. 9 is an enlarged sectional side view of a portion of the cooling liner of
FIG. 8
illustrating an effusion holes therein;
FIG. 10 is an enlarged sectional side view of a portion of the cooling liner
of FIG. 8
illustrating a mixing hole therein;
FIG. 11 is a bottom view of one embodiment of an injector face plate
constructed in
accordance with the invention; and
FIG. 12 is a schematic diagram of one embodiment of a system for introducing
and
distributing nanocatalysts in oil-bearing formations.
DETAILED DESCRIPTION OF THE INVENTION
Although the following detailed description contains many specific details for
purposes
of illustration, anyone of ordinary skill in the art will appreciate that many
variations and
alterations to the following details are within the scope of the invention.
Accordingly, the
exemplary embodiments of the invention described below are set forth without
any loss of
generality to, and without imposing limitations thereon, the present
invention.
FIG. 1 depicts a downhole burner 11 positioned in a well according to an
embodiment of
the present invention. The well may comprise various wellbore configurations
including, for
example, vertical, horizontal, SAGD, or various combinations thereof. One
skilled in the art will
recognize that the burner also functions as a heater for heating the fluids
entering the formation.
A casing 17 and a packer 23 are shown in cross-section taken along the
longitudinal axis of
casing 17. Downhole burner 11 includes an injector 13 and a cooling liner 15
comprising a
hollow cylindrical sleeve. A fuel line 19 and an oxidizer line 21 are
connected to and in fluid
communication with injector 13.
-5-
CA 02644612 2008-10-10
A separate CO2 line also may be utilized. The CO2 may be injected at various
and/or
multiple locations along the liner, including at the head end, through the
liner 15 or injector 13,
or at the exit prior to the packer 23, depending on the application. In the
one embodiment,
burner 11 is enclosed within an outer shell or burner casing 22.
The burner 11 may be suspended by fuel line 19, oxidizer line 21 and steam
line 20 while
being lowered down the well. In another embodiment, a shroud or string of
tubing (neither
shown) may suspend burner 11 by attaching to injector 13 and/or cooling liner
15. When
installed, burner 11 could be supported on packer 23 or casing 17. In one
embodiment, burner
casing 22 and burner 11 form an annular steam channel 25, which substantially
surrounds the
exterior surfaces of injector 13 and cooling liner 15.
In operation, steam having a preferable steam quality of approximately 50% to
90% (e.g.,
80% to 100%), or some degree of superheated steam, may be formed at the
surface of a well and
fluidly communicated to steam channel 25 at a pressure of, for example, about
1600 psi. The
steam arriving in steam channel 25 may have a steam quality of approximately
70% to 90% due
to heat loss during transportation down the well. In one embodiment, burner 11
has a power
output of approximately 13 MMBtu/hr and is designed to produce about 3200 bpd
(barrels per
day) of superheated steam (cold water equivalent) with an outlet temperature
of around 700 F at
full load. Steam at lower temperatures may also be feasible.
Steam communicated to burner 11 through steam channel 25 may enter burner 11
through a plurality of holes in cooling liner 15. Combustion occurring within
cooling liner 15
heats the steam and increases its steam quality. The heated, high-quality
steam and combustion
products exit burner 11 through outlet 24. The steam and combustion products
(i.e., the
combusted fuel and oxidizer (e.g., products) or exhaust gases) then may enter
an oil-bearing
formation in order to, for example, upgrade and improve the mobility of heavy
crude oils held in
the formation. Those skilled in the art will recognize that burners having the
design of burner 11
may be built to have almost any power output, and to provide almost any steam
output and steam
quality.
-6-
CA 02644612 2008-10-10
FIG. 2 depicts an upward view of the downhole burner of FIG. 1. Steam channel
25 is
formed between burner casing 22 and cooling liner wall 27 of cooling liner 15.
Injector face
plate 29 of injector 13 (see FIG. 1) has formed therein a plurality of
injection holes 31 for the
injection of fuel and oxidizer into the burner. Injector face plate 29 further
includes an igniter 33
for igniting fuel and oxidizer injected into the burner. Igniter 33 could be a
variety of devices
and it could be a catalytic device. A small gap 35 may be provided between
injector face plate
29 and cooling liner wall 27 so that steam can leak past and cool injector
face plate 29.
The invention is suitable for many different types and sizes of wells. For
example, in one
embodiment designed for use in a well having a well casing diameter of 7 5/8-
inches, burner
casing 22 has an outer diameter of 6 inches and a wall thickness of 0.125
inches; cooling liner
wall 27 has an outer diameter of 5 inches, an inner diameter of 4.75 inches,
and a wall thickness
of 0.125 inches; injector face plate 29 has a diameter of 4.65 inches; steam
channel 25 has an
annular width between cooling liner wall 27 and burner casing 22 of 0.375
inches; and gap 35
has a width of 0.050 inches.
FIG. 11 illustrates one embodiment of the injector face plate 29. Injector
face plate 29
forms part of injector 13 and includes igniter 33. Fuel holes 93, 97 may be
arranged in
concentric rings 81, 85. Oxidizer holes 91, 95, 99, 101 also may be arranged
in concentric rings
79, 83, 87, 89. Fuel holes 93, 97 and oxidizer holes 91, 95, 99, 101
correspond to injection holes
31 of FIG. 2. In one embodiment, concentric ring 79 has a radius of 1.75
inches, concentric ring
81 has a radius of 1.50 inches, concentric ring 83 has a radius of 1.25
inches, concentric ring 85
has a radius of 1.00 inches, concentric ring 87 has a radius of 0.75 inches,
and concentric ring 89
has a radius of 0.50 inches. In one embodiment, oxidizer holes 91 have a
diameter of 0.056
inches, oxidizer holes 95 have a diameter of 0.055 inches, oxidizer holes 99
have a diameter of
0.052 inches, oxidizer holes 101 have a diameter of 0.060 inches, and fuel
holes 93, 97 have a
diameter of 0.075 inches.
-7-
CA 02644612 2008-10-10
In one embodiment, fuel holes 93, 97 and oxidizer holes 91, 95, 99, 101
produce a
shower head stream pattern of fuel and oxidizer rather than an impinging
stream pattern or a
fogging effect. Although other designs may be used and are within the scope of
the present
invention, a shower head design moves the streams of fuel and oxidizer farther
away from
injector face plate 29. This provides a longer stand-off distance between the
high flame
temperature of the combusting fuel and injector face plate 29, which in turn
helps to keep
injector face plate 29 cooler.
FIG. 3 shows a cover plate 41 in accordance with an embodiment of the
invention. Cover
plate 41 forms part of injector 13 and may include oxidizer inlet 45 and
alignment holes 43.
FIG. 4 shows an oxidizer distribution manifold plate 47 according to an
embodiment of the
invention. Oxidizer distribution manifold plate 47 forms part of injector 13
and may include
oxidizer manifold 49, oxidizer holes 51, and alignment holes 43.
FIG. 5 shows a fuel distribution manifold plate 53 according to an embodiment
of the
invention. Fuel distribution manifold plate 53 forms part of injector 13 may
include oxidizer
holes 51 and alignment holes 43. Fuel distribution manifold plate 53 also may
include fuel inlet
55, fuel manifold or passages 57, and fuel holes 59. Fuel manifold 57 may be
formed to route
fuel throughout the interior of fuel distribution manifold plate 53 as a means
of cooling the plate.
FIG. 6 shows an injector face plate 29 according to an embodiment of the
invention.
Injector face plate 29 forms part of injector 13 and may include oxidizer
holes 51, fuel holes 59,
and alignment holes 43. Oxidizer holes 51 of FIG. 6 correspond to oxidizer
holes 91, 95, 99, 101
of FIG. 11 and fuel holes 59 of FIG. 6 correspond to fuel holes 93, 97 of FIG.
11.
FIG. 7 depicts the assembled components of the injector 13 according to one
embodiment
of the invention. Injector 13 may be formed by the plates of FIGS. 3-6, with
the alignment holes
43 located in each plate arranged in alignment. More specifically, injector 13
may be formed by
stacking cover plate 41 on top of oxidizer distribution manifold plate 47,
which is stacked on top
of fuel distribution manifold plate 53, which is stacked on top of injector
face plate 29. As
-8-
CA 02644612 2008-10-10
shown in the drawing, alignment holes 43, oxidizer holes 51, and fuel holes 59
are visible on the
exterior, or bottom, side of injector face plate 29. Fuel inlet 55 of fuel
distribution manifold plate
53 also is visible on the side of injector 13. A pin may be inserted through
alignment holes 43 to
secure plates 29, 41, 47, 53 in alignment. Injector 13 and the plates forming
injector 13 have
been simplified in FIGS. 3-7 to better illustrate the relationship of the
plates and the design of the
injector. Commercial embodiments of injector 13 may include a greater number
of oxidizer and
fuel holes, and may include plates that are relatively thinner than those
shown in FIGS. 3-7.
FIG. 8 illustrates one embodiment of the cooling liner 15. The cooling liner
15 forms
part of burner 11 as shown in FIG. 1. Injector 13 may be positioned at the
inlet, or upper end, 67
of cooling liner 15. Cooling liner 15 includes two major sections: effusion
cooling section 63,
and effusion cooling and jet mixing section 65. In a one embodiment, section
63 extends for
approximately 7.5 inches from the bottom of injector 13 and section 65 extends
for
approximately 10 inches from the bottom of section 63. Those skilled in the
art will recognize
that other lengths for sections 63, 65 are within the scope of the invention.
Heated steam and
combustion products exit cooling liner 15 through outlet 24.
Effusion cooling section 63 may be characterized by the inclusion of a
plurality of
effusion holes 71. Effusion cooling section 63 acts to inject small jets of
steam along the surface
of cooling liner 15, thus providing a layer of cooler gases to protect liner
15. In one
embodiment, effusion holes 71 may be angled 20 degrees off of an internal
surface of cooling
liner 15 and aimed downstream of inlet 67, as shown in FIG. 9. Angling of
effusion holes 71
helps to prevent steam from penetrating too far into burner 11 and allows the
steam to move
along the walls of liner 15 to keep it cool. The position of effusion cooling
section 63 may
correspond to the location of the flame position in burner 11. In one
embodiment, approximately
37.5% of the steam provided to burner 11 through steam channel 25 (FIG. 1) is
injected by
effusion cooling section 63.
Effusion cooling and jet mixing section 65 may be characterized by the
inclusion of a
plurality of effusion holes 71 as well as a plurality of mixing holes 73.
Mixing holes 73 are
-9-
CA 02644612 2008-10-10
larger than effusion holes 71, as shown in FIG. 10. Furthermore, mixing holes
73 may be set at a
90 degree angle off of an internal surface of cooling liner 15. Effusion holes
71 act to cool liner
15 by directing steam along the wall of liner 15, while mixing holes 73 act to
inject steam further
toward the central axial portions of burner 11.
In another embodiment, the invention further comprises injecting liquid water
into the
downhole burner and cooling the injector and/or liner with the water. The
water may be
introduced to the well and injected in numerous ways such as those described
herein.
Table 1 summarizes the qualities and placement of the holes of sections 63, 65
in one
embodiment. The first column defines the section of cooling liner 15 and the
second column
describes the type of hole. The third and fourth columns describe the starting
and ending
position of the occurrence of the holes in relation to the top of section 63,
which may correspond
to the bottom surface of injector 13 (see FIG. 1). The fifth column shows the
percentage of total
steam that is injected through each group of holes. The sixth column includes
the number of
holes while the seventh column describes the angle of injection. The eighth
column shows the
maximum percentage of jet penetration of the steam relative to the internal
radius of cooling
liner 15. The ninth column shows the diameter of the holes in each group.
-10-
CA 02644612 2008-10-10
TABLE 1. Example of Cooling Liner Properties
% of Injection Radial Hole
Hole Start End Number
Secti onTotal Angle Injection Diameter
Type (inches) (inches) of Holes
Steam (degrees) % (inches)
Effusion 0.00 3.00 15 720 20.0 3.90 0.0305
Effusion
Effusion 3.00 5.00 12.5 600 20.0 8.16
0.0305
Cooling
Effusion 5.00 7.50 10 480 20.0 6.81
0.0305
Mixing 7.50 7.50 6.5 18 90.0 74.35
0.1268
Effusion 7.50 9.50 4.8 180 20.0 6.39
0.0345
Mixing 9.50 9.50 6.5 12 90.0 75.94
0.1553
Effusion 9.50 11.50 4.8 180 20.0 5.39
0.0345
Effusion
Mixing 11.50 11.50 6.5 8 90.0 79.68
0.1902
Cooling
Effusion 11.50 13.50 4.8 180 20.0 4.66 0.0345
and Jet
Mixing 13.50 13.50 6.5 6 90.0 80.43
0.2196
Mixing
Effusion 13.50 15.50 4.8 180 20.0 4.10 0.0345
Mixing 15.50 15.50 6.5 5 90.0 78.24
0.2406
Effusion 15.50 17.50 4.8 180 20.0 3.66 0.0345
Mixing 17.50 17.50 6 4 90.0 75.93
0.2584
Embodiments of the downhole burner may be operated using various fuels. In one
embodiment, the burner may be fueled by hydrogen, methane, natural gas, or
syngas. One type
of syngas composition comprises 44.65 mole % CO, 47.56 mole % H2, 6.80 mole %
CO2, 0.37
mole % CH4, 0.12 mole % Ar, 0.29 mole % N2, and 0.21 mole % H2S+COS. One
embodiment
of the oxidizer for all the fuels includes oxygen and could be, for example,
air, rich air, or pure
oxygen. Although other temperatures may be employed, an inlet temperature for
the fuel is
about 240 F and an inlet temperature for the oxidant is about 186.5 F.
Table 2 summarizes the operating parameters of one embodiment of a downhole
burner
that is similar to that described in FIGS. 1-11. The listed parameters are
considered separately
for a downhole burner operating on hydrogen, syngas, natural gas, and methane
fuels. Other
fuels, such as liquid fuels, could be used.
-11-
CA 02644612 2008-10-10
TABLE 2. Downhole burner producing about 3200 bpd of steam
Parameter Units 1-17-07 Syngas-02 CH4-07
Power
MMBtu/hr 13.0 13.0
13.0
Required
Fuel
Mass Flow lb/hr 376 3224
985
Inlet Pressure psi 1610 1680
1608
Hole Diameter inches 0.075 0.075
0.075
Number of
30 30 30
Holes
Oxidizer
Mass Flow lb/hr 3011 2905
3939
Inlet Pressure psi 1629 1626
1648
Average
inches 0.055 0.055
0.055
Hole Diameter
Number of
60 60 60
Holes
Embodiments of the dovvnhole burner also may be operated using CO2 as a
coolant in
addition to steam. CO2 may be injected through the injector or through the
cooling liner. The
power required to heat the steam increases when diluents such as CO2 are
added. In the example
of Table 3, a quantity of CO2 sufficient to result in 20 volumetric percent of
CO2 in the exhaust
stream of the burner is added downstream of the injector. It can be seen that
the increase in inlet
pressures is minimal although the required power has increased.
-12-
CA 02644612 2008-10-10
TABLE 3. Downhole burner producing 3200 bpd of steam and 20 volumetric percent
CO2.
CO2 is added downstream of injector.
112 - Syngas-0? CH4-07
Parameter Units
Power
MMBtu/hr 14.7 14.1
14.3
Required
Fuel
Mass Flow lb/hr 427 3496
1084
Inlet Pressure psi 1614 1699
1610
Hole Diameter inches 0.075 0.075 0.075
Number of
30 30 30
Holes
Oxidizer
Mass Flow lb/hr 3413 3149
4335
Inlet Pressure psi 1637 1630
1658
Average
inches 0.055 0.055 0.055
Hole Diameter
Number of
60 60 60
Holes
In the example of Table 4, a quantity of CO2 sufficient to result in 20
volumetric percent
of CO2 in the exhaust stream of the burner has been added through the fuel
line and fuel holes of
the burner. It can be seen that the fuel inlet pressure is much higher than in
the example of Table
3. CO2 also could be delivered through the oxidizer line and oxidizer holes,
or a combination of
delivery methods could be used. For example, the CO2 could be delivered into
burner 11 with
the fuel.
In other embodiments, the diameters of the fuel and oxidizer injectors 31 may
differ to
optimize the injector plate for a particular set of conditions. In the present
embodiment, the
diameters are adequate for the given conditions, assuming that supply pressure
on the surface is
increased when necessary.
-13-
CA 02644612 2008-10-10
TABLE 4. Downhole burner producing 3200 bpd of steam and 20 volumetric percent
CO2.
CO2 is added through the fuel line and fuel holes.
Parameter Uni H2-09 Syngas-02 CH4-07
ts
Diluent / Fuel
29.68 2.14 8.67
Mass Ratio
Percent Diluent
100 100
100
in Fuel Line
Percent Diluent
0 0 0
in Oxidizer Line
Power
MMBtu/hr 14.7 14.1
14.3
Required
Fuel
Mass Flow lb/hr 427 3496
1084
Inlet Pressure psi 2416 2216
1988
Hole Diameter inches 0.075 0.075
0.075
Number of
30 30 30
Holes
Oxidizer
Mass Flow lb/hr 3413 3149
4335
Inlet Pressure psi 1637 1630
1658
Average
inches 0.055 0.055 0.055
_ Hole Diameter
Number of
60 60 60
Holes
Burner 11 can be useful in numerous operations in several environments. For
example,
burner 11 can be used for the recovery of heavy oil, tar sands, shale oil,
bitumen, and methane
hydrates. Such operations with burner 11 are envisioned in situ under tundra,
in land-based
wells, and under sea.
The invention has numerous advantages. The dual purpose cooling/mixing liner
maintains low wall temperatures and stresses, and mixes coolants with the
combustion effluent.
The head end section of the liner is used for transpiration cooling of the
line through the use of
effusion holes angled downstream of the injector plate. This allows for
coolant (primarily
partially saturated steam at about 70% to 80% steam quality) to be injected
along the walls,
which maintains low temperatures and stress levels along liner walls, and
maintains flow along
the walls and out of the combustion zone to prevent flame extinguishment.
-14-
CA 02644612 2008-10-10
The back end section of the liner provides jet mixing of steam (and other
coolants) for the
combustion effluent. The pressure difference across the liner provides
sufficient jet penetration
through larger mixing holes to mix coolants into the main burner flow, and
superheat the coolant
steam. The staggered hole pattern with varying sizes and multiple axial
distances promotes good
mixing of the coolant and combustion effluent prior to exhaust into the
formation. A secondary
use of transpiration cooling of the liner is accomplished through use of
effusion holes angled
downstream of the combustion zone to maintain low temperatures and stress
level along liner
walls in jet mixing section of the burner similar to transpiration cooling
used in the head end
section.
The invention further provides coolant flexibility such that the liner can be
used in
current or modified embodiment with various vapor/gaseous phase coolants,
including but not
limited to oil production enhancing coolants, in addition to the primary
coolant, steam. The liner
maintains effectiveness as both a cooling and mixing component when additional
coolants are
used.
The showerhead injector uses alternating rings of axial fuel and oxidizer jets
to provide a
uniform stable diffusion flame zone at multiple pressures and turndown flow
rates. It is designed
to keep the flame zone away from injector face to prevent overheating of the
injector plate. The
injector has flexibility to be used with multiple fuels and oxidizers, such as
hydrogen, natural
gases of various compositions, and syngases of various compositions, as well
as mixtures of
these primary fuels. The oxidizers include oxygen (e.g., 90-95% purity) as
well as air and
"oxygen-rich" air for appropriate applications. The oil production enhancing
coolants (e.g.,
carbon dioxide) can be mixed with the fuel and injected through the injector
plate.
In other embodiments, the invention is used to disperse nanocatalysts into
heavy oil
and/or bitumen-bearing formations under conditions of time, temperature, and
pressure that
cause refining reactions to occur, such as those described herein. The
nanocatalysts are injected
into the burner via any of the conduits or means described herein (including
an optional separate
-15-
CA 02644612 2008-10-10
line), and a nanocatalyst-reducing gas mixture is passed through the burner
where it is heated, or,
the mixture is injected alongside the downhole steam generator. In either
case, the mixture is
then injected into the formation where it promotes converting and upgrading
the hydrocarbon
downhole, in situ, including sulfur reduction. The reducing gas may comprise
hydrogen, syngas,
or hydrogen donors such as tetralin or decalin. The appropriate catalyst
causes the reactions to
take place at a temperature that is lower than the temperature of thermal
(i.e., non-catalytic)
reactions. Advantageously, less coke is formed at the lower temperature.
Alternatively, the carrier gas is preheated on the surface prior to entering
the transfer
vessel. The carrier gas may be preheated using any heat source and heat
exchange device. The
preheated gas is supplied to the transfer vessel at an elevated temperature
that provides for heat
losses in the heat transfer vessel as well as the well bore and still be
sufficient to maintain the in
situ catalytic reactions for which the catalyst was designed.
The nanocatalyst-reducing gas mixture is injected into the formation where it
promotes
converting and upgrading the hydrocarbon. When the in situ catalytic reaction
comprises
hydrovisbreaking, hydrocracking, hydrodesulfurization, or other hydrotreating
reactions,
hydrogen is the preferred carrier gas. For other types of reactions, the
carrier gas is one or more
of the reactants. For example, if the reaction that is promoted is in situ
combustion, the carrier
gas is oxygen, rich air, or air. In another embodiment, carbon dioxide is the
carrier gas for a
cracking catalyst that promotes in situ cracking of the hydrocarbon in the
foiniation.
Referring now to FIG. 12, one embodiment of the invention uses two vessels
111, 113 to
prepare and transport nanocatalysts. Vessel 111 is in catalyst preparation
mode and vessel 113 is
in transfer mode. When a catalyst preparation and transfer cycle is complete,
the roles of the two
vessels 111, 113 are reversed. When vessel 111 is in catalyst preparation
mode, valves 115 and
117 are closed. The catalyst materials are added to vessel 111 through a
separate port(s) 119,
mixed and dried. When the catalyst preparation is complete, valves 115 and 117
are opened and
the carrier gas flows through vessel 111, carrying the nanocatalysts particles
into a feedline to a
downhole steam generator 121. While vessel 111 is in catalyst preparation
mode, vessel 113 is
-16-
=
CA 02644612 2008-10-10
in transfer mode. In this configuration, valves 123 and 125 are open, valve
127 is closed, and the
carrier gas sweeps through vessel 113. Valve 127 controls the transfer of
catalyst preparation
materials (not shown) into vessel 113.
When the cycle of catalyst preparation in one vessel and the catalyst transfer
from the
other vessel is complete, the roles of the two vessels are reversed. The
vessel where the catalyst
was prepared becomes the transfer vessel, and the vessel that had the catalyst
transferred out
becomes the catalyst preparation vessel. This alternation of roles continues
until the catalyst
injection into the formation is no longer required.
One embodiment of the invention employs nanocatalysts prepared in a
conventional
manner. See, e.g., Enhancing Activity of Iron-based Catalyst Supported on
Carbon
Nanoparticles by Adding Nickel and Molybdenum, Ungula Priyanto, Kinya
Sakanishi, Osamu
Okuma, and Isao Mochida, Preprints of Symposia: 220th ACS National Meeting,
August 20-24,
2000, Washington, D.C. The catalyst is transported into a petroleum-bearing
formation by a
carrier gas. The gas is a reducing gas such as hydrogen and the catalyst is
designed to promote
an in situ reaction between the reducing gas and the oil in the reservoir.
In order for the conversion and upgrading reactions to occur in the reservoir,
the catalyst,
reducing gas, and the heavy oil or bitumen must be in intimate contact at a
temperature of at least
400 F, and at a hydrogen partial pressure of at least 100 psi. The intimate
contact, the desired
temperature, and the desired pressure are brought about by means of a downhole
steam
generator. See, e.g., U.S. Patent No. 4,465,130. The steam, nanocatalysts, and
unburned
reducing gases are forced into the formation by the pressure created by the
downhole steam
generator. Because the reducing gas is the carrier for the nanocatalysts,
these two components
will tend to travel together in the petroleum-bearing fomiation. Under the
requisite heat and
pressure, the reducing gas catalytically reacts with the heavy oil and bitumen
thereby reducing its
viscosity and % sulfur as well as increasing its API gravity.
-17-
CA 02644612 2008-10-10
Some catalysts comprise a metal adsorbed on a carbon nanotube. For those
catalysts, the
temperature of the upgrading reactions must be below the temperature that
allows the steam to
react with the carbon tubes. Other catalysts, such as TiO2 or Ti02-based, are
not affected by
steam and are effective in catalyzing upgrading reactions.
In the embodiment of FIG. 12, the two similar vessels 111, 113 operate in
parallel and
prepare the nanocatalyst and transfer it to the injection lines leading to the
downhole steam
generator. The vessels are separate from the continuous flow of reducing gas,
oxidizing gas, and
steam. For example, a nanocatalyst is prepared by impregnating Ni salt, and Mo
salt on
nanoparticles (e.g., Ketjen Black) resulting in a catalyst with 2% Ni, 10% Mo
and 88% Ketjen
Black. When the batch of catalyst is finished and dried, the carrier gas is
passed through the
catalyst-containing vessel thereby carrying the catalyst into the injection
well and then into the
formation. While the catalyst that was prepared in one vessel is being
transferred to the lines
leading to the injection well, another batch of catalyst is prepared in the
other vessel. The
alternation of catalyst preparation and transfer is continued in each of the
two vessels as long as
the in situ process benefits from use of the catalyst.
This embodiment has many advantages including that the downhole steam
generator
makes it possible to bring together hydrogen, a hydrogenation catalyst, heavy
oil in place, heat,
and pressure, thereby causing catalytic reactions to occur in the reservoir.
Because catalysts with
a wide variety of reactivities and selectivities can be synthesized, the
invention permits many
opportunities for in situ upgrading. The nature of catalysts is to promote
reactions at milder
conditions (e.g., lower temperatures and pressures) than theitnal or non-
catalytic reactions. This
means that hydrogenation, for example, may be conducted in situ at shallower
depths than
conventional pyrolysis and other thermal reactions.
Another advantage of the process when used without a downhole steam generator
is the
ease of operation without the generator. The lack of downhole equipment
results in less
maintenance and less downtime for injection of the catalyst and reactants. One
disadvantage is
the heat losses in the catalyst preparation/transfer vessels and in the well
bore. The invention
-18-
=
CA 02644612 2008-10-10
provides a platform technology that is applicable to a wide range of in situ
reactions in a wide
range of heavy oil, ultraheavy oil, natural bitumen, and lighter deposits.
Furthermore, the invention has many applications, including in situ catalytic
hydrogenation, in situ catalytic hydrovisbreaking, in situ catalytic
hydrocracking, in situ catalytic
combustion, in situ catalytic reforming, in situ catalytic alkylation, in situ
catalytic isomerization,
and other in situ catalytic refining reactions. Although all of these
reactions are used in
conventional petroleum refining, none of them are used for in situ catalytic
reactions.
Although some embodiments of the present invention have been described in
detail, it
should be understood that various changes, substitutions, and alterations can
be made hereupon
without departing from the principle and scope of the invention.
-19-
