U.S. patent number 3,680,636 [Application Number 04/889,061] was granted by the patent office on 1972-08-01 for method and apparatus for ignition and heating of earth formations.
This patent grant is currently assigned to Sun Oil Company. Invention is credited to Holland J. Berry, William C. Hardy, Dale W. Zadow.
United States Patent |
3,680,636 |
Berry , et al. |
August 1, 1972 |
METHOD AND APPARATUS FOR IGNITION AND HEATING OF EARTH
FORMATIONS
Abstract
A heater for stimulating wells which include a heat shield with
openings for air in the heat shield side walls, an air inlet
upstream of a burner to premix the fuel and air, and a burner made
up of a bundle of tubes of varying lengths to vertically spread the
flame. Alternatively, to vertically spread the flame, a burner is
provided in tubular form with perforations extending the length of
the tube. Wireline run ignitors, using energy from batteries are
used to ignite the burners. Also, a wireline run catalytic material
combined with an injected hydrogen mixture can be used for
ignition.
Inventors: |
Berry; Holland J. (Richardson,
TX), Hardy; William C. (Richardson, TX), Zadow; Dale
W. (Richardson, TX) |
Assignee: |
Sun Oil Company (Dallas,
TX)
|
Family
ID: |
25394450 |
Appl.
No.: |
04/889,061 |
Filed: |
December 30, 1969 |
Current U.S.
Class: |
166/302;
166/59 |
Current CPC
Class: |
E21B
36/02 (20130101) |
Current International
Class: |
E21B
36/00 (20060101); E21B 36/02 (20060101); E21b
043/24 () |
Field of
Search: |
;166/59,58,60,63,256,260,302 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Novosad; Stephen J.
Claims
What is claimed is:
1. Apparatus for heating an underground formation penetrated by a
wellbore, comprising: well pipe located in the wellbore; a heat
shield open at the bottom and attached to the lower end of the well
pipe; and a burner located inside the heat shield, said burner
having a plurality of burner ports which are radially and
vertically spaced on the burner and which provide individual flame
points.
2. The apparatus of claim 1 wherein the burner comprises a tubular
member having a multiplicity of perforations extending through the
burner wall.
3. Apparatus for supplying heat in a wellbore comprising: well pipe
located in the wellbore; and a burner attached to the lower end of
the well pipe, said burner comprising a plurality of varying length
burner tubes.
4. The apparatus of claim 3 including premix air admission means
located upstream of the burner, and air inlet means located in the
side wall of the heat shield.
5. The apparatus of claim 4 including means for attaching the heat
shield to the well pipe, wherein the air inlet means includes
spaces between members of said attachment means and baffles located
adjacent the spaces between attachment means members.
6. Apparatus for heating an underground formation penetrated by a
wellbore comprising: well pipe extending from the surface to the
vicinity of the underground formation; a burner attached to the
lower end of the well pipe having vertically and radially spaced
burner ports providing individual flame points; a heat shield open
at the bottom and encircling said burner; and premix air inlet
means located upstream of the burner and communicating with the
interior of the burner.
7. The apparatus of Claim 6 including means for admitting air to
the interior of the heat shield and exterior of the burner and
means for imparting turbulence to air entering the heat shield.
8. Apparatus for heating an underground formation penetrated by a
wellbore comprising: well pipe extending from the surface to a
point adjacent and above the underground formation to be heated; a
tubular burner attached to said well pipe and having an interior
communicating with the interior of the well pipe, said burner
having a multiplicity of burner ports which are vertically and
radially spaced on the burner and extend through the wall of the
tubular burner, said ports providing individual flame points; means
for insulating the burner from the wall of the wellbore; and premix
air admission means located above the burner and communicating with
the interior of the burner.
9. The apparatus of claim 8 including means for admitting air
between the insulator means and the burner, and means for baffling
the air entering the air admission means, said baffling means
located adjacent the air admission means.
10. Apparatus for heating an underground formation penetrated by a
wellbore comprising: well pipe extending from the surface to a
point above and adjacent the formation to be heated; a burner
having a multiplicity of burner ports spaced vertically and
radially on the burner, wherein the interior of the burner
communicates with the interior of the well pipe and the exterior of
the burner communicates with the space between the well pipe and
the wellbore wall; a heat shield open at the bottom and encircling
the burner; and air inlet means located in the side wall of the
heat shield, wherein the air inlet means is a tortuous channel
through the heat shield side wall.
11. The apparatus of claim 10 including premix air admission means
located above said burner and baffles located adjacent said air
inlet means in the heat shield.
12. Apparatus for heating an underground formation penetrated by a
wellbore comprising: well pipe extending from the surface to the
vicinity of the formation; a wireline retrievable burner comprising
a plurality of varying length tubes wherein the tube interiors
communicate with the well pipe interior; a heat shield open at the
bottom and encircling said burner; and premix air admission means
located above the burner and communicating with the interior of the
varying length tubes.
13. The apparatus of claim 12 including means for admitting air to
the interior of the heat shield and baffle means located adjacent
the air admission means.
14. Apparatus for heating an underground formation penetrated by a
wellbore having casing and tubing located therein, comprising: a
tubular burner connected to the lower portion of the tubing and
located adjacent the formation, said tubular burner having
vertically and radially spaced perforations extending through the
wall of the tubular burner defining burner ports; a heat shield
open at the bottom and encircling said burner, interposed between
the burner and casing, said heat shield having openings for air
admission which are arranged so that the air travels a tortuous
pathway to the interior of the heat shield; and premix air
admission means located above the burner.
15. The apparatus of claim 14 including means for baffling the air
entering the heat shield so as to impart turbulence to the entering
air stream.
16. Apparatus for heating an underground formation penetrated by a
wellbore comprising: well pipe extending between the surface and a
point adjacent the formation being heated; a burner attached to the
lower end of the well pipe, said burner having a plurality of
burner ports vertically and radially spaced; a heat shield open at
the bottom and encircling said burner, said heat shield being
secured to the lower end of the well pipe by attachment means
having connection members; and air inlet means located in the heat
shield side walls and adjacent the connection members.
17. The apparatus of claim 16 including baffle means located
adjacent the air inlet means located between the connection members
of the attachment means.
18. Apparatus for heating an underground formation penetrated by a
wellbore comprising: well pipe extending from the surface to a
point adjacent the formation to be heated; a burner attached to the
lower end of the well pipe and having a plurality of radially and
vertically spaced ports which provide individual flame points;
means for insulating the wall of the wellbore from the burner; and
means for igniting the burner;
19. The apparatus of claim 18 wherein the burner ignition means is
a self contained electrical energy source located adjacent the
burner.
20. The apparatus of claim 18 wherein the burner ignition means is
a catalytic material located adjacent the burner.
21. Apparatus for heating an underground formation penetrated by a
wellbore comprising: well pipe extending from the surface to a
point adjacent the formation to be heated; a burner having a
plurality of varying length burner tubes attached to the lower end
of the well pipe; ignitor means located adjacent the burner
comprising a shelf contained electrical energy source, means for
increasing the intensity of the electrical energy flowing from the
electrical energy source and means for flowing the electrical
energy between spaced electrical contacts at spaced intervals of
time; and means for insulating the burner from the wall of the
wellbore.
22. Apparatus for heating an underground formation penetrated by a
wellbore comprising: a tubular burner having a multiplicity of
burner ports extending through the wall of the tubular burner
arranged such that the ports are vertically and radially spaced and
provide individual flame points; means for supplying a fuel mixture
to the burner; means for insulating the wall of the wellbore from
the burner; means for igniting the burner located adjacent the
burner comprising an independent source of electrical energy, and
means for increasing the voltage of the electrical energy; and
means for converting the electrical energy to an electric arc.
23. The apparatus of claim 22 wherein the electrical arc means is a
pair of spaced electrical contacts separated by air which contacts
are located in the interior of the burner and arranged to receive
the electrical energy from the ignitor means.
24. Apparatus for heating an underground formation penetrated by a
wellbore comprising: a tubular burner having a multiplicity of
burner ports spread vertically and radially on the surface of the
burner; means for insulating the wall of the wellbore from the
burner; means for introducing a gaseous fuel to the burner; means
for introducing air to the exterior of the burner; and means to
ignite the burner comprising a catalytic material located adjacent
the burner and communicating with the interior and exterior of the
burner.
25. The apparatus of claim 24 wherein the ignition means comprises
a tubular member having a permeable inner wall, a permeable
retaining means constituting an outer wall, baffle means located
between the inner and outer walls, and wherein the catalytic
material is located adjacent the retaining means.
26. Apparatus for heating an underground formation penetrated by a
wellbore comprising: a gas burner having a plurality of radially
and vertically spaced ports on the burner surface; a heat shield
open at the bottom and encircling said burner; means for
introducing a fuel mixture to the burner surface; and means for
igniting the burner comprising a tubular member located adjacent
the burner, said member having a permeable inner wall communicating
with the well pipe, permeable retaining means, baffle means located
between the retaining means and the inner wall, and catalytic
material adjacent the retaining means.
27. The apparatus of claim 26 wherein the gas burner includes a
tubular member with the ports being perforations in the sidewall of
the tubular member and wherein the ignition means is of smaller
diameter than the burner, and the ignition means is located inside
the burner.
28. A process for supplying heat in a wellbore having well pipe
therein including the steps of: attaching a burner; to the lower
end of the well pipe, flowing air down the annulus between the well
pipe and the wellbore so that air contacts the exterior of the
burner; flowing a fuel gas down the interior of the well pipe and
into the burner; dispersing the fuel so as to vertically and
radially spread the fuel on the burner surface; insulating the
wellbore from the burner; admitting an air stream between the
insulation and burner and creating turbulence in the air stream by
use of a baffle; and igniting the burner.
29. The process of claim 28 including the step of admitting premix
air into the interior of the burner.
30. The process of claim 28 wherein ignition of the burner is
effected by generating a spark gap in the presence of a combustible
mixture with stepped up electrical energy derived from an energy
source located in the wellbore.
31. The process of claim 28 wherein spontaneous ignition of the
burner is effected by contacting a catalytic surface, located
adjacent the burner, with a hydrogen containing fuel gas.
32. A process of heating an underground formation penetrated by a
wellbore having well pipe extending from the surface to a point
near the top of the formation, comprising: attaching a burner to
the lower end of the well pipe so that the burner interior
communicates with the interior of the well pipe; insulating the
burner from the wall of the wellbore; flowing fuel gas through the
well pipe and into and through the burner so that fuel gas is
radially and vertically distributed on the outside surface of the
burner; flowing air down the annular space between the well pipe
and wellbore wall to the formation; passing a portion of the air
flowing down the annulus between the insulation and burner so as to
contact the outside surface of the burner; and igniting the fuel
gas and air mixture present at the burner surface.
33. The process of claim 32 including admitting premix air into the
fuel gas flow at a point immediately prior to the burner.
34. The process of claim 32 wherein ignition of the burner is
accomplished by creating a spark gap at the burner by using stepped
up electrical energy provided by a self contained energy source
located adjacent the burner.
35. The process of claim 32 wherein ignition of the burner is
accomplished by catalytically reacting hydrogen and air at the
burner by injecting hydrogen into the fuel gas flow so that it
contacts a catalytic material located adjacent the burner.
Description
BACKGROUND OF THE INVENTION
This invention relates to a burner device for heating oil well
formations and is related to two co-pending applications filed of
even date herewith and entitled "METHOD AND APPARATUS FOR IGNITING
WELL HEATERS", Ser. No. 889.06.0, and "METHOD AND APPARATUS FOR
CATALYTIC IGNITION OF EARTH FORMATIONS" Ser. No. 889,059, now
abandoned and the continuation-in-part of that application entitled
"Method and Apparatus for Catalytically Heating Wellbores" Ser. No.
92,836. In the stimulation of oil wells, several methods have been
utilized to apply heat to the formations. This heat may be provided
for several purposes. One purpose is to supply enough heat to lower
the viscosity of the petroleum, or to melt paraffin which is in the
vicinity of the wellbore. Another purpose is to ignite the oil in
the formation, which ignition is termed "in situ combustion."
Essentially, an "in situ combustion" process involves igniting the
formation so that the heat from the combustion lowers the viscosity
of the oil in front of it and also gasifies lighter hydrocarbons
providing pressure to drive the oil in the direction of a producing
well. The "in situ combustion" process involves several steps.
First, air is injected into the oil bearing formation through an
injection well. The injection pressure is sufficient to cause air
to flow through the formation from the injection well to one or
more producing wells, and it is injected at a sufficient rate to
support a combustion reaction of a fraction of the oil in the
formation. Additionally, the air pressure forces the oil away from
the casing of the injection well so that the well is relatively
free of liquids. In order to initiate a combustion reaction in most
oil bearing formations, it is necessary to inject heat along with
the air. The heat is carried by the air into the reservoir where it
contacts the formation oil. By flowing a sufficient volume of hot
air into the reservoir, the crude oil in the vicinity of the
injection well is heated to its ignition temperature and commences
to burn.
Several popular methods of igniting the oil in the formation are by
downhole electrical heaters, downhole gas burners, and natural
spontaneous combustion reactions occurring when unheated air is
injected into the formation. There are limitations to the methods
now being employed. The downhole electrical heater requires an
electrical cable from the surface to the heater. High voltages are
required for the electrical heater, since the cable operates as a
resistance. Because of voltage dissipation due to cable resistance,
it may be difficult to maintain sufficient voltage at the heater if
the cable length exceeds about 3,000 ft.
The formations that ignite by natural spontaneous combustion
reactions depend upon a set of circumstances that do not readily
occur in all reservoirs. Most napthenic crudes spontaneously ignite
while paraffinic crudes do not. Therefore, downhole gas burners
have been used mostly in deep paraffinic wells. There however have
been problems related to downhole well pipe damage due to the
intense heat generated by gas burners.
Ordinarily, in downhole gas burners an orifice or nozzle surrounded
by a cylindrical heat shield is run on standard oil field tubing to
the vicinity of the top of the formation which is to be heated. Gas
is flowed down the tubing through the nozzle and into the heat
shield. Air is flowed down the annular spaced between the tubing
and the casing to the bottom of the hole where part of the air
enters the heat shield and mixes with the gas entering from the
tubing, while the balance of the air enters the formation being
heated. When the burner is ignited, heat from the burner is
transferred to the balance of air entering the formation. This
heated air raises the temperature in the formation surrounding the
wellbore until the formation oil is ignited. Upon formation
ignition, fuel gas is no longer injected, and air is pumped to the
formation to support combustion of the formation oil.
To ignite this gas-air mixture within the heat shield, pyrophoric
chemicals are introduced, which are highly combustible in air at
standard conditions. Therefore, special precautions must be taken,
such as purging the lubricator and tubing of air with nitrogen so
that the pyrophoric chemical does not react with air before
reaching the burner. This method of ignition is not often
successful, since the fuel mixture and pyrophoric material must be
present in the right proportions to initiate combustion of the fuel
gas. If the fuel-air mixture is too rich when the pyrophoric
chemical ignites, an explosion will occur which can cause serious
damage to the heat shield, tubing, and casing. The rich mixture is
usually caused by poor mixing, creating areas which are
predominantly fuel gas or air. Poor mixing is not uncommon, and the
explosions resulting therefrom can cause such extensive damage that
the well can no longer be used.
When the burner is successfully ignited, other problems arise with
the burners now being used. Damage to the well pipe can result from
having a single flame area at the nozzle which concentrates the
heat so that it acts on only a small area of the heat shield,
causing the shield to burn through, thus exposing the casing to
high temperature oxidation and resultant damage.
If the fuel-gas velocities are too high, the flame stand-off
distance between flame and nozzle becomes excessive and the flame
can jump to the end of the heat shield. When the flame is
transferred to the end of the heat shield, the casing is left
totally unprotected. If this happens for any length of time, the
casing will be damaged, since the heat of combustion of natural gas
can run in the neighborhood of 4,000.degree. F.
Because of the problems created by current formation heating
practices, it is an object of the present invention to provide new
and improved downhole gas burners and related ignitors.
SUMMARY OF THE INVENTION
With this and other objects in view, the present invention includes
a burner which is in tubular form with perforations extending along
the length of the tube. This effectively vertically spreads the
flame to eliminate concentration of the flame in one area, and
thereby reduces the chances of damage to downhole equipment. An
opening is provided upstream of the gas burner to allow air to
enter and mix with the fuel gas prior to reaching the burner, so
that the flame does not stand off from the burner tip. A heat
shield surrounding the burner has air inlets with adjacent baffles
to admit turbulent air to the burner area, thereby substantially
eliminating extremely lean and rich mixtures.
Additionally, an alternate burner is provided consisting of a
bundle of varying length tubes to vertically spread out the flame
area to avoid concentration of the heat of combustion.
Ignitors are provided for use with the burners, which can be run on
wireline and are battery operated, eliminating the need for
pyrophoric materials. Also, the burners can be ignited by
contacting a catalytic material, run to the heater area by
wireline, with an injected hydrogen mixture.
A complete understanding of this invention may be had by reference
to the following description, when read in conjunction with the
accompanying drawings illustrating embodiments thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-section of a multiple length tubular burner in
position in a well;
FIG. 2 is a cross-sectional view of the multiple length tubular
burner in the wellbore surrounded by the heat shield taken along
lines 2--2 of FIG. 1;
FIGS. 3 and 3A are a side view and schematic respectively, of a
burner ignitor for use in the multiple tube burner shown in FIGS. 1
and 2;
FIG. 4 is a cross-section of a perforated tubular burner in
position in a well;
FIGS. 5 and 5A are a side view and schematic respectively, of an
ignitor used to ignite the burner of FIG. 4; and
FIG. 6 is a catalytic ignitor which is run on a wireline.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring first to FIG. 1, there is seen a heat shield 26 attached
to tubing 14 located inside of casing 12 where the heat shield is
attached to the tubing by attachment member 20. Attached to the
lower end of the tubing 14 inside the heat shield 26 are multiple
length tubes 24 comprising a burner. These multiple length burner
tubes 24 have burner tube ports 28. Located upstream from the
burner is a premix air inlet 16. The heat shield has air scoops 18
for admitting air to the interior of the heat shield and to the
vicinity of the burner tube ports 28. Tubing 14 has a seating
nipple 22 located at its lower extremity. The seating nipple 22 is
used to support a shoulder 34 located at the top of burner 52. The
burner 52 also has an inside shoulder 42 making the burner wireline
retrievable.
In the operation of the apparatus shown in FIG. 1, the multiple
length burner tubes are seated on seating nipple 22, and are
located just above perforations 30 inside the heat shield 26. Air
is pumped down the annulus between casing 12 and tubing 14. This
air operates to force reservoir fluids away from the wellbore and
support combustion at the burner. Fuel gas is pumped down the
inside of tubing 14 to the burner area. As the air proceeds down
the annulus, some air enters the tubing through premix air inlet 16
to allow the air to mix with the fuel gas before reaching the
burner tubes 24. After this fuel gas and air has been ignited,
preferably by the ignitor shown in FIGS. 3 and 3A, a flame caps the
burner ports 28. Additional air is supplied to the burner tube
ports 28 and heat shield interior by air inlets 18. Baffles are
located below the uppermost air inlets 18 which are adjacent the
attachment members 20. These baffles are illustrated in FIG. 2, and
indicated as 32. The premix air inlet 16 affords the fuel gas and
air an opportunity to mix before reaching the burner tube ports,
thereby preventing the flame from standing off from burner tube
ports 28. If stand-off were allowed to happen, damage to casing 12
located below the heat shield could occur.
The air inlets 18 and baffles 32 shown in FIG. 2 provide turbulent
air for association with the gas exiting burner tube ports 28. This
prevents hot spots from occurring due to localization of the heat
emanating from the burner, related to localized enriched mixtures
resulting from poor mixing of air and fuel gas.
The multiple length burner tube serves the purpose of spreading out
the flame area so that intense heat does not localize at one point
as in the prior art burner where a single flame emanates from a
nozzle. This reduces the possibility of damage due to the
concentration of intense heat. When the oil formation has been
heated or ignited, fuel gas is no longer injected and the burner
can be retrieved by wireline.
In lieu of making the burner wireline retrievable, it can be welded
to the end of the tubing or to the inside of the heat shield 26. In
that event, shoulders 34 and 42 would not be needed. Making the
burner retrievable by use of a wireline retrieving tool which
engages the flange 36 is desirous in order to allow the burner to
be easily pulled for repairs or inspection, or upon occurrence of
ignition.
FIG. 2 illustrates a cross-sectional plan view of the burner as
arranged in FIG. 1. There the tubes are shown at 24 inside of
tubing 14 which is located in casing 12. The heat shield 26 is
attached to the tubing by attachment members 20. Baffles 32 are
located adjacent the attachment members 20 to give the air
turbulence as it enters the burner area. Additional air is provided
to the interior of the heat shield 26 by air inlets 18 to supply
air to the burner area. Once the formation is heated, or "in situ"
combustion has commenced, the fuel gas will be terminated, and in
the case of "in situ" combustion, the air will be supplied
continuously to the formation to support combustion, or both air
and fuel gas will be shut off and burner equipment removed from the
wellbore if the formation is no longer to be heated.
FIGS. 3 and 3A depict an ignitor for use with the burner of FIG. 1.
The ignitor 72 is suspended from wireline 76. The ignitor has a
series of batteries 70 mounted above a pressure switch 80. An
electrode probe 74 is located below the switch 80 and terminates
with electrodes 82 formed into a spark gap 86. An adjustable stop
88 is located on the electrode probe 74. When the ignitor 72 is run
into the tubing 14, the stop 88 contacts the top of the burner 52
of FIG. 1. This allows the weight of the batteries 70 to compress
the spring 90 whereupon the contacts 92 and 94 touch together.
Sufficient electrical energy is then available by operation of the
equipment shown in FIG. 3A. The electrical energy provided by
battery pack 70 is converted to alternating current by oscillator
78, and boosted by high voltage step-up transformer 96. From the
transformer 96, the energy proceeds to electrodes 82 and generates
a spark across spark gap 86 of FIG. 3. The stop 88 can be adjusted
so that the spark generated will be located at the burner tube
ports 28 of FIG. 1.
FIG. 4 is illustrative of a burner which is a perforated tubular
member with a spark gap built therein. Tubing 14 is located inside
a casing 12. Attached to the lower portion of tubing 14 is a burner
52 consisting of a tubular member with perforations 44 extending
along its length. The heat shield 26 surrounds the burner 52 and is
attached by members 20. Air inlets 18 are located in the side walls
of heat shield 26. Premix air inlet 16 allows air to enter the
tubing prior to reaching the burner 52. A seating nipple 22 is
provided which allows use of a wireline retrievable burner.
Therefore, at the top of burner 52 is located a shoulder 34 for
engaging the seating nipple 22. There is also an inside shoulder 42
opposite shoulder 34, for engaging the wireline pulling tool.
In the operation of the apparatus of FIG. 4, fuel gas is flowed
down the tubing into and through the burner 52. Air is flowed down
the annulus between the tubing 14 and the casing 12, and a portion
enters the premix air inlet 16 and air inlets 18, with the
remainder exiting perforations 30 located in the casing wall.
Adjacent the upper air inlets 18 are baffles similar to those shown
at 32 in FIG. 2, for imparting turbulence to the air entering the
heat shield 26. The air entering premix air inlet 16 mixes with the
fuel gas so that upon ignition of the fuel, the flame caps the
burner perforations 44 on the burner 52, since a proper air-fuel
mixture is available at the perforations 44 to support combustion.
The multiplicity of perforations 44 spreads the flame so that the
flame is not concentrated in one area which could cause damage to
the heat shield 26, tubing 14, and the casing 12.
Ignition of the burner of FIG. 4 may be initiated by use of the
ignitor shown in FIGS. 5 and 5A. The electrode probe 74 of the
ignitor 72 is lowered by wireline 76 of FIG. 5 into the electrode
probe socket 50 and properly seated by guide 58. Energy emanating
from the batteries 70 surges across the spark gap 56 to ignite the
fuel mixture flowing down the annulus of the tubing when the fuel
reaches the burner 52. The heat from burner 52 is transmitted to
the air stream flowing to perforations 30 on its way to the
formation. Upon ignition of the formation in an "in situ"
combustion operation, the fuel gas flowing down the tubing is
terminated and the air flowing down the annulus supports the "in
situ" combustion in the formation.
Electrical energy sufficient to generate a spark across spark gap
56 is provided by the apparatus illustrated in FIG. 5A. There the
energy provided by battery pack 70 is converted to alternating
current by oscillator 78 and boosted by transformer 96 connected to
electrodes 82 which make up part of the spark gap 56 of FIG. 4 when
the ignitor is properly positioned by guide 58. Upon ignition of
the burner the ignitor can be removed by wireline.
FIG. 6 illustrates a catalytic ignitor for use in the burner of
FIG. 4 with or without the electrode probe socket located at its
bottom. Proper spacing of the ignitor would allow its use in the
burner having an electrode probe socket, however it is shown in a
burner without a spark gap in FIG. 6. The ignitor 38, preferably
having platinum supported on asbestos, asbestos-burlap, or ceramic
material, is run by cable 40 to the interior of the burner 52
having perforations 44. The ignitor 38 is supported by seating
nipple 22 which is in contact with a no-go landing flange 46. The
ignitor exterior is sealed from the tubing 14 by "O-rings" 48. The
burner 52 is surrounded by heat shield 26 which protects casing 12
from excessive heat. The casing 12 has perforations 30 located
below the heat shield 26. The heat shield 26 is attached to the
lower end of the tubing 14 by attachment members 20 and has air
inlets 18. Baffles are located next to the uppermost air inlets 18
and are similar to those shown at 32 in FIG. 2. The tubing 14 has
centralizers 60 for keeping the heat shield 26 out of contact with
the casing 12. A stand-off section 62 insures that the catalytic
surface is not close enough to damage the seating area of the
ignitor.
A thermocouple 64 is located on the skin of the catalytic surface
of the ignitor 38 and is connected to the cable 40 which is adapted
to transmit temperature indications to the surface. The
thermocouple 64 allows surface personnel to be able to determine
when ignition of the burner occurs so that the ignitor can be
withdrawn. Gas inlet ports 68 allow fuel gas flowing down the
tubing 14 to enter the interior of the ignitor pipe 66 so that it
will flow through the catalytic surface of ignitor 38 to the
interior of the heat shield 26.
In the operation of the catalytic ignitor 38, air is injected into
the annulus between casing 12 and tubing 14 and a mixture of
natural gas and hydrogen is injected into the tubing. The
hydrogen-natural gas fuel mixture enters ports 68 and flows down
pipe interior 66. The fuel then exits through the catalytic surface
where it reacts spontaneously with air which has entered heat
shield 26 and burner perforations 44 through air inlets 18. Once a
reaction has commenced between the hydrogen-natural gas mixture and
air and the temperature is raised sufficiently to support a
reaction of natural gas and air alone, the hydrogen is no longer
injected. Natural gas will react with air at approximately
250.degree. F. if a catalyst is present and hydrogen will react at
approximately 20.degree. F. so no additional energy source is
required. Accordingly, the hydrogen reaction will raise the
temperature sufficiently to react the natural gas and air which in
turn will go to flame to ignite the burner 52. When ignition is
indicated by thermocouple 64, the ignitor 38 is removed to the
surface. The catalytic ignitor 38 is easily and inexpensively
fabricated and the thermocouple 64 allows knowledgeable control of
the ignition process. For these reasons it appears superior to the
prior art ignitors.
Not shown but contemplated herein are sealing elements between the
wireline retrievable burners of FIGS. 1 and 4 and the seating
nipples. The sealing elements could be "O-rings" similar to those
shown at 48 in FIG. 6. Also, in lieu of having wireline retrievable
burners, the burners of FIGS. 1 and 4 can be welded in place at the
end of the tubing or attached to the heat shield.
Additionally, thermocouples could be employed in all the burners
while being ignited and/or after ignition. Automatic controls and
alarms might then be connected to the thermocouple indicator so
that excessive or deficient temperatures could be avoided.
While particular embodiments of the present invention have been
shown and described, it is apparent that changes and modifications
may be made without departing from this invention in its broader
aspects, and therefore, the aim in the appended claims is to cover
all such changes and modifications as fall within the true spirit
and scope of this invention.
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