CA2436480A1 - Porous media gas burner - Google Patents
Porous media gas burner Download PDFInfo
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- CA2436480A1 CA2436480A1 CA002436480A CA2436480A CA2436480A1 CA 2436480 A1 CA2436480 A1 CA 2436480A1 CA 002436480 A CA002436480 A CA 002436480A CA 2436480 A CA2436480 A CA 2436480A CA 2436480 A1 CA2436480 A1 CA 2436480A1
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- zone
- air
- gas
- burner
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- 230000015572 biosynthetic process Effects 0.000 claims abstract description 33
- 238000006243 chemical reaction Methods 0.000 claims abstract description 23
- 238000000034 method Methods 0.000 claims abstract description 21
- 238000010438 heat treatment Methods 0.000 claims abstract description 11
- 239000007789 gas Substances 0.000 claims description 39
- 238000002485 combustion reaction Methods 0.000 claims description 26
- 239000000446 fuel Substances 0.000 claims description 24
- 239000000203 mixture Substances 0.000 claims description 19
- 239000011148 porous material Substances 0.000 claims description 19
- 238000010791 quenching Methods 0.000 claims description 16
- 230000000171 quenching effect Effects 0.000 claims description 16
- 239000002737 fuel gas Substances 0.000 claims description 11
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 5
- 239000011324 bead Substances 0.000 claims description 4
- 239000000919 ceramic Substances 0.000 claims description 4
- 239000011261 inert gas Substances 0.000 claims description 4
- 230000004888 barrier function Effects 0.000 claims 1
- 238000005755 formation reaction Methods 0.000 description 29
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 6
- 239000002245 particle Substances 0.000 description 6
- 239000000376 reactant Substances 0.000 description 6
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- 239000003546 flue gas Substances 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 230000007423 decrease Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 230000004907 flux Effects 0.000 description 3
- 239000003345 natural gas Substances 0.000 description 3
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 230000000903 blocking effect Effects 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 239000012530 fluid Substances 0.000 description 2
- 229930195733 hydrocarbon Natural products 0.000 description 2
- 150000002430 hydrocarbons Chemical class 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 239000003921 oil Substances 0.000 description 2
- 239000007800 oxidant agent Substances 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 230000035699 permeability Effects 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- 239000007790 solid phase Substances 0.000 description 2
- 230000000638 stimulation Effects 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- 238000010793 Steam injection (oil industry) Methods 0.000 description 1
- 208000013201 Stress fracture Diseases 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 239000004927 clay Substances 0.000 description 1
- 239000002734 clay mineral Substances 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- KZHJGOXRZJKJNY-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Si]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O KZHJGOXRZJKJNY-UHFFFAOYSA-N 0.000 description 1
- 238000011143 downstream manufacturing Methods 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
- 239000002360 explosive Substances 0.000 description 1
- 239000000295 fuel oil Substances 0.000 description 1
- 239000008246 gaseous mixture Substances 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 229910052863 mullite Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000011236 particulate material Substances 0.000 description 1
- 239000012071 phase Substances 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 230000000644 propagated effect Effects 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 150000003254 radicals Chemical class 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000011819 refractory material Substances 0.000 description 1
- 230000001718 repressive effect Effects 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 1
- 229910010271 silicon carbide Inorganic materials 0.000 description 1
- 239000002912 waste gas Substances 0.000 description 1
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C99/00—Subject-matter not provided for in other groups of this subclass
- F23C99/006—Flameless combustion stabilised within a bed of porous heat-resistant material
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B36/00—Heating, cooling or insulating arrangements for boreholes or wells, e.g. for use in permafrost zones
- E21B36/02—Heating, cooling or insulating arrangements for boreholes or wells, e.g. for use in permafrost zones using burners
Landscapes
- Engineering & Computer Science (AREA)
- Geology (AREA)
- Life Sciences & Earth Sciences (AREA)
- Mining & Mineral Resources (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Environmental & Geological Engineering (AREA)
- Fluid Mechanics (AREA)
- Chemical & Material Sciences (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
Abstract
A porous media gas burner is adapted to operate in a pressurized environment.
The burner may have three zones: a mixing zone, an ignition zone and a reaction zone. The burner may be used as a downhole burner in a formation heat treatment method for oil an gas wells.
The burner may have three zones: a mixing zone, an ignition zone and a reaction zone. The burner may be used as a downhole burner in a formation heat treatment method for oil an gas wells.
Description
CANADIAN PATENT APPLICATION
File \o. 45074.60 P~ROUS MEDIA. G~-1S BURNER
FIELD OF THE INVENTION
The present invention relates to a porous media gas burner and methods for its use. In particular, the invention relates to a downhole gas burner used in formation heat treatment methods.
BACKGROUND OF THE TNVENTION
Combustion of gases in porous media is a process where a combustible gaseous mixture is injected into a porous matrix and is combusted within the porous matrix.
Flames in porous media have higher burning velocities and Leaner flammability limits than open flames. These effects are well known and are the consequence of excess enthalpy combustion.
Essentially, heat that is generated in the combustion zone is transferred by radiation and conduction through the solid phase of the porous media to unburned gases. As a result, it is possible to achieve temperatures higher than the adiabatic flame temperature, and the increase in burning velocities can be significantly higher than the open flame laminar burning velocity for the same mixture in an open space.
Formation heat treatment is a process that is intended to improve hydrodynamic conditions around the wellbore. If formati~n temperatures reach an adequate level, blocking water may be vapourized, clay structure may be dehydrated, clay minerals may be partially destroyed, and microfractures may be induced in the formation near the wellbore. As a result, permeability around the wellbore may be significantly improved.
It is known to use a downhole electrical heater in a formation heating method.
The electrical heater is placed as close as possible to the target zone, and an inert gas such as nitrogen is co-injected through the annulus. The temperature of the injected gas may rise to as high as 800° C before entering the formation. However, this method involves large energy requirements which makes it cost-prohibitive, particularly with rising electrical energy costs.
Combustion stimulation is a known technique to promote fluid production in a formation.
S A combustion front is initiated in a wellbore by means of a surface heater or burner and the front is propagated into the formation to a distance of up to about 6 meters. The formation in this zone is reduced to clean burnt sand, which is very fluid permeable. I~owever, the well casing is subjected to high temperatures, which is undesirable, and there is an elevated risk of explosions or well bumouts using this technique. It is necessary to maintain wellbore temperatures below 600° C in order to prevent damage to the liner, which limits the temperature which may be reached in the formation.
Therefore, there is a need in the art for a gas burner which may be used downhole in a formation heating process.
1 S SUMMARY ~F THE IIVVEl~TI~lIT
In one aspect, the invention may comprise a gas burner comprising a tubular housing adapted to operate in a pressurized environment, the housing defining an intake opf~ning and a flue opening and comprising means for receiving a supply of fuel and air; a mixing zone where the fuel and air are mixed comprising a packed bed of porous media; an ignition zone comprising a packed bed of porous media, and a reaction zone comprising a packed bed of porous media;
wherein the pore size of the mixing zone and the reaction zone is smaller than a minimum quenching distance of a fuel gas under standard conditions while the pore size of the ignition zone is larger than the minimum quenching distance.
2S In another aspect, the invention may comprise a downhole formation heating system for a wellbore including a well casing, the system comprising:
File \o. 45074.60 P~ROUS MEDIA. G~-1S BURNER
FIELD OF THE INVENTION
The present invention relates to a porous media gas burner and methods for its use. In particular, the invention relates to a downhole gas burner used in formation heat treatment methods.
BACKGROUND OF THE TNVENTION
Combustion of gases in porous media is a process where a combustible gaseous mixture is injected into a porous matrix and is combusted within the porous matrix.
Flames in porous media have higher burning velocities and Leaner flammability limits than open flames. These effects are well known and are the consequence of excess enthalpy combustion.
Essentially, heat that is generated in the combustion zone is transferred by radiation and conduction through the solid phase of the porous media to unburned gases. As a result, it is possible to achieve temperatures higher than the adiabatic flame temperature, and the increase in burning velocities can be significantly higher than the open flame laminar burning velocity for the same mixture in an open space.
Formation heat treatment is a process that is intended to improve hydrodynamic conditions around the wellbore. If formati~n temperatures reach an adequate level, blocking water may be vapourized, clay structure may be dehydrated, clay minerals may be partially destroyed, and microfractures may be induced in the formation near the wellbore. As a result, permeability around the wellbore may be significantly improved.
It is known to use a downhole electrical heater in a formation heating method.
The electrical heater is placed as close as possible to the target zone, and an inert gas such as nitrogen is co-injected through the annulus. The temperature of the injected gas may rise to as high as 800° C before entering the formation. However, this method involves large energy requirements which makes it cost-prohibitive, particularly with rising electrical energy costs.
Combustion stimulation is a known technique to promote fluid production in a formation.
S A combustion front is initiated in a wellbore by means of a surface heater or burner and the front is propagated into the formation to a distance of up to about 6 meters. The formation in this zone is reduced to clean burnt sand, which is very fluid permeable. I~owever, the well casing is subjected to high temperatures, which is undesirable, and there is an elevated risk of explosions or well bumouts using this technique. It is necessary to maintain wellbore temperatures below 600° C in order to prevent damage to the liner, which limits the temperature which may be reached in the formation.
Therefore, there is a need in the art for a gas burner which may be used downhole in a formation heating process.
1 S SUMMARY ~F THE IIVVEl~TI~lIT
In one aspect, the invention may comprise a gas burner comprising a tubular housing adapted to operate in a pressurized environment, the housing defining an intake opf~ning and a flue opening and comprising means for receiving a supply of fuel and air; a mixing zone where the fuel and air are mixed comprising a packed bed of porous media; an ignition zone comprising a packed bed of porous media, and a reaction zone comprising a packed bed of porous media;
wherein the pore size of the mixing zone and the reaction zone is smaller than a minimum quenching distance of a fuel gas under standard conditions while the pore size of the ignition zone is larger than the minimum quenching distance.
2S In another aspect, the invention may comprise a downhole formation heating system for a wellbore including a well casing, the system comprising:
(a) a gas burner comprising a cylindrical housing defining an intake opening and a flue opening, the housing comprising means for receiving a supply of fuel and air;
a mixing zone where the fuel and air are mixed; an ignition zone comprising an igniter and a reaction zone, each zone comprising a packed bed of porous media;
(b) an igniter for igniting the fuel and air within the gas burner;
(c) fuel and air supply tubing for delivering fuel and air to the burner; and (d) means for delivering pressurized air or an inert gas in an annular space between the well casing and the fuel and air supply tubing.
In another aspect, the invention may comprise a method of heat treating a formation comprising the steps of:
(a) inserting a gas burner comprising a cylindrical housing defining an intake opening and a flue opening, the housing comprising means for receiving a supply of fuel and air; a mixing zone where the fuel and air are mixed; an ignition zone comprising an igniter and a reaction zone, each zone comprising a packed bed of porous media, into a wellbore;
(b) inj ecting a fuel gas and air into the gas burner to create a combustible mixture and igniting the mixture to create a combustion front; and (c) causing the combustion front to travel out the gas burner and into the formation.
BRIEF DESCRIPTIOly1 OF THE DI~IhTG~
The invention will now be described by way of an exemplary embodiment with reference to the accompanying simplified, diagrammatic, not-to-scale drawings.
_3_ Figure 1 is a schematic representation of one embodiment of the present invention.
Figure 2 is a schematic representation of one embodiment of a formation heat treatment system.
DETAILED DESCRIPTI~1~T ~F' TIIE IliT'VEI~TTI~l~T
The present invention provides for a gas bunler and methods of using a gas burner. When describing the present invention, all terms not defined herein have their common art-recognized meanings.
In one embodiment, the invention comprises a gas burner as shown schematically in Figure 1. The burner generally includes a body (10) which comprises a mixing zone (I2), an ignition zone (14) and a reaction zone (16) where combustion will take place.
The body may have any shape. In one embodiment, the body may be cylindrical or conical or have both cylindrical and conical sections. The body is preferably Iined with a heat-refractory material such as a ceramic Iiner.
As shown in Figure l, the mixing zone (12) and ignition zone (14) comprise cylindrical portions of the tubular body (10) while the reaction zone (16) comprises a truncated conical portion, with an expanding diameter as the reactants flow away from the mixing zone of the inlet end. In one embodiment, the outlet end diameter of the reaction zone may be about twice that of the inlet end. The reaction zone may have a length about 4 to 5 times the diameter of the inlet end. The mixing and ignition zones may have a length approximately equal to their diameter.
All three zones (12, 14, 16) may be packed with a porous media bed within the burner.
The packed bed may comprise heat resistant ceramic spheres such as alumina beads or any other suitable particulate material to create a porous media bed for example, but not limited to, zirconia-alumina composites, silicon carbide, or mullite (alumina-silicon dioxide). As shown in Figure l, air or oxygen is provided to the burner in the mixing zone (I2), along with the combustible gas. The gases mix in the mixing zone (12) and are ignited in the ignition zone (14) by means of an igniter (not shown), which may be a small open flame burner or a spark device.
Once ignited, the flame front will be allowed to advance into the reaction zone (16).
In one embodiment, the mixing zone (12) may be packed with small size particles so that the pore size in the mixing zone is smaller than the minimum quenching distance (MQD). The second section would the ignition zone (14) and may be packed with larger size particles so that the pore size is larger than the minimum quenching distance. Tl~e size and nature of the reaction zone (16) particles (pore size) would depend on energy and operational requirements, type of fuel gas and operating conditions and could be of either uniform size or a combination of sizes.
As used herein, the phrase '"minimum quenching distance'° or "I~iIQD°' shall mean the minimum diameter or opening dimension through which a flame may travel under standard conditions. It may be observed that a flame in a mixture within a flammable range will be extinguished if forced to propagate through a constriction. The walls of the constriction exert a repressive influence on the flame. A flame is quenched in a constriction because of two mechanisms which otherwise permit flame propagation: the diffusion of species, and the diffusion of heat. The walls of the constriction may extract heat and the smaller the restriction, the greater the surface to volume ratio will be. Similarly, the smaller the constriction, the greater the number of collisions of the active radical species with the wall, and the greater the number of these species which are destroyed. Accordingly, one skilled in the art will understand that increased temperature decreases the quenching distance and that quenching distance decreases as pressure increases.
MQD is a physical property of each fuel and may be determined in the laboratory or by using the criteria of Peclet number equal to 65. The T'eclet number is a dimensionless parameter that is based on the specific heat, laminar burning velocity, density, thermal conductivity and thermal diffusivity of the gas mixture, however the heating of the porous media bed will affect the minimum quenching distance.
It is generally accepted that main driving factor in the combustion of gases in a porous -S-media is heat recirculation through the porous media to preheat unburned reactants. This preheating of the reactants may permit combustion even if the pore size is smaller than the MQD
of the porous media under standard conditions.
In one embodiment, the burner (IO) is adapted to operate in a pressurized environment.
The body of the burner (10) is designed to withstand the desired pressure.
This provides the opportunity to integrate the burner in the middle of a process stream, so that exhaust gases may be recovered at pressure for further treatment, separation or other downstream processes. It may allow use in subterranean hydrocarbon formations as will be subsequently described. The porosity of the packed bed may be controlled for specific applications. In one embodiment, the packed bed in the mixing zone and the reaction zone has a pore size smaller than the minimum quenching distance, while the ignition zone pore size may be larger than the minimum quenching distance. The pore size, combustible mixture flux, concentration of fuel gas in oxidant (air), type of fuel and shape of the burner may be varied to permit and optimize the process in a pressurized environment. A person skilled in the art may determine these matters with minimal and routine experimentation.
The main effect of operating pressure in the gas burner is a reduction in the combustion front velocity. Maximum temperatures attainable when operating at elevated pressures are generally lower than those temperatures observed for the same gas mixtures and fluxes at atmospheric pressure. While the effect of pore size is almost negligible at atmospheric operating pressure, as the operating pressure is increased, the velocity of the combustion front increases as the pore size decreases. At elevated operating pressures, burning velocities appear to increase as the inlet gas velocity increases. Additionally, burning velocities appear to increase as the fuel gas concentration is decreased.
The relatively smaller pore size of the mixing and the reaction zone promotes mixing of the reactants and preheating of the reactants due to heat transfer from the solid phase to the gas phase. The relatively larger pore size of the ignition zone allows easier ignition of the reactants and propagation of the flame into the reaction zone.
The gas burner (10) may be used as a downhole gas burner to be used in a formation heating method. Generally, the formation heating method may comprise two stages. In a first stage, the burner is placed in the wellbore at the level of the formation by means of coiled tubing or the like. The tubing also provides the means by which a combustible mixture is provided to the burner. The combustible mixture may be a lean mixture of natural gas and air which is below the flammability limits of natural gas at atmospheric pressure. The mixture may sustain a combustion front within the burner which expels hot flue gases into the formation. :(f desired, the combustion front may be controlled to travel outward from the burner into the formation. The combustion front is controlled by increasing or decreasing the fuel gas flux, changing the concentration of fuel gas in the mixture fuel-air (oxidant) and by using different particle size or a combination of particle sizes in the reaction zone. These variable elements may be varied either singly or in combination.
Depending on the composition of the formation hydrocarbons, the amount of oxygen in the flue gas and the flue gas temperature, some oxidation/combustion reactions may start to take place in the formation at the same time as gas combustion is occurring in the burner. Once the combustion front leaves the burner, it is preferred to increase the concentration of the fuel, so that the temperature of the reaction front increases. This may be done safely because the temperature in the burner and the wellbore will not be high enough to facilitate or sustain combustion. In other words, the burner becomes a flame arrester once the combustion front travels outward into the formation.
The burner described herein may be used as a downhole burner in alternative methods.
As described above, the burner may be used in well stimulation method where blocking water is vapourized, clays may be partially destroyed, asphaltenic deposits may be burned and rnicrofractures in the formation may be propogated. In another example, the downhole gas burner may be used in a downhole steam generation method for cyclic or continuous steam injection in deep heavy oil wells. In another example, the downhole gas burner may be used in a high pressure air injection technique, where combustion is initiated in the formation and air is _ then continuously injected into the producing layer. The combustion of in-place oil may provide thermal and gas drive to the oil reservoir.
In one embodiment, with reference to Figure 2, a downhole burner (10) is positioned near the producing formation (20) by means of continuous or coiled tubing (22) and anchored to the well casing by means of an anchor {24). Air is injected through the tubing (22) and a combustible gas such as natural gas is injected through a separate tubing (26) to the burner. Air or an inert gas such as nitrogen may be inj ected in the annulus between the well casing and the tubing (22). The burner has a mixing zone (120), an ignition zone (122) and a reaction zone (124), each packed with a suitable porous media. As described above, in a preferred embodiment, the particle size or minimum quenching distances in each zone may be varied. The combustion front (126) will be established in the reaction zone (124) and move outward into the formation. At the same time, hot flue gases (128) are pushed outward into the formation.
In each case, the ignition and combustion downhole and/or in the formation may be initiated using a lean combustible mixture, which may include waste gases. The lean mixture reduces the risk of explosive mixtures accumulating in the system.
As will be apparent to those skilled in the art, various modifications, adaptations and variations of the foregoing specific disclosure can be made without departing from the scope of the invention claimed herein. The various features and elements of the described invention may be combined in a manner different from the combinations described or claimed herein, without departing from the scope of the invention.
-g-EXAMPLES
The following examples describe specific embodiments which are exemplary of the present invention. They are not intended to limit the claimed invention.
Example 1 Porous Media In one embodiment, the porous media comprises relatively uniform alumina spheres (90% alumina and 10% silica) having the following physical and hydrodynamic properties:
(a) specific heat capacity at 20 C, 920 J/kgK
(b) thermal conductivity at 20 C, W/mK 1607 (c) Density, kg/m3 3,600 (d) diameter, m ~.6 E-3 to 2.9 (e) Porosity, fraction 0.383 (f) Pore size, m 2.31 E-3 to 1.18 (g) Permeability (Carman-Kozeny equation)2.544 E-8 to 6.625 m2 E-9
a mixing zone where the fuel and air are mixed; an ignition zone comprising an igniter and a reaction zone, each zone comprising a packed bed of porous media;
(b) an igniter for igniting the fuel and air within the gas burner;
(c) fuel and air supply tubing for delivering fuel and air to the burner; and (d) means for delivering pressurized air or an inert gas in an annular space between the well casing and the fuel and air supply tubing.
In another aspect, the invention may comprise a method of heat treating a formation comprising the steps of:
(a) inserting a gas burner comprising a cylindrical housing defining an intake opening and a flue opening, the housing comprising means for receiving a supply of fuel and air; a mixing zone where the fuel and air are mixed; an ignition zone comprising an igniter and a reaction zone, each zone comprising a packed bed of porous media, into a wellbore;
(b) inj ecting a fuel gas and air into the gas burner to create a combustible mixture and igniting the mixture to create a combustion front; and (c) causing the combustion front to travel out the gas burner and into the formation.
BRIEF DESCRIPTIOly1 OF THE DI~IhTG~
The invention will now be described by way of an exemplary embodiment with reference to the accompanying simplified, diagrammatic, not-to-scale drawings.
_3_ Figure 1 is a schematic representation of one embodiment of the present invention.
Figure 2 is a schematic representation of one embodiment of a formation heat treatment system.
DETAILED DESCRIPTI~1~T ~F' TIIE IliT'VEI~TTI~l~T
The present invention provides for a gas bunler and methods of using a gas burner. When describing the present invention, all terms not defined herein have their common art-recognized meanings.
In one embodiment, the invention comprises a gas burner as shown schematically in Figure 1. The burner generally includes a body (10) which comprises a mixing zone (I2), an ignition zone (14) and a reaction zone (16) where combustion will take place.
The body may have any shape. In one embodiment, the body may be cylindrical or conical or have both cylindrical and conical sections. The body is preferably Iined with a heat-refractory material such as a ceramic Iiner.
As shown in Figure l, the mixing zone (12) and ignition zone (14) comprise cylindrical portions of the tubular body (10) while the reaction zone (16) comprises a truncated conical portion, with an expanding diameter as the reactants flow away from the mixing zone of the inlet end. In one embodiment, the outlet end diameter of the reaction zone may be about twice that of the inlet end. The reaction zone may have a length about 4 to 5 times the diameter of the inlet end. The mixing and ignition zones may have a length approximately equal to their diameter.
All three zones (12, 14, 16) may be packed with a porous media bed within the burner.
The packed bed may comprise heat resistant ceramic spheres such as alumina beads or any other suitable particulate material to create a porous media bed for example, but not limited to, zirconia-alumina composites, silicon carbide, or mullite (alumina-silicon dioxide). As shown in Figure l, air or oxygen is provided to the burner in the mixing zone (I2), along with the combustible gas. The gases mix in the mixing zone (12) and are ignited in the ignition zone (14) by means of an igniter (not shown), which may be a small open flame burner or a spark device.
Once ignited, the flame front will be allowed to advance into the reaction zone (16).
In one embodiment, the mixing zone (12) may be packed with small size particles so that the pore size in the mixing zone is smaller than the minimum quenching distance (MQD). The second section would the ignition zone (14) and may be packed with larger size particles so that the pore size is larger than the minimum quenching distance. Tl~e size and nature of the reaction zone (16) particles (pore size) would depend on energy and operational requirements, type of fuel gas and operating conditions and could be of either uniform size or a combination of sizes.
As used herein, the phrase '"minimum quenching distance'° or "I~iIQD°' shall mean the minimum diameter or opening dimension through which a flame may travel under standard conditions. It may be observed that a flame in a mixture within a flammable range will be extinguished if forced to propagate through a constriction. The walls of the constriction exert a repressive influence on the flame. A flame is quenched in a constriction because of two mechanisms which otherwise permit flame propagation: the diffusion of species, and the diffusion of heat. The walls of the constriction may extract heat and the smaller the restriction, the greater the surface to volume ratio will be. Similarly, the smaller the constriction, the greater the number of collisions of the active radical species with the wall, and the greater the number of these species which are destroyed. Accordingly, one skilled in the art will understand that increased temperature decreases the quenching distance and that quenching distance decreases as pressure increases.
MQD is a physical property of each fuel and may be determined in the laboratory or by using the criteria of Peclet number equal to 65. The T'eclet number is a dimensionless parameter that is based on the specific heat, laminar burning velocity, density, thermal conductivity and thermal diffusivity of the gas mixture, however the heating of the porous media bed will affect the minimum quenching distance.
It is generally accepted that main driving factor in the combustion of gases in a porous -S-media is heat recirculation through the porous media to preheat unburned reactants. This preheating of the reactants may permit combustion even if the pore size is smaller than the MQD
of the porous media under standard conditions.
In one embodiment, the burner (IO) is adapted to operate in a pressurized environment.
The body of the burner (10) is designed to withstand the desired pressure.
This provides the opportunity to integrate the burner in the middle of a process stream, so that exhaust gases may be recovered at pressure for further treatment, separation or other downstream processes. It may allow use in subterranean hydrocarbon formations as will be subsequently described. The porosity of the packed bed may be controlled for specific applications. In one embodiment, the packed bed in the mixing zone and the reaction zone has a pore size smaller than the minimum quenching distance, while the ignition zone pore size may be larger than the minimum quenching distance. The pore size, combustible mixture flux, concentration of fuel gas in oxidant (air), type of fuel and shape of the burner may be varied to permit and optimize the process in a pressurized environment. A person skilled in the art may determine these matters with minimal and routine experimentation.
The main effect of operating pressure in the gas burner is a reduction in the combustion front velocity. Maximum temperatures attainable when operating at elevated pressures are generally lower than those temperatures observed for the same gas mixtures and fluxes at atmospheric pressure. While the effect of pore size is almost negligible at atmospheric operating pressure, as the operating pressure is increased, the velocity of the combustion front increases as the pore size decreases. At elevated operating pressures, burning velocities appear to increase as the inlet gas velocity increases. Additionally, burning velocities appear to increase as the fuel gas concentration is decreased.
The relatively smaller pore size of the mixing and the reaction zone promotes mixing of the reactants and preheating of the reactants due to heat transfer from the solid phase to the gas phase. The relatively larger pore size of the ignition zone allows easier ignition of the reactants and propagation of the flame into the reaction zone.
The gas burner (10) may be used as a downhole gas burner to be used in a formation heating method. Generally, the formation heating method may comprise two stages. In a first stage, the burner is placed in the wellbore at the level of the formation by means of coiled tubing or the like. The tubing also provides the means by which a combustible mixture is provided to the burner. The combustible mixture may be a lean mixture of natural gas and air which is below the flammability limits of natural gas at atmospheric pressure. The mixture may sustain a combustion front within the burner which expels hot flue gases into the formation. :(f desired, the combustion front may be controlled to travel outward from the burner into the formation. The combustion front is controlled by increasing or decreasing the fuel gas flux, changing the concentration of fuel gas in the mixture fuel-air (oxidant) and by using different particle size or a combination of particle sizes in the reaction zone. These variable elements may be varied either singly or in combination.
Depending on the composition of the formation hydrocarbons, the amount of oxygen in the flue gas and the flue gas temperature, some oxidation/combustion reactions may start to take place in the formation at the same time as gas combustion is occurring in the burner. Once the combustion front leaves the burner, it is preferred to increase the concentration of the fuel, so that the temperature of the reaction front increases. This may be done safely because the temperature in the burner and the wellbore will not be high enough to facilitate or sustain combustion. In other words, the burner becomes a flame arrester once the combustion front travels outward into the formation.
The burner described herein may be used as a downhole burner in alternative methods.
As described above, the burner may be used in well stimulation method where blocking water is vapourized, clays may be partially destroyed, asphaltenic deposits may be burned and rnicrofractures in the formation may be propogated. In another example, the downhole gas burner may be used in a downhole steam generation method for cyclic or continuous steam injection in deep heavy oil wells. In another example, the downhole gas burner may be used in a high pressure air injection technique, where combustion is initiated in the formation and air is _ then continuously injected into the producing layer. The combustion of in-place oil may provide thermal and gas drive to the oil reservoir.
In one embodiment, with reference to Figure 2, a downhole burner (10) is positioned near the producing formation (20) by means of continuous or coiled tubing (22) and anchored to the well casing by means of an anchor {24). Air is injected through the tubing (22) and a combustible gas such as natural gas is injected through a separate tubing (26) to the burner. Air or an inert gas such as nitrogen may be inj ected in the annulus between the well casing and the tubing (22). The burner has a mixing zone (120), an ignition zone (122) and a reaction zone (124), each packed with a suitable porous media. As described above, in a preferred embodiment, the particle size or minimum quenching distances in each zone may be varied. The combustion front (126) will be established in the reaction zone (124) and move outward into the formation. At the same time, hot flue gases (128) are pushed outward into the formation.
In each case, the ignition and combustion downhole and/or in the formation may be initiated using a lean combustible mixture, which may include waste gases. The lean mixture reduces the risk of explosive mixtures accumulating in the system.
As will be apparent to those skilled in the art, various modifications, adaptations and variations of the foregoing specific disclosure can be made without departing from the scope of the invention claimed herein. The various features and elements of the described invention may be combined in a manner different from the combinations described or claimed herein, without departing from the scope of the invention.
-g-EXAMPLES
The following examples describe specific embodiments which are exemplary of the present invention. They are not intended to limit the claimed invention.
Example 1 Porous Media In one embodiment, the porous media comprises relatively uniform alumina spheres (90% alumina and 10% silica) having the following physical and hydrodynamic properties:
(a) specific heat capacity at 20 C, 920 J/kgK
(b) thermal conductivity at 20 C, W/mK 1607 (c) Density, kg/m3 3,600 (d) diameter, m ~.6 E-3 to 2.9 (e) Porosity, fraction 0.383 (f) Pore size, m 2.31 E-3 to 1.18 (g) Permeability (Carman-Kozeny equation)2.544 E-8 to 6.625 m2 E-9
Claims (8)
1. A downhole formation heating system for a wellbore including a well casing, the system comprising:
(a) a gas burner comprising a cylindrical housing defining an intake opening and a flue opening, the housing comprising means for receiving a supply of fuel and air;
a mixing zone where the fuel and air are mixed; an ignition zone comprising an igniter and a reaction zone, each zone comprising a packed bed of porous media;
(b) an igniter for igniting the fuel and air within the gas burner;
(c) fuel and air supply tubing for delivering fuel and air to the burner; and (d) means for delivering pressurized air or an inert gas in an annular space between the well casing and the fuel and air supply tubing.
(a) a gas burner comprising a cylindrical housing defining an intake opening and a flue opening, the housing comprising means for receiving a supply of fuel and air;
a mixing zone where the fuel and air are mixed; an ignition zone comprising an igniter and a reaction zone, each zone comprising a packed bed of porous media;
(b) an igniter for igniting the fuel and air within the gas burner;
(c) fuel and air supply tubing for delivering fuel and air to the burner; and (d) means for delivering pressurized air or an inert gas in an annular space between the well casing and the fuel and air supply tubing.
2. The system of claim 1 wherein the porous media comprises ceramic beads.
3. The system of claim 2 wherein the ceramic beads comprises alumina beads.
4. The system of claim 1 wherein the mixing zone and reaction zone comprise a pore size less than a minimum quenching distance under standard conditions of a fuel gas and the ignition zone comprises a pore size greater than the minimum quenching distance under standard conditions of the fuel gas.
5. A method of heat treating a formation comprising the steps of:
(a) inserting a gas burner comprising a cylindrical housing defining an intake opening and a flue opening, the housing comprising means for receiving a supply of fuel and air; a mixing zone where the fuel and air are mixed; an ignition zone comprising an igniter and a reaction zone, each zone comprising a packed bed of porous media, into a wellbore;
(b) injecting a fuel gas and air into the gas burner to create a combustible mixture and igniting the mixture to create a combustion front; and (c) causing the combustion front to travel out the gas burner and into the formation.
(a) inserting a gas burner comprising a cylindrical housing defining an intake opening and a flue opening, the housing comprising means for receiving a supply of fuel and air; a mixing zone where the fuel and air are mixed; an ignition zone comprising an igniter and a reaction zone, each zone comprising a packed bed of porous media, into a wellbore;
(b) injecting a fuel gas and air into the gas burner to create a combustible mixture and igniting the mixture to create a combustion front; and (c) causing the combustion front to travel out the gas burner and into the formation.
6. The method of claim 5 wherein one zone of the gas barrier has a pore size smaller than a minimum quenching distance for an operating condition of pressure and fuel
7. A gas burner comprising a tubular housing adapted to operate in a pressurized environment, the housing defining an intake opening and a flue opening and comprising means for receiving a supply of fuel and air; a mixing zone where the fuel and air are mixed comprising a packed bed of porous media; an ignition zone comprising a packed bed of porous media, and a reaction zone comprising a packed bed of porous media; wherein the pore size of the mixing zone and the reaction zone is smaller than a minimum quenching distance of a fuel gas under standard conditions while the pore size of the ignition zone is larger than the minimum quenching distance.
8. The burner of claim 5 wherein the flue opening combines with a pressure regulator for controlling the pressure within the gas burner above atmospheric pressure.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US10/604,574 US20050026094A1 (en) | 2003-07-31 | 2003-07-31 | Porous media gas burner |
| CA002436480A CA2436480A1 (en) | 2003-07-31 | 2003-07-31 | Porous media gas burner |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US10/604,574 US20050026094A1 (en) | 2003-07-31 | 2003-07-31 | Porous media gas burner |
| CA002436480A CA2436480A1 (en) | 2003-07-31 | 2003-07-31 | Porous media gas burner |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2436480A1 true CA2436480A1 (en) | 2005-01-31 |
Family
ID=34378575
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002436480A Abandoned CA2436480A1 (en) | 2003-07-31 | 2003-07-31 | Porous media gas burner |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US20050026094A1 (en) |
| CA (1) | CA2436480A1 (en) |
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| GB2475812B (en) * | 2005-08-17 | 2011-08-24 | Halliburton Energy Serv Inc | Communicated fluids with a heated-fluid generation system |
| US7640987B2 (en) * | 2005-08-17 | 2010-01-05 | Halliburton Energy Services, Inc. | Communicating fluids with a heated-fluid generation system |
| US7809538B2 (en) | 2006-01-13 | 2010-10-05 | Halliburton Energy Services, Inc. | Real time monitoring and control of thermal recovery operations for heavy oil reservoirs |
| US7770643B2 (en) * | 2006-10-10 | 2010-08-10 | Halliburton Energy Services, Inc. | Hydrocarbon recovery using fluids |
| US7832482B2 (en) | 2006-10-10 | 2010-11-16 | Halliburton Energy Services, Inc. | Producing resources using steam injection |
| BR112012022826A2 (en) * | 2010-03-08 | 2018-05-15 | Worldenergy Systems Incorporated | Wellhead steam generator and method of use |
| US20170033455A1 (en) * | 2015-07-27 | 2017-02-02 | Google Inc. | Active Interference Avoidance in Unlicensed Bands |
| US10543387B2 (en) * | 2017-03-28 | 2020-01-28 | The Boeing Company | Combustion arrester test systems and methods |
| CN107051033A (en) * | 2017-06-08 | 2017-08-18 | 山东大学 | A kind of organic waste gas treatment system and processing method |
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| US1331022A (en) * | 1919-06-26 | 1920-02-17 | Mathy Maurice | Burner |
| US3010516A (en) * | 1957-11-18 | 1961-11-28 | Phillips Petroleum Co | Burner and process for in situ combustion |
| US3363663A (en) * | 1965-06-07 | 1968-01-16 | United States Gypsum Co | Combustion chamber burner and a method for its operation |
| US4154568A (en) * | 1977-05-24 | 1979-05-15 | Acurex Corporation | Catalytic combustion process and apparatus |
| US4440356A (en) * | 1981-07-23 | 1984-04-03 | Erwin Kampf Gmbh & Co. | Machine for separating and slitting thin sheet |
| US4415537A (en) * | 1982-02-01 | 1983-11-15 | United Technologies Corporation | Catalytic combustor |
| IT1197078B (en) * | 1986-08-07 | 1988-11-25 | Umberto Viani | BOILERS WITH METHANE CATALYTIC COMBUSTION FOR WATER HEATING FOR DOMESTIC USE |
| US5141432A (en) * | 1990-07-18 | 1992-08-25 | Radian Corporation | Apparatus and method for combustion within porous matrix elements |
| US5147201A (en) * | 1990-11-19 | 1992-09-15 | Institute Of Gas Technology | Ultra-low pollutant emissions radiant gas burner with stabilized porous-phase combustion |
| US5160254A (en) * | 1991-10-04 | 1992-11-03 | Radian Corporation And The Board Of Regents | Apparatus and method for combustion within porous matrix elements |
| US5165884A (en) * | 1991-07-05 | 1992-11-24 | Thermatrix, Inc. | Method and apparatus for controlled reaction in a reaction matrix |
| EP0524736B1 (en) * | 1991-07-05 | 1998-01-28 | THERMATRIX INC. (a Delaware Corporation) | Method and apparatus for controlled reaction in a reaction matrix |
| AU5741594A (en) * | 1992-12-17 | 1994-07-04 | Thermatrix Inc. | Method and apparatus for control of fugitive voc emissions |
| DE4322109C2 (en) * | 1993-07-02 | 2001-02-22 | Franz Durst | Burner for a gas / air mixture |
| US5544624A (en) * | 1993-07-12 | 1996-08-13 | Institute Of Gas Technology | Gas-fired, porous matrix, combustor-steam generator |
| US5476375A (en) * | 1993-07-12 | 1995-12-19 | Institute Of Gas Technology | Staged combustion in a porous-matrix surface combustor to promote ultra-low NOx Emissions |
| US5375563A (en) * | 1993-07-12 | 1994-12-27 | Institute Of Gas Technology | Gas-fired, porous matrix, surface combustor-fluid heater |
| EP0710150A4 (en) * | 1993-07-16 | 1997-12-29 | Thermatrix Inc | Method and afterburner apparatus for control of highly variable flows |
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| US5989010A (en) * | 1997-09-02 | 1999-11-23 | Thermatrix, Inc. | Matrix bed for generating non-planar reaction wave fronts, and method thereof |
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- 2003-07-31 CA CA002436480A patent/CA2436480A1/en not_active Abandoned
- 2003-07-31 US US10/604,574 patent/US20050026094A1/en not_active Abandoned
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|---|---|
| US20050026094A1 (en) | 2005-02-03 |
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