US2997105A

US2997105A - Burner apparatus

Info

Publication number: US2997105A
Application number: US614760A
Authority: US
Inventors: Frank E Campion; Eugene D Glass; John W Kirkpatrick; Joseph C Vaughn
Original assignee: Pan American Petroleum Corp
Current assignee: Pan American Petroleum Corp
Priority date: 1956-10-08
Filing date: 1956-10-08
Publication date: 1961-08-22
Anticipated expiration: 1978-08-22

Description

g- 1961 F. E. CAMPION ETAL 2,997,105

BURNER APPARATUS Filed Oct. 8, 1956 3 Sheets-Sheet 1 i 2s 3s 29 27 IO I? H 112; jg 26 L3 24 "W 55 FRANK E. CAMPION EUGENE D. GLASS /39 JOHN W. KIRKPATRICK JOSEPH C. VAUGHN IN V EN TORS.

FIG. I 0

ATTORNEY 1961 F. E. CAMPION ET AL 2,997,105

BURNER APPARATUS Filed 001;. 8, 1956 5 Sheets-Sheet 2 FIG. 4

FIG. 3

FRANK E. CAMPION EUGENE D. GLASS JOHN w. KIRKPATRICK JOSEPH c. VAUGHN INVENTORSZ ATTORNEY 1951 F. E. CAMPION ETAL 2,997,105

BURNER APPARATUS FRANK E. CAMPION EUGENE D; GLASS JOHN W. KIRKPATRICK JOSEPH C. VAUGHN INVENTORS.

lax/m ATTORNEY United StatesPatent O 2,997,105 BURNER APPARATUS Frank E. Campion, Eugene D. Glass, and John W. Kirkpatrick, Tulsa, and Joseph C. Vaughn, Nowata, Okla, assignors to Pan American Petroleum Corporation, a corporation of Delaware Filed Oct. 8, 1956, Ser. No. 614,760 10 Claims. (Cl. 166-59) This invention relates to method and apparatus for creating and sustaining inverted combustion (at or near subterranean formations) in a well. More particularly, the invention relates to a retrievable pilot igniter which creates uniform burning or combustible mixtures in wells. The resulting heat from such combustion is frequently used in the underground combustion or gasification of carbonaceous deposits.

We have found that the principal difficulty in obtaining uniform burning of combustible gases in a relatively confined space, such as a well, is in the ignition of these gases. Once a sizable heat source is created, then sustained, nonexplosive combustion in a well is easily maintained. The term explosion, as used herein, shall mean that type of flame propagation which is relatively fast, on the order of 6,50010,O(l feet per second, and often accompanied by detonation. (See: Haslam and Russell, Fuels and Their Combustion, 1926, p. 275;)

' In a system where the combustible fluid and air are separately introduced into a well and then mixed, it appears that several factors enter into eflicient ignition of the resulting combustible mixture. Of primary importance is the proper ratio of combustible fluid to air to produce a non-explosive combustible mixture. At atmos- We have tried to ignite large volumes of a combustible mixture in a well with such heat sources as a hot resistance wire, fusee, and spark plug, and in every instance intermittent explosions have resulted until a sizable heat source is created to sustain uniform combustion. these explosions occur principallybecause the heat source is of insufiicient size for the volume of combustible mix ture formed in the well in addition to the factorsmentioned above. In any event, such heatsource for igniting a combustible mixture is undesirable, for theexplosive force usually damages the equipment in the well. Additionally, the high voltage requirements of a spark plug and the high heat loss of an open resistance wire are undesirable. A burning fusee traveling the length of a well often goes out before it reaches the zone where the combustible mixture is to be ignited. It is therefore an object of this invention to provide a method and apparatus that overcomes all of the above objections in igniting a combustible mixture in a relatively confined space.

Other objects and advantages of this invention will beapparent from the following description. In this description reference will be made to the accompanying drawings in which: i

FIGURE 1 is a longitudinal cross-sectional view of a preferred embodiment of our pilot igniter;

FIGURE 2 is a cross-sectional view of the pilot igniter taken on a line 22 of FIGURE 1;

We believe.

FIGURE 3 is an electrical circuit for the apparatus shown in FIGURE 1;

FIGURE 4 is a longitudinal crosssectional view of an embodiment of our apparatus installed in a well; and

FIGURE 5 is a plot which indicates the operable combustion gas and air rates to obtain nonexplosive combustion in the pilot igniter.

In brief, our invention consists of a wire line retrievable pilot burner and method of mixing, at the bottom of a well, a small amount of a combustible fluid with air to produce a combustible mixture, which has a relatively small volume compared with the volume surrounding the pilot igniter, to ignite that mixture in nonexplosive combustion, and finally to ignite a larger volume of a combustible mixture after the pilot igniter has been removed and when the surrounding well is of sufficient temperature to sustain nonexplosive combustion. Additionally, our invention includes means for measuring the temperature opposite the pilot igniter, and for withdrawing the pilot igniter. The term combustible fluid, as used herein, shall include all gases and vapors which upon being mixed with any amount, preferably a stoichiometric amount, of oxygen-containing gas such as air, will ignite and burn.

Referring to FIGURE 1, the pilot igniter 9 of our invention will now be more particularly described. It consists of an upper support member 10 with packing such as an O-ring 11 to seal the space between the pilot igniter and tubing 12. In the preferred embodiment, O-ring 11 is adapted to tapered shoulder 13 on the support member which haltsthe downward travel of the pilot igniter in sealing engagement with seating nipple 14 placed in tubing 12. Connected to the upper support member 10 are longitudinal supports, such as rods 15, running the length of the pilot igniter which, with

members

21 and 25, form anopening 16 and an opening 17. A fluid passage or orifice tube 18 provides a fluid passage through the upper support member 10 and forms or connects to a nozzle 19 so that the flow of gas through the tubing 12. will be directed through the nozzle 19. Downstream from nozzle 19 and between openings 16 land 17 an imperforate mixing tube 21 with a tapered internaldiameter forming the throat 22 is connected to rods 15. Downstream from the mixing tube 21 is the heater or igniter element such I as a spark plug, but preferably an electric resistance element 23 such as that shown which is suitably formed about a longitudinal insulated support such as porcelain stream end of the housing open to receive the gases emerging from the downstream end of mixing tube 21 and open- 7 ing 17. Heater element 23 is connected to leads 27 and provided by a cylinder of 28 which are protected by suitable heat resistant insula mica 31 inside housing 25.

The functioning and design of electric heating element 23 can best'be described by reference to FIGURE 3. A power source 35, either'A.C. or D.C.,is connected to the single conductor wire line cable 30 by one lead 36 to the center insulated conductor which connects at junction 37' to lead 27 which is preferably a Nichrome wire. This lead, which is properly insulated, connects to heating element 23 where it is coiled about porcelain rods 24 in housing 25. The Nichrome wire is returned to junction with the outside metallic sheath 38 at point 40 of the Wire line cable 30 either directly or through a dissimilar lead 28, typically a constantan wire, to form a temperature sensitive junction 39, i.e., a thermocouple, which Patented Aug. 22, 1961* porous insulation such as linen is grounded to complete the circuit. The thermocouple is desirably located at any point below the mixing tube 21.

A double-pole double-throw switch 41, in the upper position as shown, connects the power source 35 to the heating element and thermocouple. In the lower position, switch 41 disconnects the power supply and connects a millivoltmeter 42 to indicate the temperature in the well in the vicinity of the igniter. There are other junctions of dissimilar materials in addition to Nichromeconstantan temperature-sensitive junction 39, i.e., Nichrome-copper junction 37 and constantan-iron junction 40; however, the potential which they generate is very low and for all practical purposes negligible principally because these junctions are located-above the igniter and away from the heat source.

Referring now to FIGURE 4, the pilot igniter 9 is shown in a well 45 at approximately the elevation of exposed formation 46. The well may be lined with a casing 47. Tubing 12, which is placed within the well, forms an annular space 48 with the casing. An oxidizing gas such as air enters the well either through a separate string of tubing or preferably into the annular space through casing inlet 49. A combustible fluid, preferably in a vapor or gaseous form such as methane, is injected into tubing 12 through inlet 50. By means of wire line cable 30 the pilot igniter can be lowered into and withdrawn from the well through lubricator 51. A suitable weight bar 52 may be adapted to upper support member 10 in order to hold the tapered shoulder 13 in sealing engagement with seating nipple 14. Weight bar 52 is also adapted so as to permit fuel gas in tubing 12 to enter the interior of support member 10 and flow out through orifice tube 18.

In operation, the igniter is lowered by wire line 30 through lubricator 51 and tubing 12 until its downward travel is halted when the tapered shoulder 13 reaches seating nipple 14. Combustible fluid is supplied to the tubing 12 through inlet 50, while an oxidizing gas such as air is separately supplied through casing inlet 49 into the annular space 48. It is important to note that fuel and oxidant are supplied in such a ratio that if they were intimately mixed, whether accidentally or purposely, at any point above the seating nipple 14 the mixture would not be combustible. This is usually accomplished by injecting an excess of oxidizing gas down the annular space 48. However, when combustible fluid passes down the tubing 12 and then through the orifice tube 18 and nozzle 19 of pilot igniter 9, the high velocity of the gases created by the nozzle in combination with mixing tube 21 and venturi throat 22 causes a small part of the excess air, preferably a stoichiometric amount, to be drawn through a first perforate section or opening 16 from annular space 48 to be mixed with the combustible fluid to produce a combustible mixture. This mixture, due to the high velocity of the jet produced by the nozzle, emerges from the downstream end of the mixing tube 21 into housing 25. It may be preferable to reverse the described procedure and inject the oxidizing gas through inlet 50 into tubing 12 while an excess of combustible fluid is supplied through casing inlet 49 into the annular space 48. In this instance, the action of the high velocity oxidizing gas passing through nozzle 19 of the pilot igniter will draw a small part of the excess combustible fluid, preferably a stoichiometric amount, through opening 16 to be mixed and pass through mixing tube 21 into housing 25 where it is ignited.

Simultaneously with the injection of oxidizing gas and combustible fluid into the well, the heater element 23 is connected to power source 35 through wire line cable 30 at amperage which will create a heat source equal to but preferably greater than the ignition temperature of the combustible mixture. Preferably the total area of small orifices 26 is equal to or less than the crosssectional area of throat 22, so that only a portion of the total volume of the combustible mixture in mixing tube 21 is ignited inside housing 25. The remaining portion which emerges from mixing tube 21 bypasses the housing through the second perforate section or opening 17 and is ignited by flames which emerge from the housing. By intermittent changing of switch 41 the power supply 35 is disconnected and the millivoltmeter 42 is connected to. the wire line cable 30 to indicate the temperature at the temperature-sensitive junction 39. As soon as the millivoltmeter indicates that combustion is occurring and that nonexplosive combustion will be sustained with a larger volume of combustible mixture in the well, the pilot igniter is withdrawn from its sealing engagement with seating nipple 14 to a point well above the combustion zone, or completely out of the well. Simultaneously, the injection rates of oxidizing gas and combustible fluid are adjusted so that they will be within the combustible range.

For operation in deeper wells it may be uneconomical to have the heater element 23 at ignition temperature during the time the tubing and annular space are being filled with oxidizing gas and combustible fluid. Another method of operation, therefore, includes the steps of purging the tubing with combustible fluid with the pilot igniter sealed at the lower end of the tubing until the pressure exceeds the anticipated operating pressure. The inlet to the tubing would then be shut off. Air would be injected down the annulus at the anticipated rate to sweep out into the formation any large volumes of combustible mixture formed in the well. The heater element would then be turned on at rated amperage. When the pressure of the combustible fluid in the tubing decreases to operat- ,ing pressure, more combustible fluid would be introduced at the desired rate.

A pilot burner of the type shown has been designed for use in 2" or larger tubing. In this design, the upper support member 10 was formed of a 1 /2" modified tubing coupling having a groove for the O-ring seal 11 in the tapered shoulder 13 adapted to fit into sealing engagement with a seating nipple 14 at the lower end of tubing 12; Three longitudinal supports 15 of A" outside diameter stainless steel tubing were equally spaced around and attached to the upper support member 10. These supports act to form the frame for holding the mixing tube 21 and housing 25 and provide a conduit for leads 27 and 28. Orifice tube 18 was a seamless steel tubing, A3" outside diameter, passing through the center of support member 10. Nozzle 19, having a A diameter orifice, was attached to the orifice tube and the lower end was approximately /2" above the topmost part of the mixing tube 21. This mixing tube was concentric with the nozzle 19 and was formed of 1 outside diameter seamless steel tubing approximately 8" in length. A /z" throat 22 was provided as an integral part of the tube. Approximately 2" below the mixing tube was the housing 25 constructed of a 12" length of 1" outside diameter, thin-wall, seamless steel tubing. Within the housing, No. 20 Birmingham Wire Gage (B.W.G.) Nichrome wire heater element 23 was wrapped about a bundle of three /2" diameter porcelain rods 24. The heater element and porcelain rods were held upright and concentric in the bottom of the housing by a plug 55 of Sauereisen refractory insulating cement. Circulation of the combustible mixture about the heater element was limited by placing 20 Vs" orifices 26 in the housing 25. A sleeve of permeable linen mica was placed inside the housing 25 to further restrict the flow of gases and also provide insulation in the event the heater element 23 becomes loose or broken.

In order to provide the proper ignition temperature or greater to ignite a combustible mixture, the electrical circuit of the igniter 9 included a No. 14 B.W.G. Nichrome wire lead 27 which connects with the center conductor of wire line cable 30 at point 37. This lead 27 passed through an insulator 56 of Sauereisen cement within support member 10. This lead is insulated by the ceramic beads 29 as it passes through one of the longitudinal supports 15 to connect in series with the No. 20 B.W.G. Nichrome Wire heater element 23. The return lead of the heater element formed a thermocouple junction39 with No. l4,B.W.G. constantan wire which was similarly insulated and passed upward through another of the longitudinal supports 15 and insulator 56 of support member to a junction 40 on the outer sheath of wire line cable 30.

A pilot igniter of the type described was used in a cased well, 95 feet deep, with perforations in the interval 55-70 feet from the surface. The seating nipple at the lower end of 2 tubing was approximately 53 feet from the surface. After establishing the injectivity of the formation, i.e., after determining the rateat which the well would take air, air was injected into the annular space at a rate of 9.0 standard cubic feet per minute (s.c.f.m.) and at 27 pounds per square inch (p.s.i;) pressure while methane gas was injected down the tubing at a rate of 0.35 ,s.c.f.m. and at 40 p.s.i., which rates are well within the noncombustible operating limits represented by the portion A above the lower flammability line of FIGURE 5, specifically at point B. The velocity of the combustible gas created by nozzle 19 as the combustible gas enters the mixing tube 21 of the pilot igniter caused a small part .of .the excess air to mix with the methane gas to create a combustible mixture. This ratio of air to gas in the igniter is represented at any point between the interval marked C for a constant gas flow rate. This is within the combustible range as represented by the portion D of FIGURE 5 between the portion A and portion E or upper and lower [flammability limits. With approximately 450 watts input to the heater element, uniform burning, i.e., nonexplosive combustion, in and around the pilot igniter commenced immediately, and within a few minutes the thermocouple 39 indicated temperatures up to 700 F.

In using the igniter it is possible to leave the igniter seated in the tubing to provide the necessary combustion gases. However, it is preferred to withdraw the pilot igniter from its seat and simultaneously inject into the well combustible fluid and oxidizing gas in a ratio that is within the combustible range, when it appears that the temperature of the walls of the well will support nonexplosive combustion of a greater volume of combustible mixture. The seating nipple will then serve to jet the combustible fluid into and mix it with the oxidizing gas in the well. Accordingly, this will allow greater amounts of heat energy to be released to the formation. The time the igniter should be withdrawn from a particular well to allow the larger quantities of combustible mixtures to be ignited, is an operation which a man skilled inthe art will be capable of determining. We believe that if the walls of the well which are to be heated are above 600 F. that nonexplosive combustion of larger quantities of combustible mixtures will occur when the igniter is withdrawn. At what time that temperature will result varies from several minutes to several hours depending on the particular conditions of the well being treated. The importance of our invention, however, lies in the fact that if the igniter is withdrawn from its seating position and nonexplosive combustion does not occur then it can be quickly replaced and ignited to reheat the walls of the well until they will support noncxplosive combustion.

From the foregoing 'it can be seen that various modifications of the apparatus and operating procedure can be made without departing from the spirit of the invention. For example, while we have described our invention in relation to creating and igniting combustible gas mixtures in a well, it is readily adaptable to the submerged combustion art where hot gases are in direct heat exchange with the liquid to be heated or evaporated.

We contemplate that the various change in form and equivalents are within the scope of the following claims.

1. An apparatus for igniting a combustible mixture in a well having a first conduit and a second conduit installed in said well andisurrounding said first conduit which comprises an assemblage includinga support member resting in fluid-tight relationship with the lower end of said first conduit, a tube (1) extending into said member placing the interior of said first conduit in communication with the exterior thereof, individual means for supplying a gas to said first and second conduit, a combustible mixture igniter below tube (1) and coaxial therewith, a mixing tube open at both ends and coaxially spaced apart from and between tube (1) and said igniter to define an open space at either end of said mixing tube, the spaceyrelationship of said mixing tube with respect to tube 1) and, said igniter being such that the jetting of a first fluid through tube 1) causes entrainment of a second fluid into the resulting stream and into said mixing tube such that at least a portion of said stream coming from said mixing tube contacts said igniter, means attached to said support member for holding said mixing tube and said igniter in coaxial relationship, and means to raise said assemblage so that said support member is no longer in fluid-tight relationship with the lower end of said first conduit.

-2. The apparatus of claim 1 in which the mixing tube is a venturi tube.

3. An apparatus according to claim 1 in which said assemblage is small enough to pass through said first conduit so that said assemblage can be removed from said Well after said combustible mixture is ignited.

4. An apparatus according to claim 3 wherein said igniter comprises an electrical heating element and said means to raise said assemblage includes an insulated electrical conductor connected at the lower end to said heating element and extending through said first conduit to the surface.

5. An apparatus according to claim 4 wherein said electrical heating element includes in series a thermo couple and wherein there is included at the surface an indicator connected to said electrical conductor for indicating the temperature at said igniter.

6. In an apparatus for igniting a combustible mixture in a well equipped with tubing, a wire line retrievable pilot burner comprising an assemblage including a shoulder on the interior of the lower end of said tubing, a support member resting in fluid-tight relationship with respect to said shoulder, a tube 1) extending into said member placing the interior of said tubing in communication with the exterior thereof, individual means for supplying a gas to said tubing, a combustible mixture igniter below tube 1) and coaxial therewith, a mixing tube open at both ends and coaxially spaced apart from and between said tube and said igniter to define an open space at either end of said mixing tube, the space relationship of said mixing tube with respect to tube (1) and said igniter being such that the jetting of a first fluid through tube (1) causes entrainment of a second fluid into the resulting stream and into said mixing tube such that at least a portion of said stream coming from said mixing tube contacts the igniter, means attached to said support member for holding said mixing tube and said igniter in coaxial relationship, and means to raise said assemblage so that said support is no longer in fluid-tight relationship with the lower end of said first conduit.

7. The apparatus of claim 6 in which the mixing tube is a venturi tube.

8. In an apparatus for igniting a combustible mixture in a well equipped with tubing, a Wire line retrievable pilot burner comprising an assemblage including a shoulder on the interior of the lower end of said tubing, a support member resting in fluid-tight relationship with respect to said shoulder, a tube 1) extending into said member placing the interior of said tubing in communication with the exterior thereof, individual means for supplying a gas to said tubing, a combustible mixture igniter below tube (1) and coaxial therewith, a venturi tube coaxially spaced apart from and between tube (1) and said igniter to define an open space at either end of said venturi tube, the distance between the lower end of tube (1) and said venturi tube being approximately equal to the diameter of the restriction in said venturi tube, means for holding said venturi tube, said igniter and tube (1) in coaxial relationship with one another, and means for raising said assemblage so that said support member is no longer in fluid-tight relationship with the lower end of said first conduit.

9. In a burner apparatus the combination which comprises an assemblage including a supporting member, a frame depending therefrom, a tube (1) extending through the vertical axis of said member, an igniter below tube (1) coaxial therewith, and a mixing tube afiixed to said frame coaxially spaced apart from and between tube (1) and said igniter to define an open space at either end of said mixing tube, said igniter being recessed in a perforated enclosure open at the end adjacent said tube and affixed to said frame, the space relationship of said mixing tube with respect to tube (1) and said igniter being such that the jetting of a first fluid through tube (1) causes entrainment of a second fluid into the resulting stream and into said mixing tube such that only a portion of said stream coming from said mixing tube flows into said enclosure and contacts said igniter.

10. In a burner apparatus the combination which comprises an assemblage including a supporting member, a

frame depending therefrom, a tube (1) extending through the vertical axis of said member, an igniter below tube 1) coaxial therewith, and a venturi tube aflixed to said frame coaxially spaced apart from and between tube (1) and said igniter to define an open space at either end of said venturi tube, said igniter being recessed in a perforated enclosure open at the end adjacent said tube and afiixed to said frame, the space relationship of said venturi tube with respect to tube (1) and said igniter being such that the jetting of a first fluid through tube (1) causes entrainment of a second fluid into the resulting ,stream and into said venturi tube such that only a portion of said stream coming from said venturi tube flows into said enclosure and contacts said igniter.

References Cited in the file of this patent UNITED STATES PATENTS 1,626,940 Kreager May 3, 1927 1,676,785 Lewis July 10, 1928 2,159,257 Danuser et a1. May 23, 1939 2,410,881 Hunter Nov. 12, 1946 2,584,606 Merriam et a1. Feb. 5, 1952 2,666,480 Peterson Jan. 19, 1954 2,668,592 Piros et a1. Feb. 9, 1954 2,733,605 Buck Feb. 7, 1956 2,776,013 Tausch Jan. 1, 1957 2,776,816 Jackson Jan. 8, 1957 2,785,741 Grauers Mar. 19, 1957 2,787,906 Piety Apr. 9, 1957 2,887,160 De Priester et a1 May 19, 1959