US2895555A - Gas-air burner with check valve - Google Patents

Description

July 21, 1959 c. L. DE FRIESTER` GAS-AIR BURNER WITH CHECK VALVE A Filed Oct. 2, 1956 FIGB INVENTOR CORAL L. DE DR/ESTER FIG.1A

United States vPatent O fornia Research Corporation, San Francisco, Calif., a corporation of Delaware Application ctober 2, 1956, Serial No. 613,465

2 Claims. (Cl. 166-59) This invention relates in general to apparatus for stimulating the flow of oil from subterranean formations and relates more particularly to improvements in apparatus for burning a gaseous combustible mixture adjacent a subterranean oil-bearing formation to heat such formation and the oil contained in the formation.

It is well known that the productivity of most oil wells decreases with time. Such decrease may be caused, for example, by a natural depletion of the reservoir or by plugging or clogging of the formation adjacent the well bore by waxes, parafns, or other material. Numerous systems have been proposed for remedying this decrease in productivity, and many of such systems employ the application of heat adjacent the formation to melt the plugging materials, to decrease the viscosity of the oil to increase the pumpability thereof and to decrease the viscosity of the uids in the formation to increase the flow of fluids into the well bore.

Among the methods proposed for producing this heat have been the use of chemicals producing an exothermic reaction in the producing zone, electric heating units for radiating heat to the formation, and the circulation of heated fluids such as steam or oil to transfer heat to the treated formation. However, these systems have the inherent disadvantage of poor efficiency in the transfer of heat from the heating medium to the formation to be heated, thus increasing the cost of obtaining a given amount of heating effect. Additionally, the use of electric heaters requires electric cables from the surface to the heater location, thus increasing the complexity and hazards of the device. Similarly, systems employing the circulation of heated fluids require insulation for the fluidcarrying conduits from the surface to the zonev to be treated to avoid excessive thermal losses to the surrounding fluids and formation.

Another proposed solution is to dispose adjacent the formation to be heated a burner device in which a gaseous combustible mixture is burned and the resulting heated combustion products utilized to heat the oil in which the burner is submerged and/or the surrounding formation. The use of such burners appears to oifer the most efficient method of well stimulation, owing to the fact that the burner device itself may be located adjacent the formation to be treated, and may thus operate without any substantial thermal losses between the surface of the earth and the burner location.

Numerous problems are encountered in the operation of such downhole gas-air burners, and one of the most serious problems is the prevention of backllow of fluids or other materials into the burner. Such backow may occur, for example, when the burner is being run into the well bore, in which case the backllow may cause plugging of the burner orifices, with a consequent undesirable elfect on the subsequent operation of the burner. Similarly, backlow of fluids or other material into the burner may result during burner operation when sudden surges in the fluid level in the bore hole in which the burner is being operated tend to flood the burner and Patented July 21, 1959 ICC 2 extinguish combustion in the `combustion chamber. Also, during operation of the burner, backow may occur when the ow of the gaseous combustible mixture is interrupted by compressor shutdown `or piping failure. y

Such flooding or plugging of the burner is obviously undesirable, since, in the first case, it may necessitate withdrawal -of the burner, or a portion thereof, and associated tubing from the well bore to remedy the plugging, and in the second case it requires a clean-out of crude oil from the tubing by washing with solvents prior to reignition of combustion in the burner.

Broadly the present invention contemplates a downhole gas-air burner provided with suitable check valve means which will permit the ilow of fluid from the combustion chamber out into the well fluid, but which will prevent a reverse ow of iluid or other material from the well bore into the burner proper. Such check valve means may be in any suitable form, but preferably comprises a ball check valve located in a portion of the burner disposed below the combustion chamber. The check valve is preferably situated in the passageway which provides communication from the combustion chamber to the well Huid to be heated so that substantially all of the combustion products pass through the passageway.

In operation, the check valve means is retained in the open position by the pressure of the ilow of combustion products from the combustion chamber, against the action of suitable spring means. When the pressure of this flow of combustion products decreases to a predetermined extent, or when the pressure in the well iiuid exceeds a predetermined amount, the check valve means is closed to prevent entry of fluid or other material into the valved passageway and into the combustion chamber. Thus a simple, effective means is provided by the present invention to prevent entry of fluids or other undesirable matter into the burner proper during running of the burner into the well bore and to prevent surges in the well fluid pressure from forcing fluid into the burner during operation.

Objects and advantages of the present invention will be apparent from the following description when read in connection with the accompanying drawings, in which:

Fig. 1A illustrates the disposition of the upper portion of a gas-air burner in a well bore;

Fig. 1B is a continuation of Fig. 1A and represents the dispositon of the lower portion of the gas-air burner, including the check valve means of the present invention, in the well bore;

Fig. 2 is a sectional View, on an enlarged scale, of a portion of the check valve means of Fig. 1B, illustrating the' check valve in the open position; and

Fig. 3 is a sectional view along plane Ill-Ill of Fig. 2.

Referring to the drawing by character of reference, numeral 11 designates the wall of a well bore extending from the surface of the earth into a formation which is to be treated with a burner built according to the present invention. The apparatus includes a length of tubing 16 extending from the surface of the earth to the formation to be treated. The elements of the gaseous combustible mixture are fed through conduit 16 to the burner proper. `Such mixture may, as is well known in the art, comprise air and a fuel gas supplied to conduit 16 through suitable surface compressors. The fuel gas may be obtained from a supply of field gas which may be available. from other wells in the area.

The check valve means of the present invention may be used in connection with any suitable gas-air burner, and for the purposes of illustration the check valve means is illustrated in connection with a burner whose features are disclosed and claimed' in a copending application of Coral L. De Priester and C. N. Simm, Serial No. 525,505.

This burner as shown in Figs. 1A and 1B, may be divided into component portions comprising a nozzle and ignition portion 21, a combustion chamber portion 22, and a diiuser and exhaust portion 23,4 containing the check valve means of the present invention. Nozzle and ignition portion 21 includes a generally cylindrical nozzle support member 26, which fits inside the lower end of conduit 16 and is preferably welded thereto. The upper edge of support member 26 forms a landing shoulder for engaging the upper end of a slotted nozzle assembly 32. Nozzle assembly 32 is provided with a plurality of delivery slots 34 about the periphery thereof, which extend the length of the nozzle assembly and which serve as passageways for the gaseous combustible mixture from conduit 16. The burner is also provided with means for igniting the gaseous combustible mixture issuing from slots 34, and such means may be in the form of an electrical heating coil 35 disposed inside nozzle assembly 32.

Combustion chamber 22 has its outer walls formed by a length of conduit 31 having its upper end welded to nozzle support member 26. The combustion chamber is preferably provided with a refractory liner to prevent thermal damage to conduit 31 forming the outer wall of the combustion chamber. Such refractory liner may be of any suitable form, but preferably the liner is one whose features are disclosed and claimed in the copending application of Coral L. De Priester, Serial No. 588,782, now abandoned. Refractory liner 41 comprises a plurality of cylindrical segments 41a which abut or are closely ad jacent each other. Segments `41a may be formed, for example, by sawing the unitary liner 41 into a series of cylindrical segments 41a and placing these segments inside the combustion chamber, as shown in the drawing.

Segments 41a are preferably press-fitted into the combustion chamber and are held in place by a diffuser cone piece 42 which is Welded to the lower end of conduit 31. Diffuser 42 is provided with a conical opening 43 therein which communicates with the combustion chamber 22 through an oriiice 44 of reduced diameter. An additional length of conduit 45, of length up to 30 feet or more, may be welded to the lower edge of diluser cone piece 42 to provide cooling of the combustion gases by heat transfer to liuids in the well bore. An additional length of conduit 46, containing the check valve means of the present invention, is connected to conduit 45 by a suitable coupling. The joining ends of conduit means 45 and 46 and coupling member 55 are provided with openings 47 and 48 therein forming a passageway through which combustion products from the diiuser chamber pass.

The check valve means of the present invention is disposed at the lower end of this passageway and may include a ball and cage assembly such as is utilized to coutrol the direction of ow of uids. Such an assembly includes a ball 52 which seat against a valve seat formed by a ring 51. Ball 52 is moved by a push rod 53 which is actuated by a spring 54. Ring 51 is pressed against ya seating shoulder by a coupling member 55. The seating shoulder for ring 51 is formed in the upper portion of a cage member 61 which is part of the check valve assembly. Coupling member 55 and cage member 61 form the coupling member for connecting conduits 45 and 46. Ball 52 and ring 51 are preferably made of some heat-resistant material, such as tungsten carbide or titanium carbide. Similarly, rod 53 is made of some heat-resistant material, such as stainless steel. The assembly also includes a cage member 61 surrounding ball 52 and having four ports 62 spaced 90 from each other about the periphery of the cage. Rod 53 extends through an opening in the bottom of cage 61 to contact ball 52. The lower end of rod 53 is connected to spring 54 through a thrust washer 60 which is positioned on rod 53 by butting against a shoulder machined on rod 53, as shown in Fig. 1B.

Spring 54 is preferably located at some distance from the combustion chamber of the burner, so that the temperature at the spring location does not exceed 300-400 F. This provision prevents thermal failure of spring 54 and also prevents thermal changes in the characteristics of spring 54 which would render the check valve means inoperative. Venting openings 68 are preferably provided in the lower end of member 46 to prevent accumulation of sand or sediment inside conduit 46 and to permit smooth operation of spring 54 and push rod 53.

When the valve assembly is in the position shown in Fig. 1B, with ball 52 pressed by spring 54 against the valve seat formed by ring 51, no fluid ows through the valve assembly in either direction, because the opening in ring 51 is sealed by ball 52, and hence fluid cannot llow from openings 47, 48 through ports 62. When the valve assembly is in the open position shown in Fig. 2, with ball 52 away from ring 51, communication is established between openings `47, 48 and ports 62, so that uid may flow through this passageway in the manner indicated by the arrows in Fig. 2. The gaseous combustion products issuing through the lower ends of ports 62 pass out of conduit 46 through a plurality of openings 66 therein. These gaseous combustion products thus pass through openings 66 into contact with well uids and formation to be heated.

The assembly, including nozzle assembly 32 and igniter 35, is a separate unit from nozzle support member 26, member 42, and conduits 16, 31, 45 and 46, and may be run into and out of the Well bore independently of these latterelements. Nozzle assembly 32 is connected through a cross-over or coupling member 69 to a sinker bar 70 which is in turn connected to a hoisting cable 71. An electric cable 72 passes through hoist cable 71, sinker bar 70, cross-over 69 and nozzle 32 to supply current to heating unit 35 of the igniting mechanism.

In operation, tubing 16 is lowered into the well bore to be treated and the supply of air and fuel gas connected thereto. During this running of the tubing the ball check valve is in the closed position illustrated in Fig. 1B, to prevent entry into the burner of well fluids or foreign matter from the Well bore. After running conduit 16 and the attached assemblies to the desired position, the nozzle and igniter assembly is then lowered into conduit 16 by cable 71 until the lower end of noz zle assembly 32 engages the landing shoulder on nozzle support member 26. As indicated in Fig. 1A, conduit 16 and the burner proper are preferably of such size as to permit the burner to be operated in a well bore simultaneously with the regular production tubing string so that simultaneous heating and production may occur. With the burner positioned at the desired location adjacent the formation to be heated, air and fuel gas are supplied to the inside of conduit 16, and these elements are mixed in passing down conduit 16 to the burner assembly.

The combustible mixture passes through delivery slots 34 and enters combustion chamber 22, Where it is ignited by the high temperature produced by energization of heating coil 35. The ensuing flame of combustion is conined within combustion chamber 22 by exhaust oritice 44, and orifice 44 also functions to increase the stability of the burner operation by attenuating or eliminating shock waves in the fluid surrounding the burner assembly.

The combustion products pass through orifice 44, diffuser cone 43, and openings 47 and 48 to exert pressure on ball 52 seated against ring 51. The characteristics of spring 54 are such that for normal combustion in the burner, the pressure of the combustion products against ball 52 is suicient to force ball 52 and push rod 53 downwardly' against the action of spring 54. As best shown in Fig. 2, this movement of ball 52 opens a ow path through ring 51 to provide communication between opening 48 and ports 62. The combustion products from the burner thereupon pass downwardly through ports 62 and pass out of conduit 46 through openings 66 to heat the gil All ,the Well bore and/ or the surrounding formation.

a sudden surge ot pressure arises in the well bore, the well fluids may enter ports 66. However, the check valve of this invention prevents entry of these uids into the burner proper, since the pressure caused by these uid surges combines with the force of spring 54 to seat ball 52 in ring 51 against pressure of the combustion gas products. This upward movement of ball 52 closes the opening in ring 51 so that no iiuid may pass through ports 62 to opening 48. When the uid surge has subsided, ball 52 is again forced downwardly to the position shown in Fig. 2 by the pressure of the combustion products. If this fluid surge is of extremely short duration, reignition of the burner may occur automatically from the heat retained in the combustion chamber, to resume normal operation of the burner. If. the surge is of longer duration, reignition of the burner may be necessary, but such reignition will not be complicated by the presence of crude oil in the combustion chamber, since the action of the check valve means of the present invention prevents entry of the crude oil or other material into the burner proper.

A similar operation results when the burner is shut down for any reason, either as a shut-down during operation or prior to pulling the burner from the well bore.

Although but a single embodiment of the present invention has been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without depart ing from the spirit of the invention or the scope of the appended claims.

I claim:

l. Apparatus for stimulating the production of petroleum from a subterranean formation penetrated by a well bore comprising tubing means extending into said well vbore from the surface of the earth for carrying a gaseous combustible mixture, a combustion chamber secured to the lower end of said tubing for burning said gaseous combustible mixture, ignition means for initiating combustion of said gaseous mixture within said combustion chamber, an exhaust member connected to the lower end of said combustion chamber and having openings therein communicating with said well bore, a passageway in said exhaust member establishing fluid communication between said comb-ustion chamber and said openings in said exhaust member, and check valve means in said passageway, said check valve means including a ring member in said passageway forming a valve seat,

a ball adapted to seat on said valve seat, a rod member for actuating said ball, and a spring member disposed in the lower end of said exhaust member away from said openings and connected to said rod member for urging said ball toward said valve seat, the pressure of the products of said combustion being suicient to overcome the force of said spring to open said passageway to permit said combustion products to flow from said combustion chamber to said exhaust member during combustion, said passageway being closed in response to a decrease in said pressure to prevent uid ow from said exhaust member into said combustion chamber.

2. Apparatus for stimulating the production of petroleum from a subterranean formation penetrated by a well bore comprising tubing means extending into said well bore from the surface of the earth for carrying a gaseous combustible mixture, a combustion chamber secured to the lower end of said tubing for burning said gaseous combustible mixture, ignition means for initiating combustion of said gaseous mixture within said combustion chamber, an exhaust member connected to the lower end of said combustion chamber and having openings therein communicating with said well bore, a passageway in said exhaust member establishing Huid communication between said combustion chamber and said openings in said exhaust member, and check valve means in said passageway, said check valve means including a ring member in said passageway forming a valve seat, a valve member adapted to seat on said valve seat, a rod member for actuating said valve member, and a spring member disposed in the lower end of said exhaust member away from said openings and connected to said rod member for urging said valve member toward said valve seat, the pressure of the products of said combustion being suflcient to overcome the force of said spring to open said passageway to permit said combustion products to flow frm said combustion chamber to said exhaust member during combustion, said passageway being closed in response to a decrease in said pressure to prevent fluid flow from saidA exhaust member into said combustion chamber.

References Cited in the le of this patent UNITED STATES PATENTS

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