US3055427A - Self contained igniter-burner and process - Google Patents

Description

p 25, 1952 R. c. PRYOR ETAL 3,055,427

SELF CONTAINED IGNITER-BURNER AND PROCESS Filed July 13, 1959 INVENTORS R.C. PRYOR R.J. BENNETT I BYl A T TORNEYS United States Patent Oiilice 3,055,427 Patented Sept. 25, 1962 3,055,427 SELF C(BNTAINED IGNITER- BURNER AND PROCESS Robert C. Pryor and Richard J. Bennett, Bartlesville,

@irim, assignors to Philiips Petroleum Company, a corporation of Delaware Filed July 13, 1959, Ser. No. 826,504 Claims. (Cl. 166-39) This invention relates to a self-containing-igniter burner for igniting a combustible fuel pack in a borehole adjacent a carbonaceous stratum and to a process for igniting such a fuel pack and igniting the stratum.

In situ combustion in the recovery of hydrocarbons from underground strata containing carbonaceous material is becoming more prevalent in the petroleum industry. In this technique of production, combustion is initiated in the carbonaceous stratum and the resulting combustion zone is caused to move thru the stratum by either inverse or direct air drive whereby the heat of combustion of a substantial proportion of the hydrocarbon in the stratum drives out and usually upgrades a substantial proportion of the unburned hydrocarbon material.

The ignition of carbonaceous material in a stratum around a borehole therein followed by injection of air thru the ignition borehole and recovery of product hydrocarbons and combustion gas thru another borehole in the stratum is a direct air drive process for effecting in situ combustion and recovery of hydrocarbons from the stratum. In this type of operation the stratum usually plugs in front of the combustion zone because a heavy viscous liquid bank of hydrocarbon collects in the stratum in advance of the combustion zone which prevents movement of air to the combustion process. To overcome this difiiculty and to permit the continued progress of the combustion zone thru the stratum, inverse air injection has been resorted to. By this technique, a combustion zone is established around an ignition borehole by any suitable means and air is fed thru the stratum to the combustion zone from one or more surrounding boreholes.

In situ combustion techniques are being applied to tar sands, shale, Athabasca sand and other strata in virgin state, to coal veins by fracturing, and to strata partially depleted by primary and even secondary and tertiary recovery methods.

One of the basic methods of igniting a carbonaceous stratum preparatory to producing the same by in situ combustion comprises burning a solid particulate fuel pack in a well adjacent the stratum to be ignited and, when surrounding stratum has been raised to ignition temperature, passing air or other oxygen-containing, combustionsupporting gas (diluted or enriched air) into the hot stratum so as to ignite the same.

(Dharcoal in the form of briquettes or other small pieces, alone, or in admixture with ceramic pieces such as pebbles, broken fire brick, etc., and porous ceramic pieces such as alumina pebbles soaked with heavy oil, have been successfully utilized as a fuel pack for igniting a stratum. In shallow strata, the charcoal has been successfully ignited by dropping onto the top of the charcoal pack a mass of ignited charcoal or an ignited railroad fuse and injecting combustion-supporting gas into the charcoal pack.

The problem of ignition of a fuel pack in a deep well is substantially different from that in a shallow well, since the gravitating ignited material falls thru a zone of little or no oxygen content and is rapidly cooled so that the material is not burning when it reaches the charcoal pack. This invention provides a method and device for igniting a fuel pack regardless of the depth of the stratum to be ignited.

Accordingly, the principal object of the invention is to provide a novel igniter and method for igniting a fuel pack in a well within a carbonaceous stratum. Another object is to provide an igniter-burner for igniting a combustible fuel pack which is self-contained and does not require fuel and air conduits extending from the well head to the fuel pack, and which is applicable to deep strata. A further object of the invention is to provide an igniter-burner for igniting a stratum, which is so compact that it can be lowered in the well thru conventional well tubing. It is also an object to provide a method of igniting and producing a carbonaceous stratum by inverse air injection which does not require the reversal of air flow from direct to inverse injection after igniting the stratum. Other objects of the invention will become apparent upon consideration of the accompanying disclosure.

The igniter-burner of the invention comprises a pair of cylindrical fuel tanks of small diameter supported in axial alignment with each other and with a combustion vessel and a burner nozzle, with a separate conduit connecting each tank with the combustion chamber of the combustion vessel. The igniter-burner with one of its tanks filled with compressed oxygen and the other filled with compressed fuel gas is ignited at the surface, the flame is adjusted for maximum operating efliciency, and the burner is lowered into the well containing the fuel pack on a wire or cable by a conventional Windlass or winch thru well tubing in instances where the tubing is necessary for production, and thru the well casing where the tubing is not essential to production. When the burner contacts the top of the fuel pack it is held in this position until it has burned a suificient length of time to ignite a large section of the fuel pack. This may require anywhere from 10 or 15 minutes to an hour or two.

A more complete understanding of the invention may be had by reference to the accompanying schematic drawing of which FIGURE 1 is an elevation in partial section of a preferred embodiment of the self-contained igniterburner of the invention, and FIGURE 2 is an elevation showing an arrangement of apparatus, including the burner of FIGURE 1, positioned in a borehole for igniting a carbonaceous stratum.

Referring to FIGURE 1, burner 10 comprises a cylindrical oxygen tank 12 and a cylindrical fuel tank 14 connected by a conduit 16 of the same diameter as the tanks and welded to the tanks at each end by welds 18 so as to hold same in axial alignment. The ends of tanks 12 and 14 are generally hemispherical in order to withstand high pressures of the order of 1000 or more pounds per square inch. A mixing vessel 20 having a top closure 22 threaded into its upper end at 24 is held in axial alignment with the tanks by means of a conduit 26 similar to conduit 16 welded to the lower tank by weld 28. Members 22 and 24 are of the same diameter as the internal diameter of conduit 26 and closure 24 is welded thereto by weld 3t Mixing vessel 20 has an axial orifice 32 (which may be in the form of a venturi) dividing the vessel into a. primary mixing chamber 34 and a larger storage and surge chamber 36. Flame arrester 38 is threaded into the outlet end of the mixing vessel and is provided with small holes or passageways 40 for injection of gas into nozzle or burner tip 42. Nozzle 42 is screwed into the outlet end of the mixing vessel against flame arrester 38 and is provided with annular shoulder 44 which seats against seal ring 45. Seal ring 46 is provided between end closure 22 and vessel 20. The end of burner tip 42 is provided with member 48 which contains a plurality of conduits or passageways 50 thru which the combustible mixture of fuel gas and oxygen is jetted for ignition and burning below the tip.

A conduit 52 leads from oxygen tank 12 thru fuel tank 14 into primary mixing chamber 34 and is provided with an upper valve 54 and a lower valve 56. A separate conduit 58 leads from fuel tank 14 thru closure 22 into primary mixing chamber 34 and is provided with a control valve 60. An orifice 62 is positioned in the end of each of conduits 52 and 58 to control the rate of flow of the oxygen and fuel into the mixing chamber. A valved fill line 64 and a similar valved fill line 66 are connected with tanks 12 and 14, respectively. Openings 67, 68, 69, and 70 in their respective conduits are provided for access to the valves and lines connected with the tanks.

A tip guide and shield 72 forms an annulus 74 around burner tip 42, being of the same inner diameter as the outer diameter of mixing vessel 20 and is welded thereto by weld 76. Shield 72 extends below the burner tip and is perforated by ports 78 to aid in the venting of hot gas and fiame from the tip of the burner. A threaded connector Silon the upper end of tank 12 permits attachment of a threaded ring connector or other cable attaching device (not shown) for lowering the igniterburner into the well.

Referring to FIGURE 2, la combustible stratum 82 is penetrated by a well 84 which is packed with a fuel pack 85, such as charcoal briquettes. A casing 88 extends from the well head 89 to the approximate upper level of stratum 82 land is cemented at 90. A tubing string 92 extends thru well head 89 to a level just above the lower end of the casing and burner 10 is suspended in the tubing by means of cable 94 with its lower end in the top of the fuel pack. Cable 94 is attached to winch or Windlass 96 and extends over pulley )8. A valved conduit provides for injecting or venting gas into or from the casing.

Conventional well tubing is 2 /2 or 3 inches I.D., which means that the igniter-burner must have an external diameter of about 2% or 2% inches to accommodate conventional tubing. Tanks v12 and 14 can be fabricated in lengths up to 10 or 15 feet which provides ample supplies of oxygen and fuel, even though their diameters are small, since the oxygen and fuel gas can be compressed to pressures of the order of 1,000 lbs. p.s.i.g.

In operation, the burner with tanks filled with highly compressed gases (oxygen in one tank and acetylene, ethylene, ethane, propane, propylene, butane, butylene, or mixtures thereof, or any liquefied petroleum gas) is ignited by opening valves 54-, 56, and 60 and igniting the efiluent gas at burner tip 4-2. After adjusting the flame to optimum heating efficiency, the burner is lowered by cable 94 to the position shown in FIGURE 2 and held in this position until a substantial upper section of the fuel pack is heated to ignition temperature. The hot fuel pack is contacted at this time with oxygen by means of excess provided in the combustion mixture of the mixture of the burner or by air injected into the fuel pack thru line 100 and down the casing in instances where the driving of hot gases into the stratum does not effect plugging. In most instances, it is more desirable to vent the combustion gases thin line 100 and feed combustionsupporting gas to the hot fuel pack thru stratum 82 by injecting air or other combustion-supporting was into the stratum thru a ring of offset injection wells surrounding ignition well 84. In this case an" passing thru the stratum into the fuel pack burns the fuel pack progressively from the top to the bottom thereof and, as the adjacent stratum is heated to combustion supporting temperature, ignition thereof is effected and the resulting combustion zone or front automatically moves radially thru the stratum toward the offset wells.

When simultaneously burning the fuel pack and initiating combustion of the stratum by injecting combustionsupporting gas thru the stratum to the ignition well, it is essential to include in the injected gas a low concentration of fuel gas such as any of a mixture of the normally gaseous hydrocarbons. A concentration in the range of about 1 to 4 volume percent of the fuel gas in the injected gas is effective in moving the fire front into the stratum. After a substantial area of the stratum around the ignition well has been ignited, the injected of fuel gas into the stratum may be terminated, but continued injection of fuel gas with the injected air aids in the in situ combustion process by increasing the rate of propagation of the combustion front and the percentage of hydrocarbons recovered from the stratum.

While the oxygen tank llis shown in the upper position in the burner with the fuel tank in the lower position, the position of these tanks may be reversed, of course. It is also feasible to operate the burner without tip shield 72, but use of this shield protects the burner tip and its use is preferred.

Certain modifications of the invention will become apparent to those skilled in the art and the illustrative details disclosed are not to be construed as imposing unnecessary limitations on the invention.

We claim:

1. A self-contained igniter-burner for igniting a combustible fuel pack in a well comprising in combination, when positioned in upright operating position, a first vertically elongated pressure tank and a second vertically elongated pressure tank rigidly attached one above the other in axial alignment for lowering into a well; a mixing vessel axially aligned with and below said tanks; a transverse partition across said vessel having an axial orifice therein and dividing said vessel into an upper small primary mixing zone and a lower larger secondary mixing and surge zone; a separate conduit connecting each tank with the upper end of said primary mixing chamber; a flow orifice in the end of each said conduit leading into said primary mixing chamber; a flame arrester across the lower open end of said secondary mixing zone; a terminal burner nozzle axially attached to the lower end of said mixing vessel adjacent said flame arrester, said burner nozzle having exhaust ports open to said well; a burner nozzle shield surrounding the lower end of said vessel, forming an annulus with said nozzle, and extending below said nozzle; and ports in the lower end of said shield.

2. The burner of claim 1 adapted to pass thru a well tubing, said tanks being welded to opposite ends of an interconnecting conduit of an outside diameter not exceeding the outside diameter of said tanks and said tanks having an outside diameter less than the inside diameter of said tubing; said vessel comprising an upper end closure member connected to the lower end of the adjacent tank by means of a surrounding and engaging conduit of outside diameter not exceeding the outside diameter of said tanks welded to the adjacent tank; and said shield surrounding and engaging the lower end of said vessel.

3. A process for igniting a fuel pack in a well adjacent a combustible stratum comprising positioning in said well adjacent the top said fuel pack a separate, stored supply of compressed oxygen and a separate, stored supply of compressed fluid fuel; injecting fuel and oxygen from their respective separate supplies into a mixing zone adjacent said pack to form a combustible mixture; ccmbusting said mixture and ejecting the resulting flame and hot gases onto said fuel pack until same is raised to combustion temperature; and contacting said fuel pack with free oxygen so as to ignite same.

4. The process of claim 3 wherein said free oxygen for igniting said fuel pack is supplied in said combustible mixture.

5. The process of claim 3 wherein said free oxygen for igniting said fuel pack is supplied by passing air thru said stratum from at least one offset well therein.

6. The process of claim 5 wherein said air is admixed with fuel gas in a concentration in the range of about 1 to 4 volume percent.

7. The process of igniting a permeable carbonaceous stratum around an ignition well therein which comprises effecting the steps of claim 5 and continuing the injection of air and fuel gas :thIll said stratum so as to consume sufiicient fuel pack to raise the temperature of said stratum adjacent said fiue1 pack to ignition temperature: further continuing said injection so as to ignite said stratum and move a resulting combustion front into said stratum away from said ignition Well; and recovering produced hydrocarbons rthru said ignition well.

8. The process of claim 3 wherein said fuel is propane.

9. The process of claim 3 wherein said fuel is acetylene.

10. The process of claim 3 wherein said gas is liquified petroleum gases.

References Cited in the file of this patent UNITED STATES PATENTS Stickney Sept. 20, Napolit-an May 13, De Kaiser et a1. Oct. 7, De Kaiser et a1. Oct. 7, Stroebel May 11, Shannon et all Aug. 1 6, Lurie Aug. 14, Damm July 16, Mayes et a1. Feb. 23, M acLeod Jan. 24, Koch Dec. 31, Trarrtha-m et a1. June 9, De Priester July 21,

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