US3004603A - Heater - Google Patents

Description

Oct. 17, 1961 s, o ERs ETAL 3,004,603

HEATER Filed March 7, 1958 55 56 COMBUSTION GASES AIR I 'l 57 FUEL GAS 2a FUEL GAS 30 2o PRODUCED GASES 24 INVENTORS A.S. ROGERS J.R. HURLEY BY H.W. PARKER ATTORNE Y$ "therein.

3,004,603 Patented Oct. 17, 1961 7 3,004,603 7 HEATER Allen S.',Rogers, .lames R. Hurley, and Harry W. Parker,

Bartlesville, Okla, assignors to Phillips Petroleum Company, a corporation of Delaware Filed Mar. 7, 1958, Ser. No. 719,890 1 '1 8 Claims. (Cl. 166-59) This invention relates to gas fired heaters for heating a well bore. 1 a t In situ combustion in the recoveryof hydrocarbons from underground strata containingcarbonaceous 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 remaininghydrocarbon material. i

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 fluid .bank collects in the stratum inadvance of thecombustion zone which prevents movement of air to ,the combustion process. To. overcome this difliculty and ,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 United States Patent Ofiice around an ignition. borehole by any suitable means and one or more surrounding boreholes.

carbonaceous material in thestratum around a borehole heaters have been found difiicult to design to withstand -the downhole heat and have also been rather slowin heating the formation up to combustion supporting temair is fed thru the stratum to the combustion zone from One method of ignition utilizes a "downhole heater either of the electric or gas fired type. Electric perature. -Conventiona1 gas fired heaters vent the com ,bustion gas into the. borehole and interfere to some extent with the contacting of the borehole wall with gas of, high enough oxygen concentration to readily ignite carbonaceous material. A number of downhole gasfired heaters phave been used which burned ed the tubing on which the heater was positioned before the combustion was fully established in V the adjacent stratum.

Accordingly, it is an object of the invention to provide a downhole heater of such construction that the adjacent borehole can be adequately heated to combustion supporting temperature without contacting the wall of the -borehole with combustion gas from the heater-and without overheating'the conduit on which the heater is suspended; Another object ofthe inventiomis taprovide a downhole heater of .high efliciency, for initiating in ,situ combustion in a carbonaceous stratum. jAfurther obje'ct is to provide downhole heating apparatuswhich prevents overheating .of the apparatus. I Other objects of the invention will become apparent upon consideration of the accompanying disclosure.

circulatesaround the feed line to the'heater and also in contact with the exhaust line therefrom. The heater is preferably made of a length which corresponds to the thickness of the formation to be ignited so that the upper end of the burner is adjacent the upper level of the formation and the exhaust conduit extends to the lower level of the stratum. In this manner heat is applied rather uniformly to the entire wall of the borehole from the top to the bottom of the stratum.

1 A more complete understanding of the invention may be' had by reference to the accompanying schematic drawing of which FIGURE 1 is an elevation of one embodiment of the downhole heater of the invention positioned in a borehole adjacent. a carbonaceous stratum with the auxiliary apparatus for initiating combustion in a carbonaceous stratum; FIGURE 2 is an elevation, partly in section, of one embodiment of the burner of the invention; FIGURE 3 is an elevation showing another embodiment of a downhole heater in a borehole with auxiliary equipment; and FIGURE 4 is a cross section of the apparatus of FIGURE 3 taken on the line 4-4.

Referring to FIGURE 1, a carbonaceous stratum 10 is penetrated by a borehole 12 in which is positioned a casing 14 closed at the top by well head 16.. 'Conduits .18 and .20 .are provided for introducing combustion air and for withdrawing produced gases, respectively, from the casing. Heater 22 is suspended in borehole 12 Within stratum 10 and isof alength substantially corresponding to the thickness of the stratum. The heater is suspended by means of conduits 24 and 26. Conduit 24 contains a concentric inner'conduit or burner feed line 28 which is supplied with a combustible mixture of fuel gas and air by means of lines 30 and 32, respectively, which connect with a mixing valve 34. A coolant supply line 36 connects with the annulus between conduit 24 and feed line 28.

' Referringto FIGURE 2, the heater 22 includes a burner comprising a metal shell 42 in the form of a cylinderor tube lined with a ceramic material 44 forming a downwardly flared combustion zone or chamber '46, a closure plate 50, an inlet at the upper end thru conduit 28, and outlet 58 at its lower end, and may also include an ignitor 54. Ceramic material 44 may comprise any suitable highly refractory ceramic material such as Babcock & Wilcox Companys fKaokast or Johns-Manvilles 3X Firecrete. These materials are mixed with water to form a plastic mud or mortar whichis introduced into shell 42 onwhich it is held by stainless steel rods 48 welded to the shell at the outer ends. The upper end of burner 42 is closed by plate50 thru whichfeed line 28 passes into the inlet end of the burner.

such as battery 55, through-switch 57. i

An'exhaust conduit 26 makes a U-turn or a turn of and connects with the exhaust endtof heater 22 or 'burnerf42 by means of conduit 58. A conduit 60 connects the annulus around conduit 28 with exhaust conduit 26 just above the heater to provide flow, of coolant therebetween. i 1' FIGURE 3 illustrates an embodiment of theinvention wherein burner 40, feed line 28 and exhaust line 26 are enclosed within a closed tubing 62 within well casing 14 'so as to provide an annular space between the casing and the tubing for injection of air thru line 18 to the combustion area during initiation of combustion, and withdrawal of gas and oil vapor thru line 20 after inverse air injection has been established. Burner 40 comprises an annular burner body 64 surrounding exhaust conduit 26 and is provided with a ring of downwardly directed nozzles or jets 66 on its lower side. Burner 40 is positioned at the level of the upper surface of the carbonaceous formation and the inlet end of the exhaust conduit 26 is positioned near the level of the bottom surface of thestratum so that hot combustion gases traverse the thickness of the formation before entering the exhaust conduit, thereby heating the encasing' tubin 62 along that portion of the tubing lying adjacent the stratum; Air introduced thru conduit 36 cools'the feed line 28 and exhaust conduit 26 down to the burner level and also aids the combustion process at nozzles or jets 66. The cooling air not utilized for combustion is exhausted thru conduit 26. This burner mayalso be fed a combustible mixture, of fuel gas and air as in the embodiment of the invention shown in FIG- URES 1 and 2.

FIGURE '4 merely shows the plan arrangement of the elements of FIGURES and is self-explanatory.

I In either embodiment of the invention shown in the drawing, circulation of a coolant in contact with the feed line to the burner, and the exhaust line therefrom is provided by the construction shown. This is an essential feature of the burner in that it prevents the burning off of the feed line and/ or exhaust conduit during the critical time when combustion of the oil or other carbonaceous deposit in the stratum is eflected. Another advantageous feature of the'burner construction shown lies in the length of its heating section which is co-extensive with the thickness of the formation thereby facilitating initiation of combustion along the entire wall of the borehole adjacent the carbonaceous stratum.

In utilizing the apparatus in initiating in situ combustion, fuel gas is burned in combustion zone 46 (or adjacent nozzles 66) and the hot combustion gases heat the burner shell42 (or tubing 62) adjacent the stratum and the combustion and heating are continued until the temperature of the stratum is raised to the ignition point of the carbonaceous material in the stratum and, at this time, air or other O -containing gas is brought into contact with'the hot stratum so that ignition takes place. When ignition by direct injection is practiced, air is introduced thru line 18 to initiate and sustain the combustion and when the ignition is by inverse air injection, air is injected thru the stratum from a ring of boreholes therein so that it arrives at the hot section of stratum adjacent borehole -12 and initiates and sustains combustion therein. After initiation'of combustion by direct air injection and establishment of ;-a substantial combustion area, inverse The test burner apparatus was constructed of 304 stainless steel, including the lengths of pipe connected to the burner, the exhaust conduit, and crossover conduit 60 (FIGURE 2). In fact, every element shown in FIGURE 2, except ceramic material 44, was constructed of 304 stainless steel. Of course, the apparatus shown and described maybe made of other heat resistant alloys capable of withstanding ambient temperatures in the downhole initiation of combustion.

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: j

1. Apparatus for downhole heating in an oil well comprising in combination an elongated burner including a shell enclosing a combustion chamber, an inlet for fuel and'O at one end of said shell, an outlet for exhaust gases at the opposite end thereof, and an igniter in said combustioncharnber; a fluid feed line connected with said inlet; a conduit concentric with said feed line forming an annular passageway around said feed line for a cooling fluid; an exhaust conduit connected with said outlet, making a U-turn and passing back' along said concentric conduit beyond said inlet; and a connecting conduit between said concentric conduit and said exhaust conduit just above said burner for flow of coolant into said exhaust conduit from said concentricconduit, said fluid feed line, said shell, and said exhaust conduit forming a closed circuit for gases within said well. 1

2. The apparatus of claim '1 wherein said shell is lined with ceramic material.

3. The apparatus of claim 2 wherein said shell is a cylinder of high temperature alloy and said ceramic material forms a combustion zone diverging downstream. I 4.'The apparatus of claim 1 wherein said burner is positioned in a well bore adjacenta carbonaceous stratum; said feed line is connected with a source of combustible mixture of fuel and oxygen above ground; said concentric conduit is connected to a source of air; said exhaust conduit is vented to the atmosphere; and said igniter is an electrical heating means.

5. The apparatus of claim 4 including a casing in said well bore extending to a level adjacent the top of said air injectionis readily instituted by'cutting off'the flow of direct air thru line '18 and injecting air thru the stratum to-the combustion-area from air injection boreholes positioned close by.

When utilizing either direct or inverse air injection to initiate the combustion of carbonaceous material around borehole 12, the burner-is'withdrawn from the borehole after combustion is .well established. Borehole-12 becomes a production borehole during inverse air injection through 10116201 moresurrounding air injection boreholes and production is removed thru'line 20 or thru tubing inserted thru well head'l'6', by conventional means. During direct injection insitu combustion, borehole 12 serves as an'air'injection borehole and produced hydrocarbons and combustion gases are removed from surrounding boreholes by conventional means.

burner constructed substantially as shown in FIG- URE 2 was utilized on several occasions to initiate combustion'in tar sands at a depth of 50 to 75 .feet below the surface. The time required to heat. the tar-sand adjacent the borehole in which the burner was positioned toa temperature sufiicient to support combustion and to actually initiate combustion in the tar sand was about two days in each instance. In contrast, the best available electric heaters required about 7 days and it was extremely diflicult to prevent damage to the electric heaters.

line, said concentric conduit, and said exhaust. conduit pass; conduit means connected with said well head for injecting combustion-supporting gas into said borehole 'for combustion of carbonaceous material in said stratum;

and conduit means'connected with said well head for re-v moval of combustion .gases and produced fluids.

6. Apparatus for downhole heating in an oil well comprising inwcombination an elongated upright burner including a shelbencldsinga combustion chamber, inlet .rneans forfuel and 0 at the upper'end of said shell, and

an'outlet-for exhaust gases at the lowerend of said shell; an exhaust conduit leading from said outlet upwardly out of-said well; feed conduit means connected with said inlet means for'feeding fuel and O to said burner, extending upwardly out of said well; andconduit means for circulating cooling fluidalong said feed conduitmeans and said exhaust'conduit leading outof said well, said burner and'connect ing conduits forming a closed circuit for gases "within said well so as to prevent contact of heater combustion gases with said stratum.

- 7.1 Tlie apparatus of claim "6 wherein said burner,isaid feed line, and said' exhaust conduit are housed in a well tubing 'forming an annulus with said borehole and including an inlet for air in said tubing at its upper end whereby air-circulates around said-feed line and exhaust conduit and passes into the combustion area from which unburned air passes with combustion gases into the lower end of said exhaust conduit.

8. The apparatus of claim 6 wherein said burner surfounds said exhaust conduit and comprises a ring of jets extending downwardly from said burner.

References Cited in the file of this patent UNITED STATES PATENTS Kweager May 3, 1927

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