US2847071A

US2847071A - Methods of igniting a gas air-burner utilizing pelletized phosphorus

Info

Publication number: US2847071A
Application number: US535462A
Authority: US
Inventors: Priester Coral L De
Original assignee: California Research LLC
Current assignee: California Research LLC
Priority date: 1955-09-20
Filing date: 1955-09-20
Publication date: 1958-08-12
Anticipated expiration: 1975-08-12

Description

c. DE PRIESTER METHODS OF I NITING A GAS AIR-BURNER.

G UTILIZING PELLETIZED PHOSPHORUS' Aug. 12, 1958 Filed Sept 20, 1955 m M. E s R m a 0% m T JU- N E m .a m NL T M A G G w I l c F F. Y B

FIG.2

United States Patent METHODS OF IGNITING A GAS AIR-BURNER UTILIZING PELLETIZED PHOSPHORUS Coral L. De Priester, Fullerton, Califi, assignor to California Research Corporation, San Francisco, Calif., a corporation of Delaware Application September 20, 1955, Serial No. 535,462

2 Claims. (Cl. 166-89) This invention relates to methods of generating heat in subterranean formations penetrated by a wellbore and relates more specifically to methods for generating such heat to ignite downhole gas-air burners.

The use of downhole gas-air burners for well stimulation and for initiating underground combustion drive in secondary recovery operation is becoming increasingly common in the petroleum industry, and the use of such devices offers a number of advantages over other ignition and well stimulation methods and systems. Such burners usually are disposed adjacent the formation to be treated and are supplied from the surface with a mixture of fuel gas and an oxygen-containing gas. A number of ignition methods have been proposed for such burners, but so far as I am aware none of such proposed systems have been entirely satisfactory. Some of such burners are ignited by electrical means such as an electric heating coil or a spark plug disposed in or adjacent the burner combustion chamber and energized from the surface to produce the required temperature for ignition. However, such systems have the disadvantage that they require an electrical conduit from the surface to the burner location, thus increasing the complexity and cost of the burner installation and increasing the possibility of malfunctioning through failure of the electrical conduit. The use of such systems has the additional disadvantage that the electrical igniting units often fail, owing to the elevated temperature to which they are exposed adjacent the burner, and this failure usually necessitates theremoval of the entire burner assembly from the well bore for replacement or repair.

Numerous chemical methods have been proposed for igniting downhole gas-air burners or for otherwise providing an elevated temperature in a well bore. One proposed system for heating the well bore and contacting the formation with alkali metal hydroxides utilizes sodium or potassium capsulated in a suitable watersoluble material and injected into the well bore. Water is then injected into the well bore to dissolve the capsulating material and react with the sodium or potassium to produce the desired exothermic reaction. However, this system is not suitable for burner ignition owing to the fact that heat is released from the reaction at a high er rate than can be utilized, resulting in a violent'reaction and expulsion of the unreacted sodium from "the burner prior to ignition of the gas-air mixture. This system has the further disadvantage of requiring the injection of water into the formation to dissolve the watersoluble coating, thus creating the possibility of producing water blocking of the treated formation.

Broadly the present invention contemplates the use of a pellet of elemental phosphorus encased in an inert solid having a melting point below the temperature at the burner location. The pellet is injected into the formation through tubing running from the surface to the burner, and is lodged in a position in the burner to produce ignition. The flow of the gaseous combustible mixture over the pellet produces or hastens melting of exposure of the elemental phosphorus to the passing gaseous combustible mixture the phosphorus reacts with the oxygen .in the mixture, is ignited and subsequently ignites the gaseous combustible mixture.

It is therefore an object of the present invention to provide improved methods and apparatus for igniting downhole gas-air burners.

It is an additional object of the present invention to provide methods of igniting a downhole gas-air burner utilizing the delivery to the burner location of selected chemicals capable of producing an exothermic reaction.

It is a further object of the present invention to pro-1 vide methods for igniting a downhole gas-air bnrnerin which a selected chemical capable of producing an exothermic reaction is delivered to the burner to produce ignition without requiring the injection of extraneous ma.- terials into the well bore.

It is a further object of the present invention to pro. vide methods of igniting a downhole gas-air burner by exothermic chemical reaction such that no residue from the reaction .or delivery process remains in the burner. system. a

It is an additional object of the present invention to provide methods of ignitinga downhole gas-air burner. which do not require the use of electrical cables or wire.- lines from the earths surface to the burner location;

I It is a further object of the present invention to provide methods of igniting downhole gas air burners utiliz-- ing a pellet comprising elemental phosphorusencased in. an inert solid having a melting point below the tem-- perature existing at the burner location. 1

It is a further object of the present invention to provide a method of igniting a downhole gas-air burner utilizing. a pellet comprising elemental phosphorus encased in ice; in which the pellet is delivered to the burner location and.- the encasing ice melted to expose the elemental phosphorus to the passing gaseous combustible mixture. v

Objects and advantagesother than thoseset forth above will be apparent from the following description when read in connection with the accompanying drawing, in which:

Fig. 1 illustrates a representative pellet suitable for use in the present invention in connection'with a' portion of valving associated therewith;

Fig. 2 illustrates the disposition of representative equip-1 ment in a well bore for carrying out the methodof-the present invention; and

Fig. 3 illustrates a device for retaining apellet: in a predetermined position in the combustion chamber;

Referring more particularly to the. drawing .by characterv of reference, Fig. 1 illustrates the disposition of a repre-'v sentative pellet of the present invention in aportion ofthe delivery assembly. As shown in .Fig. 11, referencecharacter 11 designates particlessofelemental-phosphorus encased in a suitable solid material 12to form a pellet 13. Material 12 may be any suitable material which is inert" to the elemental phosphorus and which'has a melt-ing; point below the temperature at the locationof the burner. 1 Suitable inert materials include benzene, tridecanerand'; triethylene glycol. Additionally, I have found that water is a particularly desirable inert material to use, since it is economical and eaily solidified. Pellet 13 may be formed in a mold or any other suitable means to form 16 and tubing 20 are connected at their lower ends to aeui'ta'ble' gas' air'burner shown diagrammatically a's21. The combustible mixture is supplied to the burner through the annulus between tubing 16 and tubing-20. Burner 21 may comprise a combustion chamber portion 22 into which conduit 16 leads and in which the combustion occurs. Combustion chamber 22 is preferably terminated at'its lower end by restricting passage 23 having a diameter less than the minor dimension of pellet 13. Burner 21 may further comprise a conical exhaust portion 24 for'directing the combustion products from combustion chamber" 22 into contact with the formation and/or the fluid in the well bore. A gas-air burner having featuressimilar to those illustrated in Fig. 2 is disclosed" and claimed in the copending application of C. L. DePri'ester and C. N. 'Simm, Serial No. 525,505, filed August 1, 195. The gaseous combustible mixture to be burned may be of any suitable type, such as a mixture of natura'l'gas and air,'and such mixture is supplied from suitable source's designated generally as' 25 and 26 to the annulus between tubing 20 and tubing 16.

Inope'ration of the present invention, pellet 13 is placed in the upper end of tubing 16 by opening valve 17 with valve '18'closed. 'After placing the capsule in the delivery chamber, valve 17 is closed, and valve 18 is opened to permit pellet 13 to fall freely through tubing 16. If desired, suitable lubricating material may be placed around pellet 13 to facilitate its fall through tubing 16, although I 'have found that when ice is used as the encasing material,"'the normal melting of the ice in the delivery chamber or tubing provides satisfactory lubrication.

Pellet 1'3 falls freely through tubing 16 to combustion chamber 22 and becomeslodged in the restricted opening 23 at thelower end of combustion chamber 22. The gas-air'mix'ture may-then be supplied from

sources

25 and 26 through the annulus between tubing 20 and tubing 16 to combustion chamber 22 to hasten the melting of the encasinghiaterial. When the' encasing material melts s'ufii'ciently to expose the elemental phosphorus particles 11' to the gas-air mixture, oxidation of the phosphorus occurs and produces a sufficiently elevated temperature to ignite thegas-air mixture. The gas-air mixture combustion flame then stabilizes in combustion chamber 22 to produce the desired heating effect.

\ In tl'ie embo'diment described in connection with Fig. 2, thepellet lodged in the restricted opening 23 in the lower end of combustion chamber 22, and it was' assumed that the pellet of phosphorus and'ice was completely dissolved so that no debris remained. However, if the nature of the pellet should be such that plugging of the burner could possibly result from'debris, the arrangement illustrated in Fig. 3 can be utilized to prevent such plugging. As shown in Fig. 3 tubing 16 is terminated at its lower end by a basket member 31 having perforations '32 therein. Me'mber'31 is clbsed atits lower end to retain capsule 13 therein. Basket member 31 may be positioned in or just above combustion chamber 22 so as to retain pellet13 in this location after it is dropped through tubing 16. Pellet 13 dissolves as before, and the phosphorus is oxidi'zed by the gas-air mixture to produce therequired ignition temperature. Any undissolved matter of aparticle size larger than perforation 32 is retained in the basket member-31 so that no plugging of burner orifices can result.

The method of the present invention was tested under simulated downhole conditions using injection apparatus similar to that shown in the drawing. A %-1HCh diameter pellet was formed by freezing phosphorus in water in a copper mold surrounded by Dry Ice. The pellet was injected through 0.824-inch I. D. tubing a distance of approximately six feet into thecombustion chamber of a gas-air burner submerged in'water. Water was utilized in these particularexperiments-rather than crude oil, but the nature of themedium surrounding the burner is immaterial to the present process. A gas-air mixture was then supplied through the annulus between the tubing to the burner, and this mixture was successfully ignited a number of 'ti'mesi In connection'with these experiments, the effects of pressure-and temperature on the reaction of phosphorus with oxygen were investigated to some extent, and it was found that at a temperature of 70 F. and above, the desired reaction proceeded satisfactorily under pressures ranging from one atmosphere to p. s. 1. g.

It will' be seen that the method of the present invention does not require the introduction of anyextraneous materials such as water or other chemicals into the well bore oi burner to dissolve the encasing material, and further," there is no debris remaining from the pellet, since thepho's'pho'rus'will be substantially consumed by oxidation and the encasing 'material will be blended in with the other'well b'ore fluids. Further, the ignition method of thejpresent'invention may easily be repeated anyde'sired numberof times until the required ignition o'c'curs.

Although but a fewembodiin'ents' of the present invention'have'been'described, it will be apparent to those skilled in' th'e' art that various' changes and modifications may be made thereinwithou't departing from the spirit of"the invention or the scope of the appended claims.

1; The rnethodof igniting a downhole gas-air burner comprising the steps of introducing into said burner a'pellet comprising elemental phosphorus surrounded by ice, said ice melting in said burner to expose said phosphorus, and supplying a gaseousfcombustible, oxygencontaining mixtureto' said burner for oxidizing said' exposed phosphorusto'produce a temperature sufiicient to ignite said combustible mixture.

2. The method of igniting a downhole gas-air burner connected to the surface of the earth through a length of tubing'comprisingthe' steps of'inj'ecting a pellet through said tubing to position said pellet adjacent'said burner, said pellet comprising elemental phosphorus surrounded by ice; said ice melting atthe temperature existing at the location of said burner to expose said phosphorus, and

supplying a gaseous combustible, oxygen-containing mix- 1,278,217 Reid- 'Sept.'10, 1918 2,188,737 I-IiXOH Jan. '30; 1940 2,558,726 Barker July 3, 1951 2,630,307 Martin Mar. 3, 1953 L 2,747,672 Simm May 29,1956

Claims

1. METHOD OF IGNITING A DOWNHOLE GAS-AIR BURNER COMPRISING THE STEPS OF INTRODUCING INTO SAID BURNER A PELLET COMPRISING ELEMENTAL PHOSPHORUS SURROUNDED BY ICE, SAID ICE MELTING IN SAID BURNER TO EXPOSE SAID PHOSPHORUS, AND SUPPLYING A GASEOUS, COMBUSTIBLE OXYGENCONTAINING MIXTURE TO SAID BURNER FOR OXIDIZING SAID EX-