US1535776A - Oil-well heater - Google Patents

Description

A ril 28, 1925.

G. s HOLLISTER OIL WELL HEATER Filed July 13, 1922 2 Sheets-Sheet 2 Patented Apr. 28, 1925.

UNITED STATES PATENT OFFICE.

GEORGE S. HOLLISTER, OF BURKBURNETT, TEXAS, ASSIGNOR TO JAMES B. PAULEY, TRUSTEE, OF CHICAGO, ILLINOIS.

OIL-WELL HEATER.

Application filed July 13,

To all whom it may concern:

Be it known that I, Gnouon S. HoLLIs'rnu, a citizen of the United States of America, and a resident of Burkburnett, county of lVichita, and State of Texas, have invented certain new and useful Improvements in Oilell Heaters, of which the following is a specification.

My invention relates to apparatus for heating oil wells so as to increase the flow of oil therefrom, and has for its object improvements in such devices.

A typical oil well may be represented as a hole about six inches in diameter and extending down about two thousand feet, more or less. At about this depth is found a stratum of rock, as limestone, some live or ten feet thick. Beneath this limestone is usually a stratum of sand from which is obtained a flow of gas, and hence is called gas sand. Under the gas sand is found forty or fifty feet of oil sand resting on a rock foundation. The hole is drilled down thru the oil sand and some eight or ten feet into the rock foundation. That part of the. hole which is above the sandstone is lined with pipe or tubing, but that which is below is not lined. The hole in the rock below the sand is in the nature of a trap or catch basin to receive sand caving in above.

Crude oil has a paraffin or an asphaltum base, and contains several volatile hydrocarbons. It is drawn from the well by a pumping operation which commonly places the oil sand under a comparatively high degree of vacuum. Under these conditions the volatile oils change to gas, and in so doing they absorb heat and consequently cool the oil bearing sand or rock in the immediate neighborhood of the well. This cooling results in solidifying the parafiin or asphaltum in the pores in the sand thru which the oil must flow to be pumped. This process gradually seals the walls of the well and stops the flow of oil. The remedy is to melt these solid deposits by the application of heat, and to pump them out when melted.

The best means for accomplishing this result is to use an electric heater, but there are a good many difliculties connected with, this operation and it is the object of the present construction to overcome these difficulties. The hole to be heated is less than 1922. Serial No. 574,649.

six inches in diameter, is frequently forty feet or more in length, and is down some two thousand feet below the surface of the earth. The heater must be immersed in the oil in the well and that oil must serve as a circulating medium to convey heat from the heater to the walls of the well. An electric heater has a high temperature at the heating element, and such high temperature has a tendency to form carbon deposits from the oil. The device must be so constructed that such deposits will not short circuit the current flowing thru the heating element.

To heat the walls of a hole forty feet or more long, the heater which is immersed in the oil of the well should be twenty feet or more in length. Such heaters are subject to two forms of peril, both of which have been very destructive to the heaters heretofore used. One of these is that the oil level in the well will sometimes subside and leave the upper end of the heater surrounded by gas in a confined space. Under such circumstances the ordinary heaters burn out at the upper end because there is no circulation of oil to carry away the heat generated in the heating element. Another menace which frequently destroys the heaters heretofore made is the caving in of the walls of the hole and the burying of the lower part of the heater in sand. Insuch cases the lower part becomes burned out and de stroyed. The present heater is designed to overcome the dangers arising from both of these conditions, neither one of which can be avoided.

In the accompanying drawings I Fig. 1 is a section of the lower part of an oil well, the present device being shown in elevation;

Fig. 2 is an enlarged elevation of the upper part of the device, the shell of which is shown in section;

Fig. 3 is a still more enlarged section of part of the devices shown in Fig. 2;

Fig. 4 is a section on the same scale as Fig. 3 of the lower part of the device shown in Fig. 1; and

Figs. 5, 6. 7 and 8 are sections on correspondingly marked lines of Figs. 3 and l.

The well is provided with a casing ll which extends down to the limestone stratum which overlies the gas and oil bearing sand. The heater is enclosed in a shell formed of parts 12 and 13 which are connected to- 1 thru this pipe, and on the upperend of the pipeis a stnihng. box 4C9 designed to prevent any quantity of water getting into thesectionlQ ot' the shell. l

The upper end of the coupling 14 is re duced in' diameter, and theentire' coupling" is boredoutior the-reception of pipe 19; on the lower end of which is a cap 20. The

' upper end of coupling 14:- is counterbored to receive" the gland 21' of' a stulhng: box for V pipe 19, which pipe is screwed into said gland. The gland 2'1is held down'hy acap 22 which-is screwed on the outside of the upper end of coupling I l. Screwed upon the cap 22 is a short piece of pipe 23, and on the upper end of this pipe is a block" which is bored out to form a second stuthng: box having a gland 25 and cap26.

Ata point near'the neck 16, the wire rope. 15' isbound' by wire' 27 wrapped around it, and the wires of the rope are unwound to form strands 28 which extend downward and thin holes 29in lugs 30 on coupling 14'. Thecore 3'1ofthe rope which is left when thesejstrands are unwound cari'ies the insulated wires 3.2 and 33 and is the body which is packed against moisture by the upper stalling box 2 l-26. i

Theca'p 22 has its upper end closed by a plate 34'. thru which plate are small holes for the passage of insulated wires 35, andilb, which extend down to heating elements helow; Above plate 34 these wires are spread apart and have secured thereon" metallic connections 37 and 38 which serveto form separable connections to the wires 32 and 38. The space within the tube23ianld around the connections 37' and 38' is filled. with sheets of nica 51 which are bored out to receive said connections.

The wire 36 is connected thrir bridge 3 with the terminals 38 of heating unitsSS), and wire is connected thru bridge 40 with terminals ll of two other lieatiiigniiits of the same hind. Art the lower endsthese heating units are connected together by bridges and 43, the corresponding terminals of t'he'hea-ting units being indicated by 38 and' ll These heating units niay be 7 of any desired type, but those'illustrated in the drawings are of the kind described in patent to Abbott, No. 1,367,31, issued February 1,1921.

The heating units 39 are each inclosed in a inetaltube 44:, and the ends of these tubcs are secured firmly in blocked-5 and 46 as show-11in Fig. 4. Secured upon the block 45 in liquid tight manner is the cap 20, and

similarly. secured to the block 46 is acap 4?. As constructed, the heating units and the caps protecting their electrical terminals are suspended by pipe 19 from the gland 21 in the coupling 14, and this coupling in turn is suspended by strands 28 of rope 15. The shell 18 is carried on the coupling l l and has its lower end closed by a plug 48.

@wing to the great length ofthe device as compared to its diameter, the drawingsshow the parts broken oil. For the-purposes of abetter understanding it is desirable to give some of the diinen'sions found useful, tho it should be understood that thesedi'niensions may be varied as circumstances may require. The shell will ordinarily be iron'r four and one half' to live inches in di-' aineter. The distance between blocks 45 and 4-6 may conveniently be from twelve to six teen feet, and the distance-from the cap 20 to the coupling ld may be some four or five feet. The coupling 14 and the plug d8 in'alze liquid tight jointsat' the twoends of the shellisect'ion 13.

Assumingdiniensions such as those given, the" shell 13 is filled up to some point between cap 20 and coupling 14 with some liquid, as herosene, which is a non-conductor of electricity. The space above the liquid is an air space, which it is desirable should be two' or three feet in length. VViththe device in this condition it is lowered into-the well to' a point about inid w-ay' of the) oil,

bearing sand or rock, and should be entirely immersed in the oil-in the well; If the electric current be t'henturned on, the center or axial part of the long column of kerosene will beheated by the heating units, and the outside of this column will be cooledby con tact of'the shell 13'with the oil in the well; Under these conditionstherewill be set up a a circulation of the kerosene, which circulation' will consist; of a central upward flow along the heating units and; an annular downward flow along the inner wall of shell- 13 Thiswill convey heat from the heating units to the shell convection as distinguished from radiation", and from here it will be adiated thrtrthe wall of shell- 13 to the oil in the well. Fronr this point the heat will be conveyed partly by radiation, and partly by convection, to the sand or rock which: has its pores choked with congealed paraffin. I

If we assume that while this heating process is on, the walls of: the Well cave in and bury some four or five feet ofthe lower end of shell 13 in a solid bed of sand, then all convection at this surface will cease and heat be conveyed to thev sand solely by radiation. As sand is a comparatively poor conductor of heat, this lower buried portion of the device will become overheated unless some means is provided to carry away the heat and thus prevent such overheating. The circulating kerosene is such means. The same is true in case the oil in the well should subside and leave the upper portion of the shell 13 surrounded by nothing but the gas in the well. The circulation of the kerosene will carry the heat from the. overheated portions to the portions of shell 13 which are in contact with oil in the well.

In oil wells there is always a certain amount of moisture, much of which condenses on the walls of the casing 11 and runs down into the well. Some of it also condenses on the rope15 and, it not prevented, will run into the apparatus and short circuit the electric connections. The stuffing box 49 is designed to prevent this, but it is not possible to make a perfectly tight stufiing box for a wire rope. Some water will get by the stuffing box 4-9. The most of the water thus getting by this stuffing box will run down the inside wall of the pipe 18 and the inside wall of shell sec tion 12 to the coupling 14. By an inspection of Figs. 2 and 3 it will be seen that the space inside section 12 and above coupling forms a trap 50 into which water may accumulate until it. rises up to the top of cap 26 before it can find entrance to the electrical connection. Of the water which runs down the rope 15, the greater part will follow the strands 28 into the same trap. Of the water which reaches the core 31 and follows down that core, a considerable quantity will be deflected by the conical top to the cap 26 and will flow intothe same trap.

These various precautions are designed to prevent water from reaching the electrical connection, but in spite of all precautions some water will get by in the long run. Such water will flow down the core 31 to the mica sheets 51, and by capillarity will cause a short circuit between the terminals of wires 32 and at the place where they connect with the connections 37 and 88. A short circuit at this point will cause much less damage than would be caused by water running down the wires 35 and 36 and causing a short circuit at the heating units.

The various devices involving the stuliing boxes and drainage into the trap will ordinarily prevent water getting to the electrical heating units. The mica packing 51 and the electrical connections at 37 and 38 constitute a safety device to protect the heating units in case the other devices should fail.

Heat is conveyed to the oil in the well, from the exterior of the shell 13. The heating units are enclosed in metal tubes 4% which are immersed in a circulating medium contained within the shell 13. The quantity of circulating medium is sufficient to completely submerge all parts directly heated by the heating units. It will be noticed that the circulating medium is not directly in contact with the heating units but is heatet indirectly thru the tubes i l, blocks 45 and lo, and caps 20 and "71. It will also be noted that the oil in the well is not heated directly by the parts ust enumerated, but indirectly thru the circulating medium and the shell 13. This process of indirect heating eliminates the formation of carbon deposits which, in ordinary practice, have been found to occur and cause trouble at numer ous and unexpected places and in numerous and unexpected ways.

lVhat I claim is:

1. In a device of the class described, a shell composed of two sections of tubular form, an interior coupling connecting the sections and having an opening therethru, a pipe supported by the upper end of the coupling and extending downward thru the opening therein, a heating device located in the lower section of said shell and supported by said pipe, and electrical connections extending downward thru said pipe to said heating device.

2. In a deviceof the class described, a shell composed of two sections, a coupling connecting said sections, a heating device located in the lower section and supported by said coupling, electrical connections extending from the upper section thru an opening in said coupling to the heating device, a circulating fluid partly filling the lower section and submerging the heating device and means for protecting the electrical connections from contact with the circulating fluid.

3. In a device of the class described, a shell composed of two sections, a coupling connecting the sections, a wire rope extending into the upper section, said rope having its exterior wires separated from the core thereof and attached to the coupling for supporting the device, a heating device located in the lower section and suspended from the coupling, and electrical connections extending from the core of the rope thru said coupling to said heating device.

4. In an oil well heater, a shell composed of two sections, a coupling connecting the sections, devices mounted upon the coupling and extending upward in the upper section, said devices being of less diameter than the interior of the shell so as to leave an annular space between the shell and the devices. a wire rope extending into the upper section of the shell and serving to support the apparatus, and electrical connections extending from the core of the rope thru said devices and said coupling to the lower section, said parts being so constructed that moisture conextending to the heating element, and a trap Iii) formed in the upper part of the shell and an ranged to receive and retain water flowing down the rope.

6. In a device-of the class described, a shell having an electric heating element in the lower portion thereof and a Water trap in the upper portion, and a wire rope by which. the shell is supported, the strands of said rope being so arranged that water running; down said rope will be conveyed by said strands to said trap.

7. In a device of the class described, a shell having a water trap in the upper portion thereof, a wire rope by which the shell is supported, and a pipe extending upward from the shell and serving to protect said rope, said parts being so arranged that upon moisture entering the pipe and flowing down the interior wall of the pipe and down the exterior of the rope will be conveyed from both places to said trap.

8. In a device of the class described. a

shell, an electric heating element therein, a

rope by which the device is suspended, an

ment in case water gets past the retarding.

devices.

9. In a device of the class described, thecombination with a heating device, an electric circuit therefor, and means for normally preventing water from gaining entrance to the channel leading to the heating device, of a safety device located in such channel and serving to shortcircuit the heating device by any water which may getpast the meansfor normally preventing such entrance.

10. In a device of the class described, the

combination with a heating unit, an electric circuit therefor, and means for normally preventing water fromv gaining entrance to:

the channel leading to the heating unit, of electrlcal connections 1n said circuit and located in said channel, and a strata 0t H1- sulatins; material such as mica filling such channel around said connections.

GEORGE S; HOLLISTERW

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