US 3859503 A
A vertical sucker rod string formed of lengths of sucker rods, each having means for attachment at each end thereof to adjacent sucker rods, is provided with electric heating means for maintaining the temperature of the crude oil being pumped to the surface above a preselected level to prevent the congealation of paraffin. An electric heating element coextensive in length with the rod is disposed in a small diamater bore hole in each rod. A solid heat conducting electrical insulation completely fills the bore hole in the rod around the heating element. Couplings are provided between adjacent sucker rods to obtain electrical continuity between the heating element in each of the adjacent rods. A terminal coupling provides a connection between the heating element of the lowermost sucker rod and the sucker rod, whereby the sucker rod string serves as a conductor to complete the circuit for energizing the heating elements.
Claims available in
Description (OCR text may contain errors)
United States Patent 1191 Palone Jan. 7, 1975 41 ELECTRIC HEATED SUCKER ROD 57] ABSTRACT Inventor: Richard 1332 Efie, A vertical sucker rod'string formed of lengths of Tl11$a,01 1a- 74112 sucker rods, each having means for attachment at  Filed, June 12 1973 each end thereof to adjacent sucker rods, is provided with electric heating means for maintaining the tem  Appl. No. 3 9, perature of the crude oil being pumped to the surface above a preselected level to prevent the congealation of paraffin. An electric heating element coextensive in  US. Cl 219/278, 166/60, 2211996550461, length with the rod is disposed in a Small (Hammer  Im Cl H05) 3/02 E2") 43/24 bore hole in each rod. A solid heat conducting electri- 58 Field of Search 219/277, 278, 541, 307, g f fills the we y 219/306; 56/57, 58 6042302, 303 around t e eatmg e ement. Coup 1ngs are prov1 e 7 between ad acent sucker rods to obtaln electncal con- [561 1:12:21 $511 2"5351115131'Zi$"$$i ci fniii tion between the heating element of the lowermost I gg t y sucker rod and the sucker rod, whereby the sucker rod string serves as a conductor to complete the cir- 1,970,295 8/1934 F1tzpatr1ck r 219/278 UX cuit for energizing the heating elements 2,598,280 5/1952 McLean 219/278 X 2,728,396 12/1955 Carpenter. 219/277 X 2,812,818 11/1957 Brusco 219/278 x 4 Chums 4 Drawmg F'gures Primary Examiner-A. Baltis a Attorney, Agent, or Firm-Head & Johnson 46 42 40A 52 40B 40 44 42 3e 1" l 1 i If 4 1. 1
l T :Iklffjjll': If: llilllji'lkl' I I I II i L 36 3 4, 51) 42 46 36 l Nm I //l 36 44 38 36 ELECTRICAL RESISTANCE 3 HEATING ELEMENT ELECTRIC HEATED SUCKERZ non BACKGROUND AND OBJECTS'bF-J "IE INVENTION When an oiliwell is completed the pressure of the oil producing formation'sometimes is' sufficiently.great-ta cause the crude oil to be forced to the earths surface. Such wells are called flowing wells. Eventually, however, inmost instances the pressure of the formation falls below that which is necessary to force the,crude 'oil to the earth s surface. This requires some means of pumping the crude oil. The most commonly" used means of lifting crude oil from a subterranean formaperature. At the temperat aie in the oil producing forrnation the crude oil is in Iiquid form but as it is pumped to the earths surfa cein a tubing string it passes upwardly through areasa of gradually declining temperatures. If Cl'UdQ/bI lfihaS a high paraffin content which congeals at higher than normal temperatures, an area .is reached iii-the upward travel of the crude oil wherein the temperature inside the tubing falls below that at which t'he paraffin contentof the crude congeals. At
pletely pluggedby the congealed paraffin.
In some areas the problem of congealed paraffin is such that wells cannot be economically produced. Othv ers have suggested means of combating the problem of paraffin formation in wells, such as theme of scrapers attached to the exterior of the sucker rods which are configured to scrape the interior of the tubing to dislodge paraffin as it accumulates. The dislodged paraffin 40 is then carried upwardly by the flow of fluid to the surface. This procedure, however, is not completely satisfactory in all instances since in some cases the rate the. paraffin congeals is so great the scrapers cannot keep it dislodged. In addition, the scrapers do not help prevent the accumulation of paraffin on the sucker rods and thereby even though the interior of the tubing is scraped the accumulation of paraffin around the sucker rods can soon approach that at which the interior of the tubing is blocked.
Others have provided heating elements positioned in the bottom of wells including electrical conductors attached to the exterior of the tubing. In some instances the heating elements are attached to the tubing at points above the lowest level at which the crude oil reaches the temperature at which paraffin content begins to congeal. In this method the electrical conductors to the heating elements are carried on the exterior of the tubing. This procedure works satisfactorily except that it is difficult to run tubing with electrical conductors. In addition, any failure of the heater or the conductors requires that the tubing string be pulled, a relatively expensive process.
This invention is directed towards a simplified means of maintaining the temperature of crude oil as it is pumped to the earths surface sufficiently high to prevent the formation of paraffin. The invention overthis point the paraffin congeals on the inside of the tub- 30 fig and on the outside of the sucker rod. If the process continues long enough the tubing can become comcomes the disadvantages of the other known methods of combating paraffin accumulation in oil wells.
It is therefore an object of this invention to provide are improved means of maintaining the temperature Within the interior of the tubing string utilized to pump crude oil so as to prevent paraffin congealation. More particularly, an object of this invention is to provide a sucker rod configuration including means of applying electrical energy to the sucker rod so as to raise the temperature thereof and thereby raise the temperature of the crude oil pumped by the sucker rod to the point wherein the temperature of the crude oil will not fall below that at which severe paraffin congealation takes place.
" Still more particularly, an object of this invention is to provide a sucker rod including improved means of heating the sucker rod with electrical energy.
Another object of this invention is to provide a sucker rod including means of electrically heating the sucker rod and means of conducting electrical energy from one sucker rod to the next.
Another object of this invention is to provide an arrangement for electrically heating sucker rods as used in producing oil wells to prevent the accumulation of paraffin within tubing and including means of conduct ing the heating element to ground at a preselected point within the sucker rod string.
These and other objects will be fulfilled in the following description and claims taken in conjunction with the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view of a pumping unit showing means of use of the electric heating sucker rods of this invention.
' FIG. 2 is a cross sectional view of a coupling and an electrically heated sucker rod showing means of electrically coupling one sucker rod to another.
FIG. 3 is a cross sectional view taken along the line 3-3 of FIG. 2.
' FIG. 4 is a cross sectional view as in FIG. 2 showing a terminal arrangement for connecting the electrically heated wire to the sucker rod body.
. SUMMARY The invention is a sucker rod construction providing I means of heating petroleum produced in an oil well so as to raise the temperature of the petroleum above that which results at which paraffin congeals. The sucker rod, which has means at each end for attachment to an adjacent sucker rod, has a small diameter axial bore through the entire length. An electrical heating element is positioned within the bore andis surrounded by heat conducting electrical insulation. Means is provided for applying voltage to the element to cause current to flow through it and thereby heat it. Heat flows through the electrical insulation to the sucker rod and then to the petroleum fluid being pumped to the surface. I-Ieat is thereby applied to the petroleum fluid to maintain the temperature thereof above the congealing temperature of paraffin. Couplings are provided between adjacent sucker rods to obtain electricalcontinuity between the electrical heating element in each of the adjacent sucker rods. Terminal coupling is provided for connecting the lower end of the heating element in the lowermost sucker rod to the sucker rod. In this way the sucker rod string serves as a conductor to 'jcompletethecircuit by whichthe heating element is energized. a K
DESCRIPTION PREFERRED EMBOIDIMENT 1 Referring to the drawiiigs and first to FIG. 1 the basic arrangement for pumping an oil well byreciprocation of a sucker rod stripg is shown. The arrangement int achme nt to a polished rod 18. The polished rod extends through a stuffing box 20 in a well head 22 attached to the upperend of casing ,24.' Pipe 26 extends from 'the well head and'carries the produced petroleum his a tankbattery 'for further distribution;
The end'of thewalking beam 12 opposite horse head 16 is attached to a counter weight 28- driven by a crank arm 30, the counter-weight and crank arm being attached to, a' connecting rod ,32extending to the walking beam 12. The crank arm 30 isattached to a shaft v34 rotated by a gear box (not 'shown),;driven in turn by a prime mover, such as an -electric"moto r., or engine, also not shown. By the rota'tion' of shaft 34" the walking upward extension of the string of sucker rods and is different only thatit-has a smooth external configuration j to=reciprocateagainst packing within the stuffing box "/20 which preventsproduced crude oil from escaping outwardly of the stuffing box rather than flowing embodiment illustrated the heating element is inthe form of a resistance wire 46. When current flows through wire 46 heat is imparted to the sucker rod 36 and thereby to the crude oil surrounding the sucker rod so as to maintain the temperature above that at which paraffin will congeal.
beam-"l2is pivotally reciprocated moving horse head 5; 16 up and down and thereby reciprocating the polished -'rod 18. The pumping jack of FIG 1 deseribed to this "point is a standard means of reciprocating sucker rods in an oil well and form no'part of the invention. The polished rod 18 connects to a string of suckerodswhich extend within a tubing (not seen) within the: casing24, the sucker rod and tubing extending downwardly within the earth to a subterranean crude oil producing formation. In effect, the polishedrod 18'is'an rods as is.;require d.
. To prevent the resistance heating wire 46 from contacting the sucker rod the wire is surrounded by electrical insulation 48 which may be of a variety of compositions and may be, as an example, a mineral insulation. While the main function of the insulation 48 is to prevent electrical contact between the resistance wire 46 and the sucker rod 36 the insulation preferably is of a type which is a good heat conductor so as to conduct the heat of the resistance wire to the surrounding sucker rod.
In order to connect the resistancewires 46 of adjacent sucker rods making up a sucker rod string, it is necessary that electrical continuity be had from one rodto another. FIG. 2 shows one method of accomplishing this. In this arrangement an axial conductive element 50 is centrally positioned within coupling in 52 which may be formed of any insulati'ng material,
such as plastic. It can be seen that the resistance wires may be interconnected for FIG. I shows one means ofimparting electrical en- .ergy t o the sucker-rods. By means of a transformer54 current is supplied' to conductors 56A and 56B. Con- 'duc tor 56A is attached to the exterior of the polished rod ISQandtherebyJtO the sucker rod string. Conductor 56.1355 attached to'g'the' resistance wire 46 which extends the resistance-wire in' each 'ofthe succeeding lower "lengths'of'sucker rods36.
Onejmethod of.;providingjalreturn current'flow isshown in FIGS. land 4. Conductor 56A-is connected i nternally. of the1polished rod 18 and is connected to to the exterior ofpolished rod 18 and thereby to each the rods areiofsolid configuration. ,However,,'in the present invention the suckerrodsineludefanaxial bore hole 38 through-the entire} length of each rod; 'Ass'h'own in FIGS. 2 and 4 onlyafs nall portion of the lengths of i the sucker rods areshownln FIG. 2 the right hand-portion'shows an end of a sucker rodin' cross "section-while I in-the left hand portion an end of a suekerrodisshow'n" in exterior configuration, with a coupling .40 shown in" I cross sectional configuration as used to connect in'end to'end relationship the adjacent sucker rods. Each of f the suckerrods 36 includesan enlarged shoulder por'-' tion 42which. terminates inan externally threaded pin of the successive lengths of 'suckerf rods '36. To provide a return path of current flow the resistance wire 46 must be connected at some point to the sucker rod string. In order: to achieve this arrangement FIG. ,4
shows a terminal conductive means including a terminal conductive element 58 positioned in the interiorlof a coupling 40. The conductive element 58 isjof cohiduc-iv f I tive materiahsuch as copper or copper' a'll oyl or the lik ef vand communicates the end 46A of there'sistance wire portion 44. The interior of the couplings 40 is threaded at 40A and 408 to threadably receive the externally sucker rods 36 is an electrical heating element. In the portions 58A and 588 at opposite ends thereof; Protr sion portion 58A contacts the end 46A of resistance wire 46. and protrusion 58B engages the pin portion 44 of the'next lower sucker rod 36 to insure connection the resistance wire 46'tfo the sucker rods 36. In addition 'to contacting the 'pin portion 44 the next lower adja': cent sucker rod 36 the conductive element 58 also providescul'rut flow-through coupling 40. Thus,'as showirijf in FIG. 1 the "conducto'r 56B communicates with the re- 156 to the couplings 40 and thereby back t o suck er rods 'i v '36. f
The conductive element 58 includes axialprot'riisi sistance element 46 i'na sucker rod string and conductor 56A connects to the-sucker rod stringitself through i polishedrod 18. so thatacomplet'e path of current flow is provided.
as many successive sucker As crude oil is pumped upwardly in a tubing the temperature gradually lowers until a point is reached wherein with high paraffin content crude, congealing begins. By the use of this invention the number of sucker rods 36 which must be heated can be regulated so as to extend downwardly into the well only that distance required to provide heat to the crude oil in the upper portion of the tubing string. In some wells the length of the sucker rod string which must be heated will be substantially the full length of the tubing. In other wells only the upper portion of the column of fluid being produced need by heated. Between each adjacent length of sucker rod 36 wherein the lower rod is to be heated the conductive element 50 as shown in FIG. 2 is utilized. At the lower end of the string of sucker rods requiring heating a terminal conductive element 58 as shown in FIG. 4 is utilized. The sucker rods below element 58 are not heated.
While the invention has been described with a certain degree of particularity it is manifest that many changes may be made in the details of construction and the arrangement of components without departing from the spirit and scope of this disclosure. It is understood that the invention is not limited to the embodiments set forth herein for purposes of illustration, but is limited only by the scope of the attached claim or claims, including the full range of equivalency to which each element thereof is entitled.
What is claimed:
1. In an oil well including a vertical string of sucker rods extending from the earths surface downward to a subterranean pump including means at the surface for reciprocation of the sucker rods for actuation of the pump, a means for maintaining the temperature of the crude oil being pumped to the surface above a preselected level to prevent the congealation of paraffin, comprising:
a vertical sucker rod string formed of lengths of sucker rods, each sucker rod having means for the attachment at each end thereof to adjacent sucker rods, each sucker rod having an axial small diameter bore hole therein;
an electrical heating element positioned in said bore hole;
solid heat conducting electrical insulation completely filling said bore hole in said sucker rod surrounding said heating element, and
means of applying a voltage to cause current to flow through said heating element.
2. A means for preventing congealed paraffin formation in an oil well according to claim 1 wherein said means of applying voltage to said resistance wire includes two conductors having voltage thereacross, one of the conductors being electrically attached to said heating element and the other electrically attached to said sucker rod and wherein the lower end of said heating element is electrically connected to said sucker rod.
3. A means for preventing congealed paraffin formation in an oil well according to claim 2 including couplings between adjacent sucker rods in said string of sucker rods, each said coupling providing electrical continuity between said sucker rods, each said coupling being tubular and having a central insulating element therein positioned between the ends of adjacent sucker rods, and an axial conductive element supported by said insulating element, said conductive element providing electrical contact between said heating element positioned within adjacent sucker rods.
4. A means for preventing congealed paraffin formation according to claim 2 including a terminal coupling means between adjacent sucker rods positioned in said sucker rod string at the lowermost point wherein heat is required to maintain the crude oil above the preselected temperature level, the terminal coupling being tubular and threadably receiving at the upper end a sucker rod having said heating element therein and threadably receiving at the lower end a lower sucker rod and said coupling having a conductive element therein contacting said heating element and providing continuity between said heating element and said lower sucker rod.