US2512226A - Electrical heating of oil wells - Google Patents

Description

June 20, 1950 J. A. EDWARDS 2,512,226

ELECTRICAL HEATING OF OIL WELLS 2 Sheets-Sheet 1 Filed June 1, 1948 NVENTOR. /Z. jdn/ardu June 20, 1950 J. A. EDWARDS ELECTRICAL HEATING OF OIL WELLS 2 sheets-sheet 2 Filed June 1, 1948 dif ' I IN V EN TOR. /z 7d/yard;

Patented `'une 20, 1950 UNITED STATES ,PATENT OFFICE Enricfrnloan HEATING oF oIL WELLS John Alton Edwards, Yucaipa, Calif Application June 1, 194s, serial No. 30,407

This invention relates to improvements in oil well equipment, and more particularly to im proved equipment for applying electrically generated heat to the casing structure at the bottom of the well, to the oil-producing geological formation and, if desired, to the oil ilow lines leading from the oil-producing formation to the top of the well.

` In flowing certain types of oil wells, particularly shallow wells producing petroleum of low specific gravity, there is a tendency for certain components of the petroleum, such as wax and tar to solidify in the oil-producing formation adjacent the well, upon the perforated casing normally provided at the bottom of 'the well in the oil-producing formation, and sometimes inthe flow lines leading from the oil-producing formationto the top of the well and to the tanks or other oil reservoirs* This solidification or precipitation of petroleum components clogs the perforated liner, the oil-producing formation itself, the flow lines and the valves, pumps and other equipment through which the oil must pass, greatly hampering the production of oil from such wells, and in some cases'necessitating the abandonment of the wells `when the flow is reduced below a commercially protable minimum, or ceases altogether* It is known that the solidified or precipitated components can be re-liqueed by the application of sufficient heat thereto and thatV the solidication or precipitation can be prevented by applying heat to the oil at the bottom of the Welland, if necessary, to that in the flow lines. So far, no commercially practical means has been found for providing such heat.

It is among the objects of the present invention to provide practical means for generating heat at the bottom of an oil ywell and along the oil flow lines leading from the bottom of the well, which means is easy to install and economical in construction, can be lowered in the well without damage, is operable by conventional types of electrical generators to generate heat in the well, and requires no material modification of the conventional well equipment.

Other objects and advantages will become apparent from a consideration of the following description and the appended claims in conjunction with the accompanying drawings, wherein:

Figure 1 is a diagrammatic vertical cross-section through an oil well showing the application thereto of well-heating means illustrative of the invention;

Figure 2 is a transverse cross-section on a 4 Claims. (Cl. 21S- 33) 2 somewhat enlarged scale taken substantially in the plane of the section line 2-2 of Figure Al;

Figure 3 is a vertical cross-section on an enlarged scale of a fragmentary portion of the perforated casing near 'the bottom of the well,l illustrating the manner of applying electrical heating means thereto;

Figure 4 is a longitudinal cross-section on an enlarged scale of a fragmentary portion of the well equipment and heating means showing the manner of electrically connecting the heatingy element to a. source of electrical energy;

Figure 5 isa longitudinal cross-section ci a fragmentary portion of a suggested heating element; and

Figure 6 is a diagrammatic vertical cross-sec-fv tion of a somewhat different type orwell from' that illustrated in Figure l showing the application thereto of a heating means illustrative of the invention.

With continued reference to the drawings, the oil well is illustrated as extending downwardly through various covering formations IG to the oil-producing.geological formation or oil sand I I; An outer casing or water string liner I2 extends downwardly through the well to the oil-producing formation and rests at its bottom end upon' an annular shoulder I3 provided in the well; The lower portion of the water string liner vI2 is surrounded by a concrete or cement filler lliv poured between the wallA of the ywell and the liner and extending upwardly from the shelf I3 for any desired distance to reinforce the lower portion of the well.

A cylindrical, perforated liner I5 extends through the oil-producing formation II and'has' a flared upper end I6 received in the lower end of the water string liner I2. A tubular oil flow line I'I extends downwardly through the liner I2 into the perforated liner I5 from the topY of the well and above the ground surface I6 andis extended by a suitable conduit I9 to an oil tank or reservoir 20. The oil ow line Il may include a conventional choke and conventional pumps, valves, and other equipment necessary to the commercial production of oil from the well. f

In order to provide heat at the bottom of the well an electrical heating element, generally indicated at 2|, is spirally wound about the outside of the perforated liner I5 and is preferably seated in a spiral groove 22 provided in the outer Surface of the casing so that the heating element can be applied to the casing and the casing and heating-element assembly lowered inthe well without damaging the heating element.

The heating element 2| may be of any one of several suitable constructions, one operative construction being particularly illustrated in Figure 5, wherein an electrically conductive wire 23 of a material having substantial electrical resistance, such as a nickel-chromium alloy, is encased in an insulated covering 24 of heatresistant material, such as asbestos or plaster of Paris, which is'inturn, enclosed in a metallic casing 25v of a malleable, moisture-proof material, such as lead or copper, and this is, in turn, enclosed in an outer casing 25 of a hard material, such as steel.

Heating elements of this vgeneral character are known to the art and are .commercially available for use as the heatingelements inelectric stoves, electric hot water heaters and'similar devices.

The electrically conductive core 23 of the heating element is electrically connected to the perforated casing 'I5 near the bottom end ofthe casing .by suitable means, such as the weld joint 2'l, and the upper end of the heating element is electrically connected to the electrically conductive band 28 of an annular collar, generally indicated Yat 29, secured on the upper portion of perforated casing I adjacent the flared upper end I6 of the casing. This collar 29 includes, in addition to the band 28 of electrically conductive material, a band 39 of insulating material rinterposed between the band 28 and the casing I5 to electrically insulate the conductive band 28 from the casing. The outer surface of the band 28 is upwardly and outwardly lbeveled for a purpose which will presently appear.

Vertically spaced above the collar `29 a second collar 3| of electrically conductive material surrounds the casing I5 in electrically conductive contact therewith and has an upwardly and outwardly-beveled outer surface 4which constitutes a conical continuation of the beveled outer surface of the band 28 of collar 29. A pair of vertically-spaced rings, generally indicated at 32 and 33, is mounted in the outer casing or water string I2 immediately above the annular shoulder I3. Each of these rings comprises an annular body of insulating material, as indicated at 34 and 35, anda block of electrically conductive material, as indicated at 35 and 31. An insulated electrical conductor 38 leads from the block 3,6 to the top of the well for connection to a suitable source of electrical energy, not illustrated, and asimilar insulated electrical conductor 39 leads from the block 3l to the top of the well and to the source of electrical energy. The two 'conductors 38 and 39 may be enclosed in a suitable cable sheath 4I) extending downwardly through the Well either outside or inside of the water string liner I2.

With the above-described arrangement, current supplied to the upper end of the heating element 2| through conductor 38, ring 32 and collar 29, flows through this heating element and to the lower end of the perforated casing I5 at the well joint `2'I4 and through the casing- 4 ing element extends to the lower end of the oil flow line and into the perforated liner I5. An electrical conductor 43 leads from the upper end of the heating element 4I to the collar 3I whereby the opposite ends of the heating element BI are electrically connected respectively to the energy-supplying conduits 38 and 39. The portion of the heating element lil surrounding the oil ow line I'l above the ground surface I8 is preferably enclosed ina heat-insulating casing i-I of suitable material, such as asbestos, to conserve the heat generated by this portion ol the heating element.

In the arrangement shown in Figure 6 the casing is somewhat different from that illustrated in Figure 1 in that in the Figure 6 arrangement the casing 5i) extends for the entire depth of the well and has its lower portion, below the annular shoulder I3, perforated to permit the passage.-

of the oil from the oil sands II to the interiory of the casing. The flow line I'l extends down-- wardly through the casing I5 to the perforated. lower portion thereof and is equipped with suit-V able pump, valves and choke, as indicated above. ln this somewhat modified arrangement the. heating means comprises a continuous heating; element, generally indicated at 5l, wound spirally about the entire length of the casing I5 from the top to the bottom of the well and preferably received in a spiral groove provided in the outer surface of the casing, as illustrated in Figure 3, and described above. 'In this modined arrangement a conductor 52 is connected to the upper end of the heating element at or above the ground level I8 and a second conductor 53 extends downwardly through the well and is connected at its lower end to the bottom end o l the heating element. In this case the heating element is not electrically connected to the cas'- ing at any point. The two conductors 52 and 53 are connected to a suitable source of electrical energy, not shown, to supply heating current to the heating element 5I. In this case, the heating element may have the same con.` struction as that illustrated in Figure 5, and de.- scribed above.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are, therefore, to be considered'in all respects as illustrative and not restrictive, the scope of the invention being indicated Vby the appended claims rather Vthan by the fore'- going description, and all changes which come within the meaning and range of equivalency of the claims are, therefore,'intended to be embraced therein.

What is claimed is:

l. in an oil v/ell having a perforated casing in the bottom portion thereof and an oil flow line extending from said perforated casing out of the top of the Well, heating means for the well comprising an insulated electric heating element Wound spirally about said perforated casing and electrically connected to said perforated casing near the bottom end of the latter, a vcollar on rthe upper end of said perforated casing electrically insulated from the casing andelectrically connected to the upper end of said heating element, a second collar o n said casing in electrically con; ductive contact therewith, and respective lelectrif cal conductors leading from said collars out of the well at the top of the latter.

2A. In an oil well having a perforated casing` in the bottom portion thereof and an oil ow line extending from said perforated casing out of the top of the well, heating means for the Well comprising an electrical heating element spirally wound about said perforated casing and electrically connected to the latter near the bottom thereof, and electrical heating elements spirally wound about said oil iiow line, a iirst collar on said perforated casing near the upper end of said casing electrically insulated therefrom and electrically connected to the upper end of said casing heating element and the lower end of said iiow line heating element, a second collar on said perforated casing adjacent said rst collar in electrically conductive contact with said perforated casing, conduit means electrically connecting the upper end of saidflow line heating element to said second collar, and respective electrical conductors extending from said collars out of the well at the top thereof.

3. In an oil well having a perforated casing in the bottom portion thereof and an annular shoulder near the upper end of said perforated casing, heating means for the well comprising an insulated electrical heating element wound spirally about said perforated casing and electrically connected to said casing near the bottom end of the latter, a pair of vertically-spaced, upwardly and outwardly-beveled collars on said perforated casing near the upper end of the latter, one of said collars including a contact band electrically insulated from said casing and electrically connected to the upper end of said heating element and the other of said collars being in electrically conductive contact with said casing, a pair of vertically-spaced, downwardly and inwardly-tapering rings mounted above said shoulder and arranged to respectively receive said collars when said perforated casing is lowered into the well, an electrically-conductive band in each ring electrically insulated from the well and in electrically- 6 conductive contact with the respective collars, and respective electrical conductors extending from said rings out of said well at the top of the latter.

4. In an oil well having a perforated liner therein and an oil flow line extending downwardly through said well and into said liner, an electrical heating element wound on said liner and electrically connected thereto at one end, an electrical heating element wound on said flow line, a rst connector carried by said liner and insulated therefrom electrically connected to said heating elements, a second connector positioned in said well for electrical contact with said iirst connector, a third connector secured on said liner in electrical contact therewith and electrically connected to said now line heating element at the end of the latter opposite the end connected to said first connector, a fourth connector positioned in said well for electrical contact with said third connector, and electrical conductors leading from said second and fourth connectors out of the well.

JOHN ALTON EDWARDS.

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PA'IENTS Number Name Date 48,584 Parry et al July 4, 1865 798,504 Gardner Aug. 29, 1905 809,917 Gardner ,Jan. 9, 1906 1,012,777 Wigle Dec. 26, 1911 1,291,302 Waring Jan. 14, 1919 1,354,757 Popcke et al Oct. 5, 1920 1,426,407 Pennington Aug. 22, 1922 2,208,087 Somers July 16, 1940 2,484,063 Ackley Oct. 11, 1949

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