US2690934A - Insulated sucker rod and tubing to prevent electrolysis and corrosion - Google Patents

Description

UCL 5, 1954 s. M. HoLcoMBE INSULATED SUCKER ROD AND TUBING TO PREVENT ELECTROLYSIS AND CORROSION Filed Aug. 28, 1950 Z. /f /0 2 )0MM w waz f1/p. f Ymo .M VHN 0 Z. m f5 M m i l l l i i i I l l l I I Il lllllllllllllllllll li l W M m .0 n, .b Z0, 8

Patented Oct. 5, 1954 UNITED STATES PATENT OFFICE INSULATED SUCKER ROD AND TUBING-T0 y"PREVENT ELECTROLYSIS AND CORROSION 3 Claims.

This invention relates to partsin an oil well subject to corrosion and electrolytic action ot the well fluids and particularly to the tubing and sucker rods oi a well. It is -knownthat when wells produce uids containing electrolytic and corrosive elements such as salts, sulphur dioxide, and hydrogen sulphide, the rods and tubing are of relatively short'life and are constantly subject to failure. When such elements are present in the well fluids, electrolytic and corrosive action takes place at the more vulnerable areas such as the joints and particularly the threads thereof. Also rubbing or the rods on the tubing provides points where the electrolytic action concentrates. Consequently, stress .in the rod-s at these points causes them to give awayin operation and results in expensive vfishing jobs.

The objects of the present invention are thereiore to protect the tubing and sucker rods by substantially the sucker rods and tubing; to provide for the maintenance of tight joints and thereby prevent contact of the well iiuids with the threads; to provi le thev sucker rod string `with insulating couplings; to provide selected lcouplings with guides to prevent Contact of the rodswith-the tubing; to provide the tubing and/or sucker rods with an electrically insulating covering or skin whereby the sucker rods may be vmanufactured from the tougher butmore easily attacked metals; to provide insulating guides having flow passageways through which the Well iiuids pass the couplings with a minimum of resistance to the ilow and yet provide ample `bearing contact of the insulating material with the Wall of the tubing, and to dampen vibrations of the rods.

in accomplishing these vand other objects of the invention as hereinafter pointed out, I have provided improved structure, the preferred form oi which is illustrated in the accompanying drawings wherein:

Fig. l is a longitudinal section through a string of Well tubing and sucker rods embodying the features of the present invention.

Fig. 2 is an enlarged longitudinal section through the tubing and one of the coupling members particularly illustrating the insulating guide thereon.

Fig. 3 is a cross-section on'the line 3--3 of Fig. 2.

Fig. 4 is a section through one4 of the standard sucker rod couplings modied in'accordance with the present invention.

Fig. 5 isa cross-sectionthroughone of the rods lon the line 5-5 vof Fig-'4.

eliminating electrolysis between J Fig. 6 is an enlarged section through one oi' the tubing couplings.

Fig. 7 is a fragmentary section through one of the sucker rod couplings.

Referring more in detail to the drawings:

l designates a bore hole of a vwell extending from the top of the ground'to a formation 2 producing, for example, petroleum oil. Extending downwardly in the bore hole is a tubing il carrying a pump L3 and a strainer section 5 .through which the oil is admitted to the pump. The pump t includes a standing valve 6 seated in the lower end of thexpump cylinder "i, and reciproca-ble in the cylinder. is a piston B carrying a Working valve 9 to which astring of sucker rods I@ is connected. Thestring of sucker rods continue upwardly through the tubing for reciproca-tion above ground by ymeans of a suitable pumping jack (not shown). lThe tubing Si is composed of a series of pipe `sections il interconnected by couplings l2 having internal threads I3 engaging external threads-lli on the adjacent ends of the pipe sections. The sucker rod string includes plurality of sucker rods l5 having rodlike body portions lli formed at the ends to provide upsets ll and I8 on the respective sides of wrench-engaging faces I9. Also formed on the ends of the sucker rods are shoulders 2li and tapered pins 2| having external threads 22 which engage in the threaded-sockets or boxes 23 and it at the respective ends of rod couplings 25. The threaded sockets ror boxes may lbe formed at the ends of a continuoous bore 2B if desired. The strainer 5 usually consists of one or more sections of pipe having periorations for admitting the well fluids to the pump. VThe structure thus far disclosed is conventional of sucker rods and tubing used in the pumping of oil wells. Usually crude petroleum contains corrosive and electrolytic fluids that attack the 'metals of the sucker rods and. tubing and cause fatigue failures, particularly at` the threaded joints of the couplings.

The electrolyticaction produced by the presence of electrolytes contained with the petroleum causes electric vcurrents to flow from the rods to the tubing and results in rapid pitting and reduction of the cross-'sectional area ofthe' rods so that the rods are subject to failure under stress and especially repetitions of'stresses as occur in loading and unloading of the rods incidental to reciprocationv thereof.

As labove pointed'out, suchA Wellsv are usually vout-'of plumb'due-.to the impossibility of drilling 11a `straight .'.bore :hole i with f the-(result i that the string of sucker rods rubs upon the tubing at various points throughout the depth of the well. This rubbing action during reciprocation of the rods effects rapid wear of the tubing and rods which also adds to the hazard and increases fatigue failures promoted by electrolytic and corrosive effects of the fluid.

In carrying out the present invention, I have provided a tubing and socker rod, tubing and coupling construction which eliminates the above difficulties by preventing any direct contact of the metal with the well liquids. This is eiected by provision of the rods, tubing, and couplings with an electrically insulating coating or skin to prevent passage of the electrolytic currents that cause deterioration. Each section of pipe composing the string of tubing is provided with a lining-like coating 21 on the inner surface and extending the full length thereof. The coating may be formed of any suitable insulating material that is resistant to action of the well liquids. For example, one of the synthetic rubbers commonly known as neoprene or the equivalent which is applied to the inner surface by dipping the sections of pipe into a liquid body of self-vulcanizing synthetic rubber.

The sections of sucker rod are similarly coated as indicated at 28 with the exception of the threads the pins 2l.

The standard sucker rod couplings are also preferably covered with a similar coating 29. Therefore, when the sections of sucker rods are connected together by couplings, the entire surface of the entire string is electrically insulated along the entire length thereof to prevent passage of electrolytic currents from the rods through the electrolytic content of the well fluids to the tubing as long as the pins 22 and boxes are tightly engaged. To assure tight connections of the threads, the bore of the couplings are closed midway the length thereof by plugs 3B which are threaded into the bore and form backing for blocks 3| of rubber or preferably synthetic resilient material. The blocks are of ample thickness relatively to the depths of the sockets and length of the pins so that when the pins of the rods are completely engaged within the sockets of the couplings, the resilient material is compressed to provide a resistance to backward turning of the rods and thereby assure suiciently tight joints to prevent intrusion of the well liquids. The material from which the blocks are formed is of suiiicient resiliency so that when the rods are to be uncoupled, they will yield suiciently to permit turning of the rods. To prevent the end of the rod from tearing the surface of the blocks, suitable washers 32 may be inserted therebetween as best shown in Fig. '7.

The ends of the pipe sections Il when turned up tightly within the couplings leave gaps 33 therebetween which ordinarily expose the threads I3 to the action of the well iiuids, but to overcome this diificulty each coupling is provided with a ring 31% of the resilient insulating material and which is compressed between the ends of the adjacent pipe sections to assure leak-tight joints therebetween. The rings 34 also assure resistance to backward turning of the pipe sections.

In order to prevent contact of the sucker rods on the tubing and avoid destruction of the resilient insulating coatings, special guide couplings 35 are provided at spaced intervals along the length of the sucker rods. These couplings may be substituted for the couplings illustrated in Fig. 4 at the points at which the guides are necessary. The couplings include a relatively short length of sucker rod section 36 having box ends 3l and 38 provided with internal threads 39 and 40 to receive the pins on the ends of the adjacent sucker rods. The sucker rod sections 3S have the usual wrench engaging faces lil and collar-like upsets 42. Mounted on the body of the coupling rodV sections are substantially cylindrical guides d3 which are preferably molded thereon and retained from longitudinal movement by the upsets 42 and key slots 44 that connect with an axial channel 45 through which the material flows to the socket ends to provide the resilient abutments 46 and 4l for the pins of the adjacent rod sections. The guides are preferably of slightly smaller diarneter than the tubing to allow free movement of the rods and the ends are rounded as at 48 to assure easy entrance thereof into the open upper end of the well tubing as when running the sucker rods into the well. In order to permit free passage of the well liquid, the circumferences of the guides are provided with intersecting flow passages 49 and 49' that extend in criss-crossing relation from one end of the guide to the other as best shown in Fig. l. With this arrangement, diamond shaped islands 5B are formed between the passageways which give ample contact surface 5! with the tubing to assure su'icient support of the tubing to prevent too rapid wear of the rubbing surfaces.

The screen section may be coated on the inner and outer sides with a synthetic rubber as indi'- cated at 52 and 53 and the openings may be provided with magnesium inserts 54 having ports 55.

In using the structure as aboveV described, the tubing and sucker rods are run into the well in 'the same manner as conventional tubing and sucker rods so that when the elements are in place and the pump in operation, the metal of the sucker rods and tubing are completely insulated by the coatings and the sucker rod and tubing sections are retained in tight relation with their couplings by the resilient action of the rubber abutting blocks. During reciprocation of the rods, the resilient bodies 43 of the guide couplings move in sliding contact to hold the rods concentric in the tubing.

It is thus obvious that any electric currents that may be carried by the rods are prevented from discharge by electrolytic `action to the tubing, consequently, the rods are free of the usual deteriorating effects of such currents and will operate for long periods without the customary hazards usually caused by corrosion and electrolysis.

From the foregoing, it is obvious that I have provided sucker rods and tubing which are amply protected from corrosion and electrolysis ordinarily produced by well nuids and that the threads are kept in tight condition so as to prevent intrusion of the well uids at these points.

What I claim and desire to secure by Letters Patent is:

1. A coupling for sucker rods having ends provided with internally threaded sockets, coaxial cylindrical body of electrically insulating niaterial exteriorly encircling the coupling and hav ing an exterior surface provided with ow pas sages, and resilient abutment means in said sockets, said abutment means being integral, with the insulating body.

2. A coupling for sucker rods comprising a rod-like body having internally threaded sockets on the ends thereof with said sockets connected by a coaxial bore through the body, a resilient material in said coaxial bore and forming bottoms for said sockets, said rod like body having a radial opening in connection. with said bore and a cylindrical body of said material having a portion extending through the radial opening and integral With the material in said bore and surrounding the rod-like body.

3. A pony rod comprising a member having a rod like body portion provided with internally threaded sockets on the ends thereof and having an axial bore interconnecting said sockets, said rod like body portion of the sucker rod having spaced apart annular upsets and having slot like openings extending through the said bore intermediate said upsets, a resilient insulating material encircling the rod like body and lling the bore for forming resilient 'bottoms in said sockets, said material extending through the 6 slot like openings for integrally connecting the encircling material with the material in the bore.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,576,767 Loomis Mar. 16, 1926 '1,804,078 Baden May 5, 1931 1,814,183 Patterson July 14, 1931 2,063,863 Zimmerman et al. Dec. 8, 1936 2,096,359 Hawthorn Oct. 19, 1937 2,166,116 Bettis July 1S, 1939 2,175,770 Dodson Oct. 10, 1939 2,178,931 Crites Nov. 7, 1939 2,181,361 Bean Nov. 28, 1939 2,337,711 Crake Dec. 28, 1943

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