US2997964A - Swab assembly - Google Patents

Description

All@ 29, 1961 R. G. TAYLOR, JR 2,997,964

swAB ASSEMBLY Aug. 29, 1961 R. G. TAYLOR, JR 2,997,964

SWAB ASSEMBLY Filed June 18, 1958 2 Sheets-Sheeil 2 I 6 w w/ d RP. 9. /I any@ M G Y\\`\\\\`7/ EW E f 1| f /l/f/l w m FM 4 Z 9 16. 7 54 s 2 n 4 .//I w 3 M 5 2 p Z 6 ,6 656 7 E WD. 7 .NW i? afi., 7H f Q fr Z 5 mi? 6% A E@ W. 9 .o

United States atey 2,997,964 SWAB ASSEll/ELY Raymond G. Taylor, Jr., Santa Monica, Calif., assignor to Borg-Warner Corporation, Chicago, Ill., a corporation of Illinois Filed June 18, 1958, Ser. No. 742,958 Claims. (Cl. 10B-225) The present invention relates to swabs for use in oil wells, and more particularly to swabs of the type adapted to be run into a well through pipe or tubing on a wire line, andadapted to be retrieved from the well to lift the overlying body of iluid in the pipe or tubing.

Swabs of the type here involved conventionally include a body or mandrel on which one or more swabrubbers may be removably disposed. The mandrel is attached to the end` of a wire line or cable for lowering the swab into a well to a desired depth in the production tubing or pipe for lifting the fluids in the tubing upon pulling of the swab from ithe well. Swabbing of wellsA is commonly resorted to following well completions, for swabbingthe wells into production, or following well treatments such asw hydraulic fracturing of the formation and/or acidizing or cleaning of the formation and the like, for pulling the injected fluid from the well bore and enabling the formation pressure to cause the well to how.

Inasmuch as swabs frequently are run into wells which are many thousands of feet deep, it is preferable that the swab be capable of rapid friction-free descent-into lthe well. Therefore, an object of the present invention is to provide a swab assemblyk which affords a large bypass ilow area therethrough, whereby the swab will fall rapidly through the well fluids, but wherein such bypass flow area will be shut off upon retrieval ofthe swab.`

Heretofore, when a plurality of swab rubbers have been employed on a single supporting mandrel or body, it has` been the practice to provide multiple seats on the mandrel to accommodate the respective swab rubbers.v This practice results in a complex, relatively expensive mandrel construction which cannot be easily manufactured. In accordance with a further object of the present invention, a novel combination of 'swab rubbersand a mandrel therefor is provided, wherein a plurality of swab rubbers may be disposed upon a mandrel which is of extremely simple construction, comprising an elongated body, a nose removably secured on one end of the body, and a connector head for attachment to a wire lineat the other end of the body, the body being longitudinally ribbedor uted and being susceptible of manufacture by an extrusion method.

A further object is to provide a swab assembly including a mandrel of the aforementioned type, whereinv the swab rubbers include a tubular rigid core extending completely through fthe swab rubbers and providing at one end of the swab rubbers valve means in the form of a valve head,`and at the other end of the swab rubbers:

valve means in the form of a valve seat, the mandrel nose being provided with valve means, for instance, in the form of a valve seat adapted to be engaged'by the valve head of the lowermost of a plurality of swab rubbers disposed upon the mandrel'body.

Asa result of such an assembly wherein the central core of the respective swab rubbers is generally centralized about the mandrel body by the ribs thereon, a large by-pass ow area, as previously referred to, is defined between the swab rubber cores and the mandrel body, enabling rapid descent of the swab into a well. Upon retrieval of the swab, the lowermost swab rubber will come into engagement with the nose of the mandrel, withl the valve head on the swabrubber seating against thevalve seat on the nose. A swab rubber disposedv above ice the just-mentioned swab rubber will engage the upper' extremity of the central core of the latter, and the valve4 head at the lower end of the upper swab rubber will seal against the seat provided at the upper end of the lower swab rubber. Thus a structure is provided wherein sepa'- rate supporting seats on the mandrel for 'the respective swab rubbers is avoided.

Inasmuch as there is a limit to the load which any swab rubber is capable of lifting, much care is generally exercised in running swabs into a well to avoid lowering of the swab to a point where the head of iluid thereabove is excessive such that the swab is incapable ofv lifting the head of uid without destruction, or to alpoint';

where the head of fluid above the swab exceeds the capacity `of the power source at the well head.

In view of the foregoing, it is an object of the present invention to provide a swab of the aforementioned type, including an automatic unloading nose on the swab mandrel. In this connection the nose is provided with. a pressure relief valve, so that if the head of fluid' above the swab exceeds a predetermined limit, the relief' valve will open, enabling the head to bleed olf through' the mandrel nose down to a safe point.

A further object is to provide a self-unloadingnose for a swab mandrel, including means dening a passageway communicating with the space between the swab mandrel and tlie central core of a swab rubber upon the mandrel, and including an easily manufactured assembled and repaired valve assembly within the nose-l for controlling the passage of uid from the passagewayv mentioned above through the swab nose.

Other objects andadvantages of the invention will'beV hereinafter described or will become apparent to those-l skilledin the art, and the novel features thereof will be dened'in the appended claims.

In the accompanying drawings:

FIG. 1 is a view in vertical section through a swab assembly, made in accordance with the invention, with the mandrel body shown in elevation and showing the assembly as being run into 'a Well through the production tubing;

FIG. 2 is a View similar to FIG. l, but showing theV entire mandrel in elevation with' the swab rubbers disposed- 'thereon as vwhen the swab is being retrieved from the well'for elevating the fluid in the tubing;

FIG 3 is an enlarged fragmentary detail view showing" the valve head construction of one form of swab rubber' andthe valve seat formation on the mandrel nose, thek parts being shown in full lines in the position assumed".

during lowering ofthe swab into a well, and the mandrel nose being shown in broken lines with the valve head of the swab rubber seated thereon under light load;

FIG. 4 is a fragmentary detail view showing the valve head ofthe swab rubber of FIG. 3 seated upon the man-- drel nose as under a medium load;

FIG; 5 is a view similar to FIG. 4, but showing the valve head as subjected Vto a heavy load;

FIG. 6 is a view in side elevation of a swab assemblymade in accordance with the invention, and including ani automatic unloading nose on the mandrel;

FIG. 7 is a view in vertical section through the assem bly as taken on the line 7--7 of FIG. 6;

FIG. 8 is a view' in transverse section as taken on the line 8 8k of FIG. 7;

FIG.v 9 isa fragmentary view in vertical` section and on anenlarged scale, as taken on the line 9-9 of FIG; 8,

and ,more particularly illustrating the relief valve detailsl with the, valve closed;

FIG..` 10 is aview corresponding generallyto FIG." 9`` but witlgthe relief valve partly open; and

BIG. l1 is a fragmentary view in detail and in vertical section, particularly showing the valve head portion of a modlfied form of swab rubber.

Referring more particularly to FIGS. l and 2, the

' swab assembly of theinvention, as shown in this embodi ment, comprises a swab mandrel M, including a longitud'inally extended body 1, at the upper extremity of which 1s threadedly secured a connector head 2, having a threaded pin 3 for connection to a Wire line ropeY socket (not shown) inra conventional manner. Preferably, the connector head 2 is iixedly secured to the upper extremity of the body 1 as by means of the threaded connection as shown, which may be permanently al'lixedv as by silver soldering the connection. It will be noted that the head 2 is of such cross-sectional area, that a substantial flow passage is provided past the head between the latter and the well pipe or tubing generally designated T. The lower extremity of the head 2 is provided with convergent, preferably arcuate, diametrically opposed faces 4, 4, whereby there is provided at the lower extremity of the head a pair of radially extended shoulders The nose 6 is preferably threadedly connected tothe lowerV extremity of the body 1, as at 10, but it should be under stood that other means may be availed of for removably connecting the nose to the body. Extending along a substantial portion of the body 1, is a series of radially proiecting circumferentially spaced ribs 11, providing flow passages 12 therebetween.

It will be apparent that the mandrel as thus far described may be simplv, constructed in three separate pieces, comprising the bodV 1, the connector head 2 and the nose 6: and that the body 1 may be inexpensively provided with the ribs 11 by extrusion of the body 1.

The body 1 is adapted to receive thereon'one or more more swab rubbers. designated S. A pair of such swab rubbers are shown in FIGS. l and 2. Each of the rubbers S includes a central core or tubular member 13, which is flared outwardlyr at its lower extremity, as at 14. Molded on tbe respective tubes or cores 13. is a rubber cup 15. reinforced bv a series of circumferentiallv snaced elongated hairpin tvne load-compensating wires 16, embraced at a point intermediate their ends by a load-compensating ring 17, and constrained at their lower extremities bv a thimble 18.

It will be noted that the rubber material of the swab cups 15, as best seen in FIGS. 3. 4 and 5 during molding of the rubber. extends beneath the lower extremitv of the flared portion 14 of the tube or core 13. and provides on the inner surface of the ared portion 14 an annular rubber valve head 19 of triangular cross section. adapted for engagement with the generally conical valve seating surface 7 of the nose 6 during pulling of the load of fluid from a well, so that tbe Vescape of fluid between the lowermost swab rubber S and the nose 6 is precluded. The rubber valve head 19 of the rubber S, when employed as the upper of a pair of rubbers as illustrated, is adapted for seating engagement at the upper extremity of the tube or core 13 of the rubber therebelow, so that the passage of uid therebetween is precluded.

Referring particularly to FIG. 3, the rubber Valve head includes a surface or wall 19a extending axially from the inner periphery of the core or tubular member 13 and a surface or wall 19b extending at an acute angle relative to the ared end portion 14 of the member 13, the head 19 being aixed along its hypotenuse side 19t' to the inner surface of-the flaredportion 14. Initial engagement of the head 19 with the conical face 7 of nose 6 is at the apex formed at the juncture of faces 19a and 19b. When the rubber S is under light loads there is a divergent clearance from the line contact of the head 19 with the seat 7 between face 19b and seat 7, and the end edge of tube 13 is spaced from seat 7. However, when the swab rubber S is subjected to a heavier load, as shown in FIG. 4, the head 19 will be compressed so that wall 19a. will be bulged slightly and wall 19h throughout its entire extent will engage seat 7. When the swab rubber S is subjected to a still heavier load the end edge of the flare 14 substantially abuts with the seat 7 and the rubber valve head 19 is further compressed between ilare 14 and seat 7, at which time a seal is effected which will fully withstand any hydrostatic pressure to which the swab rubber may be subjected. This ecient seat lis attributable to the aforementioned valve head coniigurationl or ring 20 is mounted thereon and is provided with a` radially inwardly extended ange 21 overlying the upper 4.

edge of the tube or core'13.

In the use of the swab assembly thus far described, a

pair of the rubbers S will be placed upon the body 1 of the mandrel and secured against displacement therefrom.

by the nose 6, and the connector head 2 will be mounted in a rope socket of a wire line, whereupon the swab as` sembly may be lowered into a well as shown in FIG. 1. As the assembly passes downwardly through well fluids in the tubing or well pipe T, fluid will pass upwardly through the passages 9 between ribs 8 of the nose 6, and upwardly between the tubes or cores 13 of the swab rubbers S and the body 1 through the passageways 12. Angularly disposed faces 4 of the connector head 2 enable the free flow of duid through the upper swab rubber S upon abutting contact of the upper extremity of the top rubber S with the shoulders 5 previously referred to. In addition, since the upper sections of the cups 1S are comparatively tiexible, and are preferably constructed so l as to provide a clearance in the tubing or well pipe T,' there will be little or no frictional resistance to down.

ward movement of the swab assembly in the well upon lowering the swab assembly to the desired extent. Upon commencing retrieval of the swab assembly, the lowerl most rubber S will move downwardly-into engagement with the valve seat 7, and the valve head 19 will prevent the passage of iluid from within the swab rubber S, while seating contact of the cup 1S will prevent the passage of fluid externally of the swab rubber S.

By virtue of the tapered or conical form of seat 7 on nose `6 the lowermost rubber S will be centered onthe nose, thus being centered in the tubing T since the nose 6 is centered in theV tubing by means of ribs 8` thereon.` The uppermostV swab rubber will seat upon the lower extremity of the tube or core 13 of the lower swab rubber S, thus sealing against the passage of duid from rubbers Slwhen this load` exceeds predetermined limit;

' between the swab rubbers as the swab assembly is being the well pipe or tubing pulled to elevate the fluid within abovethe swab assembly.

YThe details of construction and the functional characteristics of the cups 15'need not be more specifically described`herein, since these features are the subject ofv thus, if Vduring running of the swab assembly into a well anY operator should permit the swab to fallin a well to such an extent that an excessive head of uid overlies the,swab,irreparable'damageto the swab assembly or to thegs'wa-b rubbers, or the potential inability to retrieve the swab,`will -be positively prevented.

vThe modified nose 6 is elongated, in contrast to the nose 6 previously described, and is provided with ribsu 8 andnflow passages 9 adjacent its lower extremity, and with the tapered valve seating surface 7 atv the upper extremity of an elongated neck section 22. The neck section 22 is in two parts, comprising alower part 23 preferably formed integrally with the ribbed lower portion of the nose 6', andan upper part 24 thereof havingV a threaded stem 25 engaged in a threaded bore 26 in the lower part for-securing thesefparts-in assembly.

Extending axially through the lower part 23 of the nose 6', is a valve chamber 27, in which is reciprocally disposed a valve 28 having a depending stem 29, a centering spider 30 anda valve head 31. Radial passages 27' lead from the valve chamber 27to the space in the well pipe or tubingY Toutside ofthe nose 6'. A plug 32 is threaded into the lower extremity ofthe part 23 andis provided withgan opening 33; in which is slidably dis- POSed the valve stem 29, there being a coiled compres.- sion' spring 34 interposed between the inner end face of the plug 32 and the spider 30, normally biasing the valve 28 upwardly, as viewed in the drawings.

Seating on a shoulder 35 formed in the bore 26, -is a reversible valve seat 36 in the form of a disc, which is sealed against the bore 26, as by means of an O-ring 37 or the like. It will be noted that the reversible valve disk 36 is retained in place against the shoulder 35 by the lower extremity of the threaded stem 25 of upper neck section 24. As best seen in FIGS. 9 and l0, the valve disk 36 is provided with opposed central bores 38 and 39, adapted to closely receive the valve head 31. A central ow passage 40 extends through the disc between the bores 38 and 39, and bevelled seats 41 and 42 are provided for engagement by a tapered end 43 of the valve head 31. When the tapered end 43 of valve head 31 is seated against one of the seats 41, 42, the valve head 31 at its upper region is disposed within one of the bores 38, 39. This construction prolongs the life of the respective seats 41 and 42 in a manner which will hereinafter be more particularly described.

Extending through the threaded stem 25 of upper neck section 24, is a central ow passage 44 communicating at its upper end with a cross-passage 45, leading at its opposite ends to an annulus 46 formed between the stem of the upper neck section 24 and the upper portion of the lower neck section 23. Extending upwardly through the upper neck section 24 and communicating Yat the lower ends with the annulus 46, is a series of circumferentially spaced ow passages 47 leading to an annular chamber 48 adjacent the upper end of the neck section 24. The upper extremity of the neck section 24 is bored at 49 to provide an annular ow path communicating with the chamber 48 about the body 1 of the mandrel which extends through the bore 49 and is threaded into a threaded socket in the upper neck section 24, as at 50. Accordingly, a continuous flow path is provided through the nose 6 communicating with the space between the tube or core 13 of the lowermost swab Irubber S and the body 1 of the mandrel, this ow path being normally closed by the spring-loaded valve 28.

'Ihe effect of the spring 34 on the valve may be varied in any suitable manner, such Ias 'by employing plugs 32 having threaded stems of diiferent axial lengths. In any event, should the swab as shown in FIGS. 6 through 10, be lowered in a well to such an extent that an excessive fluid head is disposed thereabove, the valve 28 will automatically dump such a load until the spring 34 overcomes the effect of hydrostatic pressure upon the upper end area of the valve head 31. During such dumping of excessive hydrostatic pressure through the valve means, the tapered end 43 of valve head 3-1 will initially be unseated from one of the seats 41 and 42, responsive to to the elfect of uid pressure upon the area of the valve head exposed to pressure within the bore 49. However, immediately upon unseating of the tapered end 43, pressure will be eifective upon the entire cross-sectional area of the; valve. head 31;,Withn one of the valve discbores, or 39, so that the valve thereupon will be quickly opened' to a position where the valve head 31 is fully displaced from, such bore 38 or 39. This quick-acting valve ar,-

rangement substantially lessens the eifect of high velocity. uid ow between the tapered seats I41 and 42 and the,

tapered valve end 43.

It. should be understood that the present invention is., not limited to the swab lrubbers as hereinbefore described,

but in` lieu thereof, disc-type swab rubbers, as more particularly disclosed and claimed in Patent No. 2,919,167, datedDecember 29,A 1959, may be employed. The sig- Previously described.

Accordingly, therleis illustrated in FIG. lla fragmentary section of a disc-type swab rubber ED, as disclosed and claimed in my just-mentioned co-pending application, wherein the central core or tubing 113 has a disc rubber molded thereto, with a valve head 119 underlying the lower extremity of the tube or core 113 for engagement with the tapered seating surface 107 of a mandrel nose 106 carried `at the lower extremity of a mandrel body 101. The upper extremity of the tube or core 113 will preferably be provided with a seat in the manner of the upper extremity of the tube 13 previously described. While a ilared tube end and tapered valve head, as hereinabove described, may be employed in the disc swab rubber i115 and tube 113, but since disc swabs are not capable of lifting as heavy hydrostatic loads as cup swabs there is not the need for such effective sealing between the disc swab and the mandrel nose. It will now be apparent that as a result of the present invention, an improved swab construction has been provided wherein a plurality of swab rubbers may be disposed upon a simply constructed mandrel body, and as the swab rubbers become worn they may be readily replaced by new swab rubbers simply by detaching the removable nose from the body. If a single swab rubber is employed on the mandrel, it will provide a seal against the mandrel nose to prevent the loss of fluid through the swab rubber; while if a plurality of swab rubbers are run on the mandrel, each superjacent rubber will seat upon the upper extremity of the central core of the swab rubber therebelow, and the necessity -for separate seats on the mandrel vfor each swab rubber is thereby eliminated. Moreover, where the swab assembly is to be used in wells where the likelihood of excessive and damaging hydrostatic heads is encountered, the automatic dumping nose hereof may be readily substituted for the non-dumping nose, if desired.

Other changes, lalterations or modications may be resorted to without departing Ifrom the spirit of the invention as defined in the -appended claims.

I claim:

1. A well swab assembly comprising a mandrel, said mandrel having an elongated body, a nose at one end of the body for centering the mandrel in a well pipe, a connector head at the other end of said body adapted to be connected to a wire line, and a plurality of swab rubbers slidably disposed on said body intermediate said nose and said connector head, said swab rubbers each including a central rigid core encircling said body and providing a ow path therebetween, a valve head at the lower end of each core, and a valve seat at the upper end of each core, and a valve seating surface on said nose engageable by the valve head on the lowermost swab rubber, said valve head including an outwardly ared and downwardly extended section of said core, and an annular body of rubber having a triangular cross-section bonded to said flared section and ytapering towards the lower end of said ared section.

2. A well swab assembly as delined in claim 1, wherein saidvalve seat on said nose is tapered for engagement by said rubber body on said valve head. Y

' 3. A rwell swab as deined in claim 1, wherein said valve seat at the upper end of the respective cores of said swab rubbers comprises a ring having a flange overlying theV said valve head including an outwardly ared and down-4 wardly extended section of said core, and an annularA body of rubber having a triangular cross-section bonded to said ared section and tapering towards the lower end fsaid ared section.

5. A swab rubber for use in a Well swab assembly,

comprising a' tubular core, a rubber body moldedon said core andA being constructed to lift a body of fluid in a well pipe, and a generally conical valve head extending about an end of said-core, said valve head including an outwardly ared and downwardly extended section of said core, and an annular body of rubber having a triangular cross-section bonded to said ared section and tapering towards the lower end of said flared section.

References Cited in the le of this patent l UNITED STATES PATENTS 1,402,218 Cushing Jan. 3, 1922 1,485,248 Carpenter Feb. 26, 1924 2,135,167 Cambell Nov. 1, 1938 2,144,944 Standiee Jan. 24, 1939 2,224,916 McFarlane Dec. 17, 1940 2,674,201 Talbott ..-i Apr. 6, 1954 2,674,956- Hilton -..a Apr. 13, 1954 Bowerman ---n Dec. 2, 1958

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