US3072071A

US3072071A - Well swab

Info

Publication number: US3072071A
Application number: US780827A
Authority: US
Inventors: Stroud Buck Carson
Original assignee: Mission Manufacturing Co
Current assignee: Mission Manufacturing Co
Priority date: 1958-12-16
Filing date: 1958-12-16
Publication date: 1963-01-08
Anticipated expiration: 1980-01-08

Description

Jan. 8, 1963 B. c. STROUD 3,072,071

WELLSWAB Filed Dec. 16, 1958 ATTORNEYS 3,tl72.,d'71 WELL st /Alt Buck Carson Shroud, Houston, Tern, assignor to IV Manufacturing Qornpany, Harris Unitary, "Eon. Filed Dec. 16, R9525, No. l'iithbz'i s chums. er. res-4.22;

This invention relates to apparatus for swabbing a well to lift fluid therein to the surface, and more particularly to a well swabbing assembly utilizing a new type of well swab.

Well swabs are divided broadly into swabs which are utilized to lift a heavy load and swabs which are utilized to lift a light load. An example of the former is shown in the patent to Losey, No. 2,771,939. An example of the latter is shown in the patent to Webber, No. 2,63 3,808.

All swabs presently used by the industry for lifting a heavy load employ a longitudinal cage of supporting ribs such as shown by the Losey patent. These swabs are prone to hang up in a collar and sometimes tear up into rather large chunks. It is not infrequent to part the cable in trying to remove such a stuck swab. In many instances, it is necessary to deliberately shoot the cable in two just above the swab and go in with special tools to remove the swab. Trouble with this type of swab usually occurs at the end of its useful life when one or more of the rigid cage members wears in two and provides a projection which easily hangs in a collar. in many instances the cage type of swab will have large chunks of rubber torn off. These chunks of rubber may come to the surface-at a later time and stop up the small diameter surface chokes usually employed with wells. When this occurs the well may be killed necessitating it being swabbed in again.

By this invention a swab suitable for heavy load service is provided which does not require the use of the cage of longitudinal wires and, therefore, is not subject to the several disadvantages of the prior art swab as outlined above. The swab of this invention has been extensively tested and has not hung up or stuck in a single instance. The swab is more elastic than the type utilizing a wire cage and it deforms and gives more readily. This results in fewer chunks being torn out. Where the pipe through which the swab is being run is in normal condition, it has been found that the swab merely wears until it reaches a condition at which it will not seal and lift a load. The wear results in very small particles of the resilient member being worn off. These small particles do not interfere with later production of the well.

it has been found that the wire cage of the prior art may be omitted if the resilient cup member is bonded to a tubular support whose outer surface is formed with a reducing diameter portion. This reducing diameter portion provides sufficient backup for the resilient member that the wire cage may be omitted. In association with this structure it is desirable in some way to restrict the free end of the resilient member against radial expansion so that the lip of the cup will not tend to hang in collars.

It is an object of this invention to provide a swab assembly with a swab which may be used for heavy load service and which does not require that the resilient portion of the swab cup be provided with a longitudinally supporting wire cage.

Another object of the invention is to provide a swab cup for heavy load service which will not hang up and stick in a pipe and in wh ch the tendency for large chunks of the resilient material to be torn out is greatly reduced as compared with swabs which employ a wire cage or reinforcing wires in association with the resilient cup.

Another object is to provide a swab cup for a swab assembly for use in lifting heavy loads which is much Q dfi illfil ll Patented Jan. 55, i933 less expensive than the cups of the type illustrated in the Losey patent.

Another object is to provide a swab cup for lifting heavy loads in which the cup gradually wears away to a condition in which it will not seal with the wall of a pipe without setting up conditions conducive to hanging up of the cup in a collar thus permitting the swab to be used for its entire useful life.

Other objects, features and advantages of the invention will be apparent from the drawing, the specification and claims.

in the dr wing wherein one illustrative embodiment of this invention is shown, and wherein like reference numerals indicate like parts;

l is a view partly in elevation and partly in vertical cross section through a well being swabbed in with a tool constructed in accordance with this invention;

FIGURE 2 is a view partially in elevation and partiailv in quarter section on an enlarged scale of the well swa assem ly of FIGURE 1;

E IGURE 3 is a view partially in elevation and partially in quarter section on a still further enlarged scale of the swab cups employed in the FIGURE 2 well swab assembly.

Referring to the drawings, the tool is shown swabbing in a well. In this operation, sufficient liquid is removed from the well to reduce the hydrostatic head at the producing formation to a level at which the well will flow. In carrying out this operation, the swab assembly indicated generally at 10 is run through a lubricator 11 at the top of the well and lowered through the production tubing 12 to a position below the liquid level within the well. Thereafter, the tool is pulled to the surface to raise liquid trapped above the well assembly. Usually two or more swab cups, indicated generally at 13, are employed to insure that at least one of the swabs is in sealing engagement with the well pipe at all times.

Referring to FIGURE 2, the well swab assembly includes a tubular mandrel 14 provided at its upper end with a valve assembly indicated generally at 15 for permitting flow upwardly through the mandrel while preventing flow downwardly through the mandrel. Generally this valve assembly includes a ball 16 which cooperates with a seat provided by the upper internal edge of a bushing 17. The ball and seat are enclosed in a cage 18. A pin 19 at the upper end of cage 18 is provided for attachment to a wire line socket in the conventional manner.

Telescoped over the mandrel is an upper spacer sleeve 21 positioned immediately below the seat bushing 17. immediately below the upper spacer sleeve there is provided an upper swab cup. In like manner, a lower spacer sleeve 22 is positioned between the upper swab cup and a second or lower swab cup 13. These swab cups are identical in construction and the mandrel 14 may be elongated and as many swab cups as desired carried by the mandrel. Below the lowermost swab cup a bottom guide nut 23 is provided to hold the several sleeves and swab cups in assembled position on the mandrel.

Referring now to FlGURE 3, the swab cup 13 includes a tubular support 24'- having an internal bore 25 adapted to slidably receive the mandrel 14-. The lower end of the support 2 is formed with a downwardly and inwardly inclined frustoconical surface 26 to assist in guiding each swab cup through the pipe to be swabbed as the assembly is lowered in a well,

In accordance with this invention, the remaining exterior surface of support 24 is formed with a reducing diameter portion to which a resilient member 27 is bonded. in the preferred embodiment this reducing diameter portion is provided by a section 28 which is reduced in diameter relative to the maximum diameter of the support 24 and a second section 29 whose diameter is less than section 28. These two reduced diameter portions provide endwise facing

shoulders

31 and 32 in the outer periphery of support 24. Of course, any desired number of steps such as provided by

portions

28 and 29 could be utilized. Of course, a large number of shallower steps could be used than is present in the preferred embodiment.

To assist in securing the resilient member 27 to the support 24, a plurality of

annular rings

33 and 34 are formed in the stepped exterior of the support. Also, the bore 25 is counterbored at 35 and the resilient member 27 has a portion 27a which is molded in counterbore 35 as Well as portions which extend into each of the

annular grooves

33 and 34. To assist in sealing between the spacing sleeves and swab cups a thin gasket of material 27b may extend inwardly to a point adjacent the termination of bore 25. As the internal diameter of the spacer sleeves and the diameter of bore 25 are approximately equal, the gasket portion 27b will seal between the spacer sleeves and support members in a manner to be hereinafter explained.

The resilient member 27 may be formed of any desired material which is conventionally used for swab cup service. Preferably, the resilient member 27 is neoprene of approximately 80 durometer molded to the reducing diameter section of the support 24 and to the internal face provided by counterbore 35.

In use internal pressure will tend to expand the unsupported section of the resilient member, that is, the portion extending endwise from the counterbored end of support 24. To avoid any tendency of the lip 270 of the resilient member from hanging in collars, it is desirable to restrain the lip 27c against radial expansion. This may be provided for by securing to the lip any desired form of non-elastic support. Preferably, an annular ring of non-elastic metal 38 is mounted in the free end of resilient member 27 to prevent radial expansion of lip 27c.

In operation the tool is lowered on a wire line to a position below the liquid level in the well. Upon an upward pull on the well swab assembly, the ball 16 seats and prevents flow of fluid through the well swab assembly. Fluid surrounding the well swab assembly tends to act on resilient member 27 and expand it radially into contact with the wall of the pipe through which it is being pulled. Also the weight of the column of fluid above the swab cup tends to compress the swab cup. As a result, it has been found that the resilient member bulges outwardly beginning adjacent to step 31 and contacts the Wall of the pipe beginning at approximately the uppermost groove 34. The contact with the well continues up to a point short of the lower end of ring 38. It has been found that the use of the stepped member 24 gives suflicient support to the resilient member 27 that it is not necessary to provide a cage of protecting wires for heavy load lifting.

Where a dual cup assembly such as shown in FIGURE 2 is used, it will usually be found that one of the cups will be carrying the load at any particular time. When this is the upper cup, fluid may find its way past the gasket portion 27b of the resilient member 27, and into the bore 25 of the cup. When this occurs, however, a metal to metal seal is formed between the lower end of the uppermost swab cup 13 and spacer 22. A seal is also formed between spacer 22 and the lower swab cup 13 due to the downward force on spacer 22 which results in a seal at gasket 27b of the lower swab cup. The lower swab cup is held firmly against the guide nut 23 and a metal to metal seal is formed at this point. In this way any substantial leakage through the tool is prevented. When the lower swab cup is carrying the load, fluid may pass between the lower spacer 22 and the lower swab cup into the bore 25. However, the metal to metal seal between the swab cup and the guide nut will prevent any substantial leakage through the swab cup.

The tool is raised to the surface to dump a load of fluid. During raising the bulging portions of the resilient member 27 provide a sliding seal with the wall of the tubing 12, and the restraining ring 38 prevents the lip 270' from spreading out into a collar, and in this way reduces the possibility of the cup hanging up in a collar.

In the usual manner successive loads of fluid may be raised from the well, as will be understood by those skilled in the art until it is swabbed down to a desired level.

From the above it will be seen that all of the objects of this invention have been attained. The necessity for the wire cage is eliminated by the use of the stepped exterior surface on the tubular support. This stepped surface may be provided in any desired manner so long as there is provided a reducing diameter surface to which the resilient member is bonded. As the central section of the resilient member is bulged out into sealing contact with the well pipe, wear will be through friction, and the possibility of chunks of rubber being torn off to later interfere with flowing of the Well is reduced. It has been found that usually the swab cup will last until a hole is rubbed through the wall of the cup rendering it incapable of sealing with the wall. Of course, when this happens other cups on the string will carry the load. At this time the useful life of the cup has ended, but there are no metallic projections which might hang in a collar and give trouble.

The foregoing disclosure and description of the invention is illustrative and explanatory thereof and various changes in the size, shape and materials, as well as in the details of the illustrated construction, may be made within the scope of the appended claims without departing from the spirit of the invention.

What I claim is:

1. A well swab for a well swab assembly comprising, a tubular support having a series of steps on its exterior surface formed by step-wise reducing diameter sections to provide a plurality of end-wise facing shoulders between said reducing diameter sections, and a tubular member of resilient material having one end bonded to said support sections and the other end extending end- Wise from the smaller of said reducing diameter sections in a direction away from the larger diameter sections.

2. The swab cup of claim 1 wherein annular grooves are provided in said reducing diameter sections to assist in anchoring the resilient member to the support.

3. A well swab for a well swab assembly comprising, a tubular support having a series of steps on its exterior surface formed by step-wise reducing diameter sections to provide a plurality of end-wise facing shoulders between said reducing diameter sections, a tubular member of resilient material having one end bonded to said support sections and the other end extending end-wise from the smaller of said reducing diameter sections in a direction away from the larger diameter sections, and a ring of substantially non-elastic material bonded in said other end to restrain said other end of the resilient member against radial expansion.

4. A well swab assembly comprising, an elongate tubular mandrel adapted to be suspended from a wire line in a well, valve means in said mandrel permitting upward flow through the mandrel and preventing downward flow through the mandrel, and at least one swab cup supported on the exterior of said mandrel and comprising, a tubular support having a series of steps on its exterior surface formed by step-wise reducing diameter sections to provide a plurality of endwise facing shoulders between said reducing diameter sections, annular grooves in said support sections, a tubular member of resilient material having one end bonded to said support sections and the other end extending endwise from the smaller of said reducing diameter sections in a direction away from the larger diameter sections, and a ring of substantially non-elastic material bonded in said other end to restrain said other end of the resilient member against radial expansion.

5. A swab cup for a well swab assembly comprising, a tubular support having at least a portion of its exterior surface formed with an upwardly reducing diameter to provide an upper smaller external diameter section and a lower larger external diameter section on the support, and a tubular member consisting of homogeneous resilierit material having one end bonded to said reducing diameter portion of the support and said upper smaller external diameter section and the other end extending upwardly from the smaller diameter section.

6. The swab cup of claim 5 wherein arnular grooves are provided in said reducing diameter portion to assist in anchoring the resilient member to the support.

7. A swab cup for a well swab assembly comprising, a tubular support having at least a portion of its exterior surface formed with an upwardly reducing diameter to provide an upper smaller external diameter section and a lower larger external diameter section on the support, a tubular member consisting of homogeneous resilient material having one end bonded to said reducing diameter portion of the support and said upper smaller external diameter section and the other end extending upwardly from the smaller diameter section, and a ring of substantially non-elastic material bonded in said other end to restrain the said other end of the resilient member against a radial expansion.

8. A Well swab assembly comprising, an elongate tubular mandrel adapted to be suspended from a Wire line in a well, valve means in said mandrel permitting upward flow through the mandrel and preventing downward flow through the mandrel, and at least one swab cup supported on the exterior of said mandrel and comprising, a tubular support having at least a portion of its exterior surface formed with an upwardly reducing diameter to provide an upper smaller external diameter section and a lower larger external diameter section on the support, and a tubular member consisting of homogeneous resilient material having one end bonded to said reducing diameter portion of the support and said upper smaller external diameter section and the other end extending upwardly from the smaller diameter section.

9. A well swab assembly comprising, an elongate tubular mandrel adapted to be suspended from a wire line in Well, valve means in said mandrel permitting upward flow through the mandrel and preventing downward flow through the mandrel, and at least one swab cup supported on the exterior of said mandrel and comprising, a tubular support having at least a portion of its exterior surface formed with an upwardly reducing diameter to provide an upper smaller external diameter section and a lower larger external diameter section on the support, a tubular member consisting of homogeneous resilient material having one end bonded to said reducing diameter portion of the support and said upper small external diameter section and the other end extending upwardly from the smaller diameter section, and a ring of substantially non-elastic material bonded in said other end to restrain said other end of the resilient member against radial expansion.

References Cited in the file of this patent UNITED STATES PATENTS

Claims

1. A WELL SWAB FOR A WELL SWAB ASSEMBLY COMPRISING A TUBULAR SUPPORT HAVING A SERIES OF STEPS ON ITS EXTERIOR SURFACE FORMED BY STEP-WISE REDUCING DIAMETER SECTIONS TO PROVIDE A PLURALITY OF END-WISE FACING SHOULDERS BETWEEN SAID REDUCING DIAMETER SECTIONS, AND A TUBULAR MEMBER OF RESILIENT MATERIAL HAVING ONE END BONDED TO SAID SUPPORT SECTIONS AND THE OTHER END EXTENDING ENDWISE FROM THE SMALLER OF SAID REDUCING DIAMETER SECTIONS IN A DIRECTION AWAY FROM THE LARGER DIAMETER SECTIONS.