US3677143A

US3677143A - Well swab

Info

Publication number: US3677143A
Application number: US50118A
Authority: US
Inventors: Charles D Crickmer
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-06-26
Filing date: 1970-06-26
Publication date: 1972-07-18
Anticipated expiration: 1989-07-18

Abstract

A well swab and more particularly a well swab having an improved arrangement of reinforcing members therein including inner and outer concentric rows of circumferentially spaced reinforcing members with the reinforcing members of the inner and outer rows being spaced such that there is no overlapping therebetween and further that the reinforcing members have upper portions thereof which extend axially upwardly from the swab cup body member.

Description

Umted States Patent [151 3,677,143 Crickmer 1 July 18, 1972 s41 WELL SWAB 2,912,291 11/1959 Moore ..92/241 [72] Inventor: Ch I D Cm 2923 Memorial 3,448,987 6/1969 Stowe ..277/181 Dnve Houston 77024 Primary Examiner-Martin P. Schwadron [22] Filed: June 26, 1970 Assistant Examiner-Irwin C. Cohen pp No 50 118 Attorney-Howard E. Sandler [57] ABSTRACT A we" swab and more a wab having an improved arrangement of reinforcing members therein including [58] Field Search igf {g i inner and outer concentric rows of circumferentially spaced reinforcing members with the reinforcing members of the inner and outer rows being spaced such that there is no over- [56] Rem-"Ices Cited lapping therebetween and further that the reinforcing mem- UNITED STATES PATENTS bets have upper portions thereof which extend axially upward] from the swab cu bod member. 2,723,721 11/1955 Corsette ..l66/202 X y p y 2,887,347 5/1959 Losey ..92/241 9 Claims, 4 Drawing Figures PATENTEU JUL! 81972 INVENTOI? CHARL 5 D CR/CKMFR A Home y FIG. I

WELL SWAB Well swab assemblies of a type used in oil and gas wells are lowered into a tubing to a predetermined depth and rapidly lifted upwardly therethrough to clean out drilling mud from an oil well tubing, unload water from a gas well and the like. Such swab assemblies generally have a plurality of spaced flexible swab cups positioned about the outer periphery thereof. As the swab assembly is lifted upwardly the swab cups expand radially outwardly to form a fluid tight seal between the swab assembly and the inner periphery of the tubing thereby enabling the unloading of drilling mud and the like from the tubing.

In a swabing operation the swab cups are subjected to pressures on the order of several thousand pounds per square inch and as such the design thereof must produce cups having sufficient strength to withstand such pressures while maintaining flexibility to enable the cups to pass through the tubing in sealing engagement therewith.

Various cup reinforcing means have been used in an attempt to design a swab cup having sufficient strength and flexibility, such means including: a row of reinforcing bars concentrically positioned inwardly adjacent the outer periphery of the swab cup, such bars being spaced from one another or touching; and a continuous panel reinforcing positioned inwardly adjacent the outer periphery of the swab cup. Practice has shown the reinforcing means comprising touching bars or continuous panels resulted in swab cups which lacked sufficient flexibility to contract when passing through pipe ends, necked down portions of pipe, out of round or dented pipe and the like. Additionally, the continuous panel type reinforcing is expensive to fabricate and is more susceptible to fatigue failure. The reinforcing means comprising the spaced bars has been found to be adequate insofar as initial strength and flexibility requirements, however, rubber feed wear during swabbing operation causes premature blowout failure between the bars.

By means of the present invention, which includes a swab cup having inner and outer rows of circumferentially spaced reinforcing bars, the inner bars being alternately spaced with respect to the outer bars, the strength and flexibility requirements of the swab cup are accomplished while substantially reducing the rubber feed between the outer reinforcing bars.

These and other objects and advantages of this invention will become more readily apparent from a reading of the following description and drawings, in which:

FIG. 1 is a side view, partly in section, of a well swab assembly provided with swab cups embodying the principles of this invention;

FIG. 2 is a perspective view, partly in section of a swab cup of this invention;

FIG. 3 is a cross sectional view of a swab cup taken on lines Ill-III of FIG. 2;

FIG. 4 is a cross sectional view of a swab cup taken on lines lV-IV of FIG. 2;

FIG. Sis a portion of a cross sectional view similar to FIG. 3 showing an alternative form of a swab cup embodying the principles of the present invention; and

FIG. 6 is a cross sectional view of an alternative form of a reinforcing member utilized in a swab cup embodying the principles of the present invention.

A well swab assembly 10 (FIG. 1) shown within a well casing or tubing 22 includes a hollow tubular mandrel 12 having a valve cage 14 and a nose piece 16 releasably secured thereto at the upper and lower ends thereof, respectively. Valve cage 14 has the upper end thereof releasably secured to suitable means (not shown) for moving the well swab assembly 10 through a well tubing 22. A suitable ball valve 20 is movably disposed within cage 14 such that when assembly 10 is descending into the well tubing 22, drilling fluid within tubing 22 downwardly of assembly 10 flows: through a plurality of portals 24 in nose piece 16 which portals 24 communicate between tubing 22 and the inner periphery of swab assembly 10; through mandrel 12 whereat valve 20 is moved upwardly from the normal seated position thereof, such normal seated position closes oh the mandrel 12 at the upper end thereof; and through a plurality of portals 26 in cage 24 wherefrom the fluid discharges from assembly 10 into tubing 22 adjacent the upper end of assembly 10.

A plurality of swab cup assemblies, as shown two swab cup assemblies 28, are disposed about mandrel l2 and held in spaced relationship to one another and to the valve cage 14 by means of spacer sleeves 30. The lowermost swab cup assembly 28 has the lowermost end thereof in contact with the uppermost end of nose piece 16. Mandrel 12 can be provided with suitable shoulder portions (not shown) adjacent swab cup assemblies 28 and valve cage 14 and if such shoulder portions are provided, spacer sleeves 30 would not be required.

Each assembly 28 includes an annular bowl or thimble member 32 at the lower end thereof constructed of steel or the like and a resilient tubular body or swab cup 34 formed of any suitable elastomeric type material, such as rubber or plastic which possess physical properties of tensile, elongation, hardness and the like of well known values in the swab cup art. The lower end of swab cup 34 engages thimble member 32 and extends upwardly therefrom.

As the well swab assembly 10 starts to ascend, the pressure of the well fluid upwardly of the swab cups 34 urges the upper free ends thereof radially outwardly into frictional sealing engagement with the walls of tubing 22. The weight of the fluid upwardly of the ascending assembly 10 subjects the swab cups 34 to relatively high stresses often in the order of several thousand pounds per square inch and as such the cups must have sufficient strength to withstand such pressures while maintaining sufiicient flexibility to enable the cups 34 to deform radially outwardly into sealing engagement with the walls of tubing 22 as described hereinabove. To obtain such strength while maintaining the necessary flexibility the swab cups 34 are provided with the reinforcing means of this invention, which reinforcing means include inner and outer rows of concentrically arranged reinforcing bars, such bars being indicated at 42 and 44 respectively. The reinforcing bars in each row are spaced circumferentially such that

bars

42 and 44 are staggered with respect to one another. The staggering of

bars

42 and 44 is necessary for as well swab assembly 10 is ascending, the elastomer of the swab cups 34 intermediate adjacent outer bars 44 has a tendency to extrude outwardly thereby resulting in excessive swab cup wear in such extruding areas which causes blow out and premature swab cup failure. The inclusion of an inner bar 42 intermediate adjacent outer bars 44 reduces the amount of extrusion during the ascending of assembly 10 and as such increases the life of a swab cup 34.

Bars

42 and 44, sleeve 30, thimble member 32, and swab cup 34 may be molded in one operation into a unitary swab cup assembly 28. Since the swab cup 34 is formed of a resilient elastomeric material, the upper portion thereof is free to flex inwardly and outwardly and accordingly the reinforcing

bars

42 and 44 move as required to accommodate such flexing movement.

Swab cup 34 comprises: an elongated hollow tubular main body portion 36; a lip portion 38 extending upwardly from the upper end of main body portion 36 which, as shown, has an outer diameter thereof approximately equal to the outer diameter of portion 36 and a lower inside peripheral surface 37 or portion 38 which tapers upwardly, radially outwardly from the inner periphery of portion 36 to a point intermediate the inner and outer diameter of portion 36 whereat an upper inside peripheral surface 39 of portion 38 progresses upwardly at a substantially constant inner diameter; and a plurality of circumferentially spaced finger portions 40 which extend upwardly from lip portion 38. The outer periphery of finger portions 38 taper radially inwardly from the lowermost ends thereof. Outer reinforcing bars 44 are circumferentially spaced radially inwardly adjacent the outer periphery of portion 36. The lower ends of reinforcing bars 44 can be supported in any suitable manner for example, as shown, such lower ends are received within thimble member 32 or alternatively, such lower ends can be encapsulated by portion 36 during the molding thereof such that support therefor is by the elastomeric material of portion 36 only. The upper ends of bars 44 are respectively encased within finger portions 38 and taper radially inwardly, as shown such taper being in a plane substantially parallel to the taper of respective finger portions 40. The radially inward tapering of finger portions 40 and bars 44 at the upper ends thereof reduces the probability of a well swab assembly being fouled on necked down or out of round or dented portions of well tubing 22 during a swabbing operation.

lnner reinforcing bars 42 have the lower ends thereof sup ported in a manner hereinabove described with reference to bars 44 and extend upwardly therefrom in a plane substantially parallel to the longitudinal axis of assembly 28. A lower portion 46 of bars 42 is encased within body portion 34 outwardly adjacent the inner periphery thereof. An upper portion 48 of bars 42, which portion 48 is not encased by swab cup 34, extends through peripheral surface 37 and has the uppermost end thereof spaced upwardly from the upper end of lip portion 38.

The above described arrangement of reinforcing bars 42 provides an efficient and relatively long term use of a swab cup 34 for experience has shown that the elastomeric material, intermediate adjacent bars 44 and spaced downwardly from the upper ends of lip portion 38, wears away rapidly during swabbing operations. Accordingly, if the uppermost ends of bars 42 were encased by elastomeric material and had the uppermost extent thereof below the upper end of lip portion 38, the bars 42 would have a tendency to move radially outward between adjacent bars 44 where the elastomeric material was worn away and possibly catch on necked down or dented or out of round portions of the tubing 22 during the swabbing operation. By providing for an arrangement where portion 48 extends upwardly of lip portion 38 the above described tendency of bars 42 to move radially outward between bars 44 of the worn intermediate sections of elastomeric material is greatly reduced.

The significant features of this invention include: the staggered arrangement of inner and outer rows of spaced reinforcing bars within a swab cup which staggered arrangement reduces rubber feed between adjacent outer reinforcing bars while still maintaining required swab cup flexibility; and the arrangement whereby the inner row of reinforcing bars have the upper portions extending upwardly from the main body portion 36. Accordingly, by following the principles taught by this invention one skilled in the art can achieve the hereinabove mentioned features with alterations to the preferred embodiment hereinabove described, for example: the upper radially inward tapering portions of bars 44 can be free of encasing elastomeric material, that is, swab cup assembly 28 can be constructed without finger portions 40 or; the upper radially inward tapering portions of bars 44 can be encased by an elastomeric flash rather than the molded finger portions 40; portion 48 of bars 42 can be encased by an elastomeric flash or molded finger portions which extend upwardly from main body portion 36; reinforcing

bars

42 and 44 can be of any suitable cross section, for example, circular, triangular or square and such bars need not have the same cross section in a given swab cup assembly; lip portion 38 need not have the tapering surface 37 but rather can be of a constant inner diameter throughout the length thereof; and a well known tube shaped member can be provided adjacent the inner diameter of body portion 36 and at a lower end portion thereof for additional reinforcing if required.

Some of the alternatives discussed hereinabove are shown in FIGS. 5 and 6. FIG. 5 is a portion of a cross sectional view similar to FIG. 3 and showing an alternative form of a swab cup with the primary distinction between FIG. 5 and FIG. 3 being that the upper radially inward tapering portion of bars 44 are encased by a thin elastomeric coating or flash and portion 48 of bars 42 are encased by molded finger portions which extend upwardly from the main body portion 36. FIG. 6 Illustrates a bar 44' having a generally triangular rather than a circular cross section.

The description herein does not limit the structureof this invention and the invention is defined by the scope of the claims hereinafter.

What is claimed is:

1. A swab cup comprising: an axially elongated flexible elastomeric generally annular body member; reinforcing means including inner and outer concentric rows of circumferentially spaced reinforcing members which extend generally axially of said body member; said outer row being radially inwardly adjacent the outer periphery of said body member; said inner row being radially outwardly adjacent the inner periphery of said body member; the reinforcing members of said inner row being spaced circumferentially with respect to adjacent reinforcing members of said outer row with no overlapping therebetween; and said reinforcing members of said inner row having upper portions thereof which extend generally axially upwardly from the uppermost end of said body member.

2. A swab cup as specified in claim 1 wherein said reinforcing members of said outer row have upper portions thereof which extend generally axially upwardly from said uppermost end of said body member.

3. A swab cup as specified in claim 2 wherein said upper portions of said reinforcing bars of said outer row taper radially inwardly from said uppermost end of said body member, the uppermost ends of said upper portions of said reinforcing members of said outer row being spaced radially outwardly from the inner periphery of said body member.

4. A swab cup as specified in claim 3 wherein said upper portions of said reinforcing members of said outer row are respectively encapsulated by circurnferentially spaced up wardly extending elastomeric finger portions.

5. A swab cup as specified in claim 3 wherein said upper portion of said reinforcing members of said outer row are encapsulated by a thin elastomeric coating.

6. A swab cup as specified in claim 1 wherein said upper portions of said reinforcing members of said inner row are encapsulated by circumferentially spaced upwardly extending elastomeric finger portions.

7. A swab cup as specified in claim 1 wherein said upper portions of said reinforcing members of said inner row are encapsulated by a thin elastomeric coating.

8. A swab cup as specified in claim 1 wherein said reinforcing members have a circular cross section.

9. A swab cup as specified in claim 1 wherein at least some of said reinforcing members have a polygonal cross section.

Claims

4. A swab cup as specified in claim 3 wherein said upper portions of said reinforcing members of said outer row are respectively encapsulated by circumferentially spaced upwardly extending elastomeric finger portions.