US3487753A

US3487753A - Well swab cup

Info

Publication number: US3487753A
Application number: US720267A
Authority: US
Inventors: Norman W Read; Henry W Blackwell
Original assignee: Dresser Industries Inc
Current assignee: Dresser Industries Inc
Priority date: 1968-04-10
Filing date: 1968-04-10
Publication date: 1970-01-06
Anticipated expiration: 1987-01-06
Also published as: DE1916815A1; FR2005955A1; GB1221262A; NL6905482A

Description

Jan. 6, WW N. W. READ ETAL WELL SWAB CUP 3 Sheetts -Smwt 1 Filed April 10, 1968 INVENXTORS:

HENRY W. BLACNWELL NORMAN W. READ vmi 2, TM

ATTOR NEY Filed April 10, 1968 Jan. 6 Wm W. READ ETM. @fiMWfifiE WELL swan CUP Filed April 10, 1968 I 3 Sheets-Sheet $5 I K I M124 I I {film I 128 I I I I [34* I I I420 I I40b [30/ I I! 142:; I I I I I441: I I I W II I I I I400 I I I I 142a [44C 132 I I I [46c I I, H I I h 1' 0 150 l 154 i wz I I I I /-/62a 156 I I I%Z I l64a I M /s4b [58/ I -I64c I I66 F I G I0 I 160/ I66c I I660? J I J United States Pat 3,487,753 WELL SWAB CUP Norman W. Read, Dallas County, and Henry W. Black- Well, Ellis County, Tex assignors to Dresser Industries, line, Dallas, Tex., a corporation of Delaware Filed Apr. 10, 1968, Ser. No. 720,267 Int. Cl. F01b 1/10; F163 9/08, 15/32 U.S. Cl. 92-180 17 Claims ABSTRACT OF THE DISCLOSURE A metal tubular support is bonded to a circular elastomeric body having an outside diameter slightly less than the internal diameter of a well pipe. The elastomeric body is divided into a plurality of swabbing elements by annular grooves, with each of the swabbing elements having annular sidewalls tapering radially outwardly and downwardly and then radially inwardly and downwardly as opposed frustoconical surfaces. In certain aspects of the invention, a number of such sidewalls are provided along the length of each swabbing element, with flexible annular lips disposed between the swabbing elements.

Field of the invention This invention relates to well swabbing devices, and, more particularly, to well swab cups adapted to be pulled up a tubing string to elevate well fluids in the tubing string.

The prior art It is a common practice to drop a well swab assembly down well tubing and then to withdraw the swabbing assembly to lift part of the fluid column up the well tubing. For instance, such swabbing is frequently used to start oil wells which have been shut down for short periods after making their monthly allowable. By withdrawing a portion of the fluid column from the well with several swabbing operations, the hydrostatic head in the well is reduced to allow the well to again flow.

Additionally, it is often desirable to milk a low level oil well by swabbing liquid in the well up to a prescribed level, dumping the liquid and then swabbing additional liquid up to the prescribed level. Well swabbing is also advantageous after acidizing a well to remove acid and water to determine the effectiveness of the acidizing treatment. Further, in the fracturing of oil wells, swab cup assemblies are often utilized to remove sand from the wells. Other uses for well swabbing are for routine testing of oil wells, and for removing paraflin and the like which collects in production oil well tubing.

In most of these applications, the swab assembly is connected to the end of a wire line by a rope socket member. A sinker bar extends from the rope socket and suspends one or more swab cup support members. One or more swab cups are attached to the support member and generally include a plurality of resilient sealing elements which seal against the interior of the well tubing when the swab cup assembly is drawn upwardly by the wire line. Fluid passages are disposed through the swab cup assembly to allow the assembly to easily fall downwardly through the well tubing, with structure being provided to close the passages when the swab cup assembly is moved upwardly in the Well tubing. The friction exerted on the swab cup against the interior of the well tubing when the swab cup is raised in the well, in combination with the extremely high pressures and temperatures present in the well, often result in wear and deterioration at the swab cups after only a few runs in a well.

Examples of swab cups previously developed are disclosed in US. Patent 3,166,334, issued Jan. 19, 1965;

3,487,753 Patented Jan. 6, 1970 US. Patents 3,266,385 and 3,266,386, issued Aug. 16, 1966; and US. Patent 3,352,212, issued Nov. 14, 1967. The configurations of these and other previously developed swab cups have been designed in efforts to reduce premature failure of the swab cups due to the tearing off of a resilient swabbing section, or due to the wearing away of a portion of the cup swab.

While swab cups heretofore developed have been generally effective for some applications, many swab cups have tended to tear, or to chunk out, while passing collars in well tubing. Additionally, problems have often arisen due to uneven distribution of heat and wear on swab cups, causing blistering of the sealing surfaces of the swab cups. Further, many previous swab cups have not been completely satisfactory with respect to the ease with which they fall downwardly in the well tubing.

Summary of the invention In accordance with the present invention, a swab cup comprises a circular elastomeric body having an outside diameter slightly less than the internal diameter of a well pipe, the elastomeric body being divided into a number of swabbing elements by annular grooves recessed into the body. Each swabbing element includes sidewalls which taper radially outwardly and downwardly and then radially inwardly and downwardly to form opposed frustoconical sections which slip easily through well casing, and yet which provide an excellent seal when moved upwardly through the well casing without chunking out when passing a casing collar.

In another aspect of the invention, each swabbing element includes a number of portions having frustoconical sidewalls tapering radially outwardly and downwardly and then radially inwardly and downwardly to produce an even distribution of heat and wear of the swabbing elements.

The drawings For a more complete understanding of the present invention and for further objects and advantages thereof, reference may now be had to the following description taken in conjunction with the accompanying drawings in which:

FIGURE 1 is an elevation view of one embodiment of a swab cup according to the present invention;

FIGURE 2 is a bottom view of the swab cup shown in FIGURE 1;

FIGURE 3 is a cross-sectional view taken along section lines 3-3 of FIGURE 2;

FIGURE 4 is a top view of the swab cup shown in FIGURE 1;

FIGURE 5 is a cross-sectional view of another embodiment of a swab cup according to the invention in a relaxed position within a well casing;

FIGURE 6 is a cross-sectional view of another embodiment of a swab cup shown in a relaxed position within a well casing;

FIGURE 7 is a cross-sectional view of another embodiment of a swab cup shown in a relaxed position down a well casing;

FIGURE 8 is a cross-sectional view of another embodiment of a swab cup shown in a relaxed position within a well casing;

FIGURE 9 is a cross'sectional view of another swab cup according to the invention shown in a relaxed position in a well pipe; and

FIGURE 10 is a cross-sectional view of another swab cup shown in its relaxed position down a well pipe.

The preferred embodiments Referring to FIGURE 1, a swab cup according to the invention is designated generally by numeral 10 and comprises three

swabbing elements

12, 14 and 16 which are separated by

annular grooves

18 and 20. The portion of the swab cup 10 shown in FIGURE 1 is constructed from a molded elastomeric body which may comprise any one of a number of synthetic rubbers, or any type of plastic having elastomeric properties suitable for the particular use of the swab cup.

As shown in FIGURES .2, 3 and 4, the elastomeric body is securely bonded to a cylindrical supporting member 22, which may comprise a metal or plastic sleeve. In actual use, a support mandrel is received within the sleeve 22 for support of the swab cup 10. The outside diameter of the elastomeric body is within a few thousandths of an inch of the internal diameter of the well tubing to be swabbed.

As best shown in FIGURES 1 and 3, each of the

swabbing elements

12, 14 and 16 includes a plurality of opposed frustoconical surfaces which define annular sealing surfaces. Specifically, the swabbing element 12 comprises two frustoconical sections 24a and 24b, each of which slope radially outwardly and downwardly at an angle with respect to the vertical axis of the swab cup. In practice, an angle 0 in the range 12 to 16 has been found advantageous to provide ease of passage of the swab cup past collars in well tubing, and to eliminate wear of the leading portions of the swabbing elements.

A pair of opposed frustoconical sections 26:: and 26b extend radially inwardly and downwardly from the surfaces 24a and 24b at an angle with respect to the vertical axis of the swab cup. In practice, an angle as ranging from 3 to and preferably 6, has been found to substantially eliminate chunking out of the swab cup 10 when passing across casing collars. Additionally, an angle for frustoconical surfaces 26a and 26b in the range of from 3 to 15, and preferably 6, provides free fall for the swab cup down well tubing. The length of the frustoconical surfaces 26a and 26b is about twice the length of the surfaces 24a and 24b.

The

annular grooves

18 and 20 slope upwardly at an angle p, which in practice is about from the horizontal. Further, the upper face of the swabbing element 12 comprises a surface 32 which slopes upwardly at an angle of about 25 from the horizontal. When the swab cup 10 is pulled upwardly in the well tubing, the pressure of the fluid above the swab cup acts downwardly upon the surface 32 to initiate downward and radially outward flexing of the swabbing elements. It will be seen in FIG- URES 1 and 3 that the opposed frustoconical surfaces on swabbing element 12 form two annular sealing portions, the cross sections of each of the sealing portions defining an apex. Upon the application of pressure on surface 32, these two annular sealing portions tend to move radially outwardly, or to node radially outwardly into contact with the interior surface of the well casing, thus providing controlled distribution of heat and wear over the surface of the swabbing element 12. This construction of the swabbing elements of the invention substantially reduces wear and blistering of the swab cup. While the opposed frustoconical surfaces of the invention have been shown joining at a sharp apex, it should be understood that in some instances a rounded or planar surface may separate the frustoconical surfaces.

Further, the upper annular sealing portion formed by surfaces 24a and 26a tends to contact the interior of the well tubing slightly harder than the lower annular sealing portion formed by

surfaces

24b and 26b. When this upper annular sealing portion becomes worn, the lower annular sealing portion then tends to contact the interior of the well tubing with greater force. The present swab cup thus provides a progressive downward wear that increases the useful life of the swab cup.

The construction of the swabbing

elements

14 and 16 is generally similar to that of the swabbing element 12, with the exception that one additional annular sealing portion is provided. The swabbing element 14 includes three identical frustoconical surfaces 24c-e and three identical surfaces 26ce. These opposed frustoconical surfaces define three annular sealing portions which provide a controlled distribution of heat and wear over the surface of the swabbing element. These annular sealing portions also wear progressively from the top portion downwardly.

Swabbing element 16 includes four sets of opposed frustoconical surfaces 24f-i and 26f-i. The four annular sealing portions thus formed eliminate blistering of the swabbing element, and also provide progressive downward wear. The upper frustoconical surfaces of each of the swabbing

elements

14 and 16 slope radially outwardly and downwardly at an angle in the range of 12-16 with respect to the longitudinal axis of the swa b cup. The remaining alternate frustoconical surfaces of the swabbing

elements

14 and 16 slope inwardly and downwardly at an angle in the range of from 3 to 15, with the preferred angle being 6, with respect to the vertical.

In practice, the swab cup shown in FIGURES 1-4 has been found to provide excellent durability in a number of runs in well casings up to 9,000 feet in length, without severe deterioration due to chunking out or wear. This swab cup will lift on the order of 3,000 feet of liquid in a single pull without tearing.

FIGURE 5 illustrates another embodiment of a swab cup designated generally by numeral 34 shown within a well casing 36. It will be understood that the swab cup support mandrel is not shown for ease of illustration. The swab cup 34 comprises an elastomeric body bonded to a metal cylinder 37, and is illustrated in its relaxed, free falling position. The swab cup 34 has an outer diameter sufl icient to extend to within a few thousandths of an inch of the interior walls of the well pipe 36. The swab cup includes three swabbing

elements

38, 40 and 42 which are similar to the swabbing elements shown in the embodiment of FIGURES 1-4. However, flexible annular lips 44, '46 and 48 are disposed between the swabbing elements. The flexible

annular lips

44, 46 and 48 extend radially outwardly and upwardly for slightly greater distances than the swabbing

elements

38, 40 and 42.

The opposed frustoconical surfaces of the swabbing

elements

38, 40 and 42 operate in the same manner as the embodiment previously described in order to provide free falling of the cup swab within the well pipe 36, and also to prevent chunking out and to provide even wear of the swab cup. The flexible

annular lips

44, 46 and 48 provide the additional advantage of sealing downwardly against the swabbing elements with a very slight upward movement of the swab cup, due to the fact that the flexible lips do not need an appreciable fluid load in order to flex. Thus, the swab cup embodiment shown in FIGURE 5 allows swabbing of relatively small amounts of fluid. In some instances, it may be desirable to provide opposed frustoconical surfaces, having the configuration previously described, on the outside surfaces of the

flexible lips

44, 46 and 48.

FIGURE 6 illustrates another embodiment of the present invention comprising an integral molded body 50 which is bonded to a hollow support cylinder 52. The swab cup is shown in its relaxed position down a well casing 54 which has a casing collar 56 therein. The swab cup comprises three swabbing

elements

58, 60 and 62, separated by

annular grooves

64 and 66. It will be seen that each of the swabbing

elements

58, 60 and 62 comprise a pair of opposed frustoconical surfaces having substantially the same configuration as portions of the swab cups illustrated in FIGURES 1-5.

Specifically, the swabbing elements include leading frustoconical surfaces 6811-0 which slope radially outwardly and downwardly at an angle in the range of 12 to 16 with respect to the vertical. It has been found that such leading surfaces having angles in this general range substantially reduce wear on the upper portions of the swabbing elements and enable the swab cups to easil pa s collars in the well tubing.

The swabbing elements also include lower annular surfaces 70a-c which slope radially inwardly and downwardly at an angle in the range of 3 to 15 to the vertical. As may be seen from the drawings, the length of the surfaces 70a-c are several times the length of the surfaces 68a-c. As previously described in detail, the angle of the annular surfaces 70rz-c reduce substantial chunking out of the swabbing elements during operation of the swab cup past tubing collars and the like. Further, the lengths of the swabbing

elements

58, 60 and 62 progressively increase from the top downwardly in order to provide improved wear for the swab cup. In some instances, it may be desirable to provide a progressive shortening of the length of the swabbing elements from the topmost down.

The provision of the opposed frustoconical surfaces having cross sections defining an apex causes each of the swabbing elements to node radially outwardly when pressure is applied to the upper portion of the swab cup. As previously described, this noding comprises a bulging of each of the swabbing elements in the area of the apex to seal against the interior diameter of the well pipe. This noding minimizes blistering of the swabbing elements while pulling loads, as relatively small areas of the swabbing elements are in contact with the tubing. This tends to reduce friction and more evenly distribute heat and wear on the elements.

FIGURE 7 illustrates another embodiment of the invention wherein a swab cup 80 is shown in its relaxed position within a well casing '81. Swab cup 80 comprises a hollow support tube 82 bonded to an elastomeric annular body having three swabbing

elements

84, 86 and 88 which are similar to the swabbing elements shown in FIGURE 6. However, the embodiment in FIGURE 7 includes flexible

annular lips

90, 92 and 94 which are disposed between the swabbing elements and which extend radially outwardly for a small distance beyond the apex of the swabbing elements. In practice, swab cup 80 operates in a similar manner as the swab cup shown in FIG- URE 6, with the exception that the

flexible lips

90, 92 and 94 are more easily flexed by smaller pressures to enable the swab cup to pick up light loads of liquid.

FIGURE 8 illustrates another embodiment of the invention wherein a swab cup designated generally by the numeral 96 comprises a cylindrical support 98 about which an integral elastomeric body is bonded. Swab cup 96 is shown in its relaxed position in a well tubing 100. The elastomeric body comprises three swabbing

elements

102, 104 and 106. Flexible

annular lips

108, 110 and 112 are disposed between the swabbing elements and have sufficient resiliency to enable the swab cup to lift relatively light loads in the manner previously described.

The swabbing elements comprise leading frustoconical surfaces 114x1 which slope radially outwardly and downwardly at an angle in the range of 12 to 16 to the vertical in the same manner as the leading surfaces previously described. Below the leading portions on each of the swabbing elements, frustoconical surfaces 11611-0 slope radially inwardly and downwardly at angles 111 the range of from 3 to 15 to the vertical. These opposed frustoconical surfaces facilitate the passage of the swab cup past tubing collars, reduce wear on the swabbing surfaces, and provide apex portions which tend to node outwardly to reduce wear and friction.

The lower portions of each of the swabbing

elements

102, 104 and 106 shown in FIGURE 8 are formed in saw tooth" or tiered frustoconical sections to provide multiple noding portions. Specifically, a pair of saw tooth portions 118a-b are formed on the lower part of the swabbing element 102. Each of these saw tooth portions is comprised of a face sloping radially outwardly and upwardly at an angle to the vertical of approximately 6 The lower portions of each of the saw tooth portions comprises a frustoconical section sloping radially inwardly and downwardly at an angle in the range of 3-15 to the vertical, with the preferred angle being 6 In a similar manner, saw tooth portions 120a-b of the same configuration, but of slightly greater lengths, are formed on the swabbing element 104. Similarly, two saw tooth elements 122a-b of the same configuration, but of even greater lengths, are formed on the swabbing element 105. The provision of these saw tooth, or tiered frustoconical sections, on the swab cup 96 defines a plurality of surfaces which node under pressure to provide a reduction in friction and blistering of the swabbing elements.

FIGURE 9 illustrates another embodiment of the invention wherein a swab cup designated generally as 134 comprises a cylindrical support member 126 about which an elastomeric body is bonded. The elastomeric body is divided into three swabbing

elements

128, 130 and 132 by

annular grooves

134 and 136. The swab cup 124 is shown in its relaxed position within a well casing 138.

The configuration of the swabbing elements of swab cup 124 is generally similar to the swabbing elements shown in FIGURES 1 and 3. However, in FIGURE 9, the annular projections formed by opposed frustoconical surfaces progressively decrease in outer diameter from the topmost down on each swabbing element. For instance, the annular projection 14011 has a slightly greater outer diameter than the lower annular projection 142a. Similarly, referring to the other swabbing elements, the annular projections 14022 and 1400 have slightly greater outer diameters than the respective lower annular projections 142b and 142C.

Correspondingly, the annular projections 1441) and 144c have smaller outer diameters than the respective upper annular projections, while the bottom annular projection 1460 has the smallest outer diameter of any of the annular projections. It will be noted that although the annular projections progressively decrease in diameter along the length of each swabbing element, the annular projections ac each have the same outer diameters. Similarly, the annular projections 14.2ac and 144b-c have respectively the same outer diameters. The configuration of swab cup 124 provides advantages similar to those previously discussed, and additionally provides a progressive downward wear which prolongs the useful life of the swab cup.

FIGURE 10 illustrates another embodiment of the invention comprising a swab cup shown in its relaxed position within a well pipe 152. Swab cup 150 includes a tubular support 154 which is bonded to an annular elastomeric body divided into three swabbing

elements

156, 158 and 160. The swabbing elements include a plurality of annular projections formed by opposed frustoconical surfaces in 'a manner similar to the configuration of FIGURES 1 and 3. However, in FIGURE 10, the

v annular projections of adjacent swabbing elements have slightly different outer diameters.

For instance, the annular projections 162a-b have the same outer diameters, but have larger outer diameters than the annular projections 164a-c. The annular projections 164ac have the same outer diameters, but have slightly larger outer diameters than the annular projections 166a-d. Thus, the outer diameters of the swabbing

elements

156, 158 and progressively decrease from the topmost down of the swab cup 150. This graduated outer diameter of the swab cup 150 provides a progressive downward wear which prolongs the useful life of the swab cup. The annular projections formed by opposed frustoconical surfaces according to the invention provide free fall of the swab cup down a well pipe, and reduce chunking out and blistering of the swab cup.

It will be understood that further modifications are encompassed in the invention, such as providing more or fewer pairs of opposed frustoconical sections on swabbing elements of the various embodiments, according to various use requirements. Further, the number of swabbinv elements could also be varied.

What is claimed is:

1. A resilient swab cup for swabbing out pipe of predetermined internal diameter comprising:

a circular elastomeric body having an outside diameter slightly less than said internal diameter and being divided into multiple swabbing elements by annular grooves recessed into the body, each swabbing element including frustoconical surfaces tapering radially outwardly and downwardly and then radially inwardly and downwardly.

2. The swab cup of claim 1 wherein said swabbing elements comprise a plurality of pairs of opposed frustoconical surfaces.

3. The swab cup of claim 1 wherein said frustoconical surface tapering inwardly and downwardly has a length in the axial direction of said body substantially greater than the length of the other of said frustoconical surfaces in the axial direction of said body.

4. The swab cup of claim 1 and further comprising a flexible annular lip disposed between said swabbing elements and extending radially outwardly and upwardly from said body.

5. The swab cup of claim 1 wherein said frustoconical surface tapering radially inwardly and downwardly slopes at an angle to the vertical of in the range of 3 to degrees.

6. The swab cup of claim 1 wherein said frustoconical surface tapering radially outwardly and downwardly slopes at an angle to the longitudinal axis of said body of in the range of 12 to 16 degrees.

7. The swab cup of claim 1 wherein said swabbing elements are progressively longer from one end of said body to another.

8. The swab cup of claim 1 and further comprising a plurality of tiered truncated conical sections disposed on each said swabbing element.

9. The swab cup of claim' 1 wherein like portions of adjacent swabbing elements have different exterior diameters.

10. A swab cup for swabbing fluids from a well pipe comprising:

a rigid tubular support member,

a circular elastomeric body mounted on said support member and having an outside diameter slightly less than the internal diameter of said pipe and being divided into a plurality of swabbing elements by annular grooves recessed into the body,

each said swabbing element having at least one sealing portion including a leading truncated conical portion sloping radially outwardly and downwardly and a second truncated conical section having its base adjacent the base of said first truncated conical section and tapering radially inwardly and down wardly.

11. A swab cup for swabbing a fluid from a well pip comprising:

a rigid tubular support member,

a resilient body of elastomeric material bonded to said tubular support and being divided into multiple swabbing elements by annular grooves recessed therein,

each said swabbing element including a plurality of annular projections having outer diameters slightly less than the internal diameter of said well pipe, with the diameter of said swabbing element between said annular projections being smaller than the said outside diameter of said annular projections such that the principal contact of said swab cup with the internal diameter of said well pipe is with said annular projections at least one of said annular projections comprises a first frustoconical surface extending radially outwardly and downwardly and an opposed second frustoconical surface extending radially inwardly and downwardly.

12. The swab cup defined in claim 11 wherein the outer diameters of said annular projections progressively decrease along a length of said swab cup.

13. The swab cup defined in claim, 12 wherein the outer diameter of said annular projections progressively decrease along the length of each said swabbing element.

14. The swab cup defined in claim 12 wherein the outer diameter of said annular projections decrease from one swabbing element to another.

15. The swab cup of claim 11 wherein said annular projections have a cross-sectional saw-tooth configuration.

16. The swab cup of claim .11 wherein the length of said swabbing elements progressively increases from one end of said swab cup to the other.

17. The swab cup of claim 11 comprising annular flexible lips disposed between adjacent swabbing elements.

References Cited UNITED STATES PATENTS 2,452,466 10/1948 Jaswell 277208 X 3,166,334 l/l965 Waldrop 277208 3,179,022 4/1965 Bloudoff 92180 X 3,352,212 11/1967 Read 92192 CARROLL B. DORITY, JR., Primary Examiner U.S. Cl. X.R.