US3497002A - Guided frangible slips - Google Patents

Description

Feb. 24, 1970 w. o. R A 3,497,002

GUIDED FRANGIB LE SLIPS Filed July 11, 1968 2 Sheets-Sheet 1 W/ ///am 0. Be r/ yman INVENTOR.

RYMAN Feb.- 24, 1970 Filed July 11, 1968 W////am 0, .15 e r/j/mz/r Y INVENTOR.

United States Patent M 3,497,002 GUIDED FRANGIBLE SLIPS William 0. Berryman, Houston, Tex., assignor to Schlumberger Technology Corporation, New York, N.Y., a corporation of Texas Filed July 11, 1968, Ser. No. 744,171 Int. Cl. E21b 23/06, 33/ 1 28, 33/129 US. Cl. 166123 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION This invention relates to a well tool and more particularly to anchoring means on a well tool.

Packers or plugs which are permanently set in a well bore typically use slip type anchoring means. The slips are generally provided with teeth or wickers on their external surface which, when the slips are expanded, bite or dig into the casing or tubing wall to couple or anchor the well tool in the well bore. If it is later desired to remove the tool, this can be accomplished by drilling, milling or chipping. In these cases it is desirable to fabricate the slips, as well as the tool, from a frangible material such as cast iron so that it may easily be broken up by the action of a drill bit.

The slip assembly normally must be maintained in a retracted position dring passage through the well bore until such time as it is desired to anchor the tool by setting the slips. At this time, the tool is actuated and the slips are forced radially outward to engage the surrounding casing.

The slips must be readily movable in a radial manner when desired, but not so easily movable that they can inadverently be actuated and expanded during passage through the well bore. One prior art approach has been to use shear screws or pins to releasably retain separate slip members relative to the tool body until a setting point is reached. Upon activation of the tool, these pins are sheared to allow the slips to be extended into gripping contact with the casing.

Another approach taken in the prior art has been to use a one-piece annular slip construction of a frangible material such as cast iron. To set such slips, a conical or frusto-conical expander is forced inside the slip member and fractures the frangible material to form slip segments. To enhance and control this breaking action, the slip construction can have weakened sections aolng longitudinal lines. Obviously, such a one-piece slip construction eliminates the need for shear pins or screws to prevent accidental setting.

To insure the best possible anchor of the slips with the casing, the broken slip sections should engage the casing in such a manner that they are aligned in a horizontal plane (a plane at right angles to the longitudinal axis of the casing) as well as being uniformly circumferentially distributed about the circumference of the inside of the casing. If these two conditions are not both met, then the grip provided by the slips will not be as uniform and 3,497,002 Patented Feb. 24, 1970 powerful as is possible. The uniform circumferential distribution of the slip segments will assure that the well tool is centrally aligned in the bore of the casing. If the slip segments are bunched on one side of the casing the tool body will tend to be pushed away from the side of the casing which contains most of the slip segments. Additionally, this will tend to weaken the grip of the bunched segments because the tool will be able to flex or move away from them and an even distribution of setting pressure will not be maintained.

Because there is no practical way to assure that the breaks along the longitudinal weakened sections will all occur precisely at the same instant in time, means can be provided to promote horizontal alignment of the broken slip sections. Otherwise, the first slip segment which becomes free to move can separate from the remaining, as yet unbroken, segments and slide down the expander cone and become wedged between the expander cone and the wall of the casing. If this happens, the expander cone will cause the teeth of that segment to engage the casing first. This will prevent the free upward movement of the expander cone to further fracture the slip assembly and anchor the other segments thereof, as they are broken.

This problem is more troublesome in the case where the Well bore is not vertical but rather is inclined or slanted. Here the tool will generally be oif center in the well bore when setting is started. In this case, if one slip segment becomes separated from the others and slides down the expander cone prematurely, it can wedge itself in the widest part of the annular space between the tool and the casing. If this occurs, it will keep the tool oif centered in the well bore and the maximum efiiciency of the packing element will not be realized.

This problem has been recognized in the prior art and various attempts made to obviate these difiiculties. In segmented slips, snugly fitting and loosely fitting horizontally aligned guide pins joining the slip segments to maintain some mechanical linkage between the sections and, thereby, maintaining horizontal alignment of the sections during expansion have been used. Another approach has been to equip breakable slips with internal powerful expander springs to thrust and propel the broken sections radially into immediate contact with the casing walls as soon as they are broken. Prior art attempts to achieve uniform circumferential distribution of slips have relied on the use of weakened sections of differing strengths programmed to break in a given sequence when acted on by the expander cone. Further, various radial guiding means have also been utilized such as guiding bars running longitudinally through the slips and guide pins radiating outwardly from the central tool body and carried in bores or slots in the slip sections.

The present invention does not use complicated spring arrangements, guide pins carried in bores, or weakened sections of different strengths to maintain horizontal and circumferential alignment of the broken slip sections, but rather makes use of a more simple frictional band arrangement in combination with a specially shaped setting tool in order to accomplish this end.

Accordingly, it is an object of this invention to provide a well tool with an anchoring means including a onepiece frangible slip and a combination of effective economical means for maintaining the horizontal and circumferential alignment of corresponding portions of slip segments when broken.

SUMMARY OF THE INVENTION In the well tool of the present invention, the anchor means include a unitary, hollow, cylindrical slip member of a frangible material such as cast iron. The outer surface of this member is provided with a plurality of circumferential teeth or wickers for engaging the well casing in a gripping manner upon fracture and expansion of the slip member by an expanded cone. The lower portion of the inner surface of the annular slip member embodying the present invention is conically tapered over a portion of its length to cooperatively engage an expander cone which is slidably mounted on the well tools central body. The remainder of the inner surface of the one-piece frangible slip member is of a uniform circular diameter such as to provide a sliding fit with the central body of the well tool. The upper shoulder of the slip member is provided with raised tang portions to cooperatively engage corresponding notches on the lower end of a setting tool. The setting tool is releasably coupled to the upper end of the well tool.

The tangs on the upper shoulder of the slip member cooperatively intermesh with the notches in the setting tools lower portion to circumferentially guide broken portions of the slip assembly as the assembly is expanded radially outward by the expander cone. This assures a symmetrical circumferential distribution of the broken portions of the slip assembly about the inner wall of the well casing.

A plurality of longitudinal weakened sections are defined in the slip member by a plurality of external longitudinal notches cut at uniform intervals about the circumference of the member. These notches do not extend completely through the cylindrical wall of the member. A circumferential, flanged, retaining groove is provided in the external surface of the slip member. This groove carries within it and retains there a unitary expansible steel band which, when the expander cone acts on the slip to fracture it into separate sections, maintains the horizontal alignment of corresponding portions of these broken sections.

The novel features of the present invention are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation together with further objects and advantages thereof, may best be understood by way of illustration and an example of an embodiment when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a schematic partially sectioned view illustrating the present invention utilized as an upper slip on a wireline set tool in a well bore.

FIGURE 2 is a longitudinal elevation of the slips embodying the present invention showing the notch and tang arrangement on its upper shoulder and showing the oneway expansible steel band carried in a retaining groove about the external surface.

FIGURE 2A is an enlargement showing in more detail the retaining groove on the external surface used to retain the unitary one-way expansible band.

FIGURE 3 is a top view of the same embodiment of the present invention showing in more detail the shape of the raised tang portion on its upper shoulder which cooperatively engages the corresponding setting tool notches.

FIGURE 4 is a view in cross section of a portion of the setting tool showing the notches in the lower end thereof which engage the raised tangs on the upper shoulder of the present invention.

FIGURE 5 is a schematic view showing the action of the retaining notch and extension combination of the setting sleeve and upper slip shoulder with the broken sections of the slip assembly nearly in fully expanded position.

DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention concerns an improved unitary breakable slip for use on well tools by which the slip attains improved gripping with the walls of the well casing by utilizing a novel combination of means to assure proper horizontal and circumferential alignment of corresponding portions of the broken slip segments when set.

In FIGURE 1, a well casing 11 is shown traversing earth formations and cemented in place. A well tool 12, such as a permanent bridge plug, is suspended in casing 11 by means of a wireline 13. Wireline 13 is coupled to a setting tool 14 which is releasably coupled to bridge plug 12.

Bridge plug 12 has a central mandrel 15 which carries from top to bottom an upper slip assembly 16, an upper expander 17, a packing element 18, a lower expander 19 and a lower slip 20. The arrangement is such that when mandrel 15 is moved upwardly, expander cone 17 acts to fracture upper slip 16 and expand the broken segments thereof radially outward into setting contact with the well casing 11. Further upward movement of mandrel 15 causes expansion of packer element 18 and upward movement of lower slips 20 over lower expander 19 into setting engagement with the wall of the casing 11. A oneway body lock 21 connects mandrel 15 and upper expander 17 to one another to prevent the mandrel from moving downwardly relative to expander 17 when the setting process is finished. At this point, setting tool 14 is released and withdrawn on wireline 13 leaving plug 12 permanently anchored to the casing.

Lower slips 20 have alternate, longitudinally extending grooves from respective end surfaces to provide an integral annular member which can be radially expanded without fracture of the member. Further details on lower slips 20 can be found by reference to U.S. Patent No. 3,298,440.

The upper slip assembly of bridge plug 12 is shown in detail in FIGURES 2, 2A and 3. A one-piece frangible slip element 16, preferably made of cast iron, is provided with teeth or wickers 16a on its external surface for grippingly engaging the wall of well casing 11. Longitudinal weakened sections are provided in slip member 16 by a plurality of longitudinally extending notches 22 extending partially through its thickness. The upper portion of the annular slip member 16 is provided with notches 23 which form upwardly extending tangs 24 for cooperatively engaging with downwardly extending extensions 31 and notches 33 in a steel setting sleeve 32. Setting tool notches 33 have parallel radial edges and are sized to a width slightly wider than tangs 24. The clearance provided by this excess width is suflicient to allow slight rotation of broken segments of slip member 16 as the broken segments are expanded radially outward and assume the larger circumference of the well casing 11. It should be noted that tangs 24 appear in a configuration such that each of the tangs 24 extends over a circumferential portion of annular member 16 containing two of the weakening notches 22 and that thereby setting tool notches 33 each engage portions of three sections of slip member 16 when broken.

A circumferentially extending recess 26a, of uniform diameter is provided in member 16 near its upper shoulder and is adapted to receive therein a unitary expansible steel band 25. Recess 26a, shown in larger detail in FIG. 2A, has upper and lower annular grooves 27 formed by upper and lower flanges 26. At one point around the circumference of member 16 there is a circumferential gap 28 provided in both flanges 26. Gap 28 is sized so as to permit band 25 to be inserted into recess 26a. Band 25 is greater in length than the circumference of recess 26a and the width of the grooves 27 is greater than the thickness of band 25 so that the band can he slid around the circumference of recess 26a until it completely encircles member 16 and overlaps itself. The Width of band 25 is made suflicient so that the band is contained within grooves 27 of member 16.

Band 25 is made of a material such as cold-rolled steel which is sufl'iciently flexible to permit flexing as member 16 is broken and the segments thereof are expanded radially outward. During the expansion, an expander cone 17 intrudes into the conically tapered lower portion of the inner wall of member 16 thereby breaking the member alongthe longitudinal weakened sections defined by exterior longitudinal notches 22. The action of band 25 after breaking has taken place is to exert sufiicient longitudinal retaining force to prevent any broken section of member 16 from moving longitudinally relative to the remaining part or parts of member 16. Thus all portions of the member 16 are maintained in horizontal alignment While being fragmented. The action of band 25 in retaining member 16 as an integral member during fracturing also prevents any downward movement out of contact with setting tool 14 of the entire integral member 16. This follows because the portion of member 16 which is not yet fractured still has the same inner radius of curvature as the portion of expander cone 12 which it is engaging. In order for the entire integral member 16 to slide down the expander cone 12 this radius of curvature must increase. This only occurs when all breaks along weakened sections defined by notches 22 have occurred. Thus the entire member 16 is held in engagement with setting tool 14 throughout fracturing.

Band 25, however, because of friction and composition, is a force compensating expansible band and, as such, does not exert an outward or inward radial spring force relative to any broken section of member 16. Any substantial radial spring action present in band 25 is counteracted by the forces of sliding friction of band 25 in recess 26a and grooves 27. Thus there is no effective radial spring force applied to the broken sections by band 25.

After fracturing has occurred along the weakened sections defined by notches 22, band 25 serves to maintain horizontal alignment of the broken sections of member 16 as the broken sections are expanded radially outward by expander cone 17. During this movement, of course, the diameter of the assembly formed by the broken sections and linked by band 25 is steadily increasing and the overlapping portion of band 25 in recess 2611 gets progressively shorter.

Since horizontal alignment of teeth 16a of the fractured sections is maintained throughout the expansion of the broken sections by band 25, the teeth 16a effectively engage the wall of casing 11 in uniform horizontal alignment and are thus enabled to bite evenly into the wall of the casing. This provides a more uniform load-distributed grip by teeth 16a than would otherwise be afforded. The overall length of band 25 is desirably related to the circumference of the well casing to maintain the interconnection of the slip segments when they are in a fully expanded condition.

If a pressure differential exists across tool 12, such that the pressure is greater from above, then lower slips 20 will carry most of the load. In a case such as this, the present invention will not lose its grip on casing 11 even if relieved of radial expansive pressure. The frictional engagement of force compensating expansible band 25 with flanges 26 of recess 26a and the wall of the recess is such that the expanded slips cannot collapse radially inward. If a net inward radial pressure is applied at only one section of the slip, as would generally be the case if lower slip 20 were carrying most of the load, band 25 because of its flexibility would assume an elliptical or irregular shape in grooves 27 and wedge portions of its length between flanges 26 and the wall of recess 26a so forcefully that it will effectively lock all the broken sections into place. and prevents the loss of grip of the slips once they have set.

The upper surfaces 29 of the slip assembly tangs 24 are conically tapered and engage conically tapered surfaces 30' on the lower end of setting tool notches 33. Similarly, the surfaces of notches 23 are conically tapered and engage conically tapered surfaces 30 on the lower end of setting tool extensions 31. These tapered surfaces are provided to assure proper coaxial alignment of setting tool 14 and slip member 16 since, as should be noted,

the inner diameter of setting tool 14 is greater than the inner diameter of the unbroken slip member 16 which is sized for a sliding fit on the outer diameter of mandrel 15. Setting tool 14, being coupled only at its upper end to mandrel 15, could, in the absence of tapered surfaces 29 and 30, be forced out of proper coaxial alignment by any component of force transverse to its longitudinal axis which might develop during the setting process. The provision of cooperatively engageable tapered surfaces 29 and 30 prevents this by counteracting any such transverse forces which may develop, and thus assures proper coaxial alignment of setting tool 14 and slip member 16 at all times during setting and running-in of the well tool. The taper of the setting tool is arranged to provide, during setting, an outward expanding force on the upper end of the slip assembly.

As upper expander cone 17 intrudes into slip assembly 16 and fractures the slip member into longitudinal sections, it forces the pieces of mem er 16 against cooperatively aligned surfaces in the lower end of setting tool 14. Setting tool 14 is designed with notches 33 adapted to receive raised tangs 24 of the upper end of member 16, and extensions 31 adapted to fit into notches 23 on the upper end of assembly 16. The configuration is such that each tang 24, engaging a notch 33, contains two of the longitudinal weakening notches 22.

As more clearly seen in FIGURE 5, the result of this configuration, upon expansion and fracture of assembly 16, is for the notches 33 in the setting tool to each retain three of the broken sections of slip assembly 16 in each notch. This result will occur no matter in what sequence the breaks take place along the weakened sections defined by slip notches 22. Since the tool notches 33 are symmetrically disposed about the circumference of setting tool 14, this assures a symmetric circumferential distribution of the broken slip segments about the inner wall of casing 11.

Although the present invention does not depend on a programmed sequence of breaks occurring along its weakened sections defined by notches 22 as just discussed, it should be noted that notches 22 do provide a programmed breaking sequence. This occurs because the weakened sections defined by notches 22 which extend through the portion of slip member 16 containing tangs 24 actually are stronger than the other weakened sections because these notches are longer in a longitudinal direction. Thus the slip member will tend to break first along weakened sections defined by notches 22 which extend longitudinally into slip cut outs 25. This further assists in promoting the symmetrical distribution of the broken segments during setting. Circumferential guidance of the broken sections throughout the setting process is assured because the thickness of annular slip member 16 and setting tool 14 is such that constant contact between the setting tool and the slip assembly is retained throughout the expansion of slip assembly 16 and its engagement with casing 11.

Thus a symmetric distribution of the broken slip elements is assured by the present invention through the use of means retaining the broken sections in both horizontal and circumferential alignment throughout the expansion of the slip assembly.

While the slip has been shown with a setting tool sleeve, it will be readily apparent that a sleeve on the bridge plug operated by a setting tool will perform the same functions.

While one particular embodiment of the present invention has been shown and described, it is apparent that changes may be made without departing from this invention in its broader aspects and, therefore, the aim and the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

7 What is claimed is:

1. Anchoring means for anchoring a well tool in a well bore comprising:

an annular, breakable slip assembly having spaced weakened sections along its circumference adapted to break during setting of said slip assembly to form slip segments which can move radially to engage the wall of a well bore;

means for maintaining broken slip segments, when produced, in horizontal alignment;

means for maintaining a radial distribution of slip segments, when formed, including projections on said slip member which include more than one of said weakened sections; and

means for maintaining symmetric circumferential distribution of the broken segments of said slip member as they move radially outward.

2. The apparatus of claim 1 wherein said weakened sections for breaking of said slip member are disposed along predetermined longitudinal directions and are defined by longitudinal notches extending partially through the thickness of said annular member.

3. An anchor system for anchoring a well tool in a well bore comprising:

at least one annular, breakable slip member;

means for breaking said slip member into longitudinal segments for setting;

a force compensating, one-Way expansible band around an outer surface of said slip member;

means for frictionally coupling said expansible band to said slip member, said band maintaining horizontal alignment of slip segments producing during setting of said slip member; and

guiding means including a sleeve member cooperatively engageable with said slip member for assuring a symmetric circumferential distribution of said slip segments during setting of said segments. I

4. The combination of claim 3, wherein said sleeve member has notches on the lower end thereof adapted to receive cooperatively shaped tangs on the upper portion of said slip member.

5. The combination of claim 3 wherein said frictional coupling means comprises a circumferential flanged recess in the outer surface of said slip member.

6. An anchor system for anchoring a well tool in a well bore comprising:

an annular, one-piece, breakable slip member having circumferentially spaced, longitudinal weakened sections adapted to break during setting of said slip member to form longitudinal slip segments which can move radially outward;

a force compensating, one-way expansible band about an outer surface of said slip member;

a circumferentially extending grooved recess in the outer surface of said slip member for retaining said expansible band on said slip member, said band maintaining broken longitudinal sections of said slip member in horizontal alignment when said slip member is broken; and

a setting tool, including guiding notches on its lower end adapted to receive cooperatively shaped tangs on the upper end of said slip member, said tangs and notches functioning to assure a symmetrical circumferential distribution of said broken longitudinal segments during setting of said segments.

7. The apparatus of claim 6 wherein each guiding notch on said setting tool engages a tang on said slip member extending over a circumferential portion of said slip member which includes at least two of said longitudinal weakened sections of said slip member.

8. The apparatus of claim 6 wherein said force compensating, one-way expansible band has a length such that it overlaps its end and provides a continuous horizontal support when the broken longitudinal sections of said slip member move radially outward.

9. A well tool for use in a well bore comprising:

a central mandrel;

expansible packing means on said mandrel adapted to provide a seal with respect to the wall of a well bore;

an expander cone slidably mounted on said mandrel for expanding slip anchor means radially outward into setting-engagement with the wall of a well bore;

a setting tool releasably coupled to said well tool;

slip means for anchoring said tool in a well bore including a one-piece, annular, breakable slip member having a plurality of weakened sections arcuately spaced about its circumference to promote breaking thereof along predetermined longitudinal directions;

a plurality of circumferential teeth distributed along the outer surface of said slip member;

a force compensating, one-way expansible band around an outer surface of said slip member;

a circumferentially extending grooved recess in the outer surface of said slip member for retaining said expansible band on said surface, said band maintaining broken longitudinal sections of said slip member in horizontal alignment when said slip member is broken and expanded radially outward; and

raised extensions on the upper end of said slip member said extensions cooperatively engaging guiding notches in the lower end of said setting tool and functioning to assure a symmetrical circumferential distribution of broken longitudinal sections of said slip member during setting.

10. The apparatus of claim 9 wherein each of said guiding notches in the lower end of said setting tool engages a raised extension on the upper end of said slip member which extends over a circumferential portion of said slip member possessing at least two of said plurality of arcuately spaced weakened sections, and wherein there is at least one such arcuately spaced weakened section provided in said slip member between each pair of said raised extensions.

References Cited UNITED STATES PATENTS 2,966,216 12/1960 Bigelow 166134 3,062,295 1 1/ 1962 Hanes 2771l6.2 3,229,767 1/1966 Carter 166134 3,285,343 11/1966 Urbanosky 166135 X 3,344,861 10/1967 Claycomb 166134 X 3,412,803 11/1968 Stachowiak 166134 DAVID H. BROWN, Primary Examiner US. Cl. X.R.

22 U93 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 Dated February 97 lnventofls) William O. Berryman It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 41 (application Page 2, line 15) "dring" should read during Column 5 line 65 (application Page 12, line 9) add the following:

mm m RPMFU $EP15197U lqn (SEAL) Am Edna ll- Fletch, I. :0 W, m- Mug Officer III-Iliumof Patents Band 25 behaves, therefore, as a one-way expansible band 'ORM PO-IOEO H049) UsCOMM-pg; 50375-959 ILL GOVIINIIIIIT PIIITIIG OFFICI "II O-lU-Sl

Images