WO2014004571A2

WO2014004571A2 - Composite slip system for use with a downhole tool and methods of manufacturing same

Info

Publication number: WO2014004571A2
Application number: PCT/US2013/047699
Authority: WO
Inventors: Randy A. Jones
Original assignee: Team Oil Tools, Lp
Priority date: 2012-06-28
Filing date: 2013-06-25
Publication date: 2014-01-03
Also published as: WO2014004571A3

Abstract

A downhole slip system includes a metal slip structure; and a composite undercarriage adhered to the inner surface of the metal slip structure. A method for manufacturing a downhole slip system includes: disposing a bulk molding compound in contact with the inner surface of a metal slip structure within a mold; compressing the metal slip structure and the bulk molding compound; and curing the compressed bulk molding compound.

Description

COMPOSITE SLIP SYSTEM FOR USE WITH A DOWNHOLE TOOL AND METHODS OF MANUFACTURING SAME

BACKGROUND

Field of the Disclosure

The present disclosure pertains to a slip system for use downhole on well completions and, more particularly, to a composite slip system for such a use and a method for manufacturing the same.

Related Art

This section introduces information from the art that may be related to or provide context for some aspects of the technique described herein and/or claimed below. This information is background facilitating a better understanding of that which is disclosed herein. This is a discussion of "related" art. That such art is related in no way implies that it is also "prior" art. The related art may or may not be prior art. The discussion is to be read in this light, and not as admissions of prior art.

In the context of the art to which the present disclosure pertains, slips are any self- gripping device consisting of multiple wedges that are held together and form a near circle either (1) around an object to be supported by contact with surfaces of the slips or (2) within a tubular to anchor an object within the tubular. The first type of slips is normally used to grip a well completion tool, such as a packer or frac sleeve, or similar cylindrical devices suspended in a well bore. The second type of slips is used to anchor bridge plugs, frac plugs, cement retainers and other devices temporarily or permanently placed at a selected location within tubulars.

Slips are normally deployed as part of a slip and cone system. A slip and cone system consists of a slip and a cone to displace the slips radially outward, by virtue of relative movement between the two. When some force is applied that moves either the cone or the slip, the wedge-like ramp surface on the outer surface of the cone slides along the inside surface of the slips, pressing the slips radially outward, as the cone moves axially along a mandrel or plug body located within the slips.

Normally, the slips are fitted with replaceable, hardened tool steel teeth that embed into the inside surface of a tubular, such as well casing. The embedment of the hardened steel teeth of slips can cause permanent damage to the inside surface of tubulars. Linear or nonlinear notches may be formed that can cause stress concentration in the tubular wall. Under some conditions the damage is inconsequential; but under other conditions, such as when high-strength or corrosion-resistant pipe is used, the damage may lead to stress cracking or stress failure of the tubular.

More particularly, conventional slips on downhole tools are made of mild steel, cast iron or other durable metal alloys so that they will be hard enough to "bite" into a hardened steel casing wall, or a rock formation if no casing is present. Slips are typically made with a jagged tooth pattern that extends radially when the tool is "set" down hole. The slips are forced outward by sliding over a cone or wedge piece. These designs work well for permanent or long-duration tools, but they can present problems on tools that are removed (either retrieved, or drilled out) at the end of well completion work. Thus, while slips on downhole tools should be really strong, they should not add to the time required to remove the tool after the job is done.

The presently disclosed technique is directed to resolving, or at least reducing, one or all of the problems mentioned above. Even if solutions are available to the art to address these issues, the art is always receptive to improvements or alternative means, methods and configurations. Thus, there exists and need for technique such as that disclosed herein.

SUMMARY

In a first aspect, a downhole slip system comprises: a metal slip structure; and a composite undercarriage adhered to the inner surface of the metal slip structure.

In a second aspect, a method for manufacturing a downhole slip system comprises: disposing a bulk molding compound in contact with the inner surface of a metal slip structure within a mold; compressing the metal slip structure and the bulk molding compound; and curing the compressed bulk molding compound.

The above presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an exhaustive overview of the invention. It is not intended to identify key or critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter claimed below may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements, and in which:

FIG. 1 depicts in a perspective view, a circumferential slip system in accordance with one aspect of the presently disclosed technique and provides implementation specific details of two alternative embodiments. FIG. 2A-FIG. 2C are a plan, sectioned, side view of the slip system of FIG. 1 taken along the line 2-2, a plan top view, and a plan bottom view, respectively.

FIG. 3A-FIG. 3B detail alternative locking mechanisms as may be employed in some embodiments.

FIG. 4 is a plan, sectioned, side view of a mold and a molded slip system in accordance with another aspect of the presently disclosed technique and provides implementation specific details for two alternative slip system embodiments.

FIG. 5 is a partial, plan, sectioned, side view of a mold and a molded slip system alternative to that shown in FIG. 4.

FIG. 6A-FIG. 6D illustrates the embodiment of FIG. 1 in use.

FIG. 7 depicts and alternative embodiment with respect to the shape of the slots.

FIG. 8A-FIG. 8C illustrate the disclosed principles with respect to t-slips rather than circumferential slips.

While the invention is susceptible to various modifications and alternative forms, the drawings illustrate specific embodiments herein described in detail by way of example. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION

Illustrative embodiments of the subject matter claimed below will now be disclosed. In the interest of clarity, not all features of an actual implementation are described in this specification. It will be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort, even if complex and time-consuming, would be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

In the first disclosed embodiments, the composite slips will be manufactured "from the outside in" to yield finished slips. Turning to FIG. 1 and Figure 2, a composite slip assembly 100 is shown. The composite slip assembly 100 comprises, in this particular embodiment, a pre-fabricated metal ring 105 to which a composite undercarriage 1 10 is subsequently molded. The ring 105 and composite undercarriage 1 10 are slotted with slots 1 15 (only one indicated) to define a plurality of slips 120 (only one indicated). As best shown in Figure 2, the composite undercarriage 1 10 includes a ramp 200, whose function will be discussed further below.

The illustrated embodiment includes ten (10) slips 120. The number of slips 120 is not material to the practice of the technique disclosed herein. However, those in the art having the benefit of this disclosure will recognize that the number of slips 120 will impact the functionality of the composite slip assembly 1 10 in operation. More slips 120 will be easier to fracture during use than fewer slips 120 but too many may be undesirable as well. The number of slips 120 will therefore be an implementation specific design consideration.

The metallic ring 105 is, in the disclosed embodiments, prefabricated from a metal such as Aluminum or cast iron. Suitable exemplary materials may include, for example, Aluminum 6061-T6 or ASTM A48 Gray Iron 35K MYS. Other suitable materials will become apparent to those skilled in the art having the benefit of this disclosure and any suitable material may be used.

The ring 105 may be machined from cast iron tubing and then heat treated. The machining may include the creation of features, such as wicker teeth (not shown), on the exterior surface 125 for gripping another surface such as the inner diameter surface of a casing, the interior of a tubular, or a part of another tool. Alternative embodiments may include means for gripping that are alternative to teeth. For example, some alternative embodiments may use knurls or patterned bumps to grip the casing or formation.

One particular embodiment does indeed include teeth machined on the exterior surface of the ring. In this embodiment, wicker teeth are induction or flame heated only to 50-60 HRC, case depth .04-.05". It also omits any lightening holes, although lightening holes may be used in alternative embodiments. Alternatively, in this embodiment, the ring 105 may be machined from aluminum tubing and then coated with a high friction surface or material. The high temperature work is performed prior to forming any composite "undercarriage" for the slip, in order to protect the composite material from undesirable exposure to heat.

The ring 105 is sized to occupy the outermost diameter of a compression mold such as the compression mold 400, shown in FIG. 4. In several embodiments the outer diameter of the ring 105 is 4.29" while its height is 1 .625". In one embodiment in which the ring 105 is fabricated from aluminum, the wall thickness is 0.125". Embodiments in which the ring 105 is fabricated from cast iron will have varying wall thicknesses depending on whether teeth or other means for gripping are machined therein and, if so, the design of those means.

Compression molds are normally made of steel. The mold 400 is used in a heated hydraulic press (not shown), in conjunction with composite compounds called composite molding compounds that are generally a mixture of a thermosetting resin and a chopped fiber. The chopped fiber is usually fiberglass. In the illustrated embodiment, the composite molding compounds are acquired in bulk, and so are referred to in the art as "bulk molding compounds" ("BMCs"). Examples of suitable BMCs include phenolic/fiberglass compounds made by Sumitomo Bakelite under the trade name DUREZ. Additional information can be obtained from Durez Corporation by telephone at (800) 733-3339. Durez Corporation may also be contacted through their website on the World Wide Web of the Internet at http://resins.sbna-inc.com/.

After placing the ring 105, shown in FIG. 1-Figure 2, into position in the mold 400, shown in FIG. 4, the fiber-reinforced resin mixture 405 is measured, shaped, and placed into the mold 400 as shown in FIG. 4. In some embodiments, the mold will both measure and shape the resin mixture. The mold is then closed hydraulically to special stops (not shown) that control the pressure applied during curing, and the thickness of the finished parts.

In order to remain "locked up" rotationally for "drilling out", it is desirable that the ring 105 be structurally locked to the composite slips 120. To accomplish this, before insertion into the mold 400, the mating inner surface 410 on the metal ring 105 may be pre-coated with a special resin or adhesive primer (not shown) to assure adhesion of the ring 105 to the cured composite molding compound 405. Stronger adhesion is better than weaker adhesion in this context. Adhesives and resins typically are not chemically sympathetic or compatible with metal surfaces, so some type of primer is usually needed.

Suitable resins and primers are known to the art and include, by way of example and not limitation, CHEMLOK® 205 or 220, which are parts of a series of adhesives and primers manufactured by LORD Corporation. These are readily, commercially available from LORD Corporation and its representatives. Additional information may be found over the World Wide Web of the Internet at www.lord.com.

Compression of the mold surfaces 415, 420 together forces compaction of the fiber and resin matrix of the composite molding compound 405, and intimate contact with the surface 410 of the ring 105. With adequate heat and pressure, the composite molding compound 405 will cure, or "polymerize", into the composite undercarriage 1 10, whereby the composite molding compound 405 becomes rigid, strong, and adhered to the ring 105. Thus the slips 120, shown in FIG. 1, have been formed "from the outside in".

Those in the art having the benefit of this disclosure will appreciate that what constitutes "adequate heat and pressure" will depend on a number of readily recognizable factors. These factors may include, for example, the cure profile of the composite molding compound 405, the curing temperature requirements, and the cure pressure loading needed to achieve the desired compaction. Phenolic resin-based BMCs for use in downhole tool application are typically cured in ten minutes or less, at about 350° F., with a compression load of 2,500 - 5,0001bs.

In one particular embodiment, the ring 105 is fabricated from ASTM A48 Gray Iron 35K MYS, has an outer diameter of 4.29" +.02Ύ-0.0, is 1.625" tall, and has a wall thickness of approximately .250". It has five (5) sharp circumferential teeth machined on the outer diameter that have been induction or flame heat treated teeth only to 50-60 HRC, case depth .04-.05". There are ten 10 slots, cut from one end, each 1.0" long; .12" wide. There are no lightening holes. The composite undercarriage 110 is prepared from a DUREZ 32633 composite molding compound. The ring 105 is then placed in a compression mold 400 and the process continues as discussed above.

As noted above, in some embodiments, teeth or wickers may be machined into the exterior surface 125. For present purposes, these metal rings 105 may be called "outserts" a cross section of which is shown in Fig. 5. In FIG. 5, a ring 105 includes a plurality of teeth 500 machined on the exterior surface thereof. The some degree, the manufacture of the outsert will depend upon the metal from which the ring is fabricated. For example, if the ring 105 is manufactured from cast iron, the teeth 500 may be machined into the exterior surface of the outer diameter of the ring 105. If the ring 105' is fabricated from Aluminum, then the teeth 500 may be cast with the rest of the ring 105'. Note that alternative embodiments may use other structures, such as knurls, instead of the wicker teeth 500.

Returning to FIG. 1-Figure 2, the slips 120 are defined by the slots 115. In the particular embodiments described above, the slots 1 15 are 1" long and .12" wide. In the illustrated embodiment, the composite undercarriage 1 10 is slotted with the ring 105 such that the slots 1 15 extend all the way through the ring 105 and the composite undercarriage 1 10. Thus, the slots 1 15 may be machined in the combined ring 105 and composite undercarriage 1 10 at the same time after the curing process. The slots 1 15 provide the specific places for each slip 100 to break into segments when the tool is set, and the slip pieces begin sliding up the ramp on the cone.

However, the presently disclosed technique is not so limited. In alternative embodiments, the slots 115 may be machined in the ring 105 prior to curing and the composite undercarriage 1 10 may be slotted by scoring it after the curing process. Or, in still other alternative embodiments, the slots 1 15 in the ring 105 may be pre-machined and the slots 1 15 in the composite undercarriage 110 may be formed by the mold 400 during the curing process. The interior surface of the mold 400 will be shaped appropriately to create the desired number of slots 1 15. The slots 115 in the ring 105 should also be properly aligned in the mold 400, as well. In these embodiments, the slots 1 15 in the ring 105 can be used to self-align the ring 105 in the mold 400. Still other alternatives may become apparent to those skilled in the art having the benefit of this disclosure.

The cross-sectional shape of the slots 1 15 may also vary depending upon the embodiment. If the slots 1 15 are machined straight through, the cross-section will likely, though not necessarily, be squared off. If only partially machined or scored, then they may be rounded or, as shown in FIG. 7, have an angled feature.

FIG. 6A-FIG. 6D show one particular embodiment of the composite slip assembly in operation. FIG. 6A shows the composite slip assembly 100 disposed on a tubular 600 of some kind along with a tool 610, only a portion of which is shown, having a cone 615 at the bottom thereof. The natures of the tubular 600 and the tool 610 are not material to the practice of the presently disclosed technique. Similarly, those in the art having the benefit of this disclosure will appreciate that the orientation of the composite slip assembly 100 and the tool 610 on the tubular 600 and relative to one another is also not material. Thus, the composite slip assembly 100 may be disposed above the tool 610 on the tubular 600 with both the tool 610 and the composite slip assembly 100 vertically oriented in the direction opposite that shown in FIG. 6A.

A relative motion between the tool 610 and the composite slip assembly 100 is initiated that moves the cone 615 into contact with the ramp 200 as shown in FIG. 6B-FIG. 6C. Continued relative motion generates a radially outward force caused by the interaction of the cone 615 and the ramp 200. This pressure causes the composite undercarriage 1 10 (best shown in FIG. 1) to fracture in a manner determined by the pattern and design of the slots 1 15 (also shown in FIG. 1). As shown in FIG. 6D, it also causes the metal of the ring 105 to deform and contact the casing 620 or, if there is no casing, the walls of the wellbore (not shown). The relative motion can then cease when the composite slip assembly 100 is set to the level desired.

To enhance the mechanical strength of the interface between the ring 105 and the composite undercarriage 1 10, some embodiments include one or more "locking features" on the inner surface 410 of the ring 105. The locking features allow the composite molding compound 405 to flow around them under pressure and cure in place. This creates a secondary mechanical lock between the ring 105 and the composite undercarriage 1 10 augmenting the primary lock provided by the adhesion. The locking features may be either positive features— i.e. , projecting from the surface 410— or negative features— i.e. , formed in the ring 105 below the surface 410. FIG. 3A depicts an exemplary positive feature 300 and FIG. 3B depicts an exemplary negative feature 310. The locking features could also be small holes, protruding rods, or small bumps, or possibly a curved or helical groove machined in around the inner circumference of the ring 105. A helical or spiraling shape (counter to the direction of milling) on this groove would force a tightening and constriction on the bondline, also beneficial for milling out, after the slip 120 has done its job in operation.

T-slips, which are made in smaller, plate-like segments, can also be made in this fashion. Instead of using the metal ring 105 as an outer edge, a composite t-slip would use a pre-shaped plate, placed in the bottom of a large platen mold, with a multitude of cavities shaped to hold them. The composite molding compound would then be applied and the slip built in this case "bottom up" with the upper platen mold serving to shape the wedge feature.

Consider, for example, the t-slip 800 shown in FIG. 8A. Those in the art will appreciate that the t-slip 800 will exhibit a slight implementation-specific curve (not shown) reflecting the curvature of radius of the pipe or tool with which it will be used. A groove in which a locking ring (not shown) is placed to maintain the t-slip 800 in place prior to actuation is omitted for the sake of clarity and so as not to obscure the presently claimed subject matter.

FIG. 8B conceptually illustrates various aspects of the fabrication process. Only a fragmentary view of the bottom 805 of the platen mold (not otherwise shown) is provided. Both the t-slip 800 and the fabrication process are but exemplary embodiments only. Those in the art having the benefit of this disclosure will appreciate variations thereon within the scope of the appended claims.

Turning now to FIG. 8A, also shown in a side view in FIG. 8C, the t-slip 800 comprises a metal plate 810 to which a composite undercarriage 815 is adhered as described above. Locking features may also be used as described above to assist the adherent in securing the composite undercarriage 81 5 although none are shown. Materials selection for both the metal plate 810 and the composite undercarriage 815 are also as described above relative to the embodiment of FIG. 1.

The t-slip 800 may be fabricated by placing the metal plate 810 in a recess 820 of the bottom 805 of the platen mold. Those in the art will appreciate that the t-slip 800 will typically be one of a number of such t-slips fabricated at the same time. Thus, the bottom 805 will typically include a number of recesses 820. Only one recess 820 is shown in this fragmented view of the bottom 805 for purposes of clarity and so as not to obscure the disclosed subject matter. Note, however, that the t-slips may be fabricated one at a time in some embodiments.

Once the metal plate(s) 810 are placed into the recess(es) 820, the composite material or compound can be poured and the combination subjected to heat and pressure as described above. The top (not shown) of the platen mold can be shaped on its bottom surface to mate with the recess(es) 820 to create the geometry of the composite undercarriage 815. The representation of the composite undercarriage 815 in both FIG. 8A-FIG. 8C is that after heating and pressure are applied.

Thus, a downhole slip system comprises a metal slip structure and a composite undercarriage adhered to the inner surface of the metal slip structures. In this context, the terms "inner" and "outer" modifying the term "surface" are construed relative to the orientation of the downhole slip system when deployed in the wellbore. The metal slip structure may comprise, as in FIG. 1, a metal ring 105 expansible to define a plurality of slip elements 120 wherein the composite undercarriage 110 is adhered to the inner surface 410, shown in FIG. 4, of the ring 105. Alternatively, the metal slip structure may comprise, as in FIG. 8A-FIG. 8B, the metal slip structure may comprise a plurality of expansible t-slips 800 and the undercarriage 810 is adhered at least to the t-slips 800.

Furthermore, a method for manufacturing a downhole slip system comprises disposing a bulk molding compound in contact with the inner surface of a metal slip structure within a mold; and compressing the metal slip structure and the bulk molding compound; and curing the compressed bulk molding compound. The metal slip structure may comprise a metal ring such that disposing the bulk molding compound includes disposing the bulk molding compound inside the metal ring and the method further comprises fabricating slots in the metal ring and cured bulk molding compound to define a plurality of slips. Alternatively, the metal slip structure comprises a plurality of expansible t-slips such that disposing the bulk molding compound includes disposing the bulk molding compound on top of a metal plate.

The use of composites offers a compromise of slip hardness (for performance) and brittleness, to facilitate easier removal by drilling.

This concludes the detailed description. The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below.

Claims

CLAIMS WHAT IS CLAIMED:

1. A downhole slip system, comprising:

a metal slip structure; and

a composite undercarriage adhered to the inner surface of the metal slip structure.

2. The downhole slip system of claim 1, wherein:

the metal slip structure comprises a metal ring expansible to define a plurality of slip elements; and

the composite undercarriage is adhered to the inner surface of the ring.

3. The downhole slip system of claim 2, wherein the ring and undercarriage include a plurality of co-aligned slots defining the slip elements.

4. The downhole slip system of claim 1 , wherein the metal slip structure comprises a plurality of expansible t-slips and the undercarriage is adhered at least to the t-slips.

5. The downhole slip system of claim 1, wherein the metal slip structure includes means for gripping another surface on the outer surface thereof.

6. The downhole slip system of claim 5, wherein the gripping means includes wicker teeth or knurls.

7. The downhole slip system of claim 1, wherein the metal slip structure includes wicker teeth, knurls, or bumps on the outer surface thereof.

8. The downhole slip system of claim 1, wherein the metal slip structure includes locking features on the inner surface thereof.

9. The downhole slip system of claim 8, wherein the locking features are positive features.

10. The downhole slip system of claim 8, wherein the locking features are negative features.

1 1. The downhole slip system of claim 1 , wherein the composite undercarriage is adhered to the slip structure using a resin.

12. The downhole slip system of claim 1, wherein the composite undercarriage is adhered to the slip structure using a primer.

13. A method for manufacturing a downhole slip system, comprising:

disposing a bulk molding compound in contact with the inner surface of a metal slip structure within a mold;

compressing the metal slip structure and the bulk molding compound; and

curing the compressed bulk molding compound.

14. The method of claim 13, wherein: the metal slip structure comprises a metal ring; and

disposing the bulk molding compound includes disposing the bulk molding compound inside the metal ring; and

further comprising:

fabricating slots in the metal ring and cured bulk molding compound to define a plurality of slips.

15. The method of claim 14, wherein fabricating the slot includes machining the slots in the metal ring and the cured bulk molding component.

16. The method of claim 14, wherein fabricating the slot includes machining the slots in the metal ring and molding the slots in the bulk molding compound.

17. The method of claim 14, wherein fabricating the slot includes machining the slots in the metal ring and scoring the slots in the cured bulk molding compound.

18. The method of claim 13, wherein

the metal slip structure comprises a plurality of expansible t-slips: and

disposing the bulk molding compound includes disposing the bulk molding compound on top a metal plate.

19. The method of claim 13, further comprising applying a resin or primer to the inner surface of the metal ring before disposing the bulk molding compound therein.

20. The method of claim 13, wherein the metal ring includes a locking feature on the inner face thereof.

21. The method of claim 13, further comprising fabricating a locking feature on the inner surface of the metal slip structure.

22. The method of claim 13, further comprising fabricating means for gripping in the outer surface of the metal slip structure.

23. The method of claim 22, further comprising positioning an outsert on the outer surface of the metal slip structure.