WO2015069886A2

WO2015069886A2 - Structural insert for composite bridge plug

Info

Publication number: WO2015069886A2
Application number: PCT/US2014/064334
Authority: WO
Inventors: James A. Rochen; Matthew R. STAGE; Shawn J. TREADAWAY
Original assignee: Weatherford/Lamb, Inc.
Priority date: 2013-11-06
Filing date: 2014-11-06
Publication date: 2015-05-14
Also published as: WO2015069886A3

Abstract

A composite mandrel has structural support in the inner bore. This can be accomplished in a couple of different ways. One option is to insert the composite mandrel support into the inner bore of a completed mandrel and to secure the insert into place with pins, adhesive, etc. Another option is to have a cross-beam or I-beam supported structural insert that is wound over with a filament wound composite process. Using this option, the inner bore support remains in place once manufacturing is complete and allow flows back from downhole of the bridge plug. When used, the structural support allows for higher collapse ratings [i.e., higher frac pressures or higher temperature ratings] on the composite mandrel. Providing a filament winding over the structural support also eliminates the need to use a conventional metal rod for winding on to produce the mandrel and then pulled out to leave the inner bore of the mandrel, thus also making the manufacturing process more efficient.

Description

Structural Insert for Composite Bridge Plug

-by-

James A. Rochen, Matthew R. Stage, and Shawn J. Treadaway

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Prov. Appl. 61/900,620, filed 06-NOV- 2013, which is incorporated herein by reference.

BACKGROUND OF THE DISCLOSURE

[0002] An oil or gas well includes a wellbore extending into a well to some depth below the surface. Typically, the wellbore is lined with tubulars or casing to strengthen the walls of the bore. To further strengthen the walls of the bore, the annular area formed between the casing and the bore is typically filled with cement to permanently set the casing in the wellbore. The casing is then perforated to allow production fluid to enter the wellbore and be retrieved at the surface of the well.

[0003] Downhole tools with sealing elements are placed within the wellbore to isolate the production fluid or to manage production fluid flow through the well. For example, a bridge plug or packer is placed within a wellbore to isolate upper and lower sections of production zones. Thus, by creating a pressure seal in the wellbore, these plugs allow pressurized fluids or solids to treat an isolated formation.

[0004] These tools are usually constructed of cast iron, aluminum, or other alloyed metals, but have a malleable, synthetic element system. The plug or packer system can also be composed of non-metallic components made of composites, plastics, and elastomers. The element system is typically made of a composite or synthetic rubber material that seals off an annulus within the wellbore to prevent the passage of fluids.

[0005] Figure 1A is a cross-sectional view of a conventional bridge plug 100 disposed in a wellbore 10, and Figure IB shows the conventional bridge plug 100 in partial cross-section. As shown in Figure IB, the bridge plug 100 generally includes a mandrel 102, a synthetic sealing member 108, and one or more slips 110. The sealing member 108 is used seal an annular area between the bridge plug 100 and an inner wall of casing 10 within a wellbore. The above elements are similar to the components disclosed in U.S. Pat. No. 6,712,153, which is incorporated herein by reference in its entirety.

[0006] In operation, the element system 114 of the bridge plug shown in Figure IB is compressed, thereby expanding radially outward from the tool to sealingly engage a surrounding tubular. To obtain this result, axial forces are applied to one slip 110 while the mandrel 102 and another slip 111 are held in a fixed position. As the one slip 110 moves down in relation to the mandrel 102 and the other slip 111, the sealing member 108 is actuated and the slips 110 and 111 are driven up cones 107 and 109. The movement of the cones 107 and 109 and slips 110 and 111 axially compress and radially expand the sealing member 108 thereby forcing the sealing portion radially outward from the plug 100 to contact the inner surface of the well bore casing. In this manner, the compressed sealing member 108 provides a fluid seal to prevent movement of fluids across the bridge plug 100.

[0007] Bridge plugs 100 must be designed for high temperature and/or high pressure applications and may be used in both high and low pH environments. In these extreme downhole conditions, the physical properties of the bridge plug 100 can suffer from degradation. Furthermore, bridge plugs 100 are typically limited in pressure ratings due to collapse of the mandrel 102. Mandrels 102 are designed with a cylindrical hole (i.e., bore] 105 running through the center of the plug 100 to allow for pressure equalization and well flow-back prior to milling up. One problem associated with high temperature and/or high pressure applications is that the bore 105 of the plug 100 will collapse inward. This collapse of the bore 105 within the plug 100 can cause catastrophic failure of the plug 100. For example, the collapsed plug 100 may slide downhole or may lose its sealing ability.

[0008] In many applications, aluminum mandrels are used for higher temperature and pressure ratings where a composite mandrel is limited. However, this is less desirable due to the mill-ability of aluminum. For example, plugs 100 are sometimes intended to be temporary and must be removed to access the wellbore. Rather than de-actuate the plug 100 and bring it to the surface of the well, the plug 100 is typically destroyed with a rotating milling or drilling device. As the mill contacts the plug 100, the plug 100 is "drilled up" or reduced to small pieces that are either washed out of the wellbore or simply left at the bottom of the wellbore. The more metal parts making up the plug 100, the longer the milling operation takes. Furthermore, metallic components like aluminum also typically require numerous trips in and out of the wellbore to replace worn out mills or drill bits. Also, aluminum mandrels are typically composed of very expensive aerospace grade materials, and are thus not economically feasible for such use.

[0009] Rather than using aluminum mandrel, the conventional practice to strengthen the mandrel in the downhole plug to resist collapse is to reduce the inner diameter of the bore 105, thereby increasing the overall thickness of the mandrel 102. This may work to a point. However, additional material is required, and some of the benefits of producing through the reduced bore of the mandrel during flow-back before milling may be hindered.

[0010] Accordingly, there is a need, for a non-metallic mandrel that will effectively handle the high temperatures and the high pressures downhole without experiencing physical degradation or collapse. There is also a need for a downhole tool made substantially of a non-metallic material that is easier and faster to mill, while remaining economically feasible.

[0011] The subject matter of the present disclosure is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.

SUMMARY OF THE DISCLOSURE

[0012] A composite mandrel has structural support in the inner bore. This can be accomplished in a couple of different ways. One option is to insert the composite mandrel support into the inner bore of a completed mandrel and to secure the insert into place with pins, adhesive, etc. Another option is to have a cross-beam or I-beam supported structural insert that is wound over with a filament wound composite process. Using this option, the inner bore support remains in place once manufacturing is complete and allow flows back from downhole of the bridge plug. When used, the structural support allows for higher collapse ratings [i.e., higher frac pressures or higher temperature ratings] on the composite mandrel. Providing a filament winding over the structural support also eliminates the need to use a conventional metal rod for winding on to produce the mandrel and then pulled out to leave the inner bore of the mandrel, thus also making the manufacturing process more efficient. [0013] The foregoing summary is not intended to summarize each potential embodiment or every aspect of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Fig. 1A illustrates a composite bridge plug disposed in a wellbore according to the prior art.

[0015] Fig. IB illustrates a composite bridge plug according to the prior art in partial cross-section.

[0016] Fig. 2A illustrates a composite bridge plug relative to structural inserts according to the present disclosure.

[0017] Fig. 2B illustrates additional structure inserts according to the present disclosure in various views.

[0018] Fig. 2C illustrates an end section of an exemplary structural insert according to the present disclosure.

[0019] Figs. 3A and 3B illustrate a cross-section and an end-section of an exemplary structural insert affixed in a bore of a composite bridge plug according to the present disclosure.

[0020] Fig. 3C illustrates an end-section of a bridge plug formed on an exemplary structural insert according to the present disclosure.

[0021] Fig. 4A illustrates a cross-section view of a structural insert disposed in a bridge plug according to the present disclosure.

[0022] Fig. 4B illustrates a structural insert affixed in the bore of a bridge plug according to the present disclosure.

[0023] Fig. 5 is a flow chart showing a process for manufacturing a bridge plug with a structural insert according to the present disclosure.

[0024] Fig. 6 is a flow chart showing another process for manufacturing a bridge plug with a structural insert according to the present disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

[0025] Referring to Figure 2A, a composite bridge plug 100 is illustrated relative to various structural inserts 200 according to the present disclosure. The bridge plug 100 includes a mandrel 102 and bore 105 disposed within the mandrel 102. As described above, the mandrel 102 may be comprised of iron, aluminum, or some other metal.

Preferably, the mandrel 102 can be composed of non-metal composites, plastics, and elastomers according to the techniques disclosed in incorporated reference US Pat. No. 6,712,153. The bridge plug 100 further includes an element system 114 which can be actuated to form a pressure isolation contact between the plug 100 and the inner wall of the surrounding tubular.

[0026] The structural inserts 200, although not limited to, may also be comprised of nonmetallic components made of composites, plastics, ceramics, and elastomers. For example, the structural inserts 200 can be composed of the same material as the mandrel 102 or can be composed of an entirely different material. As shown in Figures 2A and 2B, the structural inserts 200 are elongated along axis A and can be cylindrical in nature. The structural inserts 200 are designed to be disposed within the bridge plug 100, and specifically within the inner bore 105 of the mandrel 102.

[0027] As will be described below, the structural inserts 200 may be elongated along axis A to obtain any length. Furthermore, the structural inserts 200 may be disposed within the bore 105 of the bridge plug 100 in any number of combinations. For example, the structural insert 200 may be disposed within the bore 105 of the bridge plug 100 solely, or several structural inserts 200 may be disposed within the bore 105 of the bridge plug 100 along with one another in any combination.

[0028] The structural inserts 200 may also be disposed within bridge plug 100 and affixed within the inner bore 105 of bridge plug 100 using adhesive, using pins, threading, or any other sufficient method of fixing structural inserts 200 within the inner bore 105 of the plug 100. Furthermore, as will be described below, the bridge plug 100 itself may be designed or formed around the structural insert 200 using a filament wound composite process. In this aspect of the present disclosure, the structural inserts 200 may not need to be separately affixed within bore 105 of the bridge plug 100 using elements such as pins or adhesive. Instead, the structural inserts 200 can be affixed within the inner bore 105 using a chemical bond as part of the manufacturing process.

[0029] Affixing the structural insert 200 in the inner bore 105 of the plug 100 allows the plug 100 to use existing composite resin matrices at higher pressures and possibly higher temperatures due to less chance of the mandrel 102 collapsing downhole under such extreme conditions. Using the structural insert 200 also allows for using a larger inner bore 105 without sacrificing pressure ratings of the plug 100. Finally, providing a filament winding over the structural insert 200 can eliminate the need to have a metal mandrel or conventional insert for winding over to form the mandrel and then pulling out of the finished mandrel; thus also making the manufacturing process more efficient.

[0030] Referring to Figures 2A and 2B, each of the structural inserts 200 is designed to provide structural support for the bridge plug 100 when disposed within the bore 105. In general, the structural insert 200 can be a cylindrical tube without internal cross-members, if the material of the insert 200 can withstand desired collapse pressures. Otherwise, the mandrel 102 with such a cylindrical tube for the insert 200 can still suffer from possible collapse. Preferably, however, each of the individual structural inserts 200, although individually designed separately and distinctly from one another, have at least one cross member or lateral element that supports the insert 200 laterally along the axis of the insert 200 so opposing sides of the mandrel 102 can be supported.

[0031] For example, a first structural insert 210 is elongated along an axis A and has a cross-bar structure extending radially. Furthermore, a second structural insert 212 is elongated along an axis A and has an I-beam structure. A third structural insert 214 has a cylindrical body elongated along an axis A and having a cross-bar structure similar to the first structural insert 210 disposed within. Furthermore, a fourth structural insert 216 can be a cylindrical body elongated along an axis A and having an I-beam structure similar to the second structural insert 212 disposed within. It should be apparent that these are only exemplary descriptions of structural inserts.

[0032] Further variations on the structural insert 200 are depicted in Figure 2 B. In addition to those inserts 210 and 216 shown in Figure 2 A, the additional inserts include a fifth insert 213 and a sixth insert 215. As will be appreciated, each of the structural inserts 200 are designed to be disposed within the bore 105 of the bridge plug 100 and can come in many different designs and many different compositions.

[0033] Referring to Figure 2C, a cross-bar structure of an exemplary structural insert 214 is illustrated. As shown, the structural insert 214 has a cylindrical body 223 with crossbars 222 and 224 disposed within. Although not shown, the length of this particular structural insert 214 can extend any desired length.

[0034] The crossbars 224 and 222 within the cylindrical body 223 can be composed of the same material as the cylindrical body 223, the mandrel (102], and/or any other composition (i.e., composite, plastic, etc.}. Again, the purpose of this exemplary structural insert 214 is to provide structural support to the bridge plug (100} by being disposed into the inner bore (105} of the bridge plug (100}.

[0035] In addition to providing structural support, the structural insert 214 can still permit flow through the bore 105, as may be desired when setting the plug. As previously described, the bore 105 of the bridge plug (100} can allow for pressure equalization and can provide for well flow back prior to milling up the bridge plug (100}. For this reason, the insert 214 contains open pathways 220 between the cylindrical body 223 and the crossbars 222 and 224 disposed within it in order to provide a passage for fluid. It should be noted that pathways 220 are only an exemplary opening or pathway and are specific for this particular structural insert design. Openings or pathways within the structural inserts may have many different designs and many different openings, and this particular design should not be considered a limitation.

[0036] Figures 3A and 3B illustrate a cross-section and an end-section of the composite bridge plug 100 having a structural insert 200 disposed within the inner bore 105. In this illustration, the insert 200 is the exemplary structural insert 214 of Figure 2C. The structural insert 200 is disposed within the bore 105 of the mandrel 102 of the bridge plug 100. As shown, the structural insert 200 has both crossbars 224 and 222 and has many openings or pathways 220 that extend therethrough. In this arrangement, the structural insert 200 may be affixed to the inner bore 105 of mandrel 102 using a pin 112.

[0037] For this embodiment, the mandrel 102 can be formed having an inner bore 105 within it, and the structural insert 200 can be disposed within the bore 105 after the mandrel 102 has been completed. Therefore, it will be necessary to affix the structural insert 200 in the inner bore 105 of the mandrel 104 using a pin 112 or any other methods described herein.

[0038] Accordingly, it is shown that the pin 112 can be disposed within the outer wall of the mandrel 102 and in the outer wall of the structural insert 200. The pin 112 can be held in place in order to prevent the structural insert 200 from being dislodged from within the inner bore 105 of the mandrel 102. Additionally, the pin 112 may also be used to affix a lower shoulder sleeve 104 on the mandrel 102 as being part of the plug 100.

[0039] As shown, passage of the pin 112 may stop within the outer wall of the structural insert 200. The pin 112 may extend all the way through both the entire walls of the mandrel 100 and the structural insert 200, or the pin 112 may extend through the exit walls of the mandrel 102 and the structural insert 200 as indicated by the pin passage 226.

[0040] The structural insert 214 may be affixed to the inner bore 105 of the mandrel 102 by a single pin 112, or by many pins 112. Further, the entrance and exit locations of the pins 112 may be anywhere within the circumference of the mandrel 102, and the pins 112 may extend at any length throughout the plug in order to obtain a fixture of the structural insert 214 to the inner bore 105 of the mandrel 102.

[0041] It is noted that pin 112 is only an exemplary method of affixing structural insert 214 to the inner bore 105 of the bridge plug 100, and that there may be numerous ways or methods to affix structural inserts 214 in the tool. For example, the structural insert 214 may be affixed to the inner bore 105 by any means of adhesive, threading, screw, or any other method.

[0042] Referring to Figure 3C, an end-section of a bridge plug 100 formed on an exemplary structural insert 200 is shown. As shown, the structural insert 200 is disposed and affixed in the inner bore 105 of the mandrel 102 of the bridge plug 100. In particular, the structural insert 200 is affixed at an outer surface 225 on its cylindrical body 223 to the inner bore 105 of the mandrel 102. In this example, the mandrel 102 has been wound or formed over the structural insert 200 with a filament wound composite process, which is disclosed below. This embodiment provides that the mandrel 102 itself can be formed around the structural insert 200, thereby affixing the structural insert 200 to the inner bore 105 of the mandrel 102.

[0043] Figure 4A is cross-sectional view of a structural insert 200 according to the present disclosure disposed in a bridge plug 100 within a wellbore 10. The structural insert 200 is disposed within the inner bore 105 of the mandrel 102. As shown, the structural insert 200 alone has been disposed along the length of the inner bore 105 of the bridge plug 100. However, as described above, one or more structural inserts 200 may be used either alone or in combination to fill the inner bore 105 of the bridge plug 100.

[0044] The one or more structural inserts 200 used or disposed within the inner bore 105 may or may not necessarily fill the entire inner bore of the plug 100. In this aspect, the one or more structural inserts 200 may be positioned anywhere along the inner bore 105 at any length. Preferably, any sections of a single insert 200 or individual inserts 200 are disposed in the bore 105 near the location of the cones 107 and 109 on the mandrel 102 when the plug 100 is set because these areas of the mandrel 102 may experience the greatest collapse forces. In addition, either as described above, the structural inserts 200 may be affixed to the inner bore 105 of the bridge plug 100, or the bridge plug 100 itself may be formed around the structural inserts 200 in order to affix the structural inserts 200 to the inner bore 105.

[0045] An example of affixing the structural insert 200 within the inner bore 105 of the mandrel 102 of bridge plug 100 in shown in Figure 4B. The structural insert 200 according to the present disclosure is affixed in the inner bore 105 of the bridge plug 100 and held in place by pins 112.

[0046] As discussed above, affixing the structural insert 200 to the inner bore 105 of the mandrel 102 is not limited to pins, and the insert 200 can thereby be affixed by any means [i.e., by pins, adhesive, thread, etc.}. Furthermore, as previously described, the pins 112 may be disposed throughout the outer structure of the mandrel 102 into the outer surface of the structural insert 200. Alternatively, the pins 112 may be disposed throughout the maj ority of both structures, or disposed entirely throughout the bridge plug 100 itself (i.e., entering one side of the bridge plug 100 and exiting another side of the bridge plug 100, thereby extending all the way through}. Furthermore, it is noted that only two pins 112 are being used in this particular embodiment; however, a plurality of pins 112 may be used in many different positions along the mandrel 102, and in many different combinations [i.e., extending partially or completely throughout the mandrel 102}.

[0047] Having the insert 200 structurally supporting the mandrel 102 from inside the bore 105 provides a number of benefits. Primarily, the mandrel 102 having the insert 200 can support high pressures and resist collapse. Furthermore, the size of the bore 105 may be greater than typically allowed in conventional arrangements so that the wall thickness of the mandrel 102 can be less for a given outside diameter of plug. In the end, this results in less material being needed to form the mandrel 102 for the same sized plug 100.

[0048] Figure 5 illustrates a flow chart showing a process for manufacturing a bridge plug (100} having one or more structural inserts (200} disposed within the bore 105 according to the present disclosure. Initially, the bridge plug (100} is formed on a conventional metal rod, which is used temporarily for creating the inner bore 105 within the mandrel 102 (Block 410}. Forming the mandrel (102} involves a winding process using a polymeric composite reinforced by a continuous fiber such as glass, carbon, or aramid; however, the process is not limited to these examples and could be formed using other compositions.

[0049] In this process, the composite material is wound layer upon layer. Each individual layer is wound at an angle of about 30 to about 70 degrees to provide additional strength and stiffness to the composite material in high temperature and pressure downhole conditions. The polymeric composite is preferably an epoxy blend. However, the polymeric composite may also consist of polyurethanes or phenolics, for example. In one aspect, the polymeric composite is a blend of two or more epoxy resins. Preferably, the composite is a blend of a first epoxy resin of bisphenol A and epichlorohydrin and a second cycoaliphatic epoxy resin. Preferably, the cycloaphotic epoxy resin is Araldite® liquid epoxy resin, commercially available from Ciga-Geigy Corporation of Brewster, N.Y.

[0050] The fiber is typically wet wound, however, a prepreg roving can also be used to form a matrix. A post-cure process is preferable to achieve greater strength of the material. Typically, the post-cure process is a two-stage cure consisting of a gel and a cross-linking period using and anhydride hardener, as is commonly known in the art. Heat is added during the curing process to provide the appropriate reaction energy which drives the cross-linking of the matrix to completion. The composite may also be exposed to ultraviolet light or a high-intensity electron beam to perform the reaction energy to cure the composite material.

[0051] Once the mandrel (102} has been created (Block 412}, the conventional rod is removed from the mandrel 102 to leave the inner bore 105. Typically, the rod cools after the curing process so the rod can slide out of the formed bore 105 in the hardened mandrel [0052] Once the conventional rod has been removed from the inner bore 105, a structural insert 200 is disposed within the inner bore 105 of the mandrel 102 (Block 414}. In the next step of the process, the structural insert 200 is affixed into the inner bore 105 of the mandrel 102 (Block 416}. As previously described, there are many ways to affix the structural insert 200 into the inner bore 105. Any of the pre-described ways of affixing the support insert 200 [i.e., using pins, using screws, using adhesive, etc.} may be used to achieve this goal.

[0053] As further described above, disposing and affixing the structural insert 200 in the inner bore 105 of the mandrel 102 is only one example of how to affix a structural insert 200 into the mandrel 102. In particular, Figure 6 is a flow chart illustrating another process for manufacturing a bridge plug 100 having a structural insert (200} according to the present disclosure disposed within. In this embodiment, no conventional rod is necessary for forming the mandrel (102} of the plug (100}. Instead, the mandrel (102} itself is formed on an existing structural insert (200} (Block 510}.

[0054] Next, after the mandrel (102} has been formed on the structural insert (200}, thereby affixing the structural insert (200} to the inner bore (105}, the mandrel (102} goes through a curing process. This curing process introduces the mandrel (102}, including the structural insert (200} or inserts, to a heating process which further affixes the structural insert (200} to the inner bore (105} of the mandrel (102}. Thus, by using a filament wound composite process, there is no need to use pins or any other such adhesives to affix the structural inserts (200} to the inner bore (105}.

[0055] The curing process heats the wound material to a particular temperature [e.g., about 425-deg.} for a particular amount of time, which depends on the materials, dimensions, desired strength, and other known considerations. As the heat cures the mandrel, the material of the mandrel 102 can form a chemical bond with the material of the insert 200. In this respect, the insert 200 may need to be pretreated, sandblasted, or the like prior to the winding process to enhance the future bond.

[0056] Additionally, because the material of the mandrel 102 may be the same as or different from the material of the insert 200 and because the conventional metal rod is not used for forming the mandrel 102, the different heating and cooling rates between the materials of the mandrel 102 and insert 200 may need to be considered in order to achieve the desired final dimensions and chemical bonds, as one skilled in the art will appreciate with the benefit of the present disclosure.

[0057] The insert 200 on which the mandrel 102 is wound may be longer initially than the mandrel 102. Therefore, free ends of the insert 200 can be removed so that the maj ority of the insert 200 lies within the mandrel's bore 105.

[0058] In a structural sense, winding on a cylindrical shaped insert 200 (as with inserts 214 and 216 of Figs. 2A] can be similar to winding on a temporary rod. As the winding process proceeds, the outer dimension of the resulting mandrel 102 may remain substantially uniform and cylindrical. In any event, some machining of the outer surface is typically done to make the mandrel 102 have a specific diameter, a smooth surface, and particular tolerances.

[0059] Winding on a non-cylindrical insert 200 (as with the cross-shaped insert 210 of Fig. 2A] may produce an outer diameter of the resulting mandrel 102 that is not strictly cylindrical. Still, the resulting mandrel 102 can machined to the proper outer diameter after cured and cooled. For such a non-cylindrical insert 200, it may also be possible to use a filler material in the gaps or spaces on the non-cylindrical insert 200 so that the winding can be more concentric around the insert 200. This may simplify some of the later machining. The filler material can be melted during the curing process or removed later in other ways so that the port 105 allows for fluid communication.

[0060] The foregoing description of preferred and other embodiments is not intended to limit or restrict the scope or applicability of the inventive concepts conceived of by the Applicants. It will be appreciated with the benefit of the present disclosure that features described above in accordance with any embodiment or aspect of the disclosed subject matter can be utilized, either alone or in combination, with any other described feature, in any other embodiment or aspect of the disclosed subject matter.

[0061] In exchange for disclosing the inventive concepts contained herein, the Applicants desire all patent rights afforded by the appended claims. Therefore, it is intended that the appended claims include all modifications and alterations to the full extent that they come within the scope of the following claims or the equivalents thereof.

Claims

CLAIMS:

1. A downhole tool for a wellbore, the tool comprising:

a mandrel having a throughbore and defining a collapse pressure;

a sealing component disposed on the mandrel and adapted to seal in the wellbore; and

at least one structural insert disposed within the throughbore and increasing the collapse pressure of the mandrel.

2. The downhole tool of claim 1, wherein the at least one structural insert is comprised of a non-metallic material.

3. The downhole tool of claim 1, wherein the at least one structural insert is comprised of one or more materials that comprise the mandrel.

4. The downhole tool of claim 1, wherein the at least one structural insert supports a sidewall of the mandrel disposed around the throughbore.

5. The downhole tool of claim 1, wherein the at least one structural insert comprises at least one channel allowing fluid passage in the throughbore.

6. The downhole tool of claim 1, wherein the at least one structural insert comprises one or more support bars disposed laterally across the throughbore.

7. The downhole tool of claim 6, wherein the at least one structural insert comprises an I-beam, a crossbar, a cylinder with an I-beam therein, or a cylinder with a crossbar therein.

8. The downhole tool of claim 1, wherein an adhesive affixes the at least one structural insert in the throughbore.

9. The downhole tool of claim 1, wherein at least one pin affixes the at least one structural insert in the throughbore.

10. The downhole tool of claim 1, wherein the mandrel comprises filament wound on the at least one structural insert.

11. The downhole tool of claim 10, wherein a chemical bond affixes the wound filament to the at least one structural insert.

12. The downhole tool of claim 1, wherein the tool is selected from the group consisting of a plug and a packer.

13. The downhole tool of claim 1, wherein the at least one structural insert extends in the throughbore at least adjacent the sealing component.

14. A method of making a downhole tool, the method comprising:

providing a mandrel having a throughbore and having a sealing component

disposed on the mandrel for sealing in a wellbore, and

increasing a collapse pressure of the mandrel by disposing at least one structural insert within the throughbore.

15. The method of claim 14, wherein disposing the at least one structural insert within the throughbore comprises supporting a sidewall of the mandrel around the throughbore with the at least one structural insert.

16. The method of claim 14, wherein disposing the at least one structural insert within the throughbore comprises allowing fluid passage in the throughbore along at least one channel in the at least one structural insert.

17. The method of claim 14, wherein disposing the at least one structural insert within the throughbore comprises supporting lateral sides of the throughbore with one or more support bars of the at least one structural insert.

18. The method of claim 14, wherein disposing the at least one structural insert within the throughbore comprises affixing the at least one structural insert in the throughbore using an adhesive.

19. The method of claim 14, wherein disposing the at least one structural insert within the throughbore comprises affixing the at least one structural insert in the throughbore using at least one pin.

20. The method of claim 14, wherein providing the mandrel comprises forming the mandrel by winding filament on a temporary member.

21. The method of claim 20, wherein disposing the at least one structural insert within the throughbore comprises removing the temporary member from the wound filament mandrel to leave the throughbore and inserting the at least one structural insert into the throughbore.

22. The method of claim 14, wherein providing the mandrel and disposing the at least one structural insert comprises forming the mandrel by winding filament on the at least one structural insert.

23. The method of claim 22, wherein disposing the at least one structural insert within the throughbore comprises affixing the wound filament to the at least one structural insert with a chemical bond.

24. The method of claim 22, wherein disposing the at least one structural insert within the throughbore comprises disposing the at least one structural insert at least adjacent the sealing component on the mandrel.