BOREHOLE PLUG WITH SPIRAL CUT SLIP AND INTEGRATED SEALING ELEMENT

Abstract

A tapered mandrel is advanced into a spirally cut sleeve having a corresponding taper to the mandrel. The outer surface of the sleeve conforms to the surrounding borehole and features an exterior recess in which a sealing element is mounted. The sleeve diameter expands as the tapered mandrel is axially advanced. Axial cuts in the spiral sleeve further reduce the force needed for setting. A leading nose is provided for the uphole end of the sealing element to allow high treatment flow rate while the sealing element is protected from the erosive effects of high velocities.

Description

FIELD OF THE INVENTION

The field of the invention is borehole plugs and more particularly those having a body passage selectively closed by an object landing on a seat surrounding the passage and integrating functions of anchoring, sealing and prevention of sealing element extrusion

BACKGROUND OF THE INVENTION

In downhole industries including hydrocarbon exploration and recovery and carbon dioxide sequestration, it is often necessary or desirable to provide for seals and anchors within a tubular body. There have been many different types of configurations to effect such seals and or anchors, each having its advantages and drawbacks. Since the industries noted above experience nearly infinite particular situations, each of which might be better solved by one technology or another, there is a continuing need for alternate configurations to support the vast need and to provide enhancements in various instances.

Further, the art is always receptive to configurations that can reduce required axial length and reduce cost of production. Prior designs have combined a setting tool that creates relative axial movement between a tapered body advanced relatively to a sleeve that has an external gripping surface and an adjacent sealing element. Slots have been provided in an axial direction to reduce the expansion force needed for contact with the surrounding tubular. In some embodiments the slots actually break causing the sleeve to turn into adjacent segments pressed against a surrounding tubular by the tapered mandrel. There are two issues with this design, first when pumping the plug assembly (guns, adapter kit, setting tool & plug) in the horizontal the seal has low resistance to swab off and swabs off at low flowrates (typically 5 bpm) and second the backup ring does not have zero extrusion gap leading to packing element extrusion under HPHT conditions (15,000 psi & 350° F.). This design, in several variations, is shown in US 2013/0186616.

The present invention addresses the shortcomings of the design discussed above with a combination of features such as a spiral cut slip segment that spreads radially with minimal force but provides a barrier circumferentially with no gaps to retain the sealing element in position. The sealing element is secured to the slip segment short of the uphole end of the slip segment so that flow from an uphole location around the plug initially engages a tapered uphole end of the slip segment to deflect the fluid and protect the sealing element from swab effects of fluid velocity. These and other aspects of the present invention will be more readily apparent from a review of the detailed description of the preferred embodiment and the associated drawings while understanding that the full scope of the invention is to be determined from the literal and equivalent scope of the appended claims.

SUMMARY OF THE INVENTION

A tool including a cone having a single ramp surface; a backup disposed on the ramp surface; a pusher having one or more slips, the pusher in contact with the backup and configured to force the backup along the ramp surface during use of the tool.

A backup including a tubular body; a helical cut line through the body that terminates prior to reaching an end face of the body.

A method for fracturing a formation through which a borehole passes including applying an occluding member to a tool as claimed in claim 1, the tool having been installed in a borehole; pressuring up on the borehole against the occluding member and tool; and fracturing the formation.

In an embodiment, a tapered mandrel is advanced into a spirally cut sleeve having a corresponding taper to the mandrel. The outer surface of the sleeve conforms to the surrounding borehole and features an exterior recess in which a sealing element is mounted. The sleeve diameter expands as the tapered mandrel is axially advanced. Axial cuts in the spiral sleeve further reduce the force needed for setting. A leading nose is provided for the uphole end of the sealing element to allow high flow rate while the sealing element is protected from the swab effects of high velocities.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike:

FIG. 1 is a cross sectional illustration of a seal and anchor tool;

FIG. 2 is a perspective illustration of the backup illustrated in FIG. 1;

FIG. 3 is a perspective illustration of an alternate backup ring for the configuration of FIG. 1; and

FIG. 4 is a cross sectional illustration of an alternate seal and anchor tool;

FIG. 5 is a section view in the run in position of the plug with the spiral cut slip;

FIG. 6 is a perspective view of the spiral cut slip;

FIG. 7 is a section view of the spiral cut slip;

FIG. 8 is the view of FIG. 6 with axial scores to reduce expansion force;

FIG. 9 is the view of FIG. 7 with the axial cut scores.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures.

Referring to FIG. 1, a seal and anchor tool 10 is illustrated in cross section that is actuated by axial compression force. A cone 12 appears at an uphole end of the figure and provides a single ramp surface 14 (i.e. eliminating an opposing ramp surface at an opposite axial end of a cone structure like that of the prior art) and in some embodiments an occluding member seat 16. The surface exhibits an angle ranging from about 2 degrees to about 20 degrees from a longitudinal axis of the cone in some embodiments. A seal 18 is disposed about the surface 14 and exhibits a matching angle surface 20 at an inside thereof to the angle of surface 14. The seal 18 provides an outside diameter surface 22 that is cylindrical in order to reasonably closely match an inside diameter surface 24 of a tubular in which the seal and anchor tool 10 are to be set. Adjacent the seal 18 is a backup 26 whose purpose is to prevent or substantially reduce extrusion of the seal 18 when the seal and anchor tool 10 experiences a pressure differential across the seal 18. It is to be appreciated from FIG. 1 that the diameter of the seal 18 appears greater than the diameter of the backup 26. This is intended since the seal diameter is, in one embodiment, configured with a diameter from about 0.005 to about 0.500 inch greater than that of the backup 26 in order to assure that the seal is fully seated and compressed to the surface 24 prior to the backup making contact with the surface 24. This configuration ensures that sufficient compressive load on the seal 18 will be imparted before the load axially applied to the tool 10 begins to be taken up by the backup 26 and the anchor (described below).

The anchor or slip ring pusher 28 is a full ring type that is designed to break apart into a number of slips 30 upon axial compression forcing the pusher 28 up the ramp surface 14. The slips 30 engage the surface 24 as will be understood by one of ordinary skill in the art. Due to the breakage of the pusher 28, there are potentially, circumferential gaps that could allow the seal 18 to extrude under a sufficient pressure differential. The backup 26, because it bridges across such gaps, operates to prevent or reduce extrusion of the seal 18. The backup will also prevent or reduce extrusion of the seal annularly adjacent surface 24.

Based upon FIG. 1, an artisan skilled in the art will recognize that the convention two sided cone member is eliminated in the configuration of the disclosed tool. Rather only one cone is provided. This is contrary to conventional teaching and results in a reduced axial length of the tool as well as a reduced cost of manufacture thereof while still retaining the ability to support a fracturing operation. Both of these features will be well received by the art.

One embodiment of the backup 26 features a body 38 comprising single piece of material 40 composed at least in part of polymeric materials including but not limited to, Polytetrafluoroethylene (PTFE), Polyetheretherketone (PEEK), etc. and metal materials including but not limited to brass, aluminum, magnesium etc. The backup 26 is helically cut through a portion of the material but not all of the material. Reference is made to FIG. 2 wherein the material 40 is shown with a cut line 42 that terminates prior to reaching an end face 46 of the backup 26. It will be appreciated in the drawing that the cut line 42 does reach the opposite end face 48 of the backup 26 at 50 but it is to be understood that the cut line 42 could also terminate short of end face 48, if desired. In an embodiment, a range of uncut portion 44 over which the cut line 42 does not extend is from about 0.005″ to about 1.00″. The uncut portion 44 functions, in this embodiment, to provide for an initiation pressure before the backup will start to move up the ramp 14. This will help avoid premature actuation and give more positive feedback during intended deployment. As the backup 26 moves up the ramp, once the uncut portion(s) 44 tear, the diameter increases by the material 40 sliding over itself along the cut line 42. Since the material stays circumferentially complete, any axial openings along the slips 30 will be bridged by the backup 26. The result is zero extrusion gap and minimal actuation force required.

Referring to FIG. 3, the backup 26 is similar but not identical to that of FIG. 2. Rather, in FIG. 3, there are two cut lines 52 and 54 through material 40. Each cut line 52 and 54 are helically arranged making two helical parts 56 and 58 that are nested with each other. At least one, and as shown both of the cut lines 52 and 54 terminate prior to reaching an end face 60 leaving uncut portion 62 and 64. A range of uncut portion 62 and 64 over which the cut lines 52 and 54 do not extend is from about 0.005″ to about 1.00″. It is to be understood that more cut lines may be added to produce more helical parts if desired. In the case of embodiments such as FIG. 3, the uncut portions serve not only to provide for initiation pressure before deployment as in FIG. 2 but also to hold the helical parts together prior to deployment. In this embodiment of backup 26 as in the previous embodiment, both annular and axial extrusion gaps are minimized or eliminated.

It is to be appreciated that in the case of FIGS. 2 and 3, the backup is not limited to employment in the tool described herein (and as noted the tool does not necessarily require the particular backup) although they do work well together. The backup as described may be employed with any other tool requiring a backup and the tool described herein may use other backups that provide sufficient resistance to seal extrusion.

In another embodiment, referring to FIG. 4, a tool 70 is illustrated that eliminates the seal 18 as described above but maintains other components of the tool 10 of FIG. 1. It has been determined that the backup 26 can be used alone to provide sufficient differential pressure holding capability to support a fracking operation without a seal 18. Therefore, for certain operations that are cost sensitive, it may be beneficial to employ the tool illustrated in FIG. 4.

Referring to FIG. 5, a bottom sub 70 has thread 72 for attaching part of a setting tool that is not shown but can be an E-4 tool sold by Baker Hughes, a GE company that is well known in the art. Another part of the tool pushes down on mandrel 74 and that force is schematically represented by arrow 76. A setting rod that is not shown passes through passage 78 to releasably connect to threads 72 when the sealing element 80 and wickers 82 of slip sleeve assembly 84 contact the surrounding tubular or the borehole wall that is not shown. Slip sleeve assembly 84 can be one piece comprising portions 110, 118 and 82 or it can be multiple connected pieces with 110 being an end regardless of there being one or more pieces. During the setting, radial surface 86 is advanced toward mandrel 74 until sufficient tension in the rod that is connected to thread 72 is reached at which time the rod that is not shown shears and the bottom sub falls in the borehole. Eventually the bottom sub 70 breaks up or disintegrates as it responds to well fluids or other well conditions. Bottom sub 70 can be made of a controlled electrolytic material that is known and also offered by Baker Hughes, a GE company of Houston, Tex. USA. Other materials that degrade or disintegrate or otherwise go away are also contemplated. The setting rod component above the shear break during setting comes out with the known setting tool as is well known in the art.

The slip sleeve assembly 84 has an internal taper 88 that conforms to the tapered outer surface 90 of frustoconically shaped mandrel 74. Seat 92 surrounds passage 78 at top end 94 of mandrel 74. An object that is preferably a ball 96 can be pumped or otherwise delivered to seat 92 after the setting tool that is not shown is removed. Although shown in a single location those skilled in the art will appreciate that a plurality of the illustrated assemblies can be used at axially spaced locations in a borehole to treat more than one portion of a producing interval. The plug P can be delivered with a perforating gun and a ball dropped that are not shown so that after the plug P is set and the perforating gun is fired successfully a ball 96 is released to seat 92 and a treatment into the formation against plug P can begin. It should be noted that the wickers 82 in the run in position have a cylindrical shape while the internal wall 88 is a taper that is preferably the same angle as taper 90 but some angular offset is envisioned.

Referring to FIGS. 5-7 a spiral cut 98 extends preferably from downhole end 100 to uphole end 102 but ending the cut short of either end is also contemplated.

“Spiral cut” is a generic term meant to include complete through the wall cuts or scores starting from the inside wall or the outside wall or a spiral form with gaps such as a coiled spring or no gaps, with the spiral being continuous or segmented or having one or more than one pattern nested patterns. In general, the term applies to a circular treatment for a generally cylindrically shaped object that is put there to reduce force when increasing its outer dimension when engaging a surrounding borehole surface for support therefrom.

As mandrel 74 is axially advanced toward downhole end 100 that rests on surface 86 of bottom sub 70 the wickers 82 move radially. Preferably adjacent coils such as 104 and 106 remain abutting after the set position is achieved but the amount of radial extension of each can vary somewhat to conform to irregularities of the surrounding borehole wall or the surrounding tubular. An external groove 108 is presented below end 102 leaving a leading tapered segment 110 of the slip sleeve assembly 84 uphole of the sealing element 80 shown in the groove 108 in FIG. 5. Preferably, the sealing element 80 has a leading taper 112 that preferably is a continuation of the taper on the segment 110 although it is envisioned that taper 112 can extend radially either more or less than the taper of segment 110. Sealing element 80 has a preferably cylindrical segment 114 downhole from taper 114 that preferably extends radially beyond wickers 82 so that by the time the wickers 82 engage the borehole wall or the surrounding tubular, the sealing element 80 is radially compressed against the surrounding borehole wall or tubular for a seal. The outer dimension of the slip sleeve assembly 84 grows radially as the mandrel 74 is axially advanced during the setting. The spiral cut allows this radial growth to occur while keeping abutting coils such as 104 and 106 in an abutting relationship to close of an extrusion path in a downhole direction responsive to treatment pressure applied from a surface location against sealing element 80. While sealing element 80 is generically represented as a single component it can be a multi-component assembly. In the set position the radial extension of the sealing element 80 and the wickers 82 is approximately the same particularly if the set is against a surrounding tubular so that the slip sleeve assembly 84 functions to anchor and to operate as an extrusion barrier at the same time. The slip sleeve assembly 84 using recess 108 holds the sealing element 80 in position. The leading taper 110 of the slip sleeve 84 helps to deflect fluid flowing around the seal. Thus reducing the pressure differential around the sealing element 80. As used herein, “taper” is used generically to refer to different shapes that function to reduce swabbing as the plug is delivered to a predetermined location. Thus taper encompasses a transitional surface bigger in diameter at the seal end and smaller in diameter at end 102. In between it can be a wavy surface or an arcuate surface; it can be smooth or rough with surface irregularities such as peaks or valleys or grooves, for example. Should any flow get past the sealing element 80 it will be stopped or at least slowed by the wickers 82 engaging the surrounding tubular or the borehole wall. By placing the sealing element 80 in groove 108 the prospect of fluid bypass under the sealing element 80 through the groove 108 is also minimized. Inside there is an internal groove 109 with seal 111 to engage mandrel 74 to close off an internal leak path. Thin walled section 118 is more flexible than adjacent portions of the slip sleeve assembly 84 and gets reaction force radially from the set sealing element 80 to close off a leak path between the mandrel 74 and the slip sleeve assembly 84. Seal 80 can be bonded, molded or 3-D printed into groove 118. Various components of the plug P can be made of disintegrating materials to avoid a need for milling out after the treatment is over. The mandrel 74 with ball 96 can be made of disintegrating materials. In some cases the slip sleeve assembly or parts thereof can be made of a disintegrating material or material that otherwise goes away without well intervention of tools. In some instances at least a part of the sealing element 80 can also disintegrate or otherwise disappear. FIGS. 8 and 9 show axial scores 120 that can extend to downhole end 100 to make radial expansion of the slip sleeve assembly 84 easier to accomplish with a reduced force. One or more such scores can be used or other weakening devices to reduce expansion force needed can be used. Preferably such scores or undercuts do not extend to an exterior surface where the wickers 82 are located. Scores 120 also come up short of the groove 108 as shown in FIG. 9, Scores 120 could optionally be on the outside as an alternative or as an addition to those shown on the inside. It should be noted that the increase in radial dimension of the slip sleeve assembly 84 comes with a decrease of its axial length that also has the effect of adding an axial compression force to the sealing element 80 although the applied axial forces from the setting tool establish a wedging action due to relative axial movement of the slip sleeve assembly 84 with sealing element 80 relative to mandrel 74.

The teachings of the present disclosure may be used in a variety of well operations. These operations may involve using one or more treatment agents to treat a formation, the fluids resident in a formation, a wellbore, and/or equipment in the wellbore, such as production tubing. The treatment agents may be in the form of liquids, gases, solids, semi-solids, and mixtures thereof. Illustrative treatment agents include, but are not limited to, fracturing fluids, acids, steam, water, brine, anti-corrosion agents, cement, permeability modifiers, drilling muds, emulsifiers, demulsifiers, tracers, flow improvers etc. Illustrative well operations include, but are not limited to, hydraulic fracturing, stimulation, tracer injection, cleaning, acidizing, steam injection, water flooding, cementing, etc.

It is also contemplated for any or all of the components/tools described above that materials such as a controlled electrolytic metallic material (Intallic® commercially available from Baker Hughes, Houston Tex.) or other dissolvable or disintegrable material be employed so that the entirety or some portion of the entirety of the tools may be removed through dissolution via natural borehole fluids or applied fluids at an appropriate time.

The tool embodiments disclosed herein are particularly suited to fracturing a formation through which a borehole passes while reducing expense in production of the tool, reducing longitudinal axial length of the installed to and optionally reducing costs for removal of the tool. The fracturing operation comprises: installing one of the embodiments set forth above in a borehole; applying an occluding member on the tool; pressuring up on the borehole against the occluding member and tool; fracturing a formation adjacent the borehole and removing the tool from the borehole.

The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Further, it should further be noted that the terms “first,” “second,” and the like herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the particular quantity).

While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited.

Claims

1. A plug assembly for borehole use, comprising: a mandrel;a slip sleeve assembly having opposed uphole and downhole ends and externally supporting a sealing element assembly axially spaced from said uphole end such that said sealing assembly and said slip sleeve assembly move in tandem relative to an external taper on said mandrel from a run in position to wedge said sealing assembly to the borehole in a set position.

2. The plug assembly of claim 1; wherein: said uphole end further comprises an external taper.

3. The plug assembly of claim 2, wherein: said sealing element assembly comprising a tapered uphole end substantially aligned with said external taper of said uphole end of said slip sleeve assembly.

4. The plug assembly of claim 3, wherein: said tapered uphole end of said sealing element is coincident with said external taper of said slip sleeve assembly.

5. The plug assembly of claim 1; wherein: said slip sleeve assembly further comprises at least one spiral cut extending substantially over the axial distance between said uphole and downhole ends of said slip sleeve assembly.

6. The plug assembly of claim 1, wherein: said slip sleeve assembly comprises an outer cylindrical surface with a plurality of wickers and an external groove, said sealing element assembly extending radially outside of said groove and beyond said wickers in said run in position.

7. The plug assembly of claim 6, wherein: said sealing element assembly is bonded, molded or 3D printed to said external groove.

8. The plug assembly of claim 5, wherein: said slip sleeve assembly retaining an external cylindrical shape without gaps while engaging a borehole wall in said set position to act as an extrusion barrier for said sealing element assembly.

9. The plug assembly of claim 1, wherein: said mandrel comprising a seat surrounding an axial passage therethrough, said seat accepting an object to close said passage to allow pressure on the object to be communicated to a formation about the borehole.

10. The plug assembly of claim 9, wherein: said object and said mandrel selectively removable without intervention.

11. The plug assembly of claim 2, wherein: said external taper shielding said sealing element assembly from erosion and swabbing effects from fluid under high flow rates flowing around the plug when pushing the assembly in horizontal section of the wellbore

12. A plug assembly for borehole use, comprising: a mandrel;a slip sleeve assembly having opposed uphole and downhole ends and supporting a sealing element assembly such that said sealing assembly and said slip sleeve assembly move in tandem relative to an external taper on said mandrel from a run in position to a set position where said sealing assembly is wedged against the borehole;said slip sleeve assembly further comprising a spiral cut.

13. The plug assembly of claim 12, wherein: said spiral cut extending over a substantial length of said slip sleeve assembly between said uphole and said downhole ends.

14. The plug assembly of claim 12, wherein: said slip sleeve assembly retaining an external cylindrical shape without gaps while engaging a borehole wall in said set position to act as an extrusion barrier for said sealing element assembly.

15. The plug assembly of claim 12, wherein: said sealing element assembly mounted externally on said slip sleeve assembly and below said uphole end.

16. The plug assembly of claim 15, wherein: said sealing element assembly mounted in a groove on said slip sleeve assembly.

17. The plug assembly of claim 16, wherein: said uphole end further comprises an external taper;said sealing element assembly comprising a tapered uphole end substantially aligned with said external taper of said uphole end of said slip sleeve assembly.

18. The plug assembly of claim 17, wherein: said external taper shielding said sealing element assembly from erosion and swabbing effects from fluid under high flow rates delivered around the frac plug assembly while pushing it in the horizontal section of the wellbore.

19. The plug assembly of claim 12, wherein: said mandrel comprising a seat surrounding an axial passage therethrough, said seat accepting an object to close said passage to allow pressure on the object to be communicated to a formation about the borehole said object, said mandrel and at least in part said slip sleeve assembly selectively removable without intervention.

20. The plug assembly of claim 5, wherein: said slip sleeve assembly further comprises at least one internal or external axially oriented score.

21. The plug assembly of claim 12, wherein: said slip sleeve assembly further comprises at least one internal or external axially oriented score.

22. The plug assembly of claim 1, further comprising: an internal seal disposed between said slip sleeve and said mandrel.

23. The plug assembly of claim 12, further comprising: an internal seal disposed between said slip sleeve and said mandrel.

24. A borehole treatment method, comprising: applying pressure against the plug assembly of claim 1 when the plug assembly is in said set position to direct a material to a formation about the borehole for the treatment.

25. The method of claim 24, comprising: fracturing the formation as said treatment.

26. A borehole treatment method, comprising: applying pressure against the plug assembly of claim 12 when the plug assembly is in said set position to direct a material to a formation about the borehole for the treatment.

27. The method of claim 26, comprising: fracturing the formation as said treatment.