PLUG OF EXTENDED REACH

Abstract

A settable down hole tool is of increased drillability and/or of increased expansibility. The improvement in drillability can be caused by fracturing cast iron slips into a large number of small pieces that can be circulated out of a well without further reduction in size. The improvement in expansibility can be partially caused by providing an expander cone of increased hardness thereby allowing an increased angle on the expander cone and slips. The improvement in expansibility can be partially caused by increasing the thickness of the slips.

Claims

1. A settable isolation tool for fracing past at least one casing patch within 4½ inch O.D. casing in a horizontal leg of a hydrocarbon well, the tool comprising: a mandrel with a longitudinal axis; expanders around the mandrel, each expander having a frustoconical section; slips around the mandrel, each slip having a surface complementary to an expander frustoconical section, being in a retracted slip position for running the tool past the casing patch and being movable radially outward by an expander to an expanded slip position for engagement with the casing when the tool is past the casing patch; the mandrel, expanders and slips each sized and configured so the O.D. of the retracted slips is 3 inches or less and the O.D. of the tool in the retracted position is 3.25 inches or less, and the tool is small enough so the tool can be run through and past the casing patch within the casing in the horizontal leg; the mandrel, expanders and slips each comprised of materials strong enough so the tool can be expanded and set, and used in isolating and fracing in the horizontal leg past the casing patch; the mandrel, expanders and slips each sized and configured so after the retracted tool is past the casing patch, the tool can be expanded to an O.D. large enough to set the tool into gripping engagement with an unpatched section of the casing, so the tool can isolate an upper zone above the tool from a lower zone below the tool and the upper zone fraced in isolation from the lower zone, the expanded tool having a maximum expanded tool O.D. at least 20% larger than the retracted tool's O.D. with a maximum O.D. of 4.1 inches or more; the slip has an interior side and an exterior side, the exterior side is hardened or comprised of metal and hard enough to maintain a gripping engagement with the casing during setting and fracing and the tool is drillable in the horizontal leg past the casing patch with a single coiled tubing bit run, the slips producing slip pieces small enough to be circulated out of the well by fluid in the casing having an upward velocity of 100 feet/minute; the mandrel, expanders and slips comprised of materials drillable with a single coiled tubing bit run in the horizontal leg past the casing patch after the tool is expanded and set, and used in isolating and tracing in the horizontal leg to produce tool pieces small enough and light enough to be circulated out of the horizontal leg and the well by fluid having an upward velocity of 100 feet/minute so hydrocarbons can be produced from a fraced zone in the horizontal leg, the mandrel and expanders being of drillable materials being selected from the group consisting essentially of aluminum, aluminum alloys, copper, copper alloys, resins and composite materials; and wherein two or more such tools can be serially run past one or more casing patches in the horizontal leg, expanded and set, used in isolating and fracing in the horizontal leg; and then the two or more such tools drilled out with a single coiled tubing bit run, producing tool pieces small enough and light enough to be circulated out of the horizontal leg of the well by fluid having an upward velocity of 100 feet/minute so hydrocarbons can be produced from the horizontal leg of the well.

2. The tool of claim 1 wherein five or more such tools, serially run past one or more patches in the horizontal leg, can be expanded in the horizontal leg to isolate zones in the horizontal leg and used in serial fracing, each tool drillable enough so the five or more tools can be drilled out in a single coiled tubing bit run, the single drilling out coiled tubing bit run producing pieces small enough to be circulated out of the horizontal leg so hydrocarbons can be produced from the horizontal leg by fluid having an upward velocity of 100 feet/minute.

3. The tool of claim 1 wherein the two or more such tools are configured to be drilled up in pieces small enough and light enough to be circulated out of the horizontal leg of the well by fluid having an upward velocity of 300 feet/minute so hydrocarbons can be produced from the horizontal leg of the well.

4. A settable isolation tool for fracing past at least one casing patch within 5 inch O.D. casing in a horizontal leg of a hydrocarbon well, the tool comprising: a mandrel with a longitudinal axis; expanders around the mandrel, each expander having a frustoconical section; slips around the mandrel, each slip having a surface complementary to an expander frustoconical section, being in a retracted slip position for running the tool past the casing patch and being movable radially outward by an expander to an expanded slip position for engagement with the casing when the tool is past the casing patch; the mandrel, expanders and slips each sized and configured so the O.D. of the retracted slips is 3.6 inches or less and the O.D. of the tool in the retracted position is 3.75 inches or less and is small enough so the tool can be run through and past the casing patch within the casing in the horizontal leg; the mandrel, expanders and slips each comprised of materials strong enough so the tool can be expanded and set, and used in isolating and fracing in the horizontal leg past the casing patch, the materials being selected from the group consisting essentially of aluminum, aluminum alloys, copper, copper alloys, resins and composite materials; the mandrel, expanders and slips each sized and configured so after the retracted tool is past the casing patch, the tool can be expanded to an O.D. large enough to set the tool into gripping engagement with an unpatched section of the casing, so the tool can isolate an upper zone above the tool from a lower zone below the tool and the upper zone fraced in isolation from the lower zone, the expanded tool having a maximum expanded tool O. D. at least 20% larger than the retracted tool's O.D., with a maximum O.D. of 4.6 inches or more; the slips have an interior side and an exterior side, the exterior side is hard enough to maintain a gripping engagement with the casing during setting and fracing, the slips disintegrating into slip pieces small enough to be circulated out of the well by fluid in the casing having an upward velocity of 100 feet/minute; the mandrel, expanders and slips each comprised of materials drillable with a single coiled tubing bit run in the horizontal leg past the casing patch after the tool is expanded and set, and used in isolating and fracing in the horizontal leg to produce tool pieces small enough and light enough to be circulated out of the horizontal leg and the well by fluid having an upward velocity of 100 feet/minute so hydrocarbons can be produced from a fraced zone in the horizontal leg; and wherein two or more such tools can be serially run past one or more casing patches in the horizontal leg, expanded and set, used in isolating and tracing in the horizontal leg and then the two or more such tools can be drilled out with a single coiled tubing bit run, producing tool pieces small enough and light enough to be circulated out of the horizontal leg and the well by fluid having an upward velocity of 100 feet/minute so hydrocarbons can be produced from the horizontal leg and the well.

5. The tool of claim 4 wherein the two or more such tools are configured to be drilled up in pieces small enough and light enough to be circulated out of the horizontal leg of the well by fluid having an upward velocity of 300 feet/minute so hydrocarbons can be produced from the horizontal leg of the well.

6. A settable isolation tool for fracing past at least one casing patch within 5.5 inch O.D. casing in a horizontal leg of a hydrocarbon well, the tool comprising: a mandrel with a longitudinal axis; expanders around the mandrel, each expander having a frustoconical section; slips around the mandrel, each slip having a surface complementary to an expander frustoconical section, being in a retracted slip position for running the tool past the casing patch and being movable radially outward by an expander to an expanded slip position for engagement with the casing when the tool is past the casing patch; the mandrel, expanders and slips each sized and configured so the O.D. of the retracted slips is 3.88 inches or less and the O.D. of the tool in the retracted position is 4.18 inches or less and is small enough so the tool can be run through and past the casing patch within the casing in the horizontal leg; the mandrel, expanders and slips each comprised of materials strong enough so the tool can be expanded and set, and used in isolating and fracing in the horizontal leg past the casing patch; the mandrel, expanders and slips each sized and configured so after the retracted tool is past the casing patch, the tool can be expanded to an O.D. large enough to set the tool into gripping engagement with an unpatched section of the casing, so the tool can isolate an upper zone above the tool from a lower zone below the tool and the upper zone fraced in isolation from the lower zone, the expanded tool having a maximum expanded tool O. D. at least 20% larger than the retracted tool's O.D., with a maximum O.D. of 5.05 inches or more; the slips have an interior side and an exterior side, the exterior side is hard enough to maintain a gripping engagement with the casing during setting and fracing, at least some of the slips being disintegrating into slip pieces small enough to be circulated out of the well by fluid in the casing having an upward velocity of 100 feet/minute; the tool being drillable in the horizontal leg past the casing patch with a single coiled tubing bit run into the casing; the mandrel, expanders and slips each comprised of materials drillable with a single coiled tubing bit run in the horizontal leg past the casing patch after the tool is expanded and set, and used in isolating and fracing in the horizontal leg to produce tool pieces small enough and light enough to be circulated out of the horizontal leg and the well by fluid having an upward velocity of 100 feet/minute so hydrocarbons can be produced from a fraced zone in the horizontal leg; and wherein two or more such tools can be serially run past one or more casing patches in the horizontal leg, expanded and set, used in isolating and tracing in the horizontal leg and then the two or more such tools drilled out with a single coiled tubing bit run, producing tool piece small enough and light enough to be circulated out of the horizontal leg and the well by fluid having an upward velocity of 100 feet/minute so hydrocarbons can be produced from the horizontal leg and the well.

7. The tool of claim 6 wherein the two or more such tools are configured to be drilled up in pieces small enough and light enough to be circulated out of the horizontal leg of the well by fluid having an upward velocity of 300 feet/minute so hydrocarbons can be produced from the horizontal leg of the well.

8. A settable isolation tool for fracing past at least one casing patch within 4½ inch to 5½ inch O.D. casing in a horizontal leg of a hydrocarbon well, the tool comprising: a mandrel with a longitudinal axis, consisting essentially of non-metallic materials; expanders around the mandrel, consisting essentially of non-metallic materials, each expander having a frustoconical section; slips around the mandrel, each slip having an outer surface including metal and having an inner surface complementary to an expander frustoconical section, being in a retracted slip position for running the tool past the casing patch and being movable radially outward by an expander to an expanded slip position for engagement with the casing when the tool is past the casing patch, each retracted slip is comprised of multiple slip pieces held on the tool when the tool is in the tool's retracted position, the multiple slip pieces being expandable outward by the expander; the mandrel, expanders and slips each sized and configured so the tool in the tool's retracted position has an O.D. sufficient to pass through casing in the range of 4½″ to 5½″ O.D. and is small enough so the tool can be run through and past the casing patch within the casing in the horizontal leg; the mandrel, expanders and slips each comprised of materials strong enough so the tool can be expanded and set, and used in isolating and fracing in the horizontal leg past the casing patch; the mandrel, expanders and slips each sized and configured so after the retracted tool is past the casing patch, the tool can be expanded to an O.D. large enough to set the tool into gripping engagement with an unpatched section of the casing, so the tool can isolate an upper zone above the tool from a lower zone below the tool and the upper zone fraced in isolation from the lower zone, the expanded tool having a maximum expanded tool O. D. at least 20% larger than the retracted tool's O.D.; the mandrel, expanders and slips each comprised of materials drillable with a single coiled tubing bit run in the horizontal leg past the casing patch after the tool is expanded and set, and used in isolating and framing in the horizontal leg to produce tool pieces small enough and light enough to be circulated out of the horizontal leg and the well by fluid having an upward velocity of 300 feet/minute so hydrocarbons can be produced from a fraced zone in the horizontal leg; and wherein two or more such tools can be serially run past one or more casing patches in the horizontal leg, expanded and set, used in isolating and tracing in the horizontal leg and then the two or more such tools drilled out with a single coiled tubing bit run, producing tool pieces small enough and light enough to be circulated out of the horizontal leg and the well by fluid having an upward velocity of 300 feet/minute so hydrocarbons can be produced from the horizontal leg and the well.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG. 1 is a diagrammatic view of a horizontal well showing a set of perforations which have been fraced;

[0025] FIG. 2 is an enlarged view of a well section where a casing patch has been placed over an existing set of perforations;

[0026] FIG. 3 is a view, partly in cross-section, of a settable well tool;

[0027] FIG. 4 is a cross-sectional view of an expander cone used in the well tool of FIG. 3, the cross-section being taken along line 4-4 of FIG. 7 as viewed in the direction indicated by the arrows;

[0028] FIG. 5 is a cross-sectional view of an expander cone made of a composite material having a drillable metal layer on the cone;

[0029] FIG. 6 is a cross-sectional view of another embodiment of an expander cone;

[0030] FIG. 7 is an end view of the expander cones of FIGS. 4-6;

[0031] FIG. 8 is an end view of slips used in the well tool of FIG. 3;

[0032] FIG. 9 is a cross-sectional view of the slips of FIG. 8, taken substantially along line 9-9 thereof as viewed in the direction indicated by the arrows;

[0033] FIG. 10 is a cross-sectional view of the slips of FIG. 7, taken substantially along line 10-10 thereof as viewed in the direction indicated by the arrows;

[0034] FIG. 11 is a side view of the slips of FIGS. 8 and 9;

[0035] FIG. 12 is an isometric view of a slip segment following fracturing of the slips into a series of segments;

[0036] FIG. 13 is a back view of the slip segment of FIG. 12;

[0037] FIG. 14 is an isometric view of the slip segment of FIGS. 12-13 after it has been fractured along a zone of weakness perpendicular to the tool axis;

[0038] FIG. 15 is an isometric view of the upper half of the slip segment of FIG. 14 after it has been fractured along a second zone of weakness parallel to the tool axis;

[0039] FIG. 16 is an isometric view of the lower half of the slip segment of FIG. 14 after it has been fractured along a second zone of weakness parallel to the tool axis;

[0040] FIG. 17 is an end view, similar to FIG. 8, of another embodiment of a set of slips; and

[0041] FIG. 18 is a partial isometric view of another embodiment of a set of slips.

DETAILED DESCRIPTION

[0042] The present invention relates to devices for use in hydrocarbon wells drilled into the earth and completed using a variety of techniques. The materials from which the tools are made are subject to considerable variation. Some of the components can be of drillable metal and some can be of composite material. A composite material can be a fabric core impregnated with a resin which is hardened in some suitable manner. Any components left in the well are usually made of drillable materials. Various changes and adaptations can be made in the tools without departing from the spirit and scope of the invention, which is to be measured solely by the claims themselves.

[0043] Referring to FIGS. 1-2, there is illustrated a hydrocarbon well 10 having a vertical well bore section 12 and a horizontal well bore section 14. The horizontal well bore section 14 can extend through a hydrocarbon bearing formation 16. A casing string 18 can be cemented in the well bore sections 12, 14 by a cement sheath 20. The well 10 is illustrated as being a well that has already produced through a series of perforations 22 which were stimulated by a frac job to provide a series of fractures 24. In some situations, production from the well 10 can decline to an extent where it can be desirable to blank off the existing perforations 22 and fractures 24 and produce one or more new fractures.

[0044] The goal is to blank off the old perforations 22 and old fractures 24, perforate a section between the old perforations 22 or beyond the most distant perforations and frac the new perforations. To this end, FIG. 2 shows a casing patch 26 that has been run into the well 10 and expanded in a conventional manner to blank off the perforations 22 and the fracture 24. Casing patches are conventional equipment and are available from Owen Oil Tools, Weatherford International, Baker Hughes Incorporated and various independent oil field service companies. Conventional casing patches are tubular and typically include an inner metal layer and a thin outer rubber or resilient layer. The patches initially have an O.D. slightly less them the I.D. of the casing into which they are run. When the patch is positioned at its desired location, a swedge is pulled through the patch stretching the patch beyond the elastic limit of the metal layer and forcing the patch against the inside of the casing. Because the metal layer is stretched beyond its elastic limit, the patch remains against the casing and does not relax to its original O.D. As mentioned, the difficulty is that the thickness of the casing patch reduces the I.D. of the casing string 18 and thereby complicates expanding a settable well tool against the inside of the casing string 18.

[0045] Typically, a series of casing patches can be run into the well 10 and set across all existing perforations. Then, a first set of new perforations can be created at the most distant location from the surface, the first set of new perforations is fraced to produce a first fracture and a bridge plug is set near the first new fracture to seal it off temporarily. This process is repeated as many times as desired to produce a series of new fractures which hopefully will reestablish commercial production from the well 10. This process is illustrated in FIGS. 1-2 where the old perforations 22 are blanked off, a new set of perforations 28 are created and then fraced to produce a new fracture 30.

[0046] To this end, a settable tool 32 which is illustrated as a bridge plug can be run above the first new set of perforations 28 in order to shoot a second set of perforations 34 and frac through them to create a second new fracture 36. The bridge plug 32 is illustrated as being of the type shown in U.S. patent application Ser. No. 12/317,497, filed Dec. 23, 2008, which is incorporated herein by reference for a more complete description thereof. The bridge plug 32 can comprise a mandrel 38, a pair of slips 40, 42 which may be identical, a pair of expanders or expander cones 44, 46 which may be identical, an expandable seal 48, a muleshoe 50 and a setting assembly 52 including a reaction ring 54 abutting the upper slips 40 and a sliding sleeve 56.

[0047] In most applications, the settable tool 32 can be made of drillable materials. The mandrel 30, the slip expanders 44, 46, the tube 56, the muleshoe 50, the reaction ring 54 are made of drillable materials selected from the group consisting essentially of aluminum, aluminum alloys, copper, copper alloys and composites. The strength and hardness of a composite depends on the fabric material, the resin employed and the conditions under which the composite is manufactured. Composites can be made in a wide range of strengths and hardnesses, many of which are drillable. The seal 48 is typically of rubber and the slips 40, 44 may be of cast iron.

[0048] In use, a wire line or other setting tool (not shown) is threaded onto a connection 58 and including a sleeve (not shown) abutting the sleeve 56. By pulling up on the connection 58 and pushing down on the sleeve 56, the reaction ring 54 pushes against the upper slips 40. The expander cones 44, 46 are ultimately driven into the slips 40, 42. The slips 40, 42 are fractured as explained more fully hereinafter and expand into engagement with the interior of the casing string 18 thereby wedging the bridge plug 32 securely against the inside of the casing string 18. The seal 48 also expands against the inside of the casing 18 thereby providing a pressure seal. As heretofore described, those skilled in the art will recognize that the settable tool 32 its set inside the casing 18 in a more-or-less conventional manner.

[0049] As explained previously, the settable tool 32 is capable of being run through the casing patch 26 or other restriction and then expanded into gripping engagement with the inside of the casing string 18. Prior art expander cones are made of a composite material or engineered plastic. These type materials can comprise a fabric impregnated with a resin which is then cured to form a blank which is then machined into a desired shape. One modification of the settable tool 32 that facilitates increased expansibility is the design of the expander cones 44, 46. Simply increasing the angle of the frustoconical surface 60 of the cones 44, 46 and the complementary surface in the slips 40, 42 did not work. With conventional cast iron slips, the slips did not expand sufficiently to grip light weight casing while being able to pass through a casing patch in heavy wall casing. Conventional cast iron slips are, of course, made as thin and lightweight as possible because the tools they are used with commonly need to be drilled up to prepare for a subsequent well operation. In addition, in some situations, the surface of the cone extruded between the segments of the slips during setting of the tool thereby failing to expand the slips sufficiently. In other situations, the slips were expanded sufficiently at the outset but the cones later extruded between the slip segments thereby allowing the slips to relax and retract away from the casing wall thereby inappropriately releasing the settable tool from the casing.

[0050] In the embodiment of FIG. 4, the expander cone 44 is considerably harder, at least in the area of the surface 60, than is conventional. Conventional composite materials used in well tools, i.e. fiberglass impregnated with a standard plastic resin, has a Rockwell B hardness in the range of 45-50. These materials have been proven to fail when used as an expander cone in an extended reach well tool. In some embodiments of the expander cone 40, the hardness of the composite frustoconical surface 60 is at least 70 on the Rockwell B scale and preferably is at least 80 which, in the right situation, can be sufficient to prevent extruding the expander cone between the slip segments. The ability of the expander cone to withstand the forces of an extended reach tool may depend on other factors such as tensile or compressive strength, meaning the higher the better.

[0051] Increasing the angle of the surface 60 and increasing the hardness of the surface 60 provides a partial solution to increased expansibility and, in one approach, one might increase the expansibility of settable well tools without providing a single device that would operate over the entire range necessary for operation in a specific sized casing. For example, one might provide two slightly different tools for operation in 5½″ casing, e.g. one tool for 5½″ casing weighing 15.5#-17#/foot and a second tool for 5½″ casing weighing 20-26#/foot. In situations like this, one could design a tool using a high angle expandable cone of increased hardness to provide the increased expansibility.

[0052] The expander 44 can otherwise be of conventional shape and can comprise a body 62 having a central passage 64 and one or more set screw passages 66 for securing the expander cone 44 to the mandrel 30. The bottom of the expander cone 44 includes a series of tapered segments 68 which receive the seal 48. When the tool 32 is set against the casing 18, the segments 68 can act like flower petals and constrain movement of the seal 48 into sealing engagement with the casing 18. In some high pressure situations, a metal cone can be provided to further constrain movement of the seal. The cone 44 can be scored to split and thereby create the segments 68 in an appropriate manner during expansion of the seal 48.

[0053] To promote reliable fracturing of the slips 40, 42, a guide or series of guides 72 may be provided that will act in a manner to be disclosed more fully hereinafter. The guides 72 can comprise a pin glued in a blind passage 74, can comprise a set screw threaded into the passage 74 or can comprise any mechanism providing an abutment or shoulder 76 extending above the conical surface 60.

[0054] Referring to FIG. 5, another embodiment 78 of an expander cone is illustrated and can comprise a body 80 having a central passage 82 and one or more set screw passages 84 for securing the expander 78 to the mandrel 38. The body 80 can be of a conventional composite material, i.e. having conventional hardness, and can be equipped with a sleeve 86 or layer of drillable metal such as aluminum and aluminum alloys, copper and copper alloys such as brass or bronze and the like. The bottom of the expander 78 can be of the same style and shape as that of the expander 44. The sleeve 86 can have turned ends 88, 90 captivating the sleeve 86 to the expander body 80. In this manner, the hardness of the conical upper end of the expander body 80 can be increased. The expander 78 may also be provided with a guide or series of guides 92 comprising a pin or set screw 94 in a blind passage 96.

[0055] Referring to FIG. 6, there is illustrated another embodiment of an expander 98 having a one end 100 of a composite material and a conical end section 102 of a drillable metal such as aluminum, aluminum alloys, copper, copper alloys and the like. The end 100 can be shaped and configured as in the expander 44 having a threaded connection 104 for receiving threads 106 provided by the metal end section 102. One or the other of the sections 100, 102 may have passages 108 for receiving set screws 110 to fix the expander 98 to the mandrel 38. The expander 98 can have a guide or series of guides 112 on the conical surface 114 to promote reliable fracturing of the slips 40 as explained more fully hereinafter. If desired, the function of the guides 112 can foe accomplished by selecting the set screws 110 to extend beyond the conical surface 114 as will become more fully apparent hereinafter.

[0056] Another approach to increase the expansibility of the settable well tool 32 is to increase the thickness of the cast iron slips. This is counterintuitive because it is often desirable to drill up settable well tools and thicker cast iron slips segments are much harder to drill up, meaning that one has traded one large advantage for one large disadvantage.

[0057] Upon expansion of the well tool into engagement with the casing, the slips move relative to the expanders. Because the slips are made with a series of external grooves parallel to the tool axis 116, the slips fracture into a series of substantially identical elongate slip segments which are parallel to the tool axis 116. When conventional cast iron slips are thickened in an attempt to increase the expansibility of a well tool, the well tool inherently becomes more difficult to drill up.

[0058] To avoid this disadvantage, the slips 40, 42 are designed to fracture into an unusually large number of pieces. Standard cast iron slips fracture into a number of elongate slip segments corresponding to the number of external grooves that promote fracturing. Thus, conventional cast iron slips typically comprise six or eight grooves causing the slips to fracture into six or eight elongate slip segments. As disclosed herein, the slips 40, 42 also fracture into a series of elongate slip segments and each slip segment can further fractured into at least two pieces and may preferably be fractured into at least four pieces. It is believed that fracturing first occurs along the external grooves but it is not material in which order fracturing occurs. The important thing is that the slips are reduced during setting of the well tool to a much larger number of pieces. Because there are more slip pieces, each slip piece weighs much less than conventional slip pieces, meaning they are much easier to circulate out of the well without much, if any, drilling of the pieces.

[0059] Reducing the slips to pieces that are much smaller and lighter is accomplished by providing additional zones of weakness that induce fracturing when the slips 40, 42 are being expanded by the expanders 44, 46. Some of these zones of weakness may be parallel to the tool axis 116 and some may be transverse to the tool axis 116. As shown in FIGS. 8-16, the slips 40 include a body 118 that may be of one piece but which may be multipiece that is held together by a suitable mechanism in the retracted position shown in FIG. 3. The slip body 118 includes a central passage 120 having a tapered or conical surface 122 which is at a complementary angle to the conical surfaces 60, 86, 114 of the expanders 44, 78, 98.

[0060] The slip body 118 can include a series of grooves 124, 126 which can be on the exterior of the slips and which can divide the slips into a series of more-or-less identical slip segments 128. In some embodiments, some of the grooves 124 may be considerably deeper or more pronounced than alternate grooves 126. This is believed to cause fracturing along the grooves 124 first but the order in which fracturing occurs is not material. It will be seen that the grooves 124, 126 produce zones of weakness parallel to the tool axis 116.

[0061] Each of the slip segments 128 includes teeth or wickers 130 on the exterior that grip the casing 18 when the slips 40 are expanded. It may be preferred to heat treat the slips 40, 42 so that only the surface of the wickers 130 is hardened. Some or all of the slip segments 128 can include a second zone of weakness or notch 132 transverse to the tool axis 116 which causes the slip segment 128 to fracture into upper and lower halves 134, 136 as shown in FIG. 14. As shown best in FIG. 11, the notches 132 lie in a common plane. The notch or crease 132 is distinct from the inside edge or inside I.D. 138 of the teeth 130 because conventional cast iron slips do not fracture at the edge 138. In this device, the notches 132 may be coincident with one of the tooth edges 138 and, in the illustrated embodiment, are very close to one of the tooth edges 138. The second zone of weakness 132 accordingly divides the slip segment 128 into two pieces.

[0062] As will be explained more fully hereinafter, the segment halves 134, 136 may vary in the range of ⅓ to ⅔rds of the weight of the slip segment 128 and may preferably each be about half the weight of the slip segment 128. Another relevant characteristic is the tendency of the segment halves 134, 136 to fall by gravity through an upwardly moving body of liquid. The segment halves 134, 136 may preferably be equally propelled upwardly in a column of moving liquid so they may be circulated out of a well with little or no additional reduction in size, as from drilling. Thus, the location of the notch or crease 132 may vary considerably along the long dimension of the slip segment 128. It will be seen that the slips 40, 42 can be wholly of metal, or may comprise non-metallic inclusions but, in any event, the metal of the slips 40, 42 is continuous and provides the structural strength and integrity of the slips 40, 42.

[0063] A more sophisticated approach is to determine a cross-sectional parameter of the upper and lower segment halves 134, 136 that is related to their movement in an upwardly moving column of liquid. This parameter and the weight of the segment halves may be combined to provide an optimum location for the crease 132.

[0064] As shown best in FIGS. 8, 12, 14 and 15, some or all of the slip segments 128 provide a third zone of weakness or passage 140 opening between the conical surface 122 and an end 142 of the slip body 118. Although the passage 140 is conveniently illustrated as a cylindrical hole. If may be of any desired shape. The third zone of weakness can accordingly be generally parallel to the tool axis 116. During setting of the slips 40, the slip segment halves 134, 136 can divide roughly into mirror imagine halves 144, 146, meaning that each slip segment 128 has the potential to divide into four slip pieces.

[0065] It will be apparent that the slip segments 128 can include multiple horizontal creases or notches 132 thereby dividing the slip segments 128 into more than two horizontal pieces. In addition, the slip segments 128 can include multiple zones of weakness parallel to the tool axis thereby dividing the slip segments 128 into more than two vertical pieces.

[0066] Setting of the well tool 32 will now be described. The tool 32 can be run on wireline and can be conveyed by slickline or wireline and can be dropped, pumped or run on coiled tubing into the well 10. When it reaches its desired location, a setting tool (not shown) pulls on the connection 58 and pushes on the reaction ring 54. This causes the mandrel 38 to move upwardly in FIG. 3 so the expanders 44, 46 move into the central passages of the slips 40, 42. In the expanded position of the tool 32, the guides 92 can be located in or near the entrance to the grooves 124, 126 so the guides 92 enter the grooves 124, 126 and guide the slips 40, 42 in a predictable manner toward the expanders 44, 46. This can prevent the slips 40, 42 from fracturing only on one side thereby preventing the slips 40, 42 from clamshelling.

[0067] Continued pulling on the connection 58 causes the expanders 44, 46 to nest further in the slips 40, 42. Soon, the slips 40, 42 fracture along zones of weakness provided by the grooves 124, 126. It is believed the larger grooves 124 fracture first although the sequence or order of fracturing is not material. This produces the series of separate slip segments 128. Continued pulling on the connection 58 causes the expanders 44, 46 to nest further in the slips 40, 42. Shortly, the slip segments 128 can fracture to produce the pieces 134, 136 and the pieces 134, 136 can fracture to produce four pieces for every slips segment as shown in FIGS. 15-16.

[0068] Some slips may be designed to run in small enough casing to produce slip pieces of a desirable size if the slip segments 128 fracture into only two pieces. However, it may be preferred for each slip segment 128 to fracture into four pieces regardless of the size casing in which the slips 40 are run. It may be that some of the slip segments 128 do not fracture completely because of strange events but the complete fracturing of any slip segment increases the drillability of the slips 40, 42 and is thus of considerable advantage. At the end of relative movement between the slips 40, 42 and expanders 44, 46, the upper end of the well tool 32 parts along a necked down area 148 so the connection 58 and sleeve 56 can be pulled out of the well 10.

[0069] When it is time to drill up the well tool 32, a bit or mill on the bottom of coiled tubing or on the bottom of a work string is run into the well 10. The bit is rotated and advanced into engagement with the tool 32 thereby drilling up the sleeve 56 part of the mandrel 30, and the reaction ring 54. The bit is typically small enough to pass through the expanded slip pieces and can drill on the upper expander 44. When enough of the upper expander 44 is drilled up, the pieces from the slips 40 are no longer jammed against the casing 18 whereupon the slip pieces are circulated out of the well 10 by liquid pumped down the coiled tubing or down the work string.

[0070] The slip pieces created by fracturing the slips 40 may preferably be small enough and light enough to be circulated out of the well 10 without further reduction in size. Circulation can be down through a coiled tubing or conventional tubing string and up in the annulus between the tubing and casing 18 or circulation can be down in the annulus between a tubing and casing strings and up inside the tubing. The upward velocity needed to circulate the slip pieces out Of the well depends on the density of the circulating liquid or gas and properties of the slip pieces, i.e. their cross-sectional size and weight. The pieces of the slip segments can be as small and as light as possible, consistent with maintaining a grip on the inner casing wall. In well tools of increased expansibility, the pieces may preferably weigh less than one ounce and, in well tools of standard expansibility, the pieces may preferably weigh less than ¾ ounce or even one half ounce. Cast iron pieces of these sizes are readily circulated out of the well 10 at typical pumping volumes. Irregular as they are, pieces of the slip segments are not stable during upward movement as a sphere might be. The slip pieces will likely tumble during movement inside the well 10.

[0071] Most wells are completed using a water based completion liquid inside the casing string 18. A typical completion liquid is 2% by weight KCl in water or 2% by weight KCl in water with some HCl and having a density of about 9#/gallon. An upward velocity sufficient to circulate the slip pieces upwardly is less than about 400 feet/minute in a 9#/gallon completion liquid. In most situations, normal pumping volumes produce upward velocities of less than about 200 feet/minute is adequate to circulate the slip pieces out of the well 10 without further reduction in size. In a typical example, pumping four barrels per minute downwardly through 2″ O.D. coiled tubing produces an upward velocity of about 360 ft/minute inside 4½″ O.D. 13.5#/foot casing having an I.D. of 3.925″. It is recognized that not all slips segments might not fracture into two or four pieces. However, reduction of some of the slip segments into smaller pieces will allow the smaller pieces to be easily circulated out of the well 10 thereby facilitating drilling up the well tool 32. In actual field situations, a screen or basket on the return line recovers large numbers of slip segments without further reduction in size than created by the weakened zones in the slips.

[0072] Referring to FIG. 17, there is illustrated another embodiment of a set of slips 150. The slips 150 may differ from the slips 40 in the shape of the passage 152 through the slip body. The passage 152 is a groove opening through the tapered section, through one end 154 and through a central passage or side 156 of the slip body.

[0073] Referring to FIG. 18, there is illustrated another embodiment of a set of slips 160 comprising a series of individual elongate unitary metal slip segments 162 which can be more-or-less identical and which extend about the periphery of a mandrel even though only three are shown in FIG. 18. The slip segments 162 can be more-or-less identical to the segments 128 except the segments 162 are separate and independent. Some or all of the slip segments 162 include a plane or zone of weakness 164 running parallel to an axis 166 of the slips 160 and axially of a tool of which FIG. 3 is an example. This may be accomplished by the provision of a passage 168 extending through the slip segments 162. Some or all of the slip segments 162 include a plane or zone of weakness 170 extending transverse to the axis 166. The segments 162 can be individually mounted in the manner of the slips 47 and restrained in any suitable manner, as by the provision of frangible wire, frangible pins or other suitable means. In use, the slips 160 operate in much the same manner as the slips 47 except there is no requirement for the slips to break into parallel segments since the segments 162 start out as independent elements. In other words, the slip segments 162 fracture along the zones of weakness into at least two and preferably four or more slip pieces.

[0074] One process of working over a horizontal well to frac between old perforations/fractures will now be described in conjunction with FIGS. 1 and 2. Casing patches 26 are run into the casing 18 adjacent each set of existing perforations 22 and set, usually by expanding the casing patch 26 into permanent engagement with the inside of the casing. This may seal off all or selected ones of the old perforations. A new set of perforations 28 is created near the end of the horizontal leg 14 of the well 10 and the first set of new perforations are fraced to produce a new fracture 30. A bridge plug 32 is run into the casing 18 past one or more casing patches 26 to a location above the new fracture 30 and then set against the casing 18 thereby isolating the new fracture. A second new set of perforations 28 is created nearer the surface of the well 10 and then fraced to produce a second new fracture. A bridge plug 32 is run into the casing 18 past one or more casing patches to a location above the second new fracture and then set against the casing 18 thereby isolating the new fracture. This process is repeated until the desired number of new fractures are created, typically more than five. The bridge plugs 32 are then drilled up with a bit or mill on the bottom of coiled tubing or on the bottom of a tubing string. Because the slips 40, 42 are broken into so many pieces, the bridge plugs 32 can be quickly drilled up. This is most unusual because multiple cast iron bridge plugs of the prior art that are capable of passing through casing patches cannot be drilled up by coiled tubing units. Even if one cast iron bridge plug could be drilled up, a second cast iron bridge plug cannot be drilled up because of debris from the first bridge plug and the worn character of the bit.

[0075] In one example, a set of slips 40 having an O.D. of 4.25″ was designed to run in a tool of conventional expansibility inside unobstructed 5½″ casing weighing between 17-26#/foot, meaning that the casing I.D. is in the range of 4.892-4.548″. The slips 40 had ten grooves 124, 126 providing ten slip segments 128. The weight of the slips 40 was 1 pound 7.3 ounces, meaning that each slip segment 128 weighed about 2.3 ounces and each of the slip pieces, after setting, weighed in the range of from less than about ½ ounce to about ¾ ounce, averaging 0.58 ounces. Slip pieces of this size can easily be circulated out of a horizontal or vertical well without further reduction in size by drilling.

[0076] Sets of exemplary slips for conventional normally expansible well tools are found in Table II:

TABLE-US-00002 TABLE II size O.D. I.D. weight number ave wt number ave wt of of of of of of seg- of of casing slips slips slips segments ments pieces pieces 4½″ 3.45″ 2.02″ 20.8 oz 8 2.60 oz 8 2.60 oz 5½″ 4.25″ 2.85″ 34.0 oz 8 4.25 oz 8 4.25 oz

[0077] Sets of exemplary slips for improved slips for normally expansible tools are found in Table III:

TABLE-US-00003 TABLE III size O.D. I.D. weight number ave wt number ave wt of of of of of of seg- of of casing slips slips slips segments ments pieces pieces 4½″ 3.45″ 2.02″ 16.0 oz 10 1.6 oz 40 .40 oz 5½″ 4.25″ 2.85″ 24.0 oz 10 2.4 oz 40 .60 oz

[0078] Sets of slips of exemplary slips for improved slips for extended reach or Increased expansibility tools are found in Table IV:

TABLE-US-00004 TABLE IV size O.D. I.D. weight number ave wt number ave wt of of of of of of seg- of of casing slips slips slips segments ments pieces pieces 4½″ 3.00″ 1.55″ 29.0 oz 6 4.83 oz 24 1.21 oz 5½″ 3.90″ 2.53″ 32.0 oz 8 4.00 oz 32 1.00 oz
The number of slip segments in the slips can vary as desired. As larger diameter slips are made, there can be more grooves 124, 126 and thus mores slip segments 128.

[0079] In an example of the expansibility of a settable well tool described herein, a horizontal well was drilled in Rio Blanco County, Tex. and 5″O.D., 23#/foot casing cemented therein. Casing of this size has a nominal I.D. of 4.044″. It appears that minor dog legs, or direction changes, in the path of the well bore at the transition of vertical to horizontal, known as the curve or heel, caused the casing to be deformed so the interior of the casing was partially restricted to an extent where conventional 3.85-3.92″ O.D. composite bridge plugs could not be forced through the heel. Because the I.D. of this heavy wall 5″ casing is only 4.044″, a bridge plug for nominal 4½″ casing could be run into the well. A total of six 3.25″ O.D. bridge plugs of the type disclosed herein were run through the heel into the horizontal leg of the well with no apparent dragging. In the process of tracing a hydrocarbon formation to create a series of fractures, all six bridge plugs were set against the casing. At the end of the tracing operation, all of the bridge plugs were drilled up in one bit run to allow hydrocarbon production upwardly in the well. The bridge plugs met all of the required performance expectations during all stages of completing the well. The alternative to the well owner was to redrill the well at a cost above $4,000,000.

[0080] Although the slips 40 are particularly adapted for use in horizontal wells, it is apparent that an increase in drillability is desirable for settable well tools used in vertical wells. Thus, slips that are fractured in many pieces are likewise advantageously used in vertical wells thereby increasing the drillability of settable well tools.

[0081] The great majority of horizontal oil or gas wells are completed through 4½″, 5″, or 5½″ casing. Standard composite settable tools, for casing strings of these sizes, are capable of expanding, as defined below, about 10%. Extended reach tools or increased expansibility tools have the capability of expanding at least 15% and can preferably expand greater than 20%. The disclosed settable tool is capable of movement between a retracted position and an expanded position gripping the inner casing wall of these size casing strings. The expansibility of the disclosed well tools may be calculated as:

% expansibility=(exp. O.D.−ret. O.D.)/ret. O.D.×100

where exp. O.D. is the expanded outer diameter of the tool and ret. O.D. is the retracted outer diameter of the tool. The O.D. of the packer or rubber element of settable tools is typically slightly larger, e.g. 0.030″, than the O.D. of the slips to prevent the slips from snagging some obstruction in a well. Thus, Table V shows the percent expansibility of the tools of Tables II-IV, as follows:

TABLE-US-00005 TABLE V expansibility of tools maximum retracted expanded % slip O.D. tool O.D. tool O.D. expansibility normally expansible tools of Tables II and III 4½″ 3.45″ 3.75″ 4.10″  9.3% 5″ 3.82″ 4.12″ 4.60″ 11.6% 5½″ 4.25″ 4.55″ 5.05″ 10.9% extended reach tools of Table IV 4½″ 3.00″ 3.25″ 4.10″ 24.2% 5″ 3.60″ 3.75″ 4.60″ 21.1% 5½″ 3.88″ 4.18″ 5.05″ 20.8%
Of course, it may be desirable to provide two models for each casing size, one for relatively thin wall pipe and one for relatively thick wall pipe. This can have an effect on the desired expansibility of any particular tool.

[0082] Although this invention has been disclosed and described in its preferred forms with a certain degree of particularity, it is understood that the present disclosure of the preferred forms is only by way of example and that numerous changes in the details of operation and in the combination and arrangement of parts can be resorted to without departing from the spirit and scope of the invention as hereinafter claimed.