FOR SELECTIVELY EXPANDING WALL OF A TUBULAR

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a patent cooperation treaty (PCT) application that claims priority to U.S. Provisional Patent Application No. 62/764,858 having a title of“Shaped Charge Assembly, Explosive Units, and Methods for Selectively Expanding Wall of a Tubular,” filed on August 16, 2018. The disclosure of the prior application is hereby incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

[0002] Embodiments of the present invention relate, generally, to shaped charge tools for selectively expanding a wall of tubular goods including, but not limited to, pipe, tube, casing and/or casing liner, in order to compress micro annulus pores and reduce micro annulus leaks, collapse open channels in a cemented annulus, and minimize other inconstancies or defects in the cemented annulus. The present disclosure also relates to methods of selectively expanding a wall of tubular goods to compress micro annulus pores and reduce micro annulus leaks, collapse open channels in a cemented annulus, and minimize other inconstancies or defects in the cemented annulus. The present disclosure further relates to a set of explosive units that may be used in shaped charge tools. BACKGROUND

[0003] Pumping cement into a wellbore may be part of a process of preparing a well for further drilling, production or abandonment. The cement is intended to protect and seal tubulars in the wellbore. Cementing is commonly used to permanently shut off water and gas migration into the well. As part of the completion process of a prospective production well, cement may be used to seal an annulus after a casing string has been run in the wellbore. Additionally, cementing may be used to seal a lost circulation zone, or an area where there is a reduction or absence of flow within the well. Cementing is used to plug a section of an existing well, in order to run a deviated well from that point. Also, cementing may be used to seal off all leak paths from the earth’s downhole strata to the surface in plug and abandonment operations, at the end of the well’s useful life.

[0004] Cementing is performed when a cement slurry is pumped into the well, displacing the drilling fluids still located within the well, and replacing them with cement. The cement slurry flows to the bottom of the wellbore through the casing. From there, the cement fills in the annulus between the casing and the actual wellbore, and hardens. This creates a seal intended to impede outside materials from entering the well, in addition to permanently positioning the casing in place. The casing and cement, once cored, helps maintain the integrity of the wellbore.

[0005] Although the cement material is intended to form a water tight seal for preventing outside materials and fluids from entering the wellbore, the cement material is generally porous and, over time, these outside materials and fluids can seep into the micro pores of the cement and cause cracks, micro annulus leak paths, decay and/or contamination of the cement material and the wellbore. Further, the cement in the cemented annulus may inadvertently include open channels, sometimes referred to as “channel columns” that undesirably allow gas and/or fluids to flow through the channels, thus raising the risk of cracks, decay and/or contamination of the cement and wellbore. In other situations, the cement may inadvertently not be provided around the entire 360 degree circumference of the casing. This may occur especially in horizontal wells, where gravity acts on the cement above the casing in the horizontal wellbore. Further, shifts in the strata (formation) of the earth may cause cracks in the cement, resulting in“channel columns” in the cement where annulus flow would otherwise not occur. Other inconsistencies or defects of the cement in the annulus may arise from inconsistent viscosity of the cement, and/or from a pressure differential in the formation that causes the cement to be inconsistent in different areas of the annulus.

[0006] Therefore, a need exists for systems and methods that are usable to effectively reduce and/or compress micro annulus pores in the cement or other sealing materials for minimizing or eliminating the formation of cracks, micro annulus leaks, decay and/or contamination of the cement and wellbore.

[0007] In addition, a need exists for cost effective systems and methods that are usable to selectively expand a wall or portion of a wall of tubular goods to compress micro annulus pores and reduce or eliminate micro annulus leaks.

[0008] A further need exists for systems and methods that selectively expand a wall or portion of a wall of tubular goods to effectively collapse and/or compress open channels in a cemented annulus, and/or compress the cemented annulus to cure other defects or inconsistencies in the cement to minimize or eliminate the unintended flow of gas and/or fluids through the cemented annuls.

[0009] The embodiments of the present invention meet all of these needs.

SUMMARY

[0010] As set forth above, because cement material can be porous, water, gas, or other outside materials may eventually seep into the micro pores of the cement, and penetrate through the hardened concrete seal. The seepage, when driven by hydrostatic formation pressure, may cause cracks, micro annulus leak paths from downhole to surface, decay and/or contamination of the cement, casing and wellbore. And, the cemented annulus may inadvertently include open channels (e.g.,“channel columns”) that allow gas and/or fluids to flow through the channels. Furthermore, the cement may inadvertently not be provided around the entire circumference of the casing, and may have other inconsistencies or defects due to inconsistent viscosity of the cement, and/or a pressure differential in the formation that causes the cement to be inconsistent in different areas of the annulus. [0011] In view of the foregoing, an object of the present disclosure is to provide tools and methods that compress micro annulus pores in cement to further restrict/seal off micro annulus leaks migrating up a cement column in a well bore to conform to industry and/or regulatory standards. Compressing the cement reduces the porosity of the cement by reducing the number of micro annulus pores. The reduced number of micro annulus pores reduces the risk of seepage into the cement as well as the formation of micro annulus leak paths. Another object of the present disclosure is to provide tools and methods that effectively collapse and/or compress open channels in a cemented annulus, and/or that effectively compress the cemented annulus to cure other defects or inconsistencies in the cement that would otherwise allow unintended flow of gas and/or fluids through the cemented annuls. Generally, all deleterious flow through the cemented annulus caused by the above situations may be referred to as annulus flow, and the disclosure herein discusses apparatus and methods for reducing or eliminating annulus flow.

[0012] Explosive, mechanical, chemical or thermite cutting devices have been used in the petroleum drilling and exploration industry to cleanly sever a joint of tubing or casing deeply within a wellbore. Such devices are typically conveyed into a well for detonation on a wireline or length of coiled tubing. The devices may also be pumped downhole. Known shaped charge explosive cutters include a consolidated amount of explosive material having an external surface clad with a thin metal liner. When detonated at the axial center of the packed material, an explosive shock wave, which may have a pressure force as high as 3,000,000 psi, can advance radially along a plane against the liner to fluidize the liner and drive the fluidized liner lineally and radially outward against the surrounding pipe. The fluidized liner hydro-dynamically cuts through and severs the pipe. Typically, the diameter of the j et may be around 5 to 10 mm.

[0013] The inventors of the present application have determined that removing the liner from the explosive material reduces the focus of the explosive shock wave so that the wall of a pipe or other tubular member is not penetrated or severed. Instead, the explosive shock wave results in a selective, controlled expansion of the wall of the pipe or other tubular member. The liner-less shaped charge has a highly focused explosive wave front where the tubular expansion may be limited to a length of about 10.16 centimeters (4 inches) along the outside diameter of the pipe or other tubular member. Too much explosive material, even without a liner, may still penetrate the pipe or other tubular member. On the other hand, too little explosive material may not expand the pipe or other tubular member enough to achieve its intended effect. Selective expansion of the pipe or other tubular member at strategic locations along the length thereof can compress the cement that is set in an annulus adjacent the wall of the pipe or other tubular member, or of the wellbore, beneficially reducing the porosity of the cement by reducing the number of micro annulus pores, and thus the associated risk of micro annulus leaks. The expanded wall of the pipe or other tubular member, along with the compressed cement, forms a barrier. The expanded wall of the pipe or other tubular member may also collapse and/or compress open channels in a cemented annulus, and/or may compress the cemented annulus to cure other defects or inconsistencies in the cement (such as due to inconsistent viscosity of the cement, and/or a pressure differential in the formation).

[0014] One embodiment of the disclosure relates to a shaped charge assembly for selectively expanding at least a portion of a wall of a tubular. The assembly can comprise a housing comprising an outer surface facing away from the housing and an opposing inner surface facing an interior of the housing; a first explosive unit and a second explosive unit. Each of the first explosive unit and the second explosive unit can be symmetrical about an axis of revolution. Each of the first explosive unit and the second explosive unit can comprise an explosive material formed adjacent to a metallic backing plate, and can comprise an exterior surface facing and being exposed to the inner surface of the housing. An aperture can extend along said axis from an outer surface of one backing plate to at least an inner surface of the other backing plate. The explosive unit and the second explosive unit can comprise a predetermined amount of explosive sufficient to expand, without puncturing, said at least a portion of the wall of the tubular into a protrusion extending outward into an annulus adjacent the wall of the tubular or wellbore. The shaped charge assembly can comprise an explosive detonator positioned along said axis adjacent to, and externally of, said one backing plate. In an embodiment, the shaped charge assembly can comprise a connector for connecting the housing to a top sub of an explosive well tool assembly.

[0015] Each of said backing plates can comprise an external surface opposite from said explosive material and perpendicular to said axis of revolution. The external surface of at least one backing plate can have a plurality of blind pockets therein, which can be distributed in a pattern about said axis. The annulus can be formed between an outer surface of the wall of the tubular and an outer wall of another tubular or a formation, and the annulus can contain cement. The blind pockets in said at least one backing plate can comprise a plurality of blind borings into said external surface. In an embodiment, the shaped charge assembly can comprise a centralizing assembly for maintaining an axially central position of said shaped charge assembly within the tubular.

[0016] Another embodiment of the disclosure relates to a method of selectively expanding at least a portion of a wall of a tubular via a shaped charge tool. The method can include assembling a shaped charge tool, which can include a housing containing an explosive material adjacent two end plates on opposite sides of the explosive material. The explosive material and the two end plates may form a first explosive unit. The housing can comprise an inner surface facing an interior of the housing, and the explosive material can comprise an exterior surface that faces the inner surface of the housing and is exposed to the inner surface of the housing. The steps of the method can continue by positioning a detonator adjacent to one of the two end plates, positioning said shaped charge tool within the tubular, and actuating said detonator to ignite the explosive material, causing a shock wave that can travel radially outward to impact the tubular at a first location and expand said at least a portion of the wall of the tubular radially outward without perforating or cutting through said at least a portion of the wall, to form a protrusion of the tubular at said at least a portion of the wall. The protrusion can extend into an annulus between an outer surface of the wall of the tubular and an inner surface of a wall of another tubular or a formation.

[0017] In an embodiment of the method, at least a portion of the tubular can be surrounded by a sealant comprising micro pores, wherein the expansion of the tubular can cause the sealant, which is displaced by the expansion, to compress, thus reducing the number of micro pores. The sealant may be cement or another sealing material.

[0018] Embodiments of the method can further comprise positioning a second explosive unit within the tubular, and detonating the second explosive unit to expand the tubular at a second location spaced from the first location. In an embodiment, the first explosive unit and the second explosive unit can be detonated simultaneously.

[0019] In an embodiment, formation of the protrusion can cause the portion of the wall that forms the protrusion to be work-hardened so that the portion of the wall that forms the protrusion has a greater yield strength than other portions of the wall that are adjacent the protrusion. [0020] An embodiment of the disclosure relates to a set of explosive units for selectively expanding a tubular. The set of explosives can comprise a first explosive unit and a second explosive unit. Each of the first explosive unit and the second explosive unit can comprise explosive material, and each of the first explosive unit and the second explosive unit can be ffusto-conical, defining a smaller area first surface and a greater area second surface opposite to the smaller area first surface. In an embodiment, each of the first explosive unit and the second explosive unit is symmetric about a longitudinal axis extending therethrough. The smaller area first surface of the first explosive unit can be adapted to face the second explosive unit, and the smaller area first surface of the second explosive unit can be adapted to face the smaller area first surface of the first explosive unit. The smaller area first surface of the first explosive unit can comprise a recess, and the smaller area first surface of the second explosive unit can comprise a protrusion, and the protrusion can be configured to fit into the recess to join the first explosive unit and the second explosive unit together. The protrusion and the recess can have a circular shape in planform. In an embodiment, each of the first explosive unit and the second explosive unit can comprise a center portion and an aperture extending along said axis and through the center portion.

[0021] The set of explosive units can further comprise a first explosive sub unit and a second explosive sub unit. Each of the first explosive sub unit and the second explosive sub unit can be ffusto-conical, defining a smaller area first surface and a greater area second surface opposite to the smaller area first surface. The smaller area first surface of the first explosive sub unit can be adapted to face the larger area second surface of the first explosive unit, wherein the larger area second surface of the first explosive unit comprises one of a first cavity and a first projection, and the smaller area first surface of the first explosive sub unit comprises the other of the first cavity and the first projection, and wherein the first projection can be configured to fit into the first cavity to join the first explosive unit and the first explosive sub unit together. The smaller area first surface of the second explosive sub unit can be adapted to face the larger area second surface of the second explosive unit, wherein the larger area second surface of the second explosive unit comprises one of a first cavity and a first projection, and the smaller area first surface of the second explosive sub unit comprises the other of the first cavity and the first projection, and wherein the first projection can be configured to fit into the first cavity to join the second explosive unit and the second explosive sub unit together. [0022] Each of the first explosive unit and the second explosive unit may include a side surface connecting the smaller area first surface and the greater area second surface. The side surface consists of the explosive material so that the explosive material is exposed at the side surface.

[0023] A further embodiment of the disclosure relates to a method of selectively expanding at least a portion of a wall of a tubular at a well site via a shaped charge tool, comprising: receiving an unassembled set of explosive units at the well site, each explosive unit comprising explosive material, and each explosive unit being divided into two or more segments that, when joined together, form the each explosive unit. The steps of the method can continue with assembling a tool comprising a shaped charge assembly comprising a housing and two end plates, wherein the housing comprises an inner surface facing an interior of the housing; joining, at the well site, the segments of each explosive unit together to form the each explosive unit, and positioning the set of explosive units between the two end plates so that an exterior surface of the explosive material of each explosive unit faces the inner surface of the housing and is exposed to the inner surface of the housing; positioning a detonator adjacent to one of the two end plates. The steps of the method can further include positioning said shaped charge tool within the tubular, and actuating said detonator to ignite the explosive material causing a shock wave that travels radially outward to impact the tubular at a first location and expand said at least a portion of the wall of the tubular radially outward without perforating or cutting through said at least a portion of the wall, to form a protrusion of the tubular at said at least a portion of the wall, wherein the protrusion extends into an annulus between an outer surface of the wall of the tubular and an inner surface of a wall of another tubular or a formation.

[0024] In an embodiment, each explosive unit can be divided into three or more equal segments before assembly. In an embodiment, one explosive unit is positioned adjacent one of the two end plates, and another explosive unit is positioned adjacent another of the two end plates. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Various embodiments are hereafter described in detail and with reference to the drawings wherein like reference characters designate like or similar elements throughout the several figures and views that collectively comprise the drawings.

[0026] FIG. 1 is a cross-section of an embodiment of a tool, including a shaped charge assembly, for selectively expanding at least a portion of a wall of a tubular.

[0027] FIG. 2A to FIG. 2F illustrate methods of selectively expanding at least a portion of the wall of a tubular using the tool.

[0028] FIG. 2G to FIG. 21 illustrate embodiments of a tool that may be used in some of the methods illustrated in FIG. 2 A to FIG. 2F.

[0029] FIGS. 2J to 2L illustrate methods of selectively expanding at least a portion of the wall of a tubular surround by formation.

[0030] FIG. 3A and FIG. 3B illustrate graphs showing swell profiles resulting from tests of a pipe and an outer housing.

[0031] FIG. 4 is a cross-section of an embodiment of the tool, including a shaped charge assembly.

[0032] FIG. 5 is a cross-section of an embodiment of the tool, including a shaped charge assembly.

[0033] FIG. 6 is a cross-section of an embodiment of the tool, including a shaped charge assembly.

[0034] FIG. 7 is a plan view of an embodiment of an end plate showing marker pocket borings. [0035] FIG. 8 is a cross-section view of an embodiment of an end plate along plane 8-8 of FIG. 7.

[0036] FIG. 9 is a bottom plan view of an embodiment of a top sub after detonation of the explosive material.

[0037] FIG. 10 illustrates an embodiment of a set of explosive units.

[0038] FIG. 11 illustrates a perspective view of explosive units in the set.

[0039] FIG. 12 shows a planform view of an explosive unit in the set.

[0040] [0039] FIG. 13 shows a planform view of an alternative embodiment of an explosive unit in the set.

[0041] Figs. 14-17 illustrate another embodiment of an explosive unit that may be included in a set of several similar units.

[0042] FIG. 18 illustrates an embodiment of a centralizer assembly.

[0043] [0041] FIG. 19 illustrates an alternative embodiment of a centralizer assembly.

[0044] [0042] FIG. 20 illustrates another embodiment of a centralizer assembly.

[0045] [0043] FIGS. 21 and 22 illustrate a further embodiment of a centralizer assembly.

DETAILED DESCRIPTION OF THE INVENTION

[0046] Before explaining the disclosed embodiments in detail, it is to be understood that the present disclosure is not limited to the particular embodiments depicted or described, and that the invention can be practiced or carried out in various ways. The disclosure and description herein are illustrative and explanatory of one or more presently preferred embodiments and variations thereof, and it will be appreciated by those skilled in the art that various changes in the design, organization, means of operation, structures and location, methodology, and use of mechanical equivalents may be made without departing from the spirit of the invention.

[0047] As well, it should be understood that the drawings are intended to illustrate and plainly disclose presently preferred embodiments to one of skill in the art, but are not intended to be manufacturing level drawings or renditions of final products and may include simplified conceptual views to facilitate understanding or explanation. Further, the relative size and arrangement of the components may differ from that shown and still operate within the spirit of the invention.

[0048] Moreover, as used herein, the terms "up" and "down", "upper" and "lower", "upwardly" and downwardly", "upstream" and "downstream"; "above" and "below"; and other like terms indicating relative positions above or below a given point or element are used in this description to more clearly describe some embodiments discussed herein. However, when applied to equipment and methods for use in wells that are deviated or horizontal, such terms may refer to a left to right, right to left, or other relationship as appropriate. In the specification and appended claims, the terms "pipe", "tube", "tubular", "casing" and/or "other tubular goods" are to be interpreted and defined generically to mean any and all of such elements without limitation of industry usage. Because many varying and different embodiments may be made within the scope of the concept(s) herein taught, and because many modifications may be made in the embodiments described herein, it is to be understood that the details herein are to be interpreted as illustrative and non-limiting.

[0049] FIG. 1 shows a tool 10 for selectively expanding at least a portion of a wall of a tubular. The tool 10 comprises a top sub 12 having a threaded internal socket 14 that axially penetrates the "upper" end of the top sub 12. The socket thread 14 provides a secure mechanism for attaching the tool 10 with an appropriate wire line or tubing suspension string (not shown). The tool 10 can have a substantially circular cross-section, and the outer configuration of the tool 10 can be substantially cylindrical. The "lower" end of the top sub 12, as shown, can include a substantially flat end face 15. As shown, the flat end face 15 perimeter of the top sub can be delineated by an assembly thread 16 and an O-ring seal 18. The axial center 13 of the top sub 12 can be bored between the assembly socket thread 14 and the end face 15 to provide a socket 30 for an explosive detonator 31. In some embodiments, the detonator may comprise a bi-directional booster with a detonation cord. [0050] A housing 20 can be secured to the top sub 12 by, for example, an internally threaded housing sleeve 22. The O-ring 18 can seal the interface from fluid invasion of the interior housing volume. A window section 24 of the housing interior is an inside wall portion of the housing 20 that bounds a cavity 25 around the shaped charge between the outer or base perimeters 52 and 54. In an embodiment, the upper and lower limits of the window 24 are coordinated with the shaped charge dimensions to place the window "sills" at the approximate mid-line between the inner and outer surfaces of the explosive material 60. The housing 20 may be a frangible steel material of approximately 55-60 Rockwell "C" hardness.

[0051] As shown, below the window 24, the housing 20 can be internally terminated by an integral end wall 32 having a substantially flat internal end- face 33. The external end- face 34 of the end wall may be frusto-conical about a central end boss 36. A hardened steel centralizer assembly 38 can be secured to the end boss by assembly bolts 39a, 39b, wherein each blade of the centralizer assembly 38 is secured with a respective one of the assembly bolts 39a, 39b (i.e., each blade has its own assembly bolt).

[0052] A shaped charge assembly 40 can be spaced between the top sub end face 15 and the internal end-face 33 of the housing 20 by a pair of resilient, electrically non-conductive, ring spacers 56 and 58. In some embodiments, the ring spacers may comprise silicone sponge washers. An air space of at least 0.25 centimeters (0.1 inches) is preferred between the top sub end face 15 and the adjacent face of a thrust disc 46. Similarly, a resilient, non- conductive lower ring spacer 58 (or silicone sponge washer) provides an air space that can be at least 0.25 centimeters (0.1 inches) between the internal end- face 33 and an adjacent assembly lower end plate 48.

[0053] Loose explosive particles can be ignited by impact or friction in handling, bumping or dropping the assembly. Ignition that is capable of propagating a premature explosion may occur at contact points between a steel, shaped charge thrust disc 46 or end plate 48 and a steel housing 20. To minimize such ignition opportunities, the thrust disc 46 and lower end plate 48 can be fabricated of non-sparking brass.

[0054] The outer faces 91 and 93 of the end plates 46 (upper thrust disc or back up plates) and 48, as respectively shown by FIG. 1, can be blind bored with marker pockets 95 in a prescribed pattern, such as a circle with uniform arcuate spacing between adjacent pockets as illustrated by FIGS. 7 and 8. The pockets 95 in the outer faces 91, 93 are shallow surface cavities that are stopped short of a complete aperture through the end plates to form selectively weakened areas of the end plates. When the explosive material 60 detonates, the marker pocket walls are converted to jet material. The jet of fluidized end plate material scar the lower end face 15 of the top sub 12 with impression marks 99 in a pattern corresponding to the original pockets as shown by FIG. 9. When the top sub 12 is retrieved after detonation, the uniformity and distribution of these impression marks 99 reveal the quality and uniformity of the detonation and hence, the quality of the explosion. For example, if the top sub face 15 is marked with only a half section of the end plate pocket pattern, it may be reliability concluded that only half of the explosive material 60 correctly detonated.

[0055] The explosive material units 60 traditionally used in the composition of shaped charge tools comprises a precisely measured quantity of powdered, high explosive material, such as RDX, HNS or HMX. The explosive material is formed into units 60 shaped as a truncated cone by placing the explosive material in a press mold fixture. A precisely measured quantity of powdered explosive material, such as RDX, HNS or HMX, is distributed within the internal cavity of the mold. Using a central core post as a guide mandrel through an axial aperture 47 in the upper thrust disc 46, the thrust disc is placed over the explosive powder and the assembly subjected to a specified compression pressure. This pressed lamination comprises a half section of the shaped charge assembly 40.

[0056] The lower half section of the shaped charge assembly 40 can be formed in the same manner as described above, having a central aperture 62 of about 0.3 centimeters (0.13 inches) diameter in axial alignment with thrust disc aperture 47 and the end plate aperture 49. A complete assembly comprises the contiguous union of the lower and upper half sections along the juncture plane 64. Notably, the thrust disc 46 and end plate 48 are each fabricated around respective annular boss sections 70 and 72 that provide a protective material mass between the respective apertures 47 and 49 and the explosive material 60. These bosses are terminated by distal end faces 71 and 73 within a critical initiation distance of about 0.13 centimeters (0.05 inches) to about 0.25 centimeters (0.1 inches) from the assembly juncture plane 64. The critical initiation distance may be increased or decreased proportionally for other sizes. Hence, the explosive material 60 is insulated from an ignition wave issued by the detonator 31 until the wave arrives in the proximity of the juncture plane 64. [0057] The apertures 47, 49 and 62 for the FIG. 1 embodiment remain open and free of boosters or other explosive materials. Although an original explosive initiation point for the shaped charge assembly 40 only occurs between the boss end faces 71 and 73, the original detonation event is generated by the detonator 31 outside of the thrust disc aperture 47. The detonation wave can be channeled along the empty thrust disc aperture 47 to the empty central aperture 62 in the explosive material. Typically, an explosive load quantity of 38.8 grams (1.4 ounces) of HMX compressed to a loading pressure of 20.7 Mpa (3,000 psi) may require a moderately large detonator 31 of 420 mg (0.02 ounces) HMX for detonation.

[0058] The FIG. 1 embodiment obviates any possibility of orientation error in the field while loading the housing 20. A detonation wave may be channeled along either boss aperture 47 or 49 to the explosive material 60 around the central aperture 62. Regardless of which orientation the shaped charge assembly 40 is given when inserted in the housing 20, the detonator 31 will initiate the explosive material 60.

[0059] Absent from the explosive material units 60 is a liner that is conventionally provided on the exterior surface of the explosive material and used to cut through the wall of a tubular. Instead, the exterior surface of the explosive material is exposed to the inner surface of the housing 20. Specifically, the housing 20 comprises an outer surface 53 facing away from the housing 20, and an opposing inner surface 51 facing an interior of the housing 20. The explosive units 60 each comprise an exterior surface 50 that faces and is exposed to the inner surface 51 of the housing 20. Describing that the exterior surface 50 of the explosive units 60 is exposed to the inner surface 51 of the housing 20 is meant to indicate that the exterior surface 50 of the explosive units 60 is not provided with a liner, as is the case in conventional cutting devices. The explosive units 60 can comprise a predetermined amount of explosive material sufficient to expand at least a portion of the wall of the tubular into a protrusion extending outward into an annulus adjacent the wall of the tubular. For instance, testing conducted with a 72 grams (2.54 ounces) HMX, 6.8 centimeter (2.7 inches) outer diameter expansion charge on a tubular having a 11.4 centimeter (4.5 inch) outer diameter and a 10.1 centimeter (3.98 inch)inner diameter resulted in expanding the outer diameter of the tubular to 13.5 centimeters (5.32 inches). The expansion was limited to a 10.2 centimeter (4 inch) length along the outer diameter of the tubular. It is important to note that the expansion is a controlled outward expansion of the wall of the tubular, and does not cause puncturing, breaching, penetrating or severing of the wall of the tubular. The annulus may be formed between an outer surface of the wall of the tubular being expanded and an inner wall of an adjacent tubular or a formation. Cement located in the annulus is compressed by the protrusion, reducing the porosity of the cement by reducing the number of micro annulus pores in the cement or other sealing agents. The reduced-porosity cement provides a seal against moisture seepage that would otherwise lead to cracks, decay and/or contamination of the cement, casing and wellbore. The compressed cement may also collapse and/or compress open channels in a cemented annulus, and/or may compress the cemented annulus to cure other defects or inconsistencies in the cement (such as due to inconsistent viscosity of the cement, and/or a pressure differential in the formation).

[0060] A method of selectively expanding at least a portion of the wall of a tubular using the tool 10 described herein may be as follows. The tool 10 is assembled including the housing 20 containing explosive material 60 adjacent two end plates 46, 48 on opposite sides of the explosive material 60. As discussed above, the housing 20 comprises an inner surface 51 facing an interior of the housing 20, and the explosive material 60 comprises an exterior surface 50 that faces the inner surface 51 of the housing 20 and is exposed to the inner surface 51 of the housing 20 (i.e., there is no liner on the exterior surface 50 of the explosive material 60).

[0061] A detonator 31 (see Fig. 1) can be positioned adjacent to one of the two end plates 46, 48. The tool 10 can then be positioned within an inner tubular Tl that is to be expanded, as shown in FIG. 2 A. The inner tubular Tl may be within an outer tubular T2, such that an annulus“A” exists between the outer diameter of the inner tubular Tl and the inner diameter of the outer tubular T2. A sealant, such as cement“C” may be provided in the annulus“A”. When the tool 10 reaches the desired location in the inner tubular Tl, the detonator 31 is actuated to ignite the explosive material 60, causing a shock wave that travels radially outward to impact the inner tubular Tl at a first location and expand at least a portion of the wall of the inner tubular Tl radially outward without perforating or cutting through the portion of the wall, to form a protrusion“P” of the inner tubular Tl at the portion of the wall as shown in FIG. 2B. The protrusion“P” extends into the annulus“A”. The protrusion“P” compresses the cement“C” to reduce the porosity of the cement by reducing the number of micro pores. The compressed cement is shown in FIG. 2B with the label“CC”. The reduced number of micro pores in the compressed cement“CC” reduces the risk of seepage into the cement. Further, the protrusion“P” creates a ledge or barrier that helps seal that portion of the wellbore from seepage of outside materials. Note that the pipe dimensions shown in FIGS. 2A to 2F are exemplary and for context, and are not limiting to the scope of the invention.

[0062] The protrusion“P” may impact the inner wall of the outer tubular T2 after detonation of the explosive material 60. In some embodiments, the protrusion“P” may maintain contact with the inner wall of the outer tubular T2 after expansion is complete. In other embodiments, there may be a small space between the protrusion“P” and the inner wall of the outer tubular T2. For instance, the embodiment of Fig. 3B shows that the space between the protrusion“P” and the inner wall of the outer tubular T2 may be 0.07874 centimeters (0.0310 inches). However, the size of the space will vary depending on several factors, including, but not limited to, the size (e.g., thickness), strength and material of the inner tubular Tl, the type and amount of the explosive material in the explosive units 60, the physical profile of the exterior surface 50 of the explosive units 60, the hydrostatic pressure bearing on the inner tubular Tl, the desired size of the protrusion, and the nature of the wellbore operation. The small space between the protrusion“P” and the inner wall of the other tubular T2 may still be effective for blocking flow of cement, barite, other sealing materials, drilling mud, etc., so long as the protrusion“P” approaches the inner diameter of the outer tubular T2. This is because the viscosity of those materials generally prevents seepage through such a small space. That is, the protrusion“P” may form a choke that captures (restricts flow of) the cement long enough for the cement to set and form a seal. Expansion of the inner tubular Tl at the protrusion“P” causes that portion of the wall of the inner tubular Tl to be work-hardened, resulting in greater yield strength of the wall at the protrusion“P”. The portion of the wall having the protrusion“P” is not weakened. In particular, the yield strength of the inner tubular Tl increases at the protrusion“P”, while the tensile strength of the inner tubular Tl at the protrusion“P” decreases only nominally. Expansion of the inner tubular Tl at the protrusion “P” thus strengthens the tubular without breaching the inner tubular Tl.

[0063] The magnitude of the protrusion depends on several factors, including the amount of explosive material in the explosive units 60, the type of explosive material, the physical profile of the exterior surface 50 of the explosive units 60, the strength of the inner tubular Tl, the thickness of the tubular wall, the hydrostatic pressure bearing on the inner tubular Tl, and the clearance adjacent the tubular being expanded, i.e., the width of the annulus“A” adjacent the tubular that is to be expanded. In the embodiment if FIG. 1, the physical profile of the exterior surface 50 of the explosive units 60 is shaped as a side- ways“V”. The angle at which the legs of the“V” shape intersect each other may be varied to adjust the size and/or shape of the protrusion. Generally, a smaller angle will generate a larger protrusion“P”. Alternatively, the physical profile of the exterior surface 50 may be curved to define a hemispherical shape.

[0064] The method of selectively expanding at least a portion of the wall of a tubular Tl using the shaped charge tool 10 described herein may be modified to include determining the following characteristics of the tubular Tl: a material of the tubular Tl, a thickness of a wall of the tubular Tl; an inner diameter of the tubular Tl, an outer diameter of the tubular Tl, a hydrostatic force bearing on the outer diameter of the tubular Tl, and a size of a protrusion “P” to be formed in the wall of the tubular Tl. Next, the explosive force necessary to expand, without puncturing, the wall of the tubular Tl to form the protrusion“P”, is calculated, or determined via testing, based on the above determined material characteristics. As discussed above, the determinations and calculation of the explosive force can be performed via a software program executed on a computer. Physical hydrostatic testing of the explosive expansion charges yields data which may be input to develop computer models. The computer implements a central processing unit (CPU) to execute steps of the program. The program may be recorded on a computer-readable recording medium, such as a CD-ROM, or temporary storage device that is removably attached to the computer. Alternatively, the software program may be downloaded from a remote server and stored internally on a memory device inside the computer. Based on the necessary force, a requisite amount of explosive material for the one or more explosive material units 60 to be added to the shaped charge tool 10 is determined. The requisite amount of explosive material can be determined via the software program discussed above.

[0065] The one or more explosive material units 60, having the requisite amount of explosive material, is then added to the shaped charge tool 10. The loaded shaped charge tool 10 is then positioned within the tubular Tl at a desired location. Next, the shaped charge tool 10 is actuated to detonate the one or more explosive material units 60, resulting in a shock wave, as discussed above, that expands the wall of the tubular Tl radially outward, without perforating or cutting through the wall, to form the protrusion“P”. The protrusion“P” extends into the annulus“A” adjacent an outer surface of the wall of the tubular Tl. [0066] A first series of tests was conducted to compare the effects of sample explosive units 60, which did not have a liner, with a comparative explosive unit that included a liner on the exterior surface thereof. The explosive units in the first series had 15.88 centimeter (6.25 inch) outer housing diameter, and were each tested separately in a respective 17.8 centimeter (7 inch) outer diameter test pipe. The test pipe had a 16 centimeter (6.3 inch) inner diameter, and a 0.89 centimeter (0.35 inch) Wall Thickness, L-80.

[0067] The comparative sample explosive unit had a 15.88 centimeter (6.25 inch) outside housing diameter and included liners. Silicone caulk was added to fowl the liners, leaving only the outer 0.76 centimeters (0.3 inches) of the liners exposed for potential jetting. 77.6 grams (2.7 ounces) of HMX main explosive was used as the explosive material. The sample “A” explosive unit had a 15.88 centimeter (6.25 inch) outside housing diameter and was free of any liners. 155.6 grams (5.5 ounces) of HMX main explosive was used as the explosive material. The sample“B” explosive unit had a 15.88 centimeter (6.25 inch) outside housing diameter and was free of any liners. 122.0 grams (4.3 ounces) of HMX main explosive was used as the explosive material.

[0068] The test was conducted at ambient temperature with the following conditions. Pressure: 20.7 Mpa (3,000 psi). Fluid: water. Centralized Shooting Clearance: 0.06 centimeters (0.03 inches). The Results are provided below in Table 1.

Table 1

[0069] The comparative sample explosive unit produced an 18.5 centimeter (7.28 inch) swell, but the jetting caused by the explosive material and liners undesirably penetrated the inside diameter of the test pipe. Samples“A” and“B” resulted in 19.3 centimeter (7.6 inch) and 18.6 centimeter (7.32 inch) swells (protrusions), respectively, that were smooth and uniform around the inner diameter of the test pipe.

[0070] A second test was performed using the Sample“A” explosive unit in a test pipe having similar properties as in the first series of tests, but this time with an outer housing outside the test pipe to see how the character of the swell in the test pipe might change and whether a seal could be effected between the test pipe and the outer housing. The test pipe had a 17.8 centimeter (7 inch) outer diameter, a 16.1 centimeter (6.32 inch) inner diameter, a 0.86 centimeter (0.34 inch) wall thickness, and a 813.6 Mpa (118 KSI) tensile strength. The outer housing had an 21.6 centimeter (8.5 inch) outer diameter, a 18.9 centimeter (7.4 inch) inner diameter, a 1.35 centimeter (0.53 inch) wall thickness, and a 723.95 Mpa (105 KSI) tensile strength.

[0071] The second test was conducted at ambient temperature with the following conditions. Pressure: 20.7 Mpa (3,000 psi). Fluid: water. Centralized Shooting Clearance: 0.09 centimeters (0.04 inches). Clearance between the 17.8 centimeter (7 inch) outer diameter of the test pipe and the inner diameter of the housing: 0.55 centimeters (0.22 inches). After the sample“A” explosive unit was detonated, the swell on the 17.8 centimeter (7 inch) test pipe measured at 18.9 centimeters (7.441 inches) x 18.89 centimeters (7.44 inches), indicating that the inner diameter of the outer housing (18.88 centimeters (7.433 inches)) somewhat retarded the swell (19.3 centimeters (7.6 inches)) observed in the first test series involving sample“A”. There was thus a“bounce back” of the swell caused by the inner diameter of the outer housing. In addition, the inner diameter of outer housing increased from 18.88 centimeters (7.433 inches) to 18.98 centimeters (7.474 inches). The clearance between the outer diameter of the test pipe and the inner diameter of the outer housing was reduced from 0.55 centimeters (0.22 inches) to 0.08 centimeters (0.03 inches). FIG. 3A shows a graph 400 illustrating the swell profiles of the test pipe and the outer housing. FIG. 3B is a graph 401 illustrating an overlay of the swell profiles showing the 0.08 centimeter (0.03 inch) resulting clearance.

[0072] A second series of tests was performed to compare the performance of a shaped charge tool 10 (with liner-less explosive units 60) having different explosive unit load weights. In the second series of tests, the goal was to maximize the expansion of a 17.8 centimeter (7 inch) outer diameter pipe having a wall thickness of 1.37 centimeters (0.54 inches), to facilitate operations on a Shell North Sea Puffin well. Table 2 shows the results of the tests.

Table 2

[0073] Tests #1 to #3 used the shaped charge tool 10 having liner-less explosive units 60 with progressively increasing explosive weights. In those tests, the resulting swell of the 17.8 centimeter (7 inch) outer diameter pipe continued to increase as the explosive weight increased. However, in test #3, which utilized 350 grams (12.35 ounces) HMX resulting in a 204 gram (7.2 ounces) unit loading, the focused energy of the expansion charged breached the 17.8 centimeter (7 inch) outer diameter pipe. Thus, to maximize the expansion of this pipe without breaching the pipe would require the amount of explosive energy in test #3 to be delivered with less focus.

[0074] Returning to the method discussed above, the relatively short expansion length (e.g., 10.2 centimeters (4 inches)) may advantageously seal off micro annulus leaks or cure the other cement defects discussed herein. It may be the case that the cement density between the outer diameter of the inner tubular Tl and the inner diameter of the outer tubular T2 was inadequate to begin with, such that a barrier may not be formed and/or the cement“C” present between the inner tubular Tl and the outer tubular T2 may simply be forced above and below the expanded protrusion“P” (see, e.g., Fig. 2C). While there may still be a semi compression“SC” of the cement and reduction in porosity, it might not be adequate to slow a micro annulus leak in a manner that would conform to industry and/or regulatory standards. In such a case, instead of detonating just one explosive unit 60, multiple explosive units 60 may be detonated, sequentially and in close proximity to each other, or simultaneously and in close proximity to each other. For example, if two explosive units 60 were detonated sequentially or simultaneously, 10.16 centimeters (4.0 inches) apart in a zone where there is an inadequate cement job, the compression effect of the cement from the first explosive unit 60 being forced down, and from the second explosive unit 60 being forced up, may result in an adequate barrier“CB”, as shown in Fig. 2D, that conforms to industry and/or regulatory standards. An example of a shaped charge tool 10 comprising a top sub 12 and having two explosive units 60 positioned, e.g., 10.16 centimeters (4.0 inches), apart from each other is shown in Fig. 2G.

[0075] Furthermore, three explosive units 60 may be detonated as follows. To begin with, first and second explosive units 60 may be detonated 20.3 centimeters (8 inches) apart from each other to create two spaced apart protrusions“P,” as shown in Fig. 2E. The two detonations form two barriers“B” shown in Fig 2E, with the first explosive unit 60 forcing the cement“C” downward and the second explosive unit 60 forcing cement“C” upward. A third explosive unit 60 is then detonated between the first and second explosive units 60. Detonation of the third explosive unit 60 further compresses the cement“C” that was forced downward by the first explosive unit 60 and the cement“C” that was forced upward by the second explosive unit 60, to form two adequate barriers “CB” as shown in Fig. 2F. Alternatively, detonation of the third explosive unit 60 may result on one barrier above or below the third explosive unit 60 depending on the cement competence in the respective zones. Either scenario (one or two barriers) may further restrict/seal off micro annulus leaks, or cure the other cement defects discussed herein, to conform with industry and/or regulatory standards. An example of a shaped charge tool 10 comprising a top sub 12 and having three explosive units 60 positioned, e.g., 10.16 centimeters (4.0 inches), apart from each other is shown in Fig. 2H. [0076] FIGs. 2G and 2H illustrate an embodiment in which a detonation cord 61 for initiating the tool is run through the length of the tool 10. Another way to configure the detonation cord 61 is to install separate sections of detonation cords 61 between boosters 6 la, as shown in FIG. 21. Each booster 61 a can be filled with explosive material 6 lb, such as HMX. That is, a first booster 6 la, provided with a first explosive unit 60, may be associated with a first section of detonation cord 61, which first section of detonation cord 61 connects to a second booster 6la located further down the tool 10 and provided with a second explosive unit 60. A second section of detonation cord 61 is provided between the second booster 6la and a third booster 6 la, as shown in FIG. 21. If further explosive units 60 are provided, the sequence of a section of detonation cord 61 between consecutive boosters 6la may be continued.

[0077] The contingencies discussed with respect to Figs. 2C through 2F may address the situation in which, even when cement bond logs suggest a cement column is competent in a particular zone, there may still be a variation in the cement volume and density in that zone requirement is more than one expansion charge.

[0078] In the methods discussed above, expansion of the inner tubular Tl causes the sealant displaced by the expansion to compress, reducing the number of micro pores in the cement or the number of other cement defects discussed herein. The expansion may occur after the sealant is pumped into the annulus“A”. Alternatively, the cement or other sealant may be provided in the annulus“A” on the portion of the wall of the inner tubular Tl, after the portion of the wall is expanded. The methods may include selectively expanding the inner tubular Tl at a second location spaced from the first location to create a pocket between the first and second locations. The sealant may be provided in the annulus“A” before the pocket is formed. In an alternative embodiment, expansion at the first location may occur before the sealant is provided, and expansion at the second location may occur after the sealant is provided.

[0079] FIGS. 2J to 2L illustrate methods of selectively expanding at least a portion of the wall of a tubular surround by formation (earth). FIG. 2J shows that the tool 10 is positioned within the tubular Tl that is cemented into a formation that includes shale strata and sandstone strata. The cement“C” abuts the outer surface of the tubular Tl on one side, and abuts the strata on the opposite side, as shown in FIG. 2J. Shale is one of the more non- permeable earthen materials, and may be referred to as a cap rock formation. To the contrary, sandstone is known to be permeable. Accordingly, when the tool 10 is used to in a tubular/earth application to consolidate cement adjacent a formation, such as shown in FIG. 2J, it is preferable to expand the wall of the tubular Tl that is adjacent the cap rock formation (e.g., shale strata) because the non-permeable cap rock formation seals off the annulus flow, as shown in FIG. 2K. On the other hand, if the tool 10 was used to expand the wall of the tubular Tl that was adjacent the sandstone strata, as shown in FIG. 2L, even if the cement “C” is consolidated to seal against annulus flow through the consolidated cement“C”, annulus flow can bypass the consolidated cement“C” and migrate or flow through the permeable sandstone strata (see FIG. 2L), defeating the objective of expanding a wall of the tubular Tl.

[0080] A variation of the tool 10 is illustrated in FIG. 4. In this embodiment, the axial aperture 80 in the thrust disc 46 is tapered with a conically convergent diameter from the disc face proximate of the detonator 31 to the central aperture 62. The thrust disc aperture 80 may have a taper angle of about 10 degrees between an approximately 0.2 centimeters (0.08 inches) inner diameter to an approximately 0.32 centimeters (0.13 inches) diameter outer diameter. The taper angle, also characterized as the included angle, is the angle measured between diametrically opposite conical surfaces in a plane that includes the conical axis 13.

[0081] Original initiation of the FIG. 4 charge 60 occurs at the outer plane of the tapered aperture 80 having a proximity to a detonator 31 that enables/enhances initiation of the charge 60 and the concentration of the resulting explosive force. The initiation shock wave propagates inwardly along the tapered aperture 80 toward the explosive junction plane 64. As the shock wave progresses axially along the aperture 80, the concentration of shock wave energy intensifies due to the progressively increased confinement and concentration of the explosive energy. Consequently, the detonator shock wave strikes the charge units 60 at the inner juncture plane 64 with an amplified impact. Comparatively, the same explosive charge units 60, as suggested for FIG. 1 comprising, for example, approximately 38.8 grams (1.4 ounces) of HMX compressed under a loading pressure of about 20.7 Mpa (3,000 psi) and when placed in the FIG. 4 embodiment, may require only a relatively small detonator 31 of HMX for detonation. Significantly, the conically tapered aperture 80 of FIG. 4 appears to focus the detonator energy to the central aperture 62, thereby igniting a given charge with much less source energy. In FIGs. 1 and 4, the detonator 31 emits a detonation wave of energy that is reflected (bounce-back of the shock wave) off the flat internal end-face 33 of the integral end wall 32 of the housing 20 thereby amplifying a focused concentration of detonation energy in the central aperture 62. Because the tapered aperture 80 in the FIG. 4 embodiment reduces the volume available for the detonation wave, the concentration of detonation energy becomes amplified relative to the FIG. 1 embodiment that does not include the tapered aperture 80.

[0082] The variation of the tool 10 shown in FIG. 5 relies upon an open, substantially cylindrical aperture 47 in the upper thrust disc 46 as shown in the FIG. 1 embodiment. However, either no aperture is provided in the end plate boss 72 of FIG. 5 or the aperture 49 in the lower end plate 48 is filled with a dense, metallic plug 76, as shown in FIG. 5. The plug 76 may be inserted in the aperture 49 upon final assembly or pressed into place beforehand. As in the case of the FIG. 4 embodiment, the FIG. 5 tool 10 comprising, for example, approximately 38.8 grams (1.4 ounces) of HMX compressed under a loading pressure of about 20.7 Mpa (3,000 psi), also may require only a relatively small detonator 31 of HMX for detonation. The detonation wave emitted by the detonator 31 is reflected back upon itself in the central aperture 62 by the plug 76, thereby amplifying a focused concentration of detonation energy in the central aperture 62.

[0083] The FIG. 6 variation of the tool 10 combines the energy concentrating features of FIG. 2 and FIG. 5, and adds a relatively small, explosive initiation pellet 66 in the central aperture 62. In this case, the detonation wave of energy emitted from the detonator 31 is reflected off of explosive initiation pellet 66. The reflection from the off of explosive initiation pellet 66 is closer to the juncture plane 64, which results in a greater concentration of energy (enhanced explosive force). The explosive initiation pellet 66 concept can be applied to the FIG. 1 embodiment, also.

[0084] Transporting and storing the explosive units may be hazardous. There are thus safety guidelines and standards governing the transportation and storage of such. One of the ways to mitigate the hazard associated with transporting and storing the explosive units is to divide the units into smaller component pieces. The smaller component pieces may not pose the same explosive risk during transportation and storage as a full-size unit may have. Each of the explosive units 60 discussed herein may thus be provided as a set of units that can be transported unassembled, where their physical proximity to each other in the shipping box would prevent mass (sympathetic) detonation if one explosive component was detonated, or if, in a fire, would bum and not detonate. The set is configured to be easily assembled at the job site.

[0085] Fig. 10 shows an exemplary embodiment of a set 100 of explosive units. Embodiments of the explosive units discussed herein may be configured as the set 100 discussed below. The set 100 comprises a first explosive unit 102 and a second explosive unit 104. Each of the first explosive unit 102 and the second explosive unit 104 comprises the explosive material discussed herein. Each explosive unit 102, 104 may be ffusto-conically shaped. In this configuration, the first explosive unit 102 includes a smaller area first surface 106 and a greater area second surface 110 opposite to the smaller area first surface 106. Similarly, the second explosive unit 104 includes a smaller area first surface 108 and a greater area second surface 112 opposite to the smaller area first surface 108. Each of the first explosive unit 102 and the second explosive unit 104 is symmetric about a longitudinal axis 114 extending through the units, as shown in the perspective view of FIG. 11. Each of the first explosive unit 102 and the second explosive unit 104 comprises a center portion 120 having an aperture 122 that extends through the center portion 120 along the longitudinal axis 114.

[0086] In the illustrated embodiment, the smaller area first surface 106 of the first explosive unit 102 includes a recess 116, and the smaller area first surface 108 of the second explosive unit 104 comprises a protrusion 118. The first explosive unit 102 and the second explosive unit 104 are configured to be connected together with the smaller area first surface 106 of the first explosive unit 102 facing the second explosive unit 104, and the smaller area first surface 108 of the second explosive unit 104 facing the smaller area first surface 106 of the first explosive unit 102. The protrusion 118 of the second explosive unit 104 fits into the recess 116 of the first explosive unit 102 to join the first explosive unit 102 and the second explosive unit 104 together. The first explosive unit 102 and the second explosive unit 104 can thus be easily connected together without using tools or other materials.

[0087] In the embodiment, the protrusion 118 and the recess 116 have a circular shape in planform, as shown in Figs. 11 and 12. In other embodiments, the protrusion 118 and the recess 116 may have a different shape. For instance, Fig. 13 shows that the shape of the protrusion 118 is square. The corresponding recess (not shown) on the other explosive unit in this embodiment is also square to fitably accommodate the protrusion 118. Alternative shapes for the protrusion 118 and the recess 116 may be triangular, rectangular, pentagonal, hexagonal, octagonal or other polygonal shape having more than two sides.

[0088] Referring back to FIG. 10, the set 100 of explosive units can include a first explosive sub unit 202 and a second explosive sub unit 204. The first explosive sub unit 202 is configured to be connected to the first explosive unit 102, and the second explosive sub unit 204 is configured to be connected to the second explosive unit 104, as discussed below. Similar to the first and second explosive units 102, 104 discussed above, each of the first explosive sub unit 202 and the second explosive sub unit 204 can be ffusto-conical so that the sub units define smaller area first surfaces 206, 208 and greater area second surfaces 210, 212 opposite to the smaller area first surfaces 206, 208, as shown in FIG. 10.

[0089] In the embodiment shown in FIG. 10, the larger area second surface 110 of the first explosive unit 102 includes a first projection 218, and the smaller area first surface 206 of the first explosive sub unit 202 includes a first cavity or recessed area 216. The first projection 218 fits into the first cavity or recessed area 216 to join the first explosive unit 102 and the first explosive sub unit 202 together. Of course, instead of having the first projection 218 on the first explosive unit 102 and the first cavity or recessed area 216 on the first explosive sub unit 202, the first projection 218 may be provided on the smaller area first surface 206 of the first explosive sub unit 202 and the first cavity 216 may be provided on the larger area second surface 110 of the first explosive unit 102.

[0090] FIG. 10 also shows that the larger area second surface 112 of the second explosive unit 104 comprises a first cavity or recessed area 220, and the smaller area first surface 208 of the second explosive sub unit 204 comprises a first projection 222. The first projection 222 fits into the first cavity or recessed area 220 to join the second explosive unit 102 and the second explosive sub unit 204 together. Of course, instead of having the first projection 222 on the second explosive sub unit 204 and the first cavity 220 on the second explosive unit 104, the first projection 222 may be provided on the larger area second surface 112 of the second explosive unit 104 and the first cavity 220 may be provided on the smaller area first surface 208 of the second explosive sub unit 204. The first and second explosive sub units 202, 204 may also include the aperture 122 extending along the longitudinal axis 114. [0091] FIGS. 10 and 11 show that the first explosive unit 102 includes a side surface 103 connecting the smaller area first surface 106 and the greater area second surface 110. Similarly, the second explosive unit 104 includes a side surface 105 connecting the smaller area first surface 108 and the greater area second surface 112. Each side surface 103, 105 consists of only the explosive material, so that the explosive material is exposed at the side surfaces 103, 105. In other words, the liner that is conventionally applied to the explosive units is absent from the first and second explosive units 102, 104. The side surfaces 107, 109 of the first and second explosive sub units 202, 204, respectively, can consist of only the explosive material, so that the explosive material is exposed at the side surfaces 107, 109, and the liner is absent from the first and second explosive sub units 202, 204.

[0092] Figs. 14-17 illustrate another embodiment of an explosive unit 300 that may be included in a set of several similar units 300. The explosive unit 300 may be positioned in a tool 10 at a location and orientation that is opposite a similar explosive unit 300, in the same manner as the explosive material units 60 in Figs. 1 and 4-6 discussed herein. Fig. 14 is a plan view of the explosive unit 300. Fig. 15 is a plan view of one segment 302 of the explosive unit 300, and Fig. 16 is a side view thereof. Fig. 17 is a cross-sectional side view of Fig. 15. In the embodiment, the explosive unit 300 is in the shape of a frustoconical disc that is formed of three equally-sized segments 301, 302, and 303. The explosive unit 300 may include a central opening 304, as shown in Fig. 14, for accommodating the shaft of an explosive booster (not shown). The illustrated embodiment shows that the explosive unit 300 is formed of three segments 301, 302, and 303, each accounting for one third (i.e., 120 degrees) of the entire explosive unit 300 (i.e., 360 degrees). However, the explosive unit 300 is not limited to this embodiment, and may include two segments or four or more segments depending nature of the explosive material forming segments. For instance, a more highly explosive material may require a greater number of (smaller) segments in order to comply with industry regulations for safely transporting explosive material. For instance, the explosive unit 300 may be formed of four segments, each accounting for one quarter (i.e., 90 degrees) of the entire explosive unit 300 (i.e., 360 degrees); or may be formed of six segments, each accounting for one sixth (i.e., 60 degrees) of the entire explosive unit 300 (i.e., 360 degrees). According to one embodiment, each segment should include no more than 38.8 grams (1.4 ounces) of explosive material. [0093] In one embodiment, the explosive unit 300 may have a diameter of about 8.38 centimeters (3.3 inches). Figs. 15 and 16 show that the segment 302 has a top surface 305 and a bottom portion 306 having a side wall 307. The top surface 305 may be slanted an angle of 17 degrees from the central opening 304 to the side wall 307 in an embodiment. According to one embodiment, the overall height of the segment 302 may be about 1.905 centimeters (0.75 inches), with the side wall 307 being about 0.508 centimeters (0.2 inches) of the overall height. The overall length of the segment 302 may be about 7.24 centimeters (2.85 inches) in the embodiment. Fig. 17 shows that the inner bottom surface 308 of the segment 302 may be inclined at an angle of 32 degrees, according to one embodiment. The width of the bottom portion 306 may be about 1.37 centimeters (0.54 inches) according to an embodiment with respect to Fig. 17. The side wall 309 of the central opening 304 may have a height of about 0.356 centimeters (0.14 inches) in an embodiment, and the uppermost part 310 of the segment 302 may have a width of the about 0.381 centimeters (0.15 inches). The above dimensions are not limiting, as the segment size and number may be different in other embodiments. A different segment size and/or number may have different dimensions. The explosive units 300 may be provided as a set of units divided into segments, so that the explosive units 300 can be transported as unassembled segments 301, 302, 303, as discussed above.

[0094] The set of segments is configured to be easily assembled at the job site. Thus, a method of selectively expanding at least a portion of a wall of a tubular at a well site via a shaped charge tool 10 may include first receiving an unassembled set of explosive units 300 at the well site, wherein each explosive unit 300 comprising explosive material, is divided multiple segments 301, 302, 303 that, when joined together, form an explosive unit 300. The method includes assembling the tool 10 (see, e.g., Fig. 1) comprising a shaped charge assembly comprising a housing 20 and two end plates 46, 48. The housing 20 comprises an inner surface 51 facing an interior of the housing 20. At the well site, the segments 301, 302, 303 of each explosive unit 300 are together to form the assembled explosive unit 300. The explosive units 300 are then positioned between the two end plates 46, 48, for instance each explosive unit 300 is adjacent one of the end plates 46, 38, so that an exterior surface of the explosive material of explosive units 300 faces the inner surface 51 of the housing 20 and is exposed to the inner surface 51 of the housing 20. Next, a detonator 31 is positioned adjacent to one of the two end plates 46, 48, and the shaped charge tool 10 is positioned within the tubular. The detonator 31 is then actuated to ignite the explosive material causing a shock wave that travels radially outward to impact the tubular at a first location and expand at least a portion of the wall of the tubular radially outward without perforating or cutting through the portion of the wall, to form a protrusion of the tubular at the portion of the wall. The protrusion extends into an annulus between an outer surface of the wall of the tubular and an inner surface of a wall of another tubular or a formation.

[0095] FIGS. 18 - 22 show embodiments of a centralizer assembly that may be attached to the housing 20. The centralizer assembly centrally confines the tool 10 within the inner tubular Tl. In the embodiment shown in Fig. 18, a planform view of the centralizer assembly is shown in relation to the longitudinal axis 13. The tool 10 is centralized by a pair of substantially circular centralizing discs 316. Each of the centralizing discs 316 are secured to the housing 20 by individual anchor pin fasteners 318, such as screws or rivets. In the FIG. 18 embodiment, the discs 316 are mounted along a diameter line 320 across the housing 20, with the most distant points on the disc perimeters separated by a dimension that is preferably at least corresponding to the inside diameter of the inner tubular Tl. In many cases, however, it will be desirable to have a disc perimeter separation slightly greater than the internal diameter of the inner tubular Tl .

[0096] In another embodiment shown by FIG. 19, each of the three discs 316 are secured by separate pin fasteners 318 to the housing 20 at approximately 120 degree arcuate spacing about the longitudinal axis 13. This configuration is representative of applications for a multiplicity of centering discs on the housing 20. Depending on the relative sizes of the tool 10 and the inner tubular Tl, there may be three or more such discs distributed at substantially uniform arcs about the tool circumference.

[0097] FIG. 20 shows, in planform, another embodiment of the centralizers that includes spring steel centralizing wires 330 of small gage diameter. A plurality of these wires is arranged radially from an end boss 332. The wires 330 can be formed of high-carbon steel, stainless steel, or any metallic or metallic composite material with sufficient flexibility and tensile strength. While the embodiment includes a total of eight centralizing wires 330, it should be appreciated that the plurality may be made up of any number of centralizing wires 330, or in some cases, as few as two. The use of centralizing wires 330 rather than blades or other machined pieces, allows for the advantageous maximization of space in the flowbore around the centralizing system, compared to previous spider-type centralizers, by minimizing the cross-section compared to systems featuring flat blades or other planar configurations. The wires 330 are oriented perpendicular to the longitudinal axis 13 and engaged with the sides of the inner tubular, which is positioned within an outer tubular T2. The wires 330 may be sized with a length to exert a compressive force to the tool 10, and flex in the same fashion as the cross-section of discs 316 during insertion and withdrawal.

[0098] Another embodiment of the centralizer assembly is shown in FIG. 21. This configuration comprises a plurality of planar blades 345a, 345b to centralize the tool 10. The blades 345a, 345b are positioned on the bottom surface of the tool 10 via a plurality of fasteners 342. The blades 345a, 345b thus flex against the sides of the inner tubular Tl to exert a centralizing force in substantially the same fashion as the disc embodiments discussed above. FIG. 18 illustrates an embodiment of a single blade 345. The blade 345 comprises a plurality of attachment points 344a, 344b, through which fasteners 342 secure the blade 345 in position. Each fastener 342 can extend through a respective attachment point to secure the blade 345 into position. While the embodiment in FIG. 21 is depicted with two blades 345a, 345b, and each blade 345 comprises two attachment points, for a total of four fasteners 342 and four attachment points (344a, 344b are pictured in FIG. 22), it should be appreciated that the centralizer assembly may comprise any number of fasteners and attachment points.

[0099] The multiple attachment points 344a, 344b on each blade 345, being spaced laterally from each other, prevent the unintentional rotation of individual blades 345, even in the event that the fasteners 342 are slightly loose from the attachment points 344a, 344b. The fasteners 342 can be of any type of fastener usable for securing the blades into position, including screws. The blades 345 can be spaced laterally and oriented perpendicular to each other, for centralizing the tool 10 and preventing unintentional rotation of the one or more blades 345.

[0100] Although several preferred embodiments have been illustrated in the accompanying drawings and describe in the foregoing specification, it will be understood by those of skill in the art that additional embodiments, modifications and alterations may be constructed from the principles disclosed herein. These various embodiments have been described herein with respect to selectively expanding a "pipe" or a "tubular." Clearly, other embodiments of the tool of the present invention may be employed for selectively expanding any tubular good including, but not limited to, pipe, tubing, production/casing liner and/or casing. Accordingly, use of the term "tubular" in the following claims is defined to include and encompass all forms of pipe, tube, tubing, casing, liner, and similar mechanical elements.