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1. WO2006102622 - MAGNETIC TOOL FOR RETRIEVING METAL OBJECTS FROM A WELL BORE WHEN USING COIL TUBING

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[ EN ]

MAGNETIC TOOL FOR RETRIEVING METAL OBJECTS FROM A WELL BORE
WHEN USING COIL TUBING

CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of my co-pending application Serial No. 10/935,367 filed on September 7, 2004 entitled "Magnetic Tool for Retrieving Metal Objects from a Well Bore," the full disclosure of which is incorporated by reference herein. I claim priority of my co-pending prior application in Venezuela, Application Serial Number 2.004-01414 filed on August 31, 2004 entitled "Magnetic Tool for Retrieving Metal Objects from a Well Bore" and in prior U. S. Application Serial Number 10/935,367 filed on September 7, 2004 entitled "Magnetic Tool for Retrieving Metal Objects from a Well Bore."
BACKGROUND OF THE INVENTION
[0002] The present invention relates to wellbore tools and more particularly to a magnetic tool for retrieval of metal objects, such as cuttings and other foreign objects that accumulate in the process of perforating or milling over bridge plugs and other down hole obstructions from a wellbore.
[0003] As the conventional petroleum resources are becoming more difficult to access, the industry started developing means for drilling in more difficult strata, often in high-pressure or less stable environments. A new technique called coiled tubing drilling has been used in places where air drilling, mud drilling or fluid drilling are impracticable. Instead of conventional vertical drill string, the coil tubing method uses a continuous string of concentric coil tubing, which allows fluid circulation through the tubing. Coil tubing drilling is believed to reduce formation damage as it allows for drilling with less contact between a drill string and the surrounding formation. An additional advantage of coiled tubing method is related to continuous circulation while drilling, which is believed to minimize pressure fluctuations and reduces formation damage.
[0004] However, similar to conventional technique, coiled tubing method generates metal cuttings, or shavings, which have to be removed to stimulate fluid circulation. The present invention contemplates provision of a magnetic tool for retrieval of metal objects from a well bore when using coil tubing drilling method.
SUMMARY OF THE INVENTION
[0005] It is, therefore, an object of the present invention to provide an apparatus for retrieval of metal cuttings and other foreign objects from a wellbore, which can be used in a coil tubing system.
[0006] It is another object of the present invention to provide a magnetic tool for retrieving metal objects from a well bore that forms secondary debris settling area between magnet members.
[0007] These and other objects of the present invention are achieved through a provision of a magnetic tool adapted for retrieval of metal objects from a well bore. The tool has an elongated mandrel, which carries a plurality of spaced-apart magnet assemblies detachably mounted on the mandrel. The mandrel has a central opening therethrough to allow fluid circulation through the tool. Opposite ends of the tool carry connectors for securing the tool in a drill string.
[0008] Each magnet assembly comprises one or more magnet members encased in a protective sleeve, which is made from a non-corrosive, structurally stable material. Each magnet assembly has a generally ring-shaped cross section and end portions having a generally frustoconical configuration. One of the embodiments provides for a magnet member having a unitary ring-shaped configuration. Another embodiment provides for the magnet assemblies having three of more elongated magnet members, which have a magnet encased in a protective sleeve.
[0009] Mounted between adjacent magnet assemblies is a tubular spacer, the exterior surface of which forms a secondary settling area for the metal objects attracted to the magnet
i
assemblies. By strategically spacing the magnet assemblies along the length of the tool body, it is possible to create a magnetic field strong enough to cause metal objects to settle on the spacer(s).

BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Reference will now be made to the drawings, wherein like parts are designated by like numerals and wherein
[0011] Figure 1 is a perspective view of the first embodiment of the apparatus of the present invention.
[0012] Figure 2 is a perspective view of the mandrel of the magnetic tool of first embodiment of the present invention.
[0013] Figure 3 is an elevation view of the magnet member of the first embodiment of the apparatus of the present invention.
[0014] Figure 4 is a cross-sectional view of a magnet assembly of the first embodiment of the apparatus of the present invention taken along lines 4 - 4 of Figure 3.
[0015] Figure 5 is a detail elevation view of a connector member of the first embodiment of the apparatus of the present invention.
[0016] Figure 6 is a detail elevation view of a spacer member of the first embodiment of the apparatus of the present invention.
[0017] Figure 7 is a detail view showing magnetic tool connectors of the second embodiment of the present invention engaged with top and bottom subs.
[0018] Figure 8 is detail view of a mandrel of the magnet tool of the second embodiment of the present invention.
[0019] Figure 9 is a detail exploded view showing magnet assemblies and spacer members of the second embodiment of the present invention; and
[0020] Figure 10 is a detail view of set screw for securing the connector members to the mandrel.
DETAIL DESCRIPTION OF THE PREFERRED EMBODIMENT
[0021] Turning now to the drawings in more detail, numeral 10 designates the well bore magnetic tool in accordance with the first embodiment of the present invention. The tool 10 comprises a tubular cylindrical mandrel, or body 12 having a through opening 14 for admitting circulating fluid into a wellbore. An upper part 16 of the cylindrical body 12 is provided with external threads 18. The upper part 16 carries an upper connector member 20, which threadably detachably engages the upper part 16.
[0022] The upper connector member is provided with a central opening 22. The walls of the inner opening 22 are provided with two sets of internal threads. A lower set of internal threads 24 threadably matchingly engages with the threads 18 of the mandrel 12. An upper set of threads 26 is adapted for engagement with other subs forming a drill string (not shown).
[0023] A lower part 30 of the mandrel 12 carries a lower connector member 32, which has an enlarged diameter portion 34 and a reduced diameter portion 36. The reduced diameter portion 36 is provided with external threads 38. The threads 38, similarly to the threads 26 allow connection of the tool 10 to other subs forming the drill string (not shown).
[0024] Mounted in a surrounding relationship over the mandrel 12, between the upper connector 20 and the lower connector 32 is a plurality of magnet assemblies 40, 42, and 44. The tool 10 may be provided with one or more magnet assemblies, depending on the design selected by the manufacturer. The magnet assemblies 40, 42, and 44 are vertically spaced from each other. The outer surface of each of the magnet members defines a primary settling area for the metal debris.
[0025] One or more tubular spacers 46, 48 (Fig. 6) are positioned on the mandrel 12 between the magnet assemblies 40, 42, and 44; the spacers 46, 48 form secondary debris settling areas between adjacent magnet members. Due to the pre-determined spacing of the magnet assemblies on the mandrel 12, the magnetic field created by adjacent magnets overlaps the areas 46, 48, causing metal debris to settle on the exterior of the spacers 46 and 48, as well.
[0026] As can be seen in the drawings, each of the magnet members 40, 42, and 44 comprises a body having a generally ring-shaped cross-section with a central opening therethrough. Each magnet assembly 40, 42, and 44 comprises a magnet member 52 completely encased in a metal sleeve 54 (Figure 4). The sleeve 54 may be formed from a non-corrosive structurally stable material, such as for instance stainless steel. Each magnet assembly has a generally tubular configuration. The sleeve 54 has an upper portion 56, which is shaped as a truncated cone.
[0027] Each sleeve 54 comprises a lower portion 58, which also has a generally frustoconical configuration, such that the upper and lower edges of the sleeve 54 are configured with smaller diameters than the remaining portion of the sleeve body.
[0028] An upper edge 60 of each sleeve 54 of the magnet assembly 40 contacts a lower edge 62 of the upper connector 20 and matches its reduced diameter size. A lower edge 64 of the magnet assembly 40 contacts and rests on an upper edge 66 of the spacer 40. The external diameter of the spacer body substantially matches the size of the edge 64, supporting the magnet assembly 40 on the mandrel 12.
[0029] In a similar manner, an upper edge 68 of the magnet assembly 42 contacts a bottom edge 70 of the spacer 46, while a lower edge 72 contacts and rests on a top edge 74 of the spacer 48. Also similarly, an upper edge 78 of the magnet assembly 44 contacts the lower edge 76 of the spacer 48, while a lower edge 80 rests on a top edge 82 of the connector 32. As a result, the magnet assemblies and the spacers are "threaded" on the mandrel 12, supporting each other and retaining each other on the mandrel 12. The magnet assemblies and the spacers are detachably mounted on the mandrel 12.
[0030] The mandrel 12 shown in Figure 2 illustrates the lower connector member 32 unitary formed with the main body of the mandrel 12. If desired, the connectors 20 and 32 may be secured on the mandrel 12 with set screws 90, 92, as shown in Figures 1 and 5.
[0031] Turning now to Figures 7 - 10, the magnetic tool of the second embodiment of the present invention is shown. Similarly to the first embodiment, the magnetic tool of the second embodiment comprises an elongated tubular mandrel 100 having top 102 and bottom 104 threaded portions. A top connector member 106 and bottom connector member 108 are each provided with internal threaded portions 110 and 112, respectively, which match the threads on the mandrel portions 102 and 104.
[0032] A top sub 114 and a bottom sub 116 is secured to the top connector 106 and the bottom connector, respectively. Set screws 118 are configured for positioning into drilled openings 120 formed in the top connector member 106 and the bottom connector member 108. The openings 120 are trilled and tapped to receive the set screws 118. The top sub 1 14 has internal threads 122 for connecting to the drill string (not shown). The bottom sub 116 has external threads 124 for connection to other equipment lowered into a well bore (not shown).
[0033] The magnet assemblies of the second embodiment are each formed as tubular members with a central opening therethrough. In this embodiment, each magnet assembly 130 is made of a plurality of elongated magnet members 132, which are secured together to form an open center polygon in cross section. Each magnet member 132 extends longitudinally, in a generally parallel relationship to the central axis of the tool. Each magnet member 132, similarly to the first embodiment, has a magnet encased in a sleeve. Depending on a particular design, the magnet assembly 130 may have three or more magnet members 132.
[0034] Mounted between adjacent magnet assemblies 130 is a spacer member 140, which also has a generally ring-shaped cross section. The spacer member 140 comprises a plurality of elongated plates 142, which extend longitudinally in a generally parallel relationship to the central axis of the tool 100. Depending on design, the spacer member 140 may be formed with three or more plates 142.
[0035] It is envisioned that the tool 100 may be particularly beneficial in the environment, where manufacturing constraints require construction of magnet assemblies and spacer members from a plurality of smaller parts. An additional advantage may be that individual magnet assemblies 132 are easier to replace when damaged or worn. The same may be true for individual plates 142 of the spacer member 140.
[0036] It will be understood that the relative dimensions of the magnet assemblies, spacers and connectors may differ, depending on the particular design of the magnetic tool 10. If desired, the magnet assemblies may have a vertical dimension of between 3" - 6", while the spacers may have a vertical dimension of 0.5" - 2". The external diameter of the connector members may be between 2" and 3", while the diameter of the opening 50 may be 1" - 1 ,5". Of course, other dimensions may be successfully employed, when desired.
[0037] Many changes and modifications may be made in the design of the present invention without departing from the spirit thereof. I, therefore, pray that my rights to the present invention be limited only by the scope of the appended claims.