CENTRALIZER

Abstract: A centralizer (10) comprises a tubular body (12) provided with two spaced apart grooves (18). The ends of spring bows (20) are mounted on collars (24, 26) which are slidably mounted in respective ones of the grooves (18). In use, movement of the spring bow (20) against the tubular body (12) can be accommodated by movement of the collars (24, 26) along the grooves (18).

Description: CENTRALIZER This invention relates to a centralizer for centra¬ lizing a tubular in a wellbore. Centralizers are used to center one tubular member inside a wellbore or inside another tubular member, e.g. to center a first casing inside a second casing. Typic¬ ally centralizers are placed on the exterior of the inner tubular member and project outwardly therefrom. In many typical situations the annular space between the outer circumference of the inner tubular member and the inner circumference of the outer tubular member is relatively constant and it is a straightforward matter to provide a centralizer with spring bows having the desired radial projection. However, it is sometimes desirable to be able to pass an inner tubular member through a relative small tubular member into an outer tubular member of significantly greater diameter in which the inner tubular member is to be centralized. In order to accommodate the necessary radial dis- placement of the spring bow the present invention pro¬ vides a centralizer which comprises a tubular body having a plurality of spring bows, characterised in that at least one end of each spring bow is slidably disposed on said tubular body so that said spring bow can be com- pressed against said tubular body. Further features of the invention are disclosed in Claim 2 et seq. Centralizers according to this invention and/or any or all parts thereof may be made of any suitable mater- ial, including, but not limited to, metal, plastic, fiberglass, composites, cermets, aluminum, aluminum alloys, brass, copper, zinc or zinc alloys. For a better understanding of the present invention and to show how the same may be carried into effect reference will now be made, by way of example, to the accompanying drawings, in which:- Fig. la is a side view, partially in cross-section, of a first embodiment of a centralizer according to the present invention in an expanded position; Fig. lb is a cross-sectional view along line lb-lb of Fig. la; Fig. lc is an enlargement of the detail in circle c in Fig. lb; Fig. Id is an enlargement of the detail in circle d in Fig. la; Fig. le is a side view, partially in cross-section, of the centralizer of Fig. la in a compressed position; Fig. 2 is a cross-sectional view of a tubular body which forms part of the centralizer of Fig. la; Fig. 3a is an end view of an alternative spring bow which may form part of the centralizer of Fig. la; Fig. 3b is a side view of the spring bow of Fig. 3a; Fig. 4 is a side view, partially in cross-section, of a second embodiment of a centralizer according to the present invention; Fig. 5 is a side view, partially in cross-section, of a third embodiment of a centralizer according to the present invention; Fig. 6 is a side view, partially in cross-section, of a fourth embodiment of a centralizer according to the present invention; Fig. 7 is a side view, partially in cross-section, of a fifth embodiment of a centralizer according to the present invention; Fig. 7b is a partial cross-section view along line 7b-7b of Fig. 7a; Fig. 8 is a side view, partially in cross-section, of a sixth embodiment of a centralizer according to the present invention; Fig. 9a is an end view of a seventh embodiment of a centralizer according to the present invention taken in the direction of arrow 9a in Fig. 9b; Fig. 9b is a partial side view of the centralizer of Fig. 9a; Fig. 10a is a partial side view of an eighth embo- diment of a centralizer according to the present inven¬ tion; Fig. 10b is a partial side view of the centralizer of Fig. 10a; Fig. 11 is a side view of a ninth embodiment of a centralizer according to the present invention; and Fig. 12 is a side view in cross-section of a tubu¬ lar body which can form part of certain centralizers according to the present invention. Referring to Figs. 1 to 3, a centralizer 10 accord- ing to the present invention comprises a tubular body 12 with a central longitudinal bore 14 running there¬ through. The upper and lower ends of the tubular body 12 are threaded so that the centralizer 10 may be read¬ ily incorporated in a length of casing or a string of tubulars. Formed in or machined into the exterior surface 16 of the tubular body 12 are upper and lower collar grooves 18 and a spring bow groove 22. A first collar 24 is slidably disposed in the upper collar groove 18 and a second collar 26 is slidably disposed in the lower collar groove 18. A plurality of spring bows 20 are arranged circumjacent the tubular body 12 with their respective ends secured to the first and second collars 24, 26. As better shown in Fig. lc the end 28 of each spring bow 20 is recessed in a groove 32 in a respective collar so that it does not extend radially beyond the radial outer surface 34 of the first and second collars 24, 26. As shown in Fig. le, the first and second collars 24, 26 have moved apart from each other in their respec¬ tive collar grooves 18; and the spring bows 20 have collapsed with a major portion thereof in the spring bow groove 22. A bottom ridge 23 (Fig. 2) provides a stop against which the second collar 26 abuts when it has moved in response to contact of the spring bow 20 with the wall of a tubular during insertion therein. Once such abut¬ ment occurs, the spring bows 20 are deflected radially inwardly as the centralizer 10 moves downwardly. Fig. 3b shows a spring bow 50 with a body 52 and ends 54, 56. Fig. 3a shows that the end 54 (like the end 56) has a curved shape to accommodate the curved exterior surface 16 of the tubular body 12. The curved shape also permits the ends 54, 56 to "hug" the exterior surface 16. The spring bows 20 have non-curved ends 28 but may be replaced with spring bows similar to the spring bow 50. Fig. 4 illustrates a second embodiment of a centra- lizer 60 according to the present invention which is like the centralizer 10 (with like numerals indicating similar parts). However, the centralizer 60 has only one collar groove 18 and only one slidable collar 24. The lower collar 26 is held fast in a groove 27. The tubular body 13 (like the tubular body 12) has a bore 15 (like the bore 14) therethrough. Upon movement of the collar 24, the spring bows 20 can move toward and col¬ lapse against an exterior surface of the tubular body 13. Fig. 5 illustrates a third embodiment of a centra- lizer 70 according to the present invention (in which parts similar to those of centralizer 10 bear the same identifying numerals). The essential difference is that whilst the upper ends of the spring bows 23 are secured to collar 24, which is slidably mounted on the tubular body 17 the other ends are welded direct to the tubular body 17. A single continuous recess 29 is provided to accommodate the spring bows 23 when they collapse. Fig. 6 illustrates a fourth embodiment of a centra- lizer 80 according to the present invention. A plural¬ ity of spring bows 81 have a first end 82 secured to a tubular body 83 of the centralizer 80. A second end 84 of each spring bow 81 is receivable in and movable in a recess 85 formed in or milled in the tubular body 83. A bore 86 extends through the body 83. Upon contact of the spring bows 81 with an interior of another tubular or a wellbore, the spring bows move toward the tubular body 83 with their ends 84 moving in the grooves 85 so that the spring bows collapse against the tubular body 83. Figs. 7a and 7b illustrate a fifth embodiment of a centralizer 90 according to the present invention which has a tubular body 91 with a bore 92 therethrough. A plurality of spring bows 93 each has an end 94 secured to the tubular body 91 and an end 95 freely movable in a slot 96 extending through a portion of the tubular body 91. If desired a recess may be provided beneath each spring bow 93 to receive some, a major portion of, or all of it upon collapse of the spring bows against the tubular body 91. Fig. 8 shows a centralizer 40 like the centralizer 90; (and like aspects bear like identifying numerals); but the spring bows 93 have a tab end 41 which is mov¬ able in an enlarged portion 42 of a slot 43. It is within the scope of this invention to provide a tab 41 and a slot 43 for the opposing spring bow ends. Such a tab end and enlarged groove portion may be used with the ends 84 of the spring bows 81 in the centralizer 80 of Fig. 6. In one aspect the tab end may be a piece which is initially separate from the spring bow, but which is secured to a spring bow end (e.g. by welding, screws, or bolts) once the spring bow end is inserted into and through a slot. It is within the scope of this invention to provide structures which project beyond the exterior surface of a centralizer body and confine a spring bow end with the spring bow end movable in the structure so that the spring bow can collapse. Alternatively such a structure may be provided on a collar that is fixed (movably or immovably) around a centralizer body or around a groove in a centralizer body. Figs. 9a and 9b show a seventh embodiment of a centralizer 100 according to the present invention with a tubular hollow body 101, a single spring bow end retainer 102 and a spring bow 103. Any number of spring bow retainers 102 and spring bows 103 may be used spaced apart around the outer circumference of the tubular hollow body 101. The tubular retainer 102 has two upright arms 104, each with a shoulder 105, and with a gap 106 between them. A portion 107 of the spring bow 103 is movably confined beneath the shoulders 105 and an outwardly extending portion 108 moves in the gap 106. An end 109 of the spring bow is larger than a space 110 between two stop members 111, thus preventing the spring bow from separating from the tubular body 101. Figs. 10a and 10b show a centralizer 120 with a tubular body 121 and one (or more) spring bows 122. An end 123 of the spring bow 122 is movably disposed under a bar 124 which holds the end of the spring bow and prevents it separating from the tubular body 121. An arch 125 in the end of the spring bow 122 moves over a stop member 126, e.g. when the spring bow 122 moves inwardly to collapse against the tubular body 121. In preferred embodiment the various parts, grooves, reces- ses, etc. are sized, disposed and configured to permit full collapse of the spring bow(s) against and/or into the tubular body. The end of the spring bow moves in a recess 129. The end of the spring bows 122 may have tab ends similar to those shown in Fig. 8. Fig. 11 shows a centralizer 130 with a hollow tubular body 131. A top end groove 132 and a bottom end groove 133 are formed in the outer surface 134 of the hollow tubular body 131. The end grooves are sized and configured to permit ends 135 and 136 of a spring bow 140 to move therein so that a body 141 of the spring bow 140 may move into a longitudinal groove 137 in the outer surface 134 when the spring bow 140 is collapsed toward the hollow tubular body 131. Retainers 145 (like the retainers 102, Fig. 9a) hold tab ends 146 of the spring bow 140 as they move within the retainers 145. Fig. 12 illustrates a tubular body 29 (like the tubular body 12, Fig. 2); but which has only one large groove 55 therearound for accommodating two movable collars (like, e.g., collars 24, 26, Fig. la) and the spring bows. In any embodiment of this invention the tubular body may be solid or it may have a fluid flow bore or bores therethrough. In certain embodiments of the present invention it is preferred that the parts, grooves, and recesses are sized, configured, and disposed so that the collars and spring bows, upon collapse of the spring bows against the apparatuses tubular body, do not project beyond the tubular body's exterior surface more than 9.5mm (three- eighths of an inch). In other embodiments this pre- ferred length is no more than 6.4mm (one-fourth inch); 3.2mm (one-eighth inch); 1.6mm (one-sixteenth inch); or zero. In other embodiments the collars and spring bows are within grooves or recesses and are below the level of the exterior surface of the tubular body.

Claims: CLAIMS : 1. A centralizer which comprises a tubular body having a plurality of spring bows, characterised in that at least one end of each spring bow is slidably disposed on said tubular body so that said spring bow can be com¬ pressed against said tubular body. 2. A centralizer as claimed in Claim 1, including a first collar (24) slidably mounted on said tubular body (12) and wherein said at least one end (28) of each spring bow (20) is attached to said first collar (24). 3. A centralizer as claimed in Claim 2, wherein said tubular body (12) is provided with a groove (18) and said first collar (24) is slidably mounted in said groove (18). 4. A centralizer as claimed in Claim 3, wherein the outer surface of said first collar (24) is substantially flush with the outer surface of said tubular body (12). 5. A centralizer as claimed in Claim 2, 3 or 4, where¬ in said first collar (24) is provided with a groove (32) for accommodating said one end (28) of said spring bow (20). 6. A centralizer as claimed in any preceding claim, wherein the other end of each spring bow (20) is slidab¬ ly mounted on said tubular body (12). 7. A centralizer as claimed in Claim 6, including a second collar (26) slidably mounted on said tubular body (12) and wherein the other end of each spring bow (20) is connected to said second collar (26). 8. A centralizer as claimed in Claim 7, wherein said tubular body (12) is provided with a groove (18) and said second collar (26) is slidably mounted in said re¬ cess. 9. A centralizer as claimed in any preceding claim, wherein said tubular body (12) is provided with a groove (22) to accommodate said spring bow (20) when compressed against said tubular body (12). 10. A centralizer as claimed in any of Claims 1 to 5, wherein the other end of each spring bow is welded to said tubular body (17). 11. A centralizer as claimed in any of Claims 1 to 5, wherein the other end of each spring bow is mounted on a collar (26) which is secured fast to said tubular body (13). 12. A centralizer as claimed in Claim 1, wherein said tubular body is provided with a groove (85) and said at least one end of said spring bow is slidably disposed in said recess. 13. A centralizer as claimed in Claim 1, wherein said tubular body is provided with a slot (96) and said at least one end of said spring bow is slidably disposed in said slot. 14. A centralizer as claimed in Claim 12 or 13, wherein said spring bow is provided with an enlarged head por¬ tion (41) to inhibit separation of said spring bow and said tubular body.

Inventors: HEBERT BRAD WALTER, LIRETTE BRENT JAMES, MARTENS JAMES GEORGE, VILYUS ROBERT PORTER, HEBERT, BRAD, WALTER, LIRETTE, BRENT, JAMES, MARTENS, JAMES, GEORGE, VILYUS, ROBERT, PORTER
Applicants: LUCAS BRIAN RONALD, WEATHERFORD LAMB, LUCAS, BRIAN, RONALD, WEATHERFORD/LAMB, INC.
Application year: 1996
Main classification: E21B17
IPC codes: E21B17