Abstract:
A method of forming a centralizer where a flat plate is created into a tubular where the flat plate is typically rolled so that two sides of the plate contact one another and are then linked, typically by welding. Openings are then created in the tubular such that there are no corners or other points that stress cracks may originate. Once the openings are created the remaining material between adjacent openings forms ribs. The openings created in the tubular are generally aligned with the long axis of the tubular. The material at the upper and lower end of the flat plate where openings were not created serve as circumferential collars. The ribs may be radially outwardly expanded in order to provide adequate stand-off. In many instances the ribs will also be hardened by heat treating or other hardening processes.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of to U.S. patent application Ser. No. 13/957,016, filed on Aug. 1, 2013, which is a continuation-in-part of U.S. patent application Ser. No. 13/191,074, filed on Jul. 26, 2011. The entirety of both of these applications is incorporated herein by reference. 
     
    
     FIELD OF INVENTION 
       [0002]    Embodiments of the present invention generally relate to methods and apparatuses a downhole operation. More particularly, the invention relates to methods and apparatuses for centralization in wellbores or tubulars. 
       BACKGROUND 
       [0003]    In the course of drilling and producing oil and gas wells, it has been found be beneficial to keep the tubular, which may be drill pipe, casing, production pipe, or screens, generally centered in the well. In certain instances it may be desirable to center one tubular within another. By keeping the tubular generally centered in the well a substantially uniform annular area between the wellbore wall and the tubular is maintained. In certain instances, such as cementing the tubular into the well, centralization to provide a substantially uniform annular area is imperative. By having a substantially uniform annular area the cement is better able to fill all voids between the tubular and the well thereby forming a better bond with both the wellbore wall and the tubular. 
         [0004]    A common type of centralizer is a bow spring centralizer. A bow spring centralizer typically includes a number of bows attached to a collar on the upper end of the bow and on the lower end of the bow. The bow typically curves radially outward between the two collars. In its simplest form the bow spring centralizer slides over a tubular joint and is restricted only by the tubular couplings at either end of the tubular joint. In some situations, when the bow spring centralizer is pushed into a wellbore on a tubular string the leading collar may be stopped by a restriction that will cause the bows to longitudinally compress thereby radially expanding the bows radially outwards ultimately causing the bow to fail as the tubular string continues to move down into the well. The problem is compounded due to the thickness of the bow spring centralizer&#39;s collars and ribs. Usually the collars and the ribs had the same thickness however the thickness of the centralizer as a whole centralizer was effectively doubled because the ribs were welded on top of the collar. In the event that a rib was welded edge to edge to the collar a generally weaker collar to rib interface is created and stress points are created by both the welding process and the remaining corners or other sharp points. 
         [0005]    One solution has been to attach at least one of the collars of the bow spring centralizer so that the centralizer will be pulled into the wellbore rather than pushed into the wellbore. 
       SUMMARY 
       [0006]    In order to minimize any potential stress points created by either welding or by having any sharp points or corners, it was envisioned that a centralizer is fabricated wherein a planar material having an upper end, a lower end, a first side, and a second side is formed into a tubular such that the planar material first side contacts the planar material second side. The planar material first side may be linked with the planar material second side. An elongated opening is then created in the tubular. The tubular has a long axis and the opening has a long axis having a first end and a second end such that the opening first end is adjacent the planar material upper end and the opening second end is adjacent the planar material lower end. Typically the opening does not have any corners and may be an oval, or a rectangle. Preferably the rectangle has rounded corners. In most instances the opening long axis is parallel to the long axis of the tubular although in some cases the opening long axis is not parallel to the long axis of the tubular. Typically the planar material first side is linked to the planar material second side by welding. 
         [0007]    In another embodiment of fabricating a centralizer, a planar material having an upper end, a lower end, a first side, and a second side may be formed into a tubular such that the planar material first side contacts the planar material second side. The planar material first side is linked with the planar material second side. A number of elongated openings are then created in the tubular. The tubular has a long axis and each of the plurality of openings has a long axis having a first end and a second end such that the opening first end is adjacent the planar material upper end and the opening second end is adjacent the planar material lower end. While usually the planar material is rolled into a cylinder where the rolling is parallel to one side in some instances the planar material may be rolled into a cylinder by spiral winding process where the rolling is not parallel to either side. In such instances a long tubular may be formed without stopping. Typically the plurality of openings do not have corners. While usually the plurality of openings are ovals the openings may be rectangles although in most instances the rectangles have rounded corners. Typically the plurality of openings long axis are parallel to the long axis of the tubular although in some cases the plurality of openings long axis are not parallel to the long axis of the tubular. Usually the planar material first side is linked to the planar material second side by welding. In most instances the openings are created within the tubular structure that was formed from the planar material. The material in the tubular structure both above and below the openings define circumferential collars. The material in the tubular structure between the openings define ribs that are disposed between the upper collar and lower collar. Typically the ribs are expanded radially outward where the expansion process typically, but not always, plastically deforms the ribs. Typically the ribs and in many instances the entire centralizer may be heat-treated, hardened, cured, or any other process known to one skilled in the art to allow the ribs to elastically deflect after the ribs are expanded. However, in certain instances the ribs or the entire centralizer may be heat-treated, hardened, cured, or any other process known to one skilled in the art. 
         [0008]    In another embodiment of fabricating a centralizer a first planar material having an upper end and a lower end, a first side, and a second side and at least a second planar material having an upper end, a lower end, a first side, and a second side may be formed into a tubular such that the first planar material first side contacts second planar material second side and the first planar material second side contacts the at least second planar material first side. The first planar material first side may be linked with the at least second planar material second side and the first planar material second side may be linked with the second planar material first side. A number of elongated openings are then created in the tubular. The tubular has a long axis and each of the plurality of openings has a long axis having a first end and a second end such that the opening first end is adjacent the planar material upper end and the opening second end is adjacent the planar material lower end. While usually the planar material is rolled into a cylinder where the rolling is parallel to one side in some instances the planar material may be rolled into a cylinder by spiral winding process where the rolling is not parallel to either side. In such instances a long tubular may be formed without stopping. Typically the plurality of openings do not have corners. While usually the plurality of openings are ovals the openings may be rectangles although in most instances the rectangles have rounded corners. Typically the plurality of openings long axis are parallel to the long axis of the tubular although in some cases the plurality of openings long axis are not parallel to the long axis of the tubular. Usually the planar material first side is linked to the planar material second side by welding. In most instances the openings are created within the tubular structure that was formed from the planar material. The material in the tubular structure both above and below the openings define circumferential collars. The material in the tubular structure between the openings define ribs that are disposed between the upper collar and lower collar. Typically the ribs are expanded radially outward where the expansion process typically, but not always, plastically deforms the ribs. The ribs may be heat-treated, hardened, cured, or any other process known to one skilled in the art before or after the expansion or forming of the ribs. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
           [0010]      FIG. 1  depicts a generally flat material. 
           [0011]      FIG. 2  depicts the generally flat material rolled into a tubular. 
           [0012]      FIG. 3  depicts a first and a second generally flat material each formed into a portion of the tubular. 
           [0013]      FIG. 4  depicts the first and the second generally flat piece of material each formed into a portion of the tube of  FIG. 3  linked together. 
           [0014]      FIG. 5  depicts a generally flat piece of material having a length substantially greater than its width. 
           [0015]      FIG. 6  depicts the generally flat piece of material of  FIG. 5  formed into a tubular by spiral winding. 
           [0016]      FIG. 7  depicts a generally flat piece of material having a nonlinear first side and a mirrored nonlinear second side. 
           [0017]      FIG. 8  depicts the generally flat piece of material of  FIG. 7  rolled into a tubular so that the nonlinear first side and mirrored nonlinear second side mate together. 
           [0018]      FIG. 9  depicts a rolled tubular with openings created therein that are parallel to the long axis of the tubular. 
           [0019]      FIG. 10  depicts a rolled tubular with openings created therein that are not parallel to the long axis of the tubular. 
           [0020]      FIG. 11  depicts a rolled tubular where the first side and second side are partially linked. 
           [0021]      FIG. 12  depicts the rolled tubular of  FIG. 11  where at least one opening is created across the unlinked portions between the first side and second side. 
           [0022]      FIG. 13  depicts a rolled tubular having ribs that have been radially expanded. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    The description that follows includes exemplary apparatus, methods, techniques, and instruction sequences that embody techniques of the inventive subject matter. 
         [0024]      FIG. 1  depicts a generally flat material  10  having an upper end  12 , a lower end  14 , a first side  18  and a second side  16 . Typically the process of forming a tubular begins with the generally flat material  10  where the generally flat material  10  does not have any openings or notches in the material. When forming the generally flat material  10  into the tubular, the generally flat material  10  may be rolled by a plate roll, may be hydraulically formed, hydro-dynamically formed, stamped, or any other process known for forming flat material into a roll. While it is anticipated that the generally flat material  10  will typically be a steel or other ferrous material, any material may be used including most metals, plastics, or fiber reinforced materials such as carbon fiber polymers and epoxies. 
         [0025]      FIG. 2  depicts the generally flat material  10  from  FIG. 1  after the generally flat material  10  has been rolled into a tubular  20  so that the first side  18  and the second side  16  are in contact with one another along their length. With the first side  18  in the second side  16  in contact with one another the sides  16  and  18  may be linked. In some instances the sides  16  and  18  may be linked one to the other by welding, crimping, pinning, gluing, epoxy or any other linking process known in the industry. 
         [0026]    In some instances multiple generally flat materials may each be partially formed into a tubular such that when their sides come into contact with one another and are linked to multiple generally flat materials will form the tubular.  FIG. 3  depicts a first curved piece of material  30  and a second curved piece of material  40  that were formed from two pieces of generally flat material. In this instance, the first curved piece of material  30  has an upper end  32 , a lower end  34 , a first side  36 , and a second side  38 . The second curved piece of material  40  has an upper end  42 , a lower end  44 , a first side  46 , and the second side  48 . 
         [0027]      FIG. 4  depicts the curved pieces of material  30  and  40  respectively that have been aligned such that the first side  36  of the first curved piece of material  30  and the second side  48  of the second curved piece of material  40  are in contact with one another along their length while the second side  38  of the first curved piece of material  30  and the first side  46  of the second curved piece of material  40  are also in contact with one another along their length. With the first curved piece of material  30  and the second curved piece of material  40  in contact with one another, the curved pieces of material may be linked together to form a tubular  50 . 
         [0028]    In other instances a generally flat material may be spiral wound such that its first side and the second side come into contact with one another.  FIG. 5  depicts an elongated piece of generally flat material  60  where a length  63  is substantially greater than a width  61 . The generally flat material  60  has an upper end  62 , a lower end  68 , a first side  64 , and the second side  66 . As depicted in  FIG. 6 , the generally flat material  60  has been formed into a tubular  70 . The generally flat material  60  was rolled or otherwise formed into the tubular  70  at an angle that was not parallel to the upper end  62 , the lower end  68 , the first side  64 , or the second side  66 . The tubular  70  may be curved by a spiral winding process such that the first side  64  and the second side  66  may be linked to one another. 
         [0029]    In certain instances, as depicted in  FIG. 7 , a generally flat material  80  has an upper end  82 , a lower end  84 , a first side  88 , and a second side  86  where the first side  88  and the second side  86  are nonlinear reflections of one another.  FIG. 8  depicts the generally flat material  80  from  FIG. 7  after the generally flat material  80  has been formed into a tubular  90  so that the first side  88  and the second side  86  are in contact with one another along their length. With the first side  88  in the second side  86  in contact with one another the two sides  86  and  88  may be linked to form a nonlinear seam between the sides  86  and  88 . In those instances where the sides  86  and  88  are nonlinear reflections of one another the two sides may take any form such as a smooth curve, a jagged curve, zig-zags, or any other form. 
         [0030]      FIG. 9  depicts the tubular  20  of  FIG. 2  where the first and the second sides  16  and  18  are linked together and with openings  102  created through the tubular  20 . Generally the long axis of the tubular  20  is parallel to the seam created by linking first and second sides  16  and  18  although in some cases such as when the tubular is formed by spiral winding the seam will not be parallel to the long axis of the tubular. Each opening  102  has an upper end  104 , a lower end  106 , and a long axis  108  where the long axis  108  is generally parallel to the long axis of the tubular  20 . Ribs  112  are created by the material of the tubular  20  that remains between the openings  102  after the openings  102  are created in the tubular  20 . A first collar  114  and a second collar  116  are created by the material of the tubular  20  that remains above the upper end  104  of the openings  102  and below the lower end  106  of the openings  102  after the openings  102  are created in the tubular  20 . To prevent failure in the ribs  112  as the ribs  112  are being moved downhole, the ribs  112  are created from the tubular  20  thereby eliminating the potential stress point such as when the ribs in the prior art are welded onto their collars. Additionally the openings  102  are created preferably as ovals to minimize stress points in the ribs  112  that may remain after the openings  102  are created in the tubular  20  although any shape that avoids sharp corners or points may be used. The openings  122  may be formed through the tubular  50 ,  70 , and  90  in a similar manner. 
         [0031]    In certain instances such as when the material used to form the tubular is thick enough or is not hardened, heat treated, or cured to obtain spring-like properties, each rib  112  will have the ability to plastically deform when subjected to sufficient side load. In such cases, the centralizer will act like a rigid type centralizer that has the ability to give when inserted through a tight restriction. When the material is not as thick as in the case of a rigid centralizer described above and when the material is heat treated, hardened, or cured to provide spring-like properties, each rib  112  will have spring-like properties and the centralizer will act as a bow type centralizer. 
         [0032]      FIG. 10  depicts a tubular  120  having an upper end  121 , a lower end  123 , and openings  122  created through the tubular  120 . Each opening  122  has an upper end  124 , a lower end  126 , and a long axis  128  where the long axis  128  is generally not parallel to the long axis of the tubular  120 . Ribs  132  are created by the material of the tubular  120  that remains between the openings  122  after the openings  122  are created in the tubular  120 . A first collar  134  and the second collar  136  are created by the material of the tubular  120  that remains above the upper end  124  of the openings  122  and below the lower end  126  of the openings  122  after the openings  122  are created in the tubular  120 . The openings  122  may be formed through the tubular  20 ,  70 , and  90  in a similar manner. 
         [0033]      FIG. 11  depicts the generally flat material  10  from  FIG. 1  after the generally flat material  10  has been rolled into the tubular  20  so that the first side  18  and the second side  16  are in contact with one another along their length. With the first side  18  and the second side  16  in contact with one another a portion of the two sides  16  and  18  may be linked. For instance the two sides may be linked along the contact portion of the two sides  18  and  16  from the upper end  12  to any desired point such as point  19  and from the lower end  14  to any desired point such as point  17  leaving the contact portion of the two sides between point  19  and point  17  unlinked. 
         [0034]      FIG. 12  depicts the tubular  20  from  FIG. 11  having the upper end  12 , the lower end  14 , and at least one opening  150  created through the tubular  20 . 
         [0035]    When creating the opening  150  the material between the upper end  152  and the lower end  154  of the tubular where the first side  18  and second side  16  are adjacent, whether linked or not, is removed. The upper end  152  of the opening  150  may be located at point  19 , between point  19  and the upper end  12  of the tubular  20 , or between points  19  and  17 . The lower end  154  of the opening  150  may be located at point  17 , between point  17  and the lower end  14  of the tubular  20 , or between points  17  and  19 . Ribs  160  are created by the material of the tubular  20  that remains between the openings  150  after the openings  150  are created in the tubular  20 . A first collar  162  and the second collar  164  are created by the material of the tubular  20  that remains above the upper end  152  of the openings  150  and below the lower end  154  of the openings  150  after the openings  150  are created in the tubular  20 . While only the tubular with linear sides is depicted any created tubular may be used. The opening  150  may be formed through tubular  50  in a similar manner. 
         [0036]      FIG. 13  depicts a tubular  140  having an upper end  142 , a lower end  144 , openings  146 , ribs  148 , opening upper end  152 , opening lower end  154 , and upper collar  156 , and a lower collar  158 . The ribs  148  have been expanded radially outward so that each of the ribs  148  will have at least one portion, an apex  161  of each of the ribs  148  that extends further radially outward than other portions of each the ribs  148  or of the tubular  140 . So that a portion of each of the ribs  148 , typically the apex  161  of each rib  148 , will contact the wellbore or other tubular wall (not shown). In many instances at least a portion of each of the ribs  148  will be treated to enhance the ability of each of the ribs  148  to elastically deform. Any treatment process such as heat treating, cold treating, curing, or any other process known in the industry may be used to enhance the ability each of the ribs  148  to elastically deform. 
         [0037]    In practice it is generally understood that the tubular  140  (i.e. a centralizer) as depicted in  FIG. 13  is placed on a separate tubular so that the collar  158 , collar  156 , and ribs  148  are generally coaxial with the separate tubular and that each collar  158  and  156  has a reasonably tight fit on the separate tubular. The centralizer may be allowed to slide up or down the separate tubular within the limits of couplings that are typically attached at either end of the separate tubular although more preferably at least one of the collars  158  or  156  are attached to the separate tubular. Collars  158  or  156  may be attached to the separate tubular by any attachment system known in the industry. For instance the collars  158  or  156  may be attached to the separate tubular as disclosed by U.S. patent application Ser. Nos. 11/749,544, 12/042,989, 12/756,173, 13/019,084, 13/476,807, and 12/913,495 which are each incorporated by reference herein. The tubular  20 ,  50 ,  70 ,  80 , or  90  placed on a separate tubular so that the collars and the ribs may be generally coaxial with the separate tubular. The tubular  20 ,  50 ,  70 ,  80 , or  90  may be a centralizer in a similar manner as described in relation to  FIG. 13 . 
         [0038]    Bottom, lower, or downward denotes the end of the well or device away from the surface, including movement away from the surface. Top, upwards, raised, or higher denotes the end of the well or the device towards the surface, including movement towards the surface. While the embodiments are described with reference to various implementations and exploitations, it will be understood that these embodiments are illustrative and that the scope of the inventive subject matter is not limited to them. Many variations, modifications, additions and improvements are possible. 
         [0039]    Plural instances may be provided for components, operations or structures described herein as a single instance. In general, structures and functionality presented as separate components in the exemplary configurations may be implemented as a combined structure or component. Similarly, structures and functionality presented as a single component may be implemented as separate components. These and other variations, modifications, additions, and improvements may fall within the scope of the inventive subject matter. 
         [0040]    While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.