Field-Assemblable Bow-Spring Casing Centralizer and Method of Making A Centralizer

Abstract

A casing centralizer is provided that may be shipped unassembled and is then assemblable at a well site. According to one embodiment, first and second collars each have a plurality of circumferentially spaced aligning slots and a corresponding plurality of threaded, extruded through-holes. A plurality of bow-springs each have a foot at each end. Each bow-spring axially extends between the first and second collars. The foot at one end of each bow-spring is disposed in one of the aligning slots of the first collar, and the foot at the other end is disposed in one of the aligning slots on the second collar. A plurality of threaded fasteners corresponding in number to the threaded extruded through-holes secure the ends of the bow-springs to the threaded extruded through-holes. The extruded through-holes have a flange height greater than a collar thickness adjacent to the extruded through-holes. The increased flange height allows more threads to be formed within the extruded holes, resulting in a stronger threaded connection with the threaded fasteners, and a correspondingly stronger, more durable centralizer. The foot is retained within the aligning slot to reinforce the coupling between the bow-spring and the collar. A method of manufacturing the casing centralizer is also provided.

1 . A method of manufacturing a casing centralizer, comprising:
 forming a plurality of bow-springs, each having a first end and a second end; and each having a foot at each end;   forming a first collar and a second collar, each having a plurality of circumferentially spaced bow-spring aligning slots, each bow-spring aligning slot configured for receiving a foot on the end of a bow-spring;   forming at least one extruded through-hole in each collar and adjacent to each aligning slot by positioning each collar on a supporting back-up member having an opening aligned with a punch, and by driving the punch through the collar wall and into the opening, wherein the diameter of the punch is less than about 80% of a diameter of the opening on the supporting member; and   tapping each extruded through-hole to threadedly receive a fastener.   
   
   
       2 . The method of  claim 1 , wherein forming the aligning slots comprises driving a second punch through the collar into a second opening in the supporting back-up member,
 wherein a width of the second punch is smaller a width of the second opening on the supporting back-up member.   
   
   
       3 . The method of  claim 1 , further comprising:
 fastening a first end of each bow-spring to the first collar using a fastener threadedly engaged with one of the threaded extruded through-holes in the first collar; and   fastening a second end of each bow-spring to the second collar using a second fastener threadedly engaged with one of the threaded collar through-holes in the second collar.   
   
   
       4 . The method of  claim 3 , further comprising securing each bow-spring to a radially outwardly disposed surface of each collar. 
   
   
       5 . The method of  claim 1 , wherein the step of forming each extruded through-hole in a collar comprises forming an extruded through-hole having a height of at least about 1.5 times the material thickness of the collar. 
   
   
       6 . The method of  claim 1 , wherein the step of forming each extruded through-hole comprises forming an extruded through-hole having a flange height of between about 2.0 to 3.0 times the material thickness of the collar. 
   
   
       7 . The method of  claim 1 , wherein each of the aligning slots in the circumferential all of the collar have a generally circumferentially-extending slot length and a generally axially extending slot width of substantially less than the slot length. 
   
   
       8 . The method of  claim 1 , further comprising forming the feet of each bow-spring by inwardly bending the ends of the bow-springs to create an angled portion at each end of the bow spring. 
   
   
       9 . A casing centralizer, comprising:
 first and second collars each having a plurality of circumferentially spaced aligning slots and a corresponding plurality of threaded, extruded through-holes, wherein the extruded throughholes have a flange height greater than the collar thickness adjacent to the extruded throughholes;   a plurality of bow-springs, each having an aperture and a foot at each end, each bow spring extending between the first and second collars, with the foot at one end of each bow spring disposed in one of the aligning slots of the first collar to align the adjacent aperture on the end of the bow-spring with an extruded through-hole of the first collar, and the foot at the other, opposite end of the bow-spring disposed in one of the aligning slots on the second collar to align the adjacent aperture on the end of the bow-spring with an extruded through-hole of the second collar; and   a plurality of threaded fasteners corresponding in number and pitch of threads to the threaded extruded through-holes for securing one end of each of the bow springs to each of the first and second collars by inserting a fastener through each aperture aligned with an extruded through-hole and by threading the fastener into the threaded and extruded through-holes.   
   
   
       10 . The casing centralizer of  claim 9 , wherein the bow-springs are disposed on outwardly facing surfaces of each collar. 
   
   
       11 . The casing centralizer of  claim 9 , wherein the flange height of each extruded throughhole is at least 1.5 times the collar thickness. 
   
   
       12 . The casing centralizer of  claim 9 , wherein the flange height of each extruded throughhole is between about 2.0 to 3.0 times the collar thickness. 
   
   
       13 . The casing centralizer of  claim 9 , wherein the feet comprise inwardly bent portions on the ends of the bow-springs.