Apparatus for and method of securing a centralizer to a tubular

Abstract

A bow-spring centralizer ( 6 ) includes bow springs ( 5 ), moving collars ( 11 ) secured to each end of each bow spring, and interlocked stop collars ( 10 ). Extendable collars ( 8 ) may each be formed of a moving collar ( 11 ) movably interlocked with a stop collar ( 10 ). The centralizer ( 6 ) may optionally be formed from a tube cut using a laser to create two extendable collars coupled by bow springs. Each extendable collar may include heads integrally formed on extensions protruding from a collar (stop collar or moving collar). The heads may be generally rectangular, arrow, or teardrop-shaped head or some other shape. Each head may be slidably captured within a chamber on the interlocked collar (moving collar or stop collar). The extensions of each interlocked tubular member define the outer walls of the chamber in which a head of the interlocked tubular member is slidably captured. The stop collars may include or cooperate with one or more fingers extending along a casing to be secured by a sleeve that forms an interference fit about the casing.

What is claimed is: 
     
         1 . A method of securing a bow spring centralizer to a casing, comprising:
 forming a first extendable collar from a tube by laser cutting the tube into a first interlocking tubular member and a second interlocking tubular member and by removing portions of the tube wall along the interlocking interface to form a first stop collar that is rotatably locked to, but slidably interlocked with, a first moving collar;   securing a first end of a plurality of bow springs to the moving collar and a second end of the plurality of bow springs to an end collar, wherein a bore of the first extendable collar and a bore of the end collar are generally aligned for receiving a casing; and   receiving a bore of the stop collar on the casing, wherein the stop collar has a set of one or more fingers extending in a first direction along the surface of the casing;   receiving a bore of a sleeve on the casing adjacent the set of fingers;   receiving the bore of the sleeve onto the set of fingers in an interference-fit to install the stop collar on the tubular.   
     
     
         2 . The method of  claim 1 , wherein the stop collar comprises a gap in the bore to provide flexible variance of the bore. 
     
     
         3 . The method of  claim 1 , wherein the laser is used to cut an interlocking pattern in the wall of the tube and to cut and remove coupons of material from the wall of the tube to form a plurality of heads secured to a first generally tubular portion of the extendable collar that are slidably captured within chambers cut into the second generally tubular portion of the extendable collar. 
     
     
         4 . The method of  claim 3  wherein the first generally tubular portion of the extendable collar is the moving collar, and the second generally tubular portion of the extendable collar is the stop collar. 
     
     
         5 . The method of  claim 3  wherein the first generally tubular portion of the extendable collar is the stop collar, and the second generally tubular portion of the extendable collar is the moving collar. 
     
     
         6 . The method of  claim 3  wherein the head is of a generally rectangular wherein the heads form a portion of the boundaries of the chambers. 
     
     
         7 . The method of  claim 3  wherein the heads, when projected onto a plane, are of a shape selected from generally rectangular, generally arrow-shaped and generally bulbous. 
     
     
         8 . The method of  claim 2 , wherein each head of the first tubular member is integral with an axial extension from the first tubular member, and each head on the second tubular member is integral with an axial extension from the second tubular member. 
     
     
         9 . The method of  claim 8 , wherein with each extension is slidably received within a corresponding channel, wherein the circumferential width of each extension and the circumferential width of each channel are less than the circumferential width of the head in order to slidably capture the head within the chamber. 
     
     
         10 . The method of  claim 1  wherein the set of fingers comprise a taper along their extension from the base. 
     
     
         11 . A centralizer, comprising:
 a plurality of bow springs, each having a first end coupled to a first moving collar and a second end coupled to the second moving collar, the bow springs collectively flexible to vary the distance between the first and second moving collars;   the first stop collar securable to a casing and rotatably locked with but slidably coupled to the first moving collar; and   the second stop collar securable to the casing and rotatably locked with but slidably coupled to the second moving collar, wherein the first stop collar and the first moving collar form a first extendable collar and the second stop collar and the second moving collar form a second extendable collar extendable collar; and wherein each of the first and second extendable collars have a range of axial movement between a retracted position and an extended position.   
     
     
         12 . The method of  claim 11 , wherein the stop collar comprises a gap in the bore to provide flexible variance of the bore. 
     
     
         13 . The method of  claim 1 , wherein the extendable collar includes a plurality of heads secured to a first generally tubular portion of the extendable collar, wherein the plurality of heads are slidably captured within chambers cut into a second generally tubular portion of the extendable collar. 
     
     
         14 . The method of  claim 13  wherein the first generally tubular portion of the extendable collar is the moving collar, and the second generally tubular portion of the extendable collar is the stop collar. 
     
     
         15 . The method of  claim 13  wherein the first generally tubular portion of the extendable collar is the stop collar, and the second generally tubular portion of the extendable collar is the moving collar. 
     
     
         16 . The method of  claim 13  wherein the head is of a generally rectangular wherein the heads form a portion of the boundaries of the chambers. 
     
     
         17 . The method of  claim 13  wherein the heads, when projected onto a plane, are of a shape selected from generally rectangular, generally arrow-shaped and generally bulbous. 
     
     
         18 . The method of  claim 13 , wherein each head of the first tubular member is integral with an axial extension from the first tubular member, and each head on the second tubular member is integral with an axial extension from the second tubular member. 
     
     
         19 . The method of  claim 11 , wherein the set of fingers comprise a taper along their extension from the base. 
     
     
         20 . The method of  claim 11  further comprising:
 heating the sleeve to thermally expand the bore of the sleeve; and 
 dissipating heat stored in the sleeve by receiving the sleeve onto the set of fingers. 
 
     
     
         21 . The method of  claim 11  further comprising:
 applying an adhesive to the set of fingers to promote bonding of the sleeve to the set of fingers. 
 
     
     
         22 . The method of  claim 11 , wherein the stop collar has a fingerless base and is securable by:
 receiving the bore of the fingerless base onto the casing;   receiving a bore of a sleeve onto the casing adjacent the fingerless base;   positioning a set of one or more separated fingers intermediate the sleeve and the fingerless base;   engaging the fingerless base with at least a portion of the set of separated fingers to form a base; and   receiving the bore of the sleeve axially onto at least a portion of the set of fingers of the base in an interference-fit.   
     
     
         23 . The method of  claim 22  further comprising:
 connecting at least one of the separated fingers to the fingerless base. 
 
     
     
         24 . The method of  claim 23  wherein the connecting step comprises at least one of welding the separated finger to the fingerless base, wedging the finger into engagement with the fingerless base, and adhesively coupling the separating finger to the fingerless base. 
     
     
         25 . The method of  claim 22  wherein the fingerless base comprises at least one of a groove in a face to receive an end of the set separated fingers, an enlarged bore portion within the bore of the fingerless base to receive an end of the set of separated fingers, and a backing face to engage an end of the set of separated fingers. 
     
     
         26 . The method of  claim 22  wherein the separated fingers comprise an end having an exterior bevel to guide the sleeve around the set of separated fingers. 
     
     
         27 . The method of  claim 22  further comprising:
 using a sleeve hammer to install the sleeve around the separated fingers. 
 
     
     
         28 . The method of  claim 22  wherein a width of the sleeve exceeds a length of the set of separated fingers. 
     
     
         29 . The method of  claim 22  comprising:
 providing a second set of one or more separated fingers; 
 engaging the fingerless base with at least a portion of the second set of separated fingers; 
 receiving a bore of a second sleeve onto the tubular adjacent the second set of separated fingers; and 
 receiving the bore of the second sleeve onto the second set of fingers in an interference-fit.