Thin bow-string centralizer for wells

Abstract

The present disclosure provides a bow-spring centralizer by using thinner bows of advanced alloys and thermal conditioning that can reduce the thickness of the bows compared to traditional bows, and yet provide sufficient restoring force after compression in a tight annulus with little radial thickness. The present disclosure also provides a specially shaped centralizer bow with cross sections that can reduce running force, increase stiffness and strength, and/or still maintain a sufficient restoring force.

What is claimed is: 
     
         1 . A bow-spring centralizer, comprising:
 a first collar and a second collar; and   a plurality of bows disposed between the first and second collars, the bows being formed of precipitation hardening metal.   
     
     
         2 . The centralizer of  claim 1 , wherein the precipitation hardening metal comprises at least one of a precipitation hardening stainless steel and a precipitation hardening nickel alloy. 
     
     
         3 . The centralizer of  claim 1 , wherein the plurality of bows are sized between 0.030 inches (0.8 mm) to 0.130 inches (3.3 mm) thick. 
     
     
         4 . The centralizer of  claim 1 , wherein at least one of the plurality of bows is shaped longitudinally asymmetrical. 
     
     
         5 . The centralizer of  claim 1 , wherein at least one of the plurality of bows is formed with a longitudinal flat portion. 
     
     
         6 . The centralizer of  claim 5 , wherein the flat portion is disposed along the bow length symmetrically relative to the collars. 
     
     
         7 . The centralizer of  claim 5 , wherein the flat portion is disposed along the bow length asymmetrically relative to the collars. 
     
     
         8 . The centralizer of  claim 5 , wherein a transverse cross section of at least the flat portion of the bow is curved. 
     
     
         9 . The centralizer of  claim 1 , wherein a transverse cross section of the bow is curved. 
     
     
         10 . The centralizer of  claim 1 , wherein at least a portion of at least one of the plurality of bows is formed with longitudinal peaks and valleys. 
     
     
         11 . The centralizer of  claim 1 , wherein at least a portion of at least one of the plurality of bows is formed with longitudinal peaks and valleys on one face of the bow. 
     
     
         12 . The centralizer of  claim 1 , wherein the ultimate tensile strength at room temperature of at least one of the plurality of bows exceeds 100 KSI (690 MPa). 
     
     
         13 . The centralizer of  claim 1 , further comprising dimples formed in at least one of the plurality of bows. 
     
     
         14 . The centralizer of  claim 1 , further comprising a protrusion extending longitudinally from at least one end of the centralizer. 
     
     
         15 . A method of manufacturing a bow-spring centralizer, comprising:
 forming at least a portion of the centralizer from precipitation hardening steel; and   heat treating at least a portion of the centralizer by precipitation hardening.   
     
     
         16 . The method of  claim 15 , further comprising forming a protrusion extending longitudinally on at least one end of the centralizer. 
     
     
         17 . The method of  claim 15 , wherein the forming at least a portion of the centralizer comprises forming a plurality of bows from the precipitation hardening steel. 
     
     
         18 . The method of  claim 15 , wherein the heat treating is performed after the centralizer is formed. 
     
     
         19 . The method of  claim 15 , wherein forming the centralizer comprises:
 cutting one or more centralizer elements in a sheet of precipitation hardening steel;   forming a plurality of bows in a longitudinally curved shape from the one or more centralizer elements; and   forming the centralizer with the one or more plurality of bows.   
     
     
         20 . The method of  claim 19 , wherein the one or more centralizer elements comprises a plurality of collars and a plurality of bows. 
     
     
         21 . The method of  claim 19 , further comprising forming the one or more plurality of bows into a transversely curved structure.