Hardened grappling elements for retrieving downhole tools

Abstract

An annular grappling element of a grappling tool for retrieving a downhole tool includes a body extending between a first end and a second end longitudinally opposite the first end, the body defining an inner surface extending between the first end and the second end and an outer surface also extending between the first end and the second end, herein one or more engagement members for grappling the downhole tool are formed on one of the inner surface and the outer surface of the body, and wherein the body is formed from a base material having a nickel content that is equal to or greater than 0.60 percent by weight (Wt %) and a carbon content that is equal to or less than 0.20 Wt %.

What is claimed is: 
     
         1 . An annular grappling element of a grappling tool for retrieving a downhole tool, the grappling element comprising:
 a body extending between a first end and a second end longitudinally opposite the first end, the body defining an inner surface extending between the first end and the second end and an outer surface also extending between the first end and the second end;   wherein one or more engagement members for grappling the downhole tool are formed on one of the inner surface and the outer surface of the body; and   wherein the body is formed from a base material having a nickel content that is equal to or greater than 0.60 percent by weight (Wt %) and a carbon content that is equal to or less than 0.20 Wt %.   
     
     
         2 . The grappling element of  claim 1 , wherein the carbon content of the base material is equal to or less than 0.10 Wt %. 
     
     
         3 . The grappling element of  claim 1 , wherein the nickel content of the base material is equal to or greater than 1.0 Wt %. 
     
     
         4 . The grappling element of  claim 1 , wherein the base material has a chromium content of between 0.40 Wt % and 0.70 Wt %. 
     
     
         5 . The grappling element of  claim 1 , wherein the body has a surface hardness equal to or greater than 52 on the Hardness Rockwell C (HRC) scale. 
     
     
         6 . The grappling element of  claim 1 , wherein the body has a surface hardness equal to or greater than 58 on the Hardness Rockwell C (HRC) scale. 
     
     
         7 . The grappling element of  claim 1 , wherein the one or more engagement members comprises a helically extending wicker. 
     
     
         8 . The grappling element of  claim 1 , wherein the one or more engagement members comprise helically extending wickers. 
     
     
         9 . A grappling tool for retrieving a downhole tool, the grappling tool comprising:
 an outer housing comprising a first end, a second end longitudinally opposite the first end, and a central passage defined by an inner surface extending between the first end and the second end;   the grappling element of  claim 1  received in the central passage of the outer housing and coupled to the inner surface of the outer housing whereby the grappling element is permitted to travel longitudinally through the central passage of the outer housing; and   an annular grappling control positioned in the central passage of the outer housing and rotationally locked to both the outer housing and the grappling element.   
     
     
         10 . A method for manufacturing a grappling element of a grappling tool for retrieving a downhole tool, the method comprising:
 (a) machining a base material to form a grappling element;   (b) performing a carburization process on the base material to form a carburized material;   (c) performing an austenitization process on the carburized material to austenitize the carburized material and form an austenitized material;   (d) quenching the austenitized material to form a quenched material;   (e) tempering the quenched material to form a tempered material; and   (f) performing a cryogenic treatment process on the tempered material to form a cryogenically treated material.   
     
     
         11 . The method of  claim 10 , wherein the base material has a nickel content that is equal to or greater than 0.60 percent by weight (Wt %) and a carbon content that is equal to or less than 0.20 Wt %. 
     
     
         12 . The method of  claim 10 , wherein the tempered material has a surface hardness equal to or greater than 52 on the Hardness Rockwell C (HRC) scale. 
     
     
         13 . The method of  claim 10 , wherein the cryogenically treated material has a surface hardness equal to or greater than 58 on the Hardness Rockwell C (HRC) scale. 
     
     
         14 . The method of  claim 10 , wherein (b) comprises contacting a surface of the base material with both carbon and nitrogen whereby both the carbon and the nitrogen are adsorbed into the surface of the base material. 
     
     
         15 . The method of  claim 10 , wherein (f) comprises maintaining the tempered material at or below a cryogenic temperature for a predefined time period, wherein the cryogenic temperature is less than zero degrees Celsius. 
     
     
         16 . The method of  claim 10 , wherein the base material has a nickel content that is equal to or greater than 1.0 percent by weight (Wt %) and a carbon content that is equal to or less than 0.10 Wt %. 
     
     
         17 . A method for manufacturing a grappling element of a grappling tool for retrieving a downhole tool, the method comprising:
 (a) machining a base material to form a grappling element, wherein the base material has a nickel content that is equal to or greater than 0.60 percent by weight (Wt %) and a carbon content that is equal to or less than 0.20 Wt %;   (b) performing a carburization process on the base material to form a carburized material;   (c) performing an austenitization process on the carburized material to austenitize the carburized material and form an austenitized material;   (d) quenching the carburized material to form a quenched material; and   (e) tempering the quenched material to form a tempered material.   
     
     
         18 . The method of  claim 17 , wherein the carbon content of the base material is equal to or less than 0.10 Wt %. 
     
     
         19 . The method of  claim 17 , wherein the nickel content of the base material is equal to or greater than 1.0 Wt %. 
     
     
         20 . The method of  claim 17 , wherein the base material has a chromium content of between 0.40 Wt % and 0.70 Wt %.