Safety joint for a tool string

Abstract

A safety joint includes two tubular joint bodies. A plurality of circumferentially spaced first holes is formed in one tubular joint body and at least a second hole is formed in the other tubular joint body. The tubular joint bodies each have threaded sections. The threaded sections and holes are configured such that the at least one second hole is aligned with one of the first holes when a threaded connection is formed between the threaded sections. A shear pin is inserted into the aligned holes. Instead of providing the circumferentially spaced first holes in one of the tubular joint bodies, the circumferentially spaced first holes may be provided in a torque ring that is coupled to one of the tubular joint bodies by a threaded connection. The hole alignment could then be between the tubular joint body having the second hole and the torque ring.

1 . A safety joint comprising:
 an upper joint having a first threaded surface and a first cylindrical section, wherein the first cylindrical section includes an first hole set having one or more first holes arranged about a circumference of the first cylindrical section;   a lower joint having a second threaded surface and a second cylindrical section, wherein the first threaded surface is engaged with the second threaded surface, and wherein the second cylindrical section includes a second hole set having one or more second holes arranged about a circumference of the second cylindrical section; and   a shear pin engaged with one of the first holes and one of the second holes.   
     
     
         2 . The safety joint of  claim 1 , wherein the first hole set has a plurality of first holes equally spaced about the circumference of the first cylindrical section. 
     
     
         3 . The safety joint of  claim 1 , wherein the second hole set has a plurality of second holes equally spaced about the circumference of the second cylindrical section. 
     
     
         4 . The safety joint of  claim 1 , wherein the first hole set has a plurality of first holes equally spaced about the circumference of the first cylindrical section and the second hole set has a plurality of second holes equally spaced about the circumference of the second cylindrical section. 
     
     
         5 . The safety joint of  claim 4 , wherein the plurality of first holes includes a number of first holes different from the number of second holes in the plurality of second holes. 
     
     
         6 . The safety joint of  claim 1 , wherein the first cylindrical section is disposed on a torque ring that is coupled to the first threaded surface. 
     
     
         7 . The safety joint of  claim 1 , wherein the upper joint includes a shoulder that contacts an upper end face of the lower joint when the first threaded surface is fully engaged with the second threaded surface. 
     
     
         8 . The safety joint of  claim 7 , wherein the shoulder and the upper end face are tapered. 
     
     
         9 . A safety joint comprising:
 an upper joint having a first cylindrical section with one or more first holes arranged about a circumference of the first cylindrical section;   a lower joint threadably coupled to the upper joint having a second cylindrical section with one or more second holes arranged about a circumference of the second cylindrical section; and   a shear pin engaged with one of the first holes and one of the second holes.   
     
     
         10 . The safety joint of  claim 9 , wherein a plurality of first holes is equally spaced about the circumference of the first cylindrical section. 
     
     
         11 . The safety joint of  claim 9 , wherein a plurality of second holes is equally spaced about the circumference of the second cylindrical section. 
     
     
         12 . The safety joint of  claim 9 , wherein a plurality of first holes is equally spaced about the circumference of the first cylindrical section and a plurality of second holes is equally spaced about the circumference of the second cylindrical section. 
     
     
         13 . The safety joint of  claim 12 , wherein the plurality of first holes includes a number of first holes different from the number of second holes in the plurality of second holes. 
     
     
         14 . The safety joint of  claim 9 , wherein the first cylindrical section is disposed on a torque ring that is coupled to the upper joint. 
     
     
         15 . The safety joint of  claim 9 , wherein the upper joint includes a shoulder that contacts an upper end face of the lower joint when the upper joint is threadably coupled to the lower joint. 
     
     
         16 . The safety joint of  claim 15 , wherein the shoulder and the upper end face are tapered. 
     
     
         17 . A method comprising:
 engaging a first threaded surface of an upper joint with a second threaded surface of a lower joint, wherein when the first threaded surface is fully engaged with the second threaded surface, one or more first holes of the upper joint are aligned with one or more second holes of the lower joint;   inserting a shear pin into one of the aligned first holes and second holes;   coupling the lower joint to a lower segment of a tool string;   coupling the upper joint to an upper segment of the tool string; and   disposing the tool string into a borehole.   
     
     
         18 . The method of  claim 17 , further comprising:
 shearing the shear pin by applying a torque to the upper segment of the tool string;   rotating the upper segment of the tool string so as to disengage the first threaded surface from the second threaded surface; and   pulling the upper segment of the tool string and the upper joint out of the borehole.   
     
     
         19 . The method of  claim 17 , wherein the one or more first holes are disposed on a torque ring that is coupled to the upper joint. 
     
     
         20 . The method of  claim 17 , wherein the one or more first holes includes a different number of holes than the one or more second holes.