Balanced Thread Form, Tubulars Employing the Same, and Methods Relating Thereto

Abstract

A threaded pin connector disposable at one end of a tubular member and having a longitudinal axis is disclosed. The threaded pin connector includes a pin external shoulder and a pin internal shoulder axially spaced from the external shoulder. In addition, the threaded pin connector includes a plurality of threads in a region between the external shoulder and the internal shoulder that taper relative to the longitudinal axis at 1.0 to 1.5 inches per foot. The plurality of the threads have a bearing strength and a shear strength. The plurality of the threads are configured such that the bearing strength is within +/−5% of the shear strength.

What is claimed is: 
     
         1 . A threaded pin connector disposable at one end of a tubular member and having a longitudinal axis, wherein the threaded connector includes:
 a pin external shoulder configured to engage a box external shoulder on a mating threaded box connector when the pin connector is threadably engaged with the box connector;   a pin internal shoulder axially spaced from the pin external shoulder, wherein the pin internal shoulder is configured to engage with a box internal shoulder on the box connector when the pin connector is threadably engaged with the box connector; and   a plurality of threads in a region between the pin external shoulder and the pin internal shoulder that taper relative to the longitudinal axis at 1.0 to 1.5 inches per foot, wherein each of the plurality of the threads includes:
 a crest; 
 a root disposed radially inward from the crest; 
 a stab flank extending between the crest and the root; and 
 a load flank extending between the crest and the root, wherein the stab flank is more proximate the pin internal shoulder than the load flank; 
 wherein the plurality of the threads has a bearing strength that represents a measure of the force required to plastically deform the load flank; and 
 wherein the plurality of the threads has a shear strength that represents a measure of the axial force required to shear the thread between the load flank and the stab flank; and 
 wherein the plurality of the threads is configured such that the bearing strength is within +/−5% of the shear strength. 
   
     
     
         2 . The threaded pin connector of  claim 1 , wherein each of the plurality of the threads further includes:
 a first radius extending between the crest and the stab flank and having a first radius of curvature; and   a second radius extending between the crest and the load flank and having a second radius of curvature;   wherein the first radius of curvature is larger than the second radius of curvature.   
     
     
         3 . The threaded pin connector of  claim 2 , wherein the first radius of curvature is at least four times larger than the second radius of curvature. 
     
     
         4 . The threaded pin connector  claim 3 , wherein the first radius of curvature is 0.065 in, and wherein the second radius of curvature is 0.015 in. 
     
     
         5 . The threaded pin connector of  claim 1 , wherein the stab flank on each of the plurality of the threads is oriented at a first angle α relative to a radius of the longitudinal axis, and wherein the load flank on each of the plurality of threads is oriented at a second angle β relative to the radius, wherein α is equal to β. 
     
     
         6 . The threaded pin connector  claim 1 , wherein the stab flank on each of the plurality of the threads is oriented at a first angle α relative to a radius of the longitudinal axis, and wherein the load flank on each of the plurality of threads is oriented at a second angle β relative to the radius, wherein α is larger than β. 
     
     
         7 . The threaded pin connector of  claim 6 , wherein α is equal to 45° and β is equal to 30°. 
     
     
         8 . The threaded pin connector of  claim 7 , wherein the roots of each of the subset of threads have an elliptical curvature when viewed in cross-section along the longitudinal axis. 
     
     
         9 . The threaded pin connector of  claim 1 , wherein the plurality of threads taper relative to the longitudinal axis at 1.25 inches per foot.