Sucker rod assembly

Abstract

A sucker rod assembly for use in oil well production is disclosed. The sucker rod assembly comprises a sucker rod and at least one end fitting. The sucker rod comprises a rod body and two end portions, and each end portion comprises an end section and a shoulder section. The end fitting comprises a first end section and a second end section. The first end section of the end fitting is connectable to the end section of the sucker rod to form a sucker rod assembly. In some embodiments, the sucker rod comprises a corrosion-resistant coating covering the entire external surface of the sucker rod, except for the two end sections. In some embodiments, the shoulder section of the sucker rod comprises a recessed shoulder or a recessed groove or both.

What is claimed is: 
     
         1 . A sucker rod assembly comprising a sucker rod and at least one end fitting,
 wherein the sucker rod comprises a rod body and two end portions, each end portion comprising an end section and a shoulder section,   wherein the end fitting comprises a first end section, and a second end section,   wherein the first end section of the end fitting is connectable to the end section of the sucker rod to form a sucker rod assembly.   
     
     
         2 . The sucker rod assembly according to  claim 1 , wherein the end section of the sucker rod is a male end section and the first and second end sections of the end fitting are female and male end sections respectively. 
     
     
         3 . The sucker rod assembly according to  claim 2 , wherein the sucker rod comprises a corrosion-resistant coating covering the entire external surface of the sucker rod, except for the two male end sections. 
     
     
         4 . The sucker rod assembly according to  claim 3 , wherein the corrosion-resistant coating is a circumferential coating along the length of the sucker rod and extending from the shoulder section of one end portion to the shoulder section of the other end portion. 
     
     
         5 . The sucker rod assembly according to  claim 4 , wherein the corrosion-resistant coating comprises polyethylene. 
     
     
         6 . The sucker rod assembly according to  claim 5 , wherein the corrosion-resistant coating comprises high-density polyethylene (HDPE) or cross-linked polyethylene (PEX). 
     
     
         7 . The sucker rod assembly according to  claim 1 , wherein said at least one end fitting comprises a stainless steel surface. 
     
     
         8 . The sucker rod assembly according to  claim 1 , wherein the end fitting is fixedly connected to the sucker rod. 
     
     
         9 . The sucker rod assembly according to  claim 1 , wherein said at least one end fitting comprises two end fittings, and the end fittings are each connectable to one of the end sections of the sucker rod. 
     
     
         10 . The sucker rod assembly according to  claim 9 , wherein the two end fittings are fixedly connected to the sucker rod. 
     
     
         11 . The sucker rod assembly according to  claim 1 , comprising two or more centralizers which each encircle the rod body of the sucker rod, and are interspaced along the length of the rod body of the sucker rod. 
     
     
         12 . The sucker rod assembly according to  claim 4 , wherein the shoulder section of the sucker rod comprises a recessed shoulder or a recessed groove or both. 
     
     
         13 . The sucker rod assembly according to  claim 1 , wherein a portion of the end fitting comprises at least two flat sides suitable for engagement by a sucker rod turning or holding tool. 
     
     
         14 . The sucker rod assembly according to  claim 2 , further comprising a coupling, the coupling comprising two female end sections, wherein one of the female end sections is connectable to the male end section of the sucker rod of the sucker rod assembly. 
     
     
         15 . The sucker rod assembly according to  claim 14 , wherein the other female end section of the coupling is connectable to the male end section of the end fitting of an adjacent sucker rod assembly. 
     
     
         16 . The sucker rod assembly according to  claim 9 , further comprising a coupling, the coupling comprising two female end sections, wherein one of the female end sections is connectable to the male end section of the end fitting of the sucker rod assembly. 
     
     
         17 . The sucker rod assembly according to  claim 16 , wherein the other female end section of the coupling is connectable to the male end section of the end fitting of an adjacent sucker rod assembly. 
     
     
         18 . A sucker rod string assembled from multiples of sucker rods, end fittings, and couplings, and having the repeating pattern of either {coupling, end fitting, sucker rod, end fitting, coupling, end fitting, sucker rod, end fitting} or {coupling, sucker rod, end fitting, coupling, sucker rod, end fitting},
 wherein each sucker rod comprises a rod body and two end portions, each end portion comprising a male end section and a shoulder section,   wherein each end fitting comprises a female end section and a male end section,   wherein each coupling comprises two female end sections,   wherein the female end section of the end fitting is connected to the male end section of the sucker rod, and the female end section of the coupling is connected to the male end section of the sucker rod or the male section of the end fitting.   
     
     
         19 . The sucker rod string according to  claim 18 , wherein each sucker rod comprises a corrosion-resistant coating covering the entire external surface of the sucker rod, except for the two male end sections. 
     
     
         20 . The sucker rod string according to  claim 19 , wherein the shoulder section of the sucker rod comprises a recessed shoulder or a recessed groove or both.