Sucker Rod Coupling and Method of Wear Prevention in Driven Rotation of a Sucker Rod String in Production Tubing

Abstract

A sucker rod coupling features a coupler unit having internally threaded coupling sections at opposite ends for engaging sucker rod pins and one or two outer members extending about the coupler unit between the ends, each outer member being rotatable about the coupler unit and presenting contact surfaces facing outwardly at positions radially outward therefrom. Each outer member is positioned between a respective end of the coupler and a stop defining feature thereof, and a respective stop element is selectively deployable adjacent the respective end of the coupler on a side of the outer member opposite the stop-defining feature. The outer member prevents wear to the production tubing and the sucker rod string, is easily replaceable through manipulation of the stop element to allow sliding of the member off the unit and sliding of a new member thereon, and directly engages the sucker rods without needing additional threaded components.

1 . A sucker rod coupling comprising:
 a coupler unit defined by a unitary body structure having a central longitudinal axis passing therethrough and comprising first and second coupling sections defining opposite first and second ends of the coupler unit, each coupling section having internal box threading for selective threaded engagement with a respective sucker rod at an externally threaded pin end thereof; and   at least one outer member extending about the coupler unit between the first and second ends thereof, each outer member being rotatable about the central longitudinal axis relative to the coupler unit and presenting contact surfaces facing outwardly away from the coupler unit at positions radially outward therefrom relative to the central longitudinal axis;   each outer member being disposed between a respective one of the first and second ends of the coupler unit and a respective stop-defining feature of on the unitary body that projects radially outward further from the longitudinal axis than a portion of the coupler unit around which the outer member extends without reaching past the contact surfaces of the outer member so as to block sliding of the outer member past the stop-defining feature along the longitudinal axis; and   a respective stop element corresponding to each outer adjacent the respective one of the first and second ends of the coupler unit on a side of the outer member opposite the stop-defining feature to project radially outward from an outer surfaces of the coupling section without reaching past the contact surfaces of the outer member so as to block sliding of the outer member past the stop element.   
     
     
         2 . (canceled) 
     
     
         3 . The sucker rod coupling according to  claim 1  wherein each respective stop element comprises a ring releasably engagable around the coupler body adjacent the respective end of the coupler unit. 
     
     
         4 . The sucker rod coupling according to  claim 3  wherein each ring is a snap ring engagable into a respective groove in the outer surface of the coupling section defining the respective end of the coupler unit. 
     
     
         5 . The sucker rod coupling according to  claim 1  wherein an upper one of the coupling sections has a larger outer diameter than the portion of the coupler unit around which the outer member extends, and the stop defining feature is formed by a step in diameter between the upper coupling section and the portion of the coupler unit around which the outer member extends. 
     
     
         6 . The sucker rod coupling according to  claim 5  wherein the larger outer diameter of the upper coupling section of the coupler unit is equal to an outer diameter of a portion of the respective sucker rod to which the coupler unit is to be coupled to enable gripping the upper coupling section with a fishing tool dimensionally compatible with a sucker rod size of the sucker rod string. 
     
     
         7 . The sucker rod coupling according to  claim 6  wherein the larger diameter of the upper coupling section of the coupler unit is equal to the outer diameter of a pin connection shoulder of the respective sucker rod. 
     
     
         8 . The sucker rod coupling according to  claim 5  in combination with a sucker rod string, the sucker rod coupling being installed in the sucker rod string between adjacent sucker rods, the adjacent sucker rods comprising an upper rod engaged to the upper coupling section and a lower rod engaged to the lower coupling section. 
     
     
         9 . The sucker rod coupling according to  claim 1  wherein the internal box threading of both coupling sections is disposed within a common internal passage extending fully through the coupler unit along the longitudinal axis. 
     
     
         10 . The sucker rod coupling according to  claim 9  wherein a single internal thread in the common internal passage defines the box threading of both coupling sections. 
     
     
         11 . The sucker rod coupling according to  claim 1  wherein the at least one outer member comprises separate first and second outer members spaced apart along the longitudinal axis and disposed adjacent the first and second ends of the coupler unit respectively. 
     
     
         12 . The sucker rod coupling according to  claim 11  wherein the coupler comprises a wrench engagable section defined between the first and second coupling sections. 
     
     
         13 . The sucker rod coupling according to  claim 12  wherein the wrench engagable section comprises opposing planar surfaces on opposite sides of the longitudinal axis. 
     
     
         14 . The sucker rod coupling according to  claim 1  wherein each outer member is defined by an outer race of a bearing assembly, the outer face closing fully about the coupler and the bearing assembly further comprising an inner race closing about the coupler and roller elements between the inner and outer races. 
     
     
         15 . (canceled) 
     
     
         16 . The sucker rod coupling of  claim 1  coupled between adjacent sucker rods in a sucker rod string to form a section thereof, the sucker rod string being driven for rotation within production tubing in a wellbore, whereby contact of the contact surfaces of the outer member of the sucker rod coupling with an inner wall surface of the production tubing under driven rotation of the sucker rod string cooperates with allowed relative rotation between the outer member and the coupler to avoid direct contact between the production tubing and the rotating sucker rod string to prevent or limit wear to either thereof. 
     
     
         17 . A method of operating and retrieving a sucker rod string within production tubing in a well bore, the method comprising:
 providing a sucker rod coupling comprising:
 a coupler unit defined by a unitary body structure having a central longitudinal axis passing therethrough and comprising upper and lower coupling sections defining opposite upper and lower ends of the coupler unit, each coupling section having internal box threading for selective threaded engagement with a respective sucker rod at an externally threaded pin end thereof; and 
 an outer member extending about the coupler unit between the upper and lower ends thereof at a portion of the coupler unit of smaller diameter than the upper coupling section, the outer member being rotatable about the central longitudinal axis relative to the coupler unit and presenting contact surfaces facing outwardly away from the coupler unit at positions radially outward therefrom relative to the central longitudinal axis; 
   installing the sucker rod coupling between the respective sucker rods by engaging the upper and lower coupling sections of the coupler unit to the respective sucker rods to form part of the sucker rod string from the coupler unit and the respective sucker rods engaged therewith, the upper coupling section of the coupler unit being equal in outer diameter to a portion of an upper one of the respective sucker rods to which the upper coupling section of the coupler unit is engaged;   driving rotation of the sucker rod string within the production tubing;   during driven rotation of the sucker rod string, using contact between the contact surfaces the outer member of the sucker rod coupling and an inner wall surface of the production tubing to prevent contact of the production tubing with the rotating sucker rods and the coupler unit rotating therewith; and   after failure of the part of the sucker rod string at the upper one of the respective sucker rods between which the sucker rod coupling is installed, retrieving the sucker rod coupling and sucker rods therebelow by using the upper coupling section of the coupling unit as a fish neck to grip the upper coupling section with a fishing tool dimensionally compatible with a sucker rod size of the sucker rod string.   
     
     
         18 . The method according to  claim 17  wherein the outer member of the sucker rod coupling is disposed between the lower end of the coupler unit and a respective stop-defining feature of the unitary body that projects radially outward further from the longitudinal axis than the portion of the coupler unit around which the outer member extends without reaching past the contact surfaces of the outer member so as to block sliding of the outer member past the stop-defining feature along the longitudinal axis, and there is provided a respective stop element adjacent the lower end of the coupler unit on a side of the outer member opposite the stop-defining feature to project radially outward from an outer surfaces of the lower coupling section without reaching past the contact surfaces of the outer member so as to block sliding of the outer member past the top element. 
     
     
         19 . The method according to  claim 17  wherein the upper coupling section of the coupler unit is equal in outer diameter to a pin connection shoulder of the upper one of the respective sucker rods. 
     
     
         20 . The method according to  claim 18  wherein the upper coupling section of the coupler unit is equal in outer diameter to a pin connection shoulder of the upper one of the respective sucker rods. 
     
     
         21 . The sucker rod coupling according to  claim 5  wherein there is only one outer member and only one respective stop element, which is adjacent a bottom end of the coupler unit. 
     
     
         22 . A sucker rod coupling comprising:
 a coupler unit defined by a unitary body structure having a central longitudinal axis passing therethrough and comprising first and second coupling sections defining opposite first and second ends of the coupler unit, each coupling section having internal box threading for selective threaded engagement with a respective sucker rod at an externally threaded pin end thereof; and   two outer members extending about the coupler unit between the first and second ends thereof, each outer member being rotatable about the central longitudinal axis relative to the coupler unit and presenting contact surfaces facing outwardly away from the coupler unit at positions radially outward therefrom relative to the central longitudinal axis;   each outer member being disposed between a respective one of the first and second ends of the coupler unit and a respective stop-defining feature of the unitary body that projects radially outward further from the longitudinal axis than a portion of the coupler unit around which the outer member extends without reaching past the contact surfaces of the outer member so as to block sliding of the outer member past the stop-defining feature along the longitudinal axis; and   a respective stop element corresponding to each outer member adjacent the respective one of the first and second ends of the coupler unit on a side of the outer member opposite the stop-defining feature to project radially outward from an outer surfaces of the coupling section without reaching past the contact surfaces of the outer member so as to block sliding of the outer member past the stop element;   wherein the unitary body of the coupler unit comprises a wrench engagable section defined at a position between the two outer members along the central longitudinal axis.