IE53115B1

IE53115B1 - Sucker rods, pony rods and production thereof

Info

Publication number: IE53115B1
Application number: IE2033/82A
Authority: IE
Original assignee: Drilloon Ind Ltd
Priority date: 1981-08-24
Filing date: 1982-08-23
Publication date: 1988-06-22
Also published as: JPS5862284A; IN157571B; AU561534B2; ES8308388A1; GB2104936B; GB2104936A; ES515226A0; IE822033L; CA1197412A; BR8204951A; AU8754082A

Abstract

The present invention relates to sucker rods and pony rods for use in a well. Conventional sucker or pony rods are formed from a single length of rod the ends of which are upset forged, machined, heat treated and cold rolled in order to provide a respective coupling at each end of the rod. The present invention provides many advantages compared with the conventional sucker rods by fabricating the sucker rod 10 from discrete components which are friction welded together. The sucker rod 10 is formed of an elongate central member 12 having a respective coupling component friction welded to each end thereof. The couplings may comprise a male component 14 and a female component 16. The coupling components 14, 16 are each provided with a shank 22, 34 which can be held in the chuck of a friction welding device. The shanks 22, 34 are shaped so as to enable raised lettering to be provided on the shank 22, 34 without the lettering 28 degrading the alignment of the component 14, 16 in the chuck. The central member 12 may be formed from a different material to the coupling components 14, 16.

Description

The present invention relates to sucker rods and pony rods for use in wells. The only difference between a sucker rod and a pony rod is the difference in their lengths.

In this field of technology pony rods are defined as being up ' to 25 feet (7.62 m) in length, with a usual although non definative lower limit of 16 inches (406 mm), and sucker rods are defined as being rods of or exceeding 25 feet (7.62 m) in length.

In the following description, where reference is made to a sucker rod it is to be understood that the description also applies to a popy rod, unless the context requires otherwise.

Sucker rods are joined together to form a well string which is used for providing the prime movement of a pump located in a well by interconnecting the pump with surface machinery. The surface machinery imparts a reciprocating movement to the sucker rods.

Sucker rods have been known for many years and are conventionally formed from a single length of rod. The single length of rod has its ends upset forged, machined and cold rolled so as to provide couplings at the ends of the rod.

Conventional sucker rods and the production thereof include many inherent disadvantages and the present invention seeks to provide an improved sucker rod and method of production by mitigating at least some of the disadvantages, as will be apparent from the following description of embodiments of the present invention.

According to a first aspect of the present invention there is provided a sucker or pony rod for use in a well, comprising an elongate central member and two coupling components, the coupling components each being of unitary construction and having a tapered portion and a wrench engaging shank and a threaded portion for transmitting rotary torque for securing the coupling component to a coupling component on another rod to enable a string of rods to be formed, each coupling component having its tapered portion friction welded to a respective end of the elongate central member whereby the welds between the coupling components and the central member and the central member itself are not subjected to any substantial rotary torque during the interconnection of rods to form the said string.

According to a further aspect of the present invention there is provided a method of manufacturing sucker or pony rods comprising the steps of: pre-forming two coupling components each of unitary construction with a tapered portion and a wrench engaging shank and a threaded portion, for transmitting rotary torque for securing the coupling component to a coupling component on another tod to enable a string of cods to be focmed, and friction welding the tapeted portion of each coupling component to a respective end of an elongate central member, whereby the welds between the coupling components and the central member and the central member itself are not subjected to any substantial rotary torque during the interconnection of rods to form the said string.

Embodiments of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic, partly sectioned, side view of a sucker rod; 5311 Figure 2 is a diagrammatic side view to an enlarged scale of a coupling component shown in Figure 1, and, Figure 3 is a diagrammatic end view of the coupling component of Figure 2 and illustrates the retention of the component by the jaws of a chuck.

As illustrated'in Figure 1, the sucker or pony rod 10 consists of three distinct components; a central member 12 a male coupling component 14 and a female coupling component 16. The male coupling component 14 is known as the pin and the female coupling component is known as the box. The three components are secured together by friction welding. The pin 14 and box 16 may be sequentially secured to the central member 12 or, with the aid of suitable machinery, may be simultaneously secured to the central member 12. In either case, the central member 12 is held stationary and the, or both coupling components are retained in respective chucks. The chucks are rotated at high speed and the coupling components and central member 12 are brought into contact under the action of a relatively high pressure. The friction between the components is sufficient to cause the components to fuse together A certain amount of flash may be produced at the junctions of the components and this is subsequently machined off. It has been found possible to produce friction forged adhesion between components wherein the adhesion is stronger than one of the parent materials.

Manufacture of sucker rods 10 in the described manner permits many advantages as compared with conventional sucker rods.

The coupling components are preformed and hence the sucker rods 10 are easily constructed with different combinations of coupling components. Sucker rods 10 having pins 14 at both ends, boxes 16 at both ends or the illustrated pin 14/box 16.configuration are readily realised. .The correct combination of coupling components merely have to be inserted into the chuck or chucks of the friction yielding apparatus. Specialised coupling components can be provided, for example, in order to effect a change from one diameter of sucker rod to another. The provision of couplings in the conventional manufacture of sucker rods is burdensome because the entire rod has to be manipulated and machine controlled during formation of the couplings. Conventional manufacture becomes more onerous where specialised couplings or combinations are required and the necessary apparatus is considered to be relatively expensive and slow in operation compared with the method of manufacture of the present invention. The length of the sucker rod 10 is readily variable, since differing lengths of the central member 12 are easily incorporated into the rod 10.

Since the sucker rods 10 are constructed from separate components, the components need not consist of the same material unlike conventional sucker rods. The process of friction welding enables materials such as aluminium and steel to be joined even though such joints are generally regarded as being unobtainable by known methods of welding. In the known art, if it is desired to provide couplings of a high quality material, then the entire sucker rod must necessarily be formed of that material. The present invention permits a lower quality material to be used for the major, central, member and a different material having the requisite qualities to be used for the coupling components. It will often be acceptable to have a central member 12 of the sucker rod 10 fabricated from a different quality material than the coupling components. This is due to the fact that the coupling components engage with other components, by way of threaded portions, and will be subjected to rotary torques during assembly of the rods to form a well string for insertion into the well. The central members 12 are not subjected to any substantial rotary torques during assembly into a well string and under normal working conditions the sucker rods 10 are subjected to mainly tensile and compression forces rather than rotary forces. It has been found that the sucker rods 10 of the present invention can surpass the industrial strength standards specified for sucker rods. An additional benefit of forming the sucker rods 10 of discreet components is that the central member 12 can be pretreated, for example, by being provided with a coating. such coatings may be applied for a specific purpose such as anti-corrosion and a particularly convenient coating may be formed from a thermo-setting epoxy resin. This feature can be of particular benefit when the central member 12 is fabricated of a lower quality material than the coupling components.

Sucker rods 10 of the present invention are economically desirable since they may permit the raw material cost to be reduced and permit the speed of manufacture to be improved. It has been found possible, using the double ended friction welding technique, to attach the coupling components to the central member 12 in approximately seconds. The combined time for preforming the coupling components and central member and assembling the sucker rod 10 is enhanced with respect to the conventional manufacturing process involving upset forging of the ends of the sucker rod.

Improved alignment between the axes of the components can accrue 10 from the use Of the friction welding process. In known sucker rods a tolerance of l/64th of an inch (0.4 nm) in alignnent of the axes of the couplings is common. It has been found possible to obtain a repeatable value of 2/10000ths of an inch (0.005 nm) for sucker rods of the present invention. Such an improvement in alignment represents a major potential saving in the cost of well operation. Sucker rods are often used to a working depth of 15,000 to 2^000 feet (4.5to7.61 km) and the run out caused by conventional tolerance standards necessitates frequent well maintenance. The improved tolerances of the sucker rods of the present invention, when multiplied by the number of sucker rods employed in a well string, represents a substantial enhancement of alignment and corresponding reductions in essential maintenance are anticipated.

A pin 14 is shown in Figures 2 and 3. In order to be suitable for a linch (25.4 nm) diameter sucker rod, the pin 14 would typically have a length of 6 inches (152.4 nm) and a maximum diameter of 2 inches (50.8 mm). The pin 14 is formed in the required material by drop forging. There are four sections constituting the pin 14. sequentially; the threaded stub 18. collar 20, shank 22 and bull 24. λ thread 19 is cold rolled on the thread stub 18 after the pin 14 has been heat treated. Collar 20 mates with the end surface 26 of the box 16 (Figure l) when the thread 19 of the pin 14 is fully engaged with the thread of the box 16. Bull 24 is similar in shape to Chat portion of the upset end of a conventional sucker rod which remains after machining of the coupling has taken place. The bull 24 is required for handling of the sucker rods 10 during their assembly into a well string.

The shank 22 is an important portion of the pin 14. It provides the plane surfaces of the pin 14 which are held by a chuck during friction welding and ic is also the portion of the pin 14 on which the tod specifications ace located. The rod specifications are provided in this region of the sucker rod in order to comply with convention. The rod specifications would typically include; the grade (quality) of the rod, identification of manufacturer and year of manufacture. It has been found that the most efficient method of providing the rod specifications on the pin 14 is by the use of raised alpha-numeric characters 28 formed during the drop forging of the pin 14. Stamping the specifications onto the pin 14 either before or after friction welding the pin 14 to the central member 12 is uneconomic and time consuming. If the alpha-numeric characters 28 are Ο indented rather than raised, the die used during drop forging is found to become unacceptably degraded after approximately 500 operations whereas if raised characters are produced as many as 20000 to 30000 operations can be performed before degradation becomes unacceptable. It is therefore economically desirable to effect the rod specifications in raised characters 28. However, raised characters will detrimentally effect the accuracy of alignment of the pin 14 in a chuck, if the jaws of the chuck engage the lettering 28. Consequently, the shank 22 has an external configuration which enables the rod specifications to be provided without effecting alignment of the pin 14 in a chuck.

The friction welding device will typically have a two jaw chuck in which the jaws are spaced apart by 180° and in which the gripping portion of each jaw is formed by two indented surfaces which intersect each other at an angle of 90°. The jaws are shown by the phantom lines 30 in Figure 3. The shank 22 has a substantially square transverse cross-section and the gripping surfaces of each jaw 30 engage two respective sides of the shank 22. In order to provide an area on which the raised characters 28 of the.rod specifications can'be located without affecting alignment of the pin 14 in the chuck, the desired number of corners of the square cross section of the shank 22 are truncated. The truncated corners 32 provide an area having a width of 3/16ths of aninch (4.76 mn) and two such areas will usually be sufficient to contain the rod specifications.

The remaining corners of the cross-section of the shank 22 are rounded. If the truncated corners 32 are positioned between the jaws 30, the gripping surfaces of the jaws 30 engage the flat sides of the shank 22 and the raised characters 28 provided on the truncated corner 32 is not contacted by the chuck jaws 30.

Hence, the selection of corners to be gripped is not critical.

The provision of truncated corners 32 on which the rod specifications are presented enables the pin 14 to be gripped by a four jaw chuck in a corresponding manner to that described for a two jaw chuck without damaging the characters 28. The truncated comer system can be applied to other rectilinear external configurations of the shank 22 in order to secure the same advantage.

The box 16 is formed in a similar fashion to the pin 14 and in particular, the box 16 is provided with a shank 34 corresponding to the shank 22 of the pin 14.

Claims

1. λ sucker or pony rod for use In a well, conprising an elongate central member and two coupling components, the coupling components each being of unitary 5 construction and having a tapered portion and a wrench engaging shank and a threaded portion for transmitting rotary torque for securing the coupling component to a coupling component on another rod to enable a string of rods to be formed, each coupling component having its 10 tapered portion friction welded to a respective end of the elongate central member whereby the welds between the coupling components and the central member and the central member itself are not subjected to any substantial rotary torque during the interconnection of 15 rods to form the said string.

2. A sucker or pony rod as claimed in claim 1. wherein the central member and at least one coupling component are formed of different materials.

3. A sucker or pony rod as claimed in claim 2, wherein 2C the central member is provided with a coating.

4. A sucker or pony rod as claimed in claim 3. wherein the coating is a thermo-setting epoxy resin.

5. λ sucker or pony rod as claimed in any preceding claim, wherein one of Che coupling components is a male member and the other coupling component is a female member. 5

6. A sucker or pony rod as claimed in any preceding claim, wherein the wrench engaging shank of the coupling components comprise a plurality of substantially plane surfaces constituting respective circumferential portions of the shank, the planes containing the 10 substantially plane surfaces intersecting at substantially 90·.

7. A sucker or pony rod as claimed in claim 6, wherein two of the substantially plane surfaces are interconnected by a surface having alpha-numeric 15 characters provided thereon,

8. A sucker or pony rod as claimed in claim 7, wherein the surface having alpha-numeric characters provided thereon is substantially plane.

9. A sucker or pony rod as claimed in claim 7 or 8, 20 wherein the alpha-numeric characters project from the shank above the level of the surface on which they are provided.

10. Ά method of manufacturing a sucker rod or pony rod comprising the steps of: pre-forming two coupling components each of unitary construction with a tapered portion and a wrench 5 engaging shank and a threaded portion for transmitting rotary torque for securing the coupling component to a coupling component on another rod to enable a string of rods to be formed, and friction welding the tapered portion of each 10 coupling component to a respective end of an elongate central member, whereby the welds between the coupling components and the central member and the central member itself are not subjected to any substantial rotary torque during the interconnection of rods to form the 15 said string.

11. A method as claimed in claim 10. wherein the coupling components are simultaneously friction welded vith the central member.

12. A method as claimed in claim 10 or 11. wherein the 20 central member is held stationary during friction welding.

13. λ method as claimed in any of claims 10 to 12. comprising the step of forming the coupling components of a different material to that of the central member.

14. A method as claimed in claim 13. further comprising 5 the step of coating the central member with a corrosion resistant material.

15. A method as claimed in any of claims 10 to 14, comprising the step of forming the wrench engaging shank of one coupling component from a plurality of 10 substantially plane surfaces two of which are interconnected by a surface having alpha-numeric characters provided thereon.

16. A sucker or pony rod as claimed in claim 1, substantially as hereinbefore described with reference to 15 and as illustrated in the accompanying drawings.

17. A method as claimed in claim 10, of manufacturing sucker or pony rods, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

18. 20 18. A sucker or pony rod whenever manufactured by a method as claimed in any one of claims 10 to 15 or claim 17.