CN110914512A

CN110914512A - Coupling for well pumping components

Info

Publication number: CN110914512A
Application number: CN201880033472.3A
Authority: CN
Inventors: 小威廉·D·尼尔森; 黛安·M·尼尔森
Original assignee: Materion Corp
Current assignee: Materion Corp
Priority date: 2017-03-20
Filing date: 2018-03-20
Publication date: 2020-03-24
Anticipated expiration: 2038-03-20
Also published as: CA3057457A1; JP7021248B2; CN110914512B; AU2022204570A1; RU2764972C2; AU2018240114A1; EP3601714A1; AU2022204570B2; WO2018175456A1; MX2019011226A; RU2019129637A; AU2018240114B2; JP2020516788A; RU2019129637A3

Abstract

A coupling for coupling a downhole pump to a sucker rod string is disclosed. The coupler includes a core having a first end, a central portion, and a second end. The first end and the second end each have an end surface. The first end tapers linearly inward from the central portion to the first end surface. The second end has a rounded edge along a second end surface. The coupling is made of a spinodally hardened copper nickel tin alloy and has a coefficient of sliding friction of less than 0.4, as measured against carbon steel.

Description

Coupling for well pumping components

Cross Reference to Related Applications

This application claims priority to U.S. provisional patent application serial No. 62/473,792, filed on 20.03.2017, the disclosure of which is incorporated herein by reference in its entirety.

Background

The present disclosure relates to couplings made of spinodally hardened copper alloys. The coupling is particularly adapted for connecting components of a sucker rod string to a downhole pump. The alloy preferably has a coefficient of sliding friction of less than 0.4 when measured against carbon steel.

Hydrocarbon extraction devices generally comprise: a downhole pump for extracting hydrocarbons from a subterranean reservoir; a power source for powering the pump; and a sucker rod lifting system connecting the power source and the downhole pump. The sucker rod lifting system comprises a series of sucker rods coupled together by couplings. The rods and the coupling are joined by a male-female threaded connection. Additional couplings with threaded connections are also used when coupling the sucker rod lifting system with a downhole pump. Damage to the threaded connection due to wear (wear due to adhesion between sliding surfaces) may compromise the mechanical integrity of the joint and lead to failure of the connection between the power source and the pump. Additionally, a hydrocarbon extraction system operates within the pipeline. Damage to the tubing and coupling due to repeated contact between the outer surface of the coupling/pump and the inner surface of the tubing may compromise the mechanical integrity of the tubing or coupling, cause hydrocarbons carried by the tubing to leak into the environment, or cause the coupling to become disconnected from the sucker rod string. Both of these situations actually stop the pumping process and often entail very expensive additional operations to repair such failures.

Couplings used in such systems need to have characteristics including high tensile strength, high fatigue strength, high fracture toughness, wear resistance, and corrosion resistance. Conventional couplings are typically composed of steel or nickel alloys that do not have the preferred inherent characteristics of being complete, particularly wear resistance. Expensive surface treatments are often used to improve the wear resistance of couplings made of steel or nickel alloys, as well as the wear resistance of the interior of the pipe in which the coupling is disposed. These surface treatments eventually wear away and, to remain effective, must be periodically recoated throughout the life cycle of the part. In addition, while coatings can reduce wear of the components to which they are applied, these coatings are often incompatible with other components of the system with which they may come into contact.

It is desirable to develop new couplings with improved inherent wear resistance and other desirable characteristics so that the coupling and tubing materials are compatible, which means that minimal wear occurs to both the coupling and tubing during operation, no protective coating is required, and the overall frictional losses of the pumping system are reduced.

Disclosure of Invention

The present disclosure relates to a coupling made of a spinodally hardened copper alloy, and more particularly to a coupling interposed between a sucker rod of a sucker rod string and a valve stem bushing of a downhole pump. The coupling may be considered part of a sucker rod string. The coupling has a unique combination of properties including high tensile strength, high fatigue strength, high fracture toughness, wear resistance and corrosion resistance. This combination of characteristics provides mechanical functionality during hydrocarbon recovery operations while delaying the occurrence of damaging damage to couplings and other components (e.g., sucker rods and tubing) in pump systems in which the couplings are used. This also extends the useful life of these components, significantly reducing the cost of the equipment used to recover the hydrocarbons.

Disclosed herein, in various embodiments, are couplings for sucker rod strings that include a core having a first end, a central portion, and a second end. The first end and the second end each have an end surface. The first end has a linear taper extending inwardly from the central portion and terminating at a first end surface. In other words, the first end surface has a smaller diameter than the central portion. The second end surface of the second end has a rounded edge. The coupling is made of a spinodally hardened copper nickel tin alloy having reduced friction and improved wear resistance.

The diameter of the first end surface may be smaller than the diameter of the second end surface. In some particular embodiments, the threaded bore extends completely through the core from the first end to the second end. The threads of the bore may have a rockwell C Hardness (HRC) of about 20 to about 40.

The threaded bore at the first end may be adapted to couple with a valve stem bushing, which may be connected to a downhole pump. The first end surface may abut a shoulder of the stem bushing. The outer diameter of the coupling may be greater than the outer diameter of the stem bushing.

The threaded bore at the second end may be adapted to couple with a sucker rod of a sucker rod string. The second end surface may abut a shoulder of the sucker rod. The outer diameter of the coupling may be greater than the outer diameter of the sucker rod.

Also disclosed herein is a sucker rod string comprising: the end of the sucker rod is provided with a pin part with external threads; and a stem bushing having a pin portion with an external thread at an end thereof. A coupler as described above is also included. The threaded bore at the first end of the coupling is complementary to the external threads of the valve stem bushing, and the threaded bore at the second end of the coupling is complementary to the external threads of the sucker rod. The coupling includes a spinodally hardened copper nickel tin alloy.

Also disclosed herein is a pump system comprising: a downhole pump; the power source is used for providing power for the underground pump; and a rod string positioned between the downhole pump and the power source. The pole comprises: the end of the sucker rod is provided with a pin part with external threads; and a stem bushing having a pin portion with an external thread at an end thereof. A coupler as described above is also included. The threaded bore at the first end of the coupling is complementary to the external threads of the valve stem bushing, and the threaded bore at the second end of the coupling is complementary to the external threads of the sucker rod. The coupling includes a spinodally hardened copper nickel tin alloy.

Also disclosed herein, in various embodiments, is a coupling for a sucker rod string that includes a core having a first end, a central portion, and a second end. The first end and the second end each have an end surface. The first end has a linear taper extending inwardly from the central portion and terminating at a first end surface. In other words, the first end surface has a smaller diameter than the central portion. The second end also has a linear taper extending inwardly from the central portion and terminating at a second end surface. In other words, the diameter of the second end surface is smaller than the diameter of the central portion. The coupling is made of a spinodally hardened copper nickel tin alloy.

These and other non-limiting features of the present disclosure are disclosed in more detail below.

Drawings

The following is a brief description of the drawings, which are intended to illustrate exemplary embodiments disclosed herein, and not to limit them.

FIG. 1 is a side cross-sectional view of an exemplary oil well coupling of the present disclosure having a linear taper at one end and a rounded edge at the other end.

FIG. 2A is a partial cross-sectional view showing the engagement of the oil well coupling with a sucker rod and a valve stem bushing connected to a downhole pump.

FIG. 2B is a side view showing the coupling, sucker rod and valve stem bushing of FIG. 2A in an assembled state.

FIG. 3A is a drawing of an exemplary oil well coupling of the present disclosure having a linear taper at both ends.

FIG. 3B is a side cross-sectional view showing the interior of the oil well coupling of FIG. 3A.

Fig. 4 is a schematic diagram of an embodiment of a pumping system of the present disclosure.

Fig. 5 is a graph showing the general sliding friction coefficient of various materials measured by sliding the materials on carbon steel. The y-axis is dimensionless and goes from 0 to 0.8 at a pitch of 0.1. From left to right, the materials are nickel alloy, carbon steel, aluminum bronze and copper nickel tin.

FIG. 6 is a graph showing wear of various materials relative to a steel shaft. The y-axis is the increase in clearance in inches caused by wear. The y-axis goes from 0.000 to 0.050 at 0.005 intervals. The x-axis is the number of wear cycles in thousands and is spaced at 30 intervals from 0 to 180. The steepest line represents hardened steel and the flattest line represents copper nickel tin.

FIG. 7 is a drawing of an oil well coupling made of Cu-15Ni-8Sn alloy according to the present disclosure.

Detailed Description

A more complete understanding of the components, processes, and devices disclosed herein may be obtained by reference to the accompanying drawings. These drawings are merely schematic representations based on convenience and the ease of demonstrating the present disclosure, and are, therefore, not intended to indicate relative size and dimensions of the devices or components thereof and/or to define or limit the scope of the exemplary embodiments.

Although specific terms are used in the following description for the sake of clarity, these terms are intended to refer only to particular structure in selected embodiments for illustration in the drawings, and are not intended to define or limit the scope of the disclosure. In the following drawings and description, it is to be understood that like reference numerals refer to components having similar functions.

The singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise.

As used in the specification and claims, the term "comprising" may include embodiments "consisting of … … and" consisting essentially of … …. As used herein, the terms "comprises," "comprising," "has," "with," "can," "containing," and the like, as well as variations thereof, are intended to be open-ended transition phrases, terms, or words, which require the presence of the specified elements/steps and allow for the presence of other elements/steps. However, such description should be construed as also describing the enumerated ingredients/steps of the compositions or processes as "consisting of … …" and "consisting essentially of … …," which allows for the presence of only the named ingredients/steps and any impurities that may result therefrom, and excludes other ingredients/steps.

Numerical values in the specification and claims of this application should be understood to include numerical values which are the same when reduced to the same number of significant figures and numerical values which differ from the stated value by less than the experimental error of conventional measurement techniques of the type described in the present application to determine the value of the value.

All ranges disclosed herein are inclusive of the recited endpoint and independently combinable (e.g., a range of "2 grams to 10 grams" is inclusive of the endpoints, 2 grams and 10 grams, and all intermediate values).

The term "about" can be used to include any numerical value that can be changed without changing the basic function of the value. When used with a range, "about" also discloses the range defined by the absolute values of the two endpoints, e.g., "about 2 to about 4" also discloses the range "from 2 to 4". The term "about" may refer to plus or minus 10% of the number indicated.

The present disclosure relates to couplings made of metastable-strengthened copper-based alloys. The copper alloy of the present disclosure may be a copper nickel tin alloy that combines strength, ductility, high strain rate fracture toughness, and wear resistance. More particularly, the coupling is intended to be an artificial lift coupling, sucker rod coupling or sub-coupling for use in the oil and gas industry, particularly suitable for hydrocarbon recovery systems.

In particular, the sucker rod coupling of the present disclosure is contemplated for coupling a downhole pump to a sucker rod string. A typical downhole pump has a plunger that reciprocates inside a pump barrel through a sucker rod string. The plunger and the pump barrel include a fixed valve and a traveling valve. The plunger is connected to a pump drive rod or valve stem which is in turn connected to a valve stem bushing which is in turn connected to the sucker rod string through a rod coupling.

An oil well coupling 130 according to the present disclosure is illustrated in fig. 1. Sucker rod couplings are used to assemble the various components of a sucker rod string. For example, the oil well coupling 130 can be used to couple a sucker rod 210 and a valve stem bushing 220 as described in FIGS. 3A and 3B and described below.

The rod coupler 130 is itself a core 132, the core 132 having a first end 134, a central portion 170 and a second end 136, each end corresponding to a cartridge body and having internal threads (i.e., female connectors) 138, 140 for engaging a pin portion of another component in the rod string. The core is generally cylindrical in shape with a length greater than the diameter. Dashed

lines

172, 174 indicate where the central portion 170 joins the first end 134 and the second end 136. The central portion 170 has an outer diameter 175.

The first end 134 has a first end surface 135. First end 134 has a linear taper extending inwardly toward end surface 135. In other words, the first end 134 is chamfered. Alternatively, the first end surface 135 can be described as having a smaller diameter 144 than the diameter 175 of the central portion 170. The term "taper" herein refers only to a reduction in diameter from the middle to each end, and does not require that the diameter change occur in any given manner. The taper is here linear, i.e. along a straight line.

The second end 136 has a second end surface 137. The second end 136 has a rounded edge 139 that transitions to the end surface 137. Thus, the diameter 146 of the second end surface 137 is less than the diameter 175 of the central portion 170, but greater than the diameter 144 of the first end surface 135. In a particular embodiment, the diameter 146 of the second end surface is at least 1/4 inches greater than the diameter 144 of the first end surface. In some embodiments, the diameter 144 of the first end surface is 1+5/8 inches, the diameter 146 of the second end surface is about 1.9 inches, and the diameter 175 of the central portion is 2 inches.

The bore 142 extends completely through the core from the first end 134 to the second end 136 along the longitudinal axis 160 of the core. Both

internal threads

138, 140 are located on the surface of the bore. Here, the two internal threads have the same female thread size and are complementary to external threads on other components of the sucker rod string that can be coupled by the coupling 130.

As further shown in the cross-sectional view provided in fig. 1, the oil well coupling 130 includes

counterbores

152, 154 at each

end surface

135, 137, respectively. In other words, the internal thread does not extend all the way to the end surface. The longitudinal axis is also indicated by line 160. The oil well coupling 130 has a substantially smooth cylindrically curved outer surface 162 between the end surfaces 134, 136. In other words, the outer diameter remains constant along the length of the central portion 170. The outer diameter then decreases at the tapered first end 134 and at the rounded edge of the second end 136.

Fig. 2A and 2B are side views illustrating the engagement between two components of a sucker rod string with the coupling of the present disclosure. FIG. 2A is an exploded partial cross-sectional view showing the sucker rod or stabilizer bar 210 and valve stem bushing 220 coupled together via the oil well coupling 130. Fig. 2A and 2B illustrate the use of a coupling having the geometry of the oil well coupling 130 described above and shown in fig. 1.

The sucker rod or stabilizer bar 210 includes a rod body 212 and two rod ends (only rod end 214 is shown). The rod end 214 includes: an externally threaded pin portion (or male connector) 216; a shoulder 218 adapted to abut an end surface of the coupler; and a drive head 219 that can be engaged by a tool for twisting and tightening the stabilizer bar. The valve stem bushing 220 includes a bushing body 222 and two bushing ends 224, 225. The valve stem bushing includes: an externally threaded pin portion (or male connector) 226 at the first bushing end 224; and a counterbore 227 at the second bushing end 224. The shoulder 221 is between the two bushing ends 224, 225. The counterbore 227 has internal threads 228 (i.e., a female connector) on the surface of the counterbore for engaging a pin portion of another component in the sucker rod string. Also included is a drive head 229 that may be engaged by a tool used to torque and tighten the valve stem bushing.

Fig. 2B shows the components of fig. 2A in assembled form. That is, the male connector of the stabilizer bar 210 mates with the female connector at the second end of the rod coupler 130, and the male connector of the valve stem bushing 220 mates with the female connector at the first end of the rod coupler 130. Fig. 2B illustrates that the outer diameter of the coupler may be larger than the outer diameter of the stem post component to which the coupler is attached (such as the stabilization rod 210 and the valve stem bushing 220). This prevents the coupled string components from coming into contact with the production tubing surrounding the string (i.e., the conduit 411 of fig. 4). Additionally, the end of the stem bushing and stabilizer bar are threaded into the coupling until the coupling abuts the shoulders 218, 221.

Other variations of the oil well coupling 330 according to the present disclosure are shown in fig. 3A and 3B. FIG. 3A is a drawing of a rod coupling 330 used to assemble the various components of a rod string. FIG. 3B is a cross-sectional view of the sucker rod coupling 330 shown in FIG. 3A.

Here, the rod coupling 330 is itself a core 332, the core 332 having a first end 334, a central portion 370 and a second end 336, each end corresponding to one of the cassettes and having internal threads (i.e., female connectors) 338, 340 for engaging a pin portion of another component in the rod string. The core is generally cylindrical in shape with a length greater than the diameter. Dashed

lines

372, 374 indicate where the central portion 370 joins the first end 334 and the second end 336. The central portion 370 has an outer diameter 375.

The first end 334 has a first end surface 335. The first end 334 has a linear taper extending inwardly toward the end surface 335. In other words, the first end 334 is chamfered. Alternatively, the first end surface 335 may be described as having a diameter 344 that is smaller than a diameter 375 of the central portion 370.

The second end 336 has a second end surface 337. Second end 336 also has a linear taper extending inwardly toward end surface 337. In other words, the second end 336 is also chamfered. Alternatively, second end surface 337 may be described as having a smaller diameter 346 than diameter 375 of central portion 370. In a particular embodiment, a diameter 344 of the first end surface is substantially the same as a diameter 346 of the second end surface, both of which are smaller than an outer diameter 375 of the central portion. In some embodiments, the diameter 344 of the first end surface and the diameter 346 of the second end surface are both 1+5/8 inches, and the diameter 375 of the central portion is 2 inches.

As shown here, the bore 342 extends completely through the core along the longitudinal axis of the core from the first end 334 to the second end 336. Both

internal threads

338, 340 are located on the surface of the bore. Here, the two internal threads have the same female thread size and are complementary to external threads on other components of the sucker rod string that may be coupled by the coupling 330. The dimensions of the sucker rod and various portions of the sucker rod coupling are defined in accordance with API Specification 11B, 27 th edition of API Specification 11B published 5 months 2010.

As further shown in the cross-sectional view provided in fig. 3B, oil well coupling 330 includes

counterbores

352, 354 at each

end surface

335, 337, respectively. In other words, the internal thread does not extend all the way to the end surface. The longitudinal axis is also indicated by line 360. The oil well coupling 330 has a substantially smooth cylindrically curved outer surface 362 along a central portion 370 of the coupling. The outer diameter is then reduced at the

chamfered end portions

334, 336. The central outer diameter of these couplings may be larger than the outer diameter of the stem post components to which the couplings are connected, such as the stabilizer bar and the valve stem bushing. This prevents the coupled string components from coming into contact with the production tubing surrounding the string (i.e., the conduit 411 of fig. 4).

FIG. 4 illustrates various components of a pump system 400 that utilizes the various rod string components described above, such as a sucker rod coupling. The system 400 has a movable beam 422 that reciprocates a stem 424 that includes a polishing stem portion 425. The stem 224 is suspended from the beam to actuate a downhole pump 426 disposed at the bottom of the well 428.

The walking beam 422 is in turn actuated by a steering rocker arm that reciprocates through a crank arm 430 driven by a power source 432 (e.g., an electric motor), which power source 432 is coupled to the crank arm 430 through a gear reduction mechanism, such as a gear box 434. The power source may be a three-phase ac asynchronous motor or a synchronous motor and is used to drive the pumping unit. The gearbox 434 converts the motor torque to a low speed, high torque output to drive the crank arms 430. The crank arm 430 is provided with a counterweight 436 for counterbalancing the post 424 suspended from the beam 422. Counterweights may also be provided by air cylinders, such as those on a pneumatic balancing unit. The belt pumping unit may be balanced using a counter weight, or cylinder, opposite to the rod stroke direction.

The downhole pump 426 may be a reciprocating pump having: a plunger 438 connected to the end of the stem 424; and a pump barrel 440 connected to the end of tubing in well 428. The plunger 438 includes a traveling valve 442 and a fixed valve 444 at the bottom of the barrel 440. During the pump up stroke, the traveling valve 442 closes and lifts fluid (such as oil and/or water) above the plunger 438 to the top of the well, and the standing valve 444 opens and allows additional fluid from the reservoir to flow into the pump barrel 440. On the down stroke, the traveling valve 442 is open and the fixed valve 444 is closed in preparation for the next cycle. The operation of the pump 426 is controlled so that the level of fluid maintained in the pump cylinder 440 is sufficient to maintain the lower end of the stem 424 in fluid throughout its stroke. The rod string 424 is surrounded by tubing 411, which tubing 411 is in turn surrounded by the well casing 410. The post 424 below the polished rod portion 425 is comprised of sucker rods or stabilizing rods 446 held together by couplings 448. The coupling 448 may include the oil well coupling (e.g., 130, 230) and valve stem bushing (e.g., 320) described above.

The connection between the sucker rod and the valve stem bushing is one of the most problematic joints in a sucker rod string. The geometry and material of conventional couplings cause rapid wear of the tubing due to contact between the surfaces, coupled with the increased velocity of the well fluid as it exits the pump and flows through the gap between the production tubing and the coupling (which is located between the valve stem bushing and the stabilizer bar). Using the copper alloy disclosed herein as the material for the coupling of the present disclosure reduces damage to the threaded connection due to surface wear between the coupling and the tubing. Also, the geometry of the coupling disclosed herein (e.g., chamfered or rounded ends, large outer diameter) prevents high energy contact between the coupling and the inner diameter of the tubing due to misalignment. That is, conventional couplings include sharp edges that are more likely to damage components in the event of high energy contact. Moreover, the geometry of the coupling disclosed herein facilitates the flow of well fluids into the radial gap between the coupling and the tubing.

Additionally, the coupling of the present disclosure is made from the copper alloy disclosed herein, which enables the coupling to be used as a damping device. Because the copper alloys disclosed herein have a lower modulus of elasticity than conventional materials, damping is possible. This damping enables more energy to be absorbed because the lower surface of the valve stem bushing (e.g., bushing end 325 in FIG. 3A) may impact other components of the sucker rod string during the pump down stroke. This phenomenon reduces the tendency of the mating surfaces of the upper components of the pump to become heavily cold worked during use. This cold working can result in a loss of ductility and ultimately results in cracking and the formation of "extruded" metal projections that extend outwardly beyond the installed diameter of the components. These protrusions can damage the inner diameter of the tubing and the production cartridge of the pump. Metal debris may be generated when the protrusion is broken. As these debris can be left in the system, it can cause serious damage to the working surfaces of the pump and tubing. The copper alloys disclosed herein have a high modulus of resistance, enabling the coupling to perform this damping function without plastic deformation. Instead, the coupling can return to its original size after compression on the down stroke and tension on the up stroke. In other words, the coupling acts as a solid spring.

Typically, the copper alloy used to form the coupling of the present disclosure has been cold worked prior to reheating the copper alloy to affect spinodal decomposition of the microstructure. Cold working is a process of mechanically changing the shape or size of a metal by plastic deformation. This may be done by rolling, drawing, pressing, spinning, extruding or upsetting the metal or alloy. When a metal is plastically deformed, atomic dislocations occur in the material. In particular, dislocations may occur between or within grains of the metal. The dislocations overlap each other, and the dislocation density inside the material increases. The increase in overlapping dislocations makes the movement of further dislocations more difficult. This increases the hardness and tensile strength of the resulting alloy while generally reducing the ductility and impact characteristics of the alloy. Cold working also improves the surface finish of the alloy. Mechanical cold working is generally performed at a temperature below the recrystallization point of the alloy, and is typically performed at room temperature.

Metastable aging/decomposition is a process by which multiple components can separate into distinct regions or microstructures having different chemical compositions and physical properties. In particular, the dissolution of crystals with most of the components located in the central region of the phase diagram occurs. Spinodal decomposition at the surface of the alloys of the present disclosure can result in case hardening.

The metastable alloy structure consists of a homogeneous two-phase mixture resulting when the original phases separate at a certain temperature and a component known as the miscibility gap that is reached at high temperatures. The alloy phase spontaneously decomposes into other phases in which the crystal structure remains unchanged, but the atoms within the structure are modified but remain similar in size. Spinodal hardening increases the yield strength of the base metal and has a high degree of homogeneity of composition and microstructure.

In most cases, metastable alloys exhibit an anomaly in their phase diagram called miscibility gaps. Within the relatively narrow temperature range of the miscibility gap, atomic ordering occurs within the existing lattice structure. The resulting two-phase structure is stable at temperatures significantly below the gap.

Copper nickel tin alloys, as used herein, generally comprise about 9.0 wt% to 15.5 wt% nickel and about 6.0 wt% to about 8.5 wt% tin, with the balance being copper. Such alloys can harden and more readily form high yield strength products that can be used in a variety of industrial and commercial applications. This high performance alloy is designed to provide similar characteristics to copper beryllium alloys.

More particularly, the copper nickel tin alloy of the present disclosure includes from about 9 wt% to about 15 wt% nickel and from about 6 wt% to about 9 wt% tin, with the balance being copper. In a more specific embodiment, the copper nickel tin alloy includes about 14.5 wt% to about 15.5 wt% nickel and about 7.5 wt% to about 8.5 wt% tin, with the balance being copper.

Ternary copper nickel tin metastable alloys exhibit a good combination of properties, such as high strength, excellent tribological characteristics, and high corrosion resistance in seawater and acidic environments. The increase in yield strength of the base metal may be due to spinodal decomposition in the copper nickel tin alloy.

The copper alloy may include beryllium, nickel, and/or cobalt. In some embodiments, the copper alloy comprises about 1 wt% to about 5 wt% beryllium, and the sum of cobalt and nickel is in the range of about 0.7 wt% to about 6 wt%. In a specific embodiment, the alloy includes about 2 wt% beryllium and about 0.3 wt% cobalt and nickel. Other copper alloy embodiments may contain beryllium in a range between about 5 wt% and 7 wt%.

In some embodiments, the copper alloy comprises chromium. Chromium may be present in an amount less than about 5 wt% of the alloy, including from about 0.5 wt% to about 2.0 wt% chromium or from about 0.6 wt% to about 1.2 wt% chromium.

In some embodiments, the copper alloy comprises silicon. The silicon may be present in an amount less than 5 wt%, including from about 1.0 wt% to about 3.0 wt% silicon or from about 1.5 wt% to about 2.5 wt% silicon.

Optionally, the alloys of the present disclosure contain minor amounts of additives (e.g., iron, magnesium, manganese, molybdenum, niobium, tantalum, vanadium, zirconium, and mixtures thereof). The content of these additives may be up to 1 wt%, suitably up to 0.5 wt%. In addition, small amounts of natural impurities may be present. Other additives, such as aluminum and zinc, may be present in minor amounts. The presence of additional elements may have the effect of further improving the strength of the resulting alloy.

In some embodiments, some magnesium is added during the formation of the initial alloy in order to reduce the oxygen content of the alloy. The formed magnesium oxide may be removed from the alloy ingot.

In certain embodiments, the internal threads of the coupler are formed by roll forming, rather than by machining. This process appears to elongate the grains on the outer surface of the thread. Rolled threads have been found to be resistant to stripping because shear failure must pass through the grain rather than occur with the grain. This cold working process also provides additional strength and fatigue resistance. Thus, the internal threads may have a Rockwell C Hardness (HRC) of about 20-40. The HRC may vary throughout the thread and thus this limitation should not be construed as requiring the same HRC throughout the thread. In a particular embodiment, the HRC of the thread has a minimum value of 22. The HRC of the outer surface of the thread may be at least 35.

The 0.2% offset yield strength of the alloy used to make the coupling of the present disclosure may be at least 75ksi, including at least 85ksi, or at least 90ksi, or at least 95 ksi.

The alloy used to make the coupling of the present disclosure may have a combination of 0.2% offset yield strength and room temperature charpy V-notch impact absorption work as shown in table 1 below. These combinations are unique to the copper alloys of the present disclosure. The test samples used to make these measurements were oriented in the machine direction. The values listed are the minimum (i.e., the minimum is the value listed) and it is desirable that the values of offset yield strength and charpy V-notch impact absorption work be higher than the combinations listed herein. In other words, the alloy has a 0.2% offset yield strength and a room temperature Charpy V-notch impact absorption work in combination equal to or greater than the values set forth herein.

TABLE 1

Table 2 provides characteristics of another exemplary embodiment of a copper-based alloy suitable for use in a sucker rod coupling or sub-coupling of the present disclosure.

TABLE 2

The 0.2% offset yield strength and ultimate tensile strength were measured according to ASTM E8. CVN toughness was measured according to astm e 23. The rod couplers of the present disclosure may be manufactured using casting and/or molding techniques known in the art.

Couplings made from spinodally decomposed copper alloys uniquely have high tensile and fatigue strength, as well as high fracture toughness, wear and corrosion resistance. This unique combination of properties enables the coupling to meet the basic mechanical and corrosion resistance properties required while reliably protecting the system components from wear damage, thereby greatly extending the service life of the system and reducing the risk of accidental failure. One result is extended well life between maintenance shutdowns. In addition, overall yield is improved due to reduced friction.

Some copper nickel tin alloys of the present disclosure have a low coefficient of sliding friction. In some embodiments, the copper nickel tin alloy has a coefficient of sliding friction of less than 0.4 when in contact with carbon steel. In other embodiments, the copper nickel tin alloy has a slip coefficient of about 0.3 or less, including about 0.2 or less.

In particular embodiments of the present disclosure, the copper nickel tin alloy generally has a slip coefficient of less than 0.2 (including about 0.175 or less) when in contact with carbon steel. In contrast, nickel alloys typically have a sliding coefficient of friction of 0.7 when in contact with carbon steel. Carbon steel typically has a slip coefficient of 0.6 when in contact with carbon steel; and aluminum bronze typically has a slip coefficient of 0.4 when in contact with carbon steel. The graph shown in fig. 5 illustrates the results of a comparison of these values. Thus, the total friction losses in the pumping system can be significantly reduced.

The reduction in friction also results in reduced tubing wear. FIG. 6 is a graph showing the contact of three different metals with a carburized steel shaft used in a bearing with an average bearing stress of 2,000psi and an axial rocking motion under side loading. The y-axis represents the change in clearance due to wear, with smaller values indicating less wear. As shown here, the wear of copper nickel tin alloys (triangles, less than 0.010 inches) is less than the wear of aluminum bronze (squares, between 0.015 and 0.020 inches) and hardened steel (diamonds, greater than 0.045 inches).

The following examples are provided to illustrate the couplings, processes, and features of the present disclosure. These examples are merely illustrative and are not intended to limit the disclosure to the materials, conditions, or process parameters set forth herein.

Examples of the invention

Example 1

In selected well tests with an L80 carbon steel production tubing (HRC 22-23 hardness), a sucker rod coupling made of Cu-15Ni-8Sn alloy was used on the rod string. The Mean Run TimeBefore Failure (MTBF) of the steel coupling is about 10 months. The MTBF increased five times upon installation of the Cu15Ni8Sn coupler. No signs of wear or metallic contact transfer were found in the tested Cu15Ni8Sn couplings.

Due to pump leakage, one well was shut down 555 days after installation of the Cu15Ni8Sn coupling. The pipe used to form the well casing is inspected. In the case of the pipes using the steel coupling, 50% of the pipes had a wall loss of 30% or more, while in the case of the pipes using the Cu15Ni8Sn coupling, 0% of the pipes had a wall loss of 30% or more. In the case of the pipes using the steel coupling, 25% of the pipes had surface pitting of 30% or more, while in the case of the pipes using the Cu15Ni8Sn coupling, 0% of the pipes had surface pitting of 30% or more. This was calculated to increase the MTBF of the tubing by at least three times.

Example 2

55 Cu15Ni8Sn couplings were installed 1,400 feet in the bottom of the well. The following information is obtained:

TABLE 4

	Prior practice	Actual Cu15Ni8Sn
			Rod/coupler coefficient of drag	0.2	0.035
Pump stroke (inch)	141	151
			Liquid sample volume (barrels per day)	233	248
Load of polishing rod (pound)	33,000	31,570

The result of using the Cu15Ni8Sn coupler was a 6.4% increase in fluid production. Results from similar experiments indicate a 9% increase in production, a 12% reduction in maximum load, and a 21% increase in pump stroke.

It is therefore expected that, due to the use of these copper nickel tin alloys (as compared to steel), the pump stroke should be increased by about 3% to about 40%, or about 6% to about 30%, or about 3% to about 10%, or about 6% to about 10%.

Example 3

The coupling is made of a Cu15Ni8Sn alloy. Fig. 7 shows the coupling, with a cross-section as shown in fig. 3B. The tapered coupler had an outside diameter of 2 inches with 3/4 inch rolled threads. The coupling couples to the valve stem bushing and acts as a centralizer so that the valve stem bushing does not wear adjacent oil pipes.

It will be appreciated that variations of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.

Claims

1. A sucker rod string comprising:

the end of the sucker rod is provided with a pin part with external threads;

a valve stem bushing having an externally threaded pin portion at an end thereof, wherein the valve stem bushing is connected to a downhole pump; and

a coupler comprising a core having a first end, a central portion, and a second end, each of the first and second ends having an end surface, wherein the first end tapers linearly inward from the central portion to the first end surface; and wherein the coupling is made from a spinodally hardened copper nickel tin alloy having a coefficient of sliding friction, measured relative to carbon steel, of less than 0.4; and wherein a threaded bore extends completely through the core from the first end to the second end;

wherein the threaded bore at the first end of the coupler is complementary to the external thread of the valve stem bushing and the threaded bore at the second end of the coupler is complementary to the external thread of the sucker rod.

2. The sucker rod string of claim 1 wherein the second end surface has a rounded edge or wherein the second end tapers linearly inward from the central portion to the second end surface.

3. The sucker rod string of claim 1 wherein the sucker rod has an outer diameter greater than the outer diameter of the valve stem bushing.

4. The sucker rod string of claim 1 wherein the outer diameter of the coupling is greater than the outer diameter of the sucker rod and greater than the outer diameter of the valve stem bushing.

5. The sucker rod string of claim 1 wherein the first end surface abuts a shoulder of the stem bushing.

6. The sucker rod string of claim 1 wherein the second end surface abuts a shoulder of the sucker rod.

7. The sucker rod string of claim 1 wherein the alloy comprises about 8 wt% to about 20 wt% nickel and about 5 wt% to about 11 wt% tin with the balance being copper, wherein the alloy has a 0.2% offset yield strength of at least 75 ksi.

8. The sucker rod string of claim 1 wherein the alloy comprises about 14.5 wt% to about 15.5 wt% nickel and about 7.5 wt% to about 8.5 wt% tin, with the balance being copper.

9. The sucker rod string of claim 1 wherein the alloy has a 0.2% offset yield strength of at least 95ksi and a Charpy V-notch impact absorption work at room temperature of at least 22 ft-lbs.

10. A coupling for a sucker rod string comprising:

a core having a first end, a central portion, and a second end, each of the first and second ends having an end surface;

wherein (a) the first end tapers linearly inward from the central portion to the first end surface, and (B) (i) the second end surface has a rounded edge, or (ii) the second end tapers linearly inward from the central portion to the second end surface; and

wherein the coupling is made of a spinodally hardened copper nickel tin alloy and has a coefficient of sliding friction of less than 0.4 when measured relative to carbon steel.

11. The coupling of claim 10, wherein the first end surface has a diameter that is less than a diameter of the second end surface.

12. The coupling of claim 10, further comprising a threaded bore extending completely through the core from the first end to the second end.

13. The coupling of claim 12, wherein the threads of the bore have a rockwell C hardness of about 20 to about 40.

14. The coupling of claim 10, wherein the first end and the second end each further comprise a counterbore.

15. The coupling of claim 10, wherein the alloy comprises about 8 wt% to about 20 wt% nickel and about 5 wt% to about 11 wt% tin, with the balance being copper, wherein the alloy has a 0.2% offset yield strength of at least 75 ksi.

16. The coupling of claim 10, wherein the alloy comprises about 14.5 wt% to about 15.5 wt% nickel and about 7.5 wt% to about 8.5 wt% tin, with the balance being copper.

17. The coupling of claim 10, wherein the alloy has a 0.2% offset yield strength of at least 85 ksi.

18. The coupling of claim 10, wherein the alloy has a 0.2% offset yield strength of at least 95ksi and a charpy V-notch impact absorption work at room temperature of at least 22 ft-lbs.

19. A method of extracting fluid from a well, comprising:

operatively connecting a downhole pump to a motor using a sucker rod string; and

operating the downhole pump using the sucker rod string to draw fluid from the well,

wherein the downhole pump comprises a valve stem bushing;

wherein a rod coupling connects the stem bushing to the rod string; and

wherein, the oil pumping coupling includes:

20. The method of claim 19 wherein the mean time between failure of the oil well coupling is at least 4 times greater than the mean time between failure of a coupling made of L80 carbon steel.

21. A pump system, comprising:

a downhole pump;

a power source for powering the downhole pump; and

a rod string located between the downhole pump and the power source;

wherein the stem comprises:

the end of the sucker rod is provided with a pin part with external threads;

a valve stem bushing having an externally threaded pin portion at an end thereof, the valve stem bushing being connected to the downhole pump;

a coupler comprising a core having a first end, a central portion, and a second end, the first end and the second end each having an end surface, wherein the first end tapers linearly inward from the central portion to the first end surface; and (i) the second end surface has a rounded edge, or (ii) the second end tapers linearly inward from the central portion to the second end surface; and wherein the coupling is made of a spinodally hardened copper nickel tin alloy having a coefficient of sliding friction of less than 0.4 when measured relative to carbon steel; and wherein a threaded bore extends completely through the core from the first end to the second end;

wherein the threaded bore at the first end of the coupler is complementary to the external thread of the stem bushing and the threaded bore at the second end of the coupler is complementary to the external thread of the stabilizer bar.