TECHNICAL FIELD

[0001] The present disclosure relates to an assembly for connecting rods or rod segments such as sucker rods together and is particularly related for applications in the oil and gas industry,

BACKGROUND ART

[0002] The present disclosure was developed particularly (but no exclusively) for use in applications with rotating sucker rod strings. The present disclosure will therefore be discussed herein in connection with the problems associated with rotating sucker rod strings, particularly those applications which exert high torques on the sucker rod string downhole utilised in the oil and gas industry.

[0003] Subterranean deposits of coal contain substantial quantities of methane gas entrained in the coal deposits. There are substantial obstacles which heretofore have frustrated extensive development and use of methane gas deposits in coal seams. The foremost problem is the fact that coal seams, while they may extend over large areas of up to several thousand acres, typically are fairly shallow in depth, varying from a few inches to several meters. As a result, coal seams often are associated with subterranean water, which must be drained from the coal seam in order to produce the methane.

[0004] A typical CSG well head is installed on a surface level and it is important to ensure that all produced water and gas is safely handled. The pumping mechanism typically comprises a sucker rod which rotates inside tubing and transmits power from an electric motor or a hydraulic motor at the well head to the downhole progressive cavity pump (PCP), which is located at a subsurface location, either just above or below the coals of interest. This PCP when driven by the sucker rods pumps water from the coal seam to the surface through the said tubing.

[0005] The PCP is operatively coupled to a surface power source by series of connected sucker rods. Each sucker rod may for example be machined from a solid rod approximately 25 to 30 feet long with a centra! diameter between ¾" and 1 ¼" with a threaded pin and shoulder at either end of the rod. A "sucker rod coupling" known in the prior art typically comprises a cylindrically internally threaded member and is used to connect segments of sucker rod together to create an assembly called a "sucker rod string". The sucker rod couplings are typically 4" long and have a larger outer diameter than the raised shoulders of the sucker rod. Sucker rod bars are manufactured from hot rolled alloy steel and the rod bars are machine straightened and cold drawn to the required size. The rod bar ends are hot forged according to API (American Petroleum Institute) designed sizes. The rods are then heat treated over the full length. As per requirement of mechanical properties, the rods are normalized and tempered to the specified level or quenched and tempered to the required hardness and strength. Care is taken to achieve metallographic structure with no residual stresses in the rod. A sample specimen is cut from the heat treated material and is tested for ultimate tensile strength, yield strength and elongation. The rod is then again checked for straightness. The forged ends are properly aligned with its body. Rods are cleaned by shot-blasting to remove any scale and oxidation. The forged ends are machined on C.N.C. Lathe machines as per API dimensions and checked with API approved gauges.

[0006] The sucker rod string is fed through a concentric tubing string consisting of 30 foot sections of tubing which are threaded together and typically have a nominal inside diameter between 2¾" and 4½". The function of the sucker rod string is to actuate the downhoie pump to force fluid to the surface by pumping the fluid flow through the annulus formed by the sucker rod string and the tubing string. The PCP rotates the sucker rod string and reciprocating pumps typically move the sucker rod string up and down the axial direction of the sucker rod string.

[0007] Just below the PCP is the torque anchor, which fits against the inside of the casing. The anchor is positioned for preventing the tubing from being twisted out of place by the constant rotation of the sucker rod. Below the anchor is the tailpipe pump intake which is designed for ensuring downhoie separation of gas and water, and prevents gas being pulled through the PCP. The lighter gas rises and is trapped between the tubing and the steel casing, while the heavier water falls to the bottom of the well and is pumped up inside the tubing string by the PCP during operation of the wellhead.

[0008] A significant problem associated with the pumping operations involving subsurface pumps driven by rod strings is blockage of the subsurface pump. Typically the subterranean water comprises suspended solids which tend to block the subsurface pump. This can have a significant effect on production and result in extended maintenance operations because the rod strings may need to be removed and in some cases, the subsurface pump may also need to be removed.

[0009] It will be clearly understood that prior art referred to herein does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country.

SUMMARY OF INVENTION

[0010] In a first aspect, the invention provides a coupling assembly for coupling a first rod member with a second rod member, the assembly comprising: a male connecting end of the first rod member being adapted for being received into a female connecting end of the second rod member; and a locking mechanism for preventing the first and second rod members from being uncoupled, the locking mechanism comprising a stop positioned in between the male connecting end and a locking member such that during use the locking member engages at least a part of the female connecting end and the stop thereby preventing the male connecting end from being withdrawn from the female connecting end.

[0011] In a second aspect, the invention provides a rod assembly comprising: a male connecting end and a female connecting end such that the male connecting end of the rod assembly is adapted for being received into the female connecting end of another of the rod assembly; and a locking mechanism comprising a stop positioned in between the male connecting end and a locking member such that during use the locking member engages at least a part of the stop and the female connecting end of the other rod assembly and thereby prevents the male connecting end from being withdrawn from the female connecting end.

[0012] In a third aspect, the invention provides a coupling assembly for coupling a first sucker rod with a second sucker rod, the assembly comprising: a male connecting end of the first sucker rod being adapted for being received into a female connecting end of the second sucker rod; and a locking mechanism for preventing the first and second sucker rods from being uncoupled, the locking mechanism comprising a stop positioned in between the male connecting end and a locking member such that during use the locking member engages at least a part of the female connecting end and the stop thereby preventing the male connecting end from being withdrawn from the female connecting end. [0013] In a fourth aspect, the invention provides a coupling assembly for coupling a first coupling member with a second coupling member, the assembly comprising: a male connecting end of the first coupling member being adapted for being received into a female connecting end of the second coupling member; and

a locking mechanism for preventing the first and second coupling members from being uncoupled, the locking mechanism comprising a stop positioned in between the male connecting end and a locking member such that during use the locking member engages at least a part of the female connecting end and the stop thereby preventing the male connecting end from being withdrawn from the female connecting end.

[0014] The applicants have discovered that providing the locking mechanism in the invention as described above in the first, second and third aspects enables the coupled rods to be rotated in a clockwise direction or a counter-clockwise direction without the risk of uncoupling the rods used in a rod string.

[0015] In a typical operation, a rod string (comprising a plurality of coupled rods), as described in previous sections, is driven by an electrical motor, located on the surface. The rod string is deployed in a downhole for driving a PCP pump that is located at a subsurface location. It is important to appreciate that the sucker rod couplings known in the prior art comprises sucker rods having a male connector having a threaded mating surface comprising helical threads that typically threads into the female connector of another connected sucker rod. As a result of the threaded connectors known in the prior art, the sucker rod couplings of the prior art can only allow the rotation of the prior art sucker rod strings in a single direction (either clockwise or anti-clockwise), specifically the direction in which the coupling maintains the coupled configuration of the coupled sucker rods. The prior art couplings are therefore not suitable for allowing rotation of the sucker rod couplings in both directions.

[0016] The present invention alleviates the shortcomings of the prior art sucker rod couplings by providing a coupling assembly and a pipe assembly with a configuration that allows the rotation of the rotation of a rod string (utilising the coupling or pipe assembly of the present invention) in a clockwise and a counter-clockwise direction without the risk of uncoupling the coupled rods (including sucker rods).

[0017] It is important to appreciate that providing a coupling or pipe assembly as described in the present invention which allows rotation in a clockwise and counter-clockwise direction is significantly advantageous in reducing the complexity and difficulties associated with addressing blockages of the subsurface pumping apparatus (such as the PCP). For example, during a routine operation of the wellhead, the rod strings may be rotated in a clockwise direction for driving the subsurface pump in order to pump out the subsurface water. However, in the event of a blockage in the subsurface pump, it is envisioned that the coupling and/or rod assembly of the present invention may be used for inverting the direction of rotation in a counter-clockwise direction thereby flushing water (instead of pumping in the operative clockwise direction) and thereby flush water through the subsurface pump. As a result, complexity, costs and maintenance times for addressing subsurface pump blockages are significantly reduced by the assembly provided by the present invention.

[0018] The provision of the stop positioned in between the male connecting end and the locking member is also significant in that this arrangement stops or prevents the inadvertent withdrawal of the male connecting from the female connecting especially during periods of axial or reciprocal operation of the rod strings. The locking member is configured to engage the female connecting end and the stop and therefore prevents the male connecting end from being withdrawn from the female connecting end.

[0019] In some embodiments, at least a part of the male connecting end comprises an engaging surface adapted for engagement with an internal surface forming a cavity in the female connecting end, thereby preventing rotation of the male connecting end relative to the female connecting end.

[0020] Preferably, the said engagement may be provided by way of providing a rib and groove arrangement. In a further preferred embodiment, at least one of the male and female connecting ends may comprise one or more ribs and the other of the male and female connecting ends may comprise one or more channels corresponding to said one or more ribs such that during use said one or more ribs are engaged in said corresponding one or more channels thereby preventing rotation of the male connecting end relative to the female connecting end. The ribs may for example extend along a direction of an imaginary longitudinal axis of the male and/or female connecting end. In an exemplary embodiment, the ribs may be provided in the form of splines extending along the engaging surface of the male connecting end such that the splines are dimensioned to fit into the channels provided in the form of slots running along the internal walls of the cavity in the female connecting end. The ribs and the corresponding channels may extend along a direction of an imaginary longitudinal axis of the male and/or female connecting end.

[0021] The provision of a rib and groove arrangement in an embodiment as described above is highly advantageous for several reasons. Firstly, unlike helical threads used in the prior art couplings, the engagement between the male and female connecting ends allows for the assembly to be rotated in both clockwise and counter-clockwise directions without the risk of uncoupling the male and female connecting ends. Secondly, the applicants have also realised that the torsional tolerance of the coupling of an embodiment of the present invention, as a result of the rib and groove arrangement as described above, is increased significantly (at least twice) in comparison with the couplings provided by the prior art.

[0022] In at least some embodiments, the locking member is adapted for being movable relative to the male and female connecting ends. Preferably, the locking member may be provided in the form of a locking nut may be adapted for being movable along the imaginary axis of the connected rods or the rod assembly. The locking nut comprises female threads adapted for engaging the corresponding threads provided on the outer/peripheral wall/ of the female connecting end. In the locked configuration, the locking nut may receive and retain at least part of the female connecting end and the stop in an internal space defined by the nut. In one example, the locking nut may be provided in the form of a freewheeling nut that is adapted to be rotated and tightened independently without rotating the male and female connecting ends.

[0023] The provision of the nut in such a configuration assists in coupling the male and female connecting ends whilst also allowing the rotation of the coupled rods in a clockwise and anticlockwise direction without uncoupling the coupled rods in the rod string, as described in previous sections.

[0024] The locking nut may also comprise one or more notches on a shoulder portion of the nut for seating at least a part of a tool adapted for imparting torque to the nut.

[0025] In some embodiments, the female connecting end may also comprise one or more additional notches for seating at least a part of a tool adapted for positioning or engaging at least a part of the female connecting end. [0026] The locking member of the present invention is no way limited to a locking nut and may be readily replaced by an alternative locking means adapted for engaging at least a part of the female connecting end and the stop for preventing the male connecting end from being withdrawn from the female connecting end.

[0027] In some embodiments, the stop comprises a protrusion extending outwardly in a lateral direction relative to an imaginary longitudinal axis of the male connecting end. Preferably, the stop, such as the protrusion may be provided with a raised profile relative to the male connecting end. For example, the stop may be sufficiently profiled in the form of an annular profiled ring-shaped member positioned adjacent to the male connecting end such that in a coupled configuration, the profiled ring member is unable to be accommodated within the cavity formed by the female connecting end. In some embodiments, the stop may be provided in the form of a stopping member formed integrally as a part of rod adjoining the male connecting end.

[0028] Any of the features described herein can be combined in any combination with any one or more of the other features described herein within the scope of the invention.

[0029] The reference to any prior art in this specification is not, and should not be taken as an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge.

BRIEF DESCRIPTION OF DRAWINGS

[0030] Various embodiments of the invention will be described with reference to the following drawings, in which:

[0031] Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way. The Detailed Description will make reference to a number of drawings as follows:

[0032] Figure 1 is a sectional view of a first embodiment of the present invention in an uncoupled configuration.

[0033] Figure 2 is a sectional view of the rod in accordance with the first embodiment. [0034] Figure 3 is a sectional view of two rods in a coupled configuration in accordance with the first embodiment.

[0035] Figure 4 is a first perspective view of a coupling assembly comprising two rods in accordance with the first embodiment.

[0036] Figure 5 is a second perspective view of a coupling assembly of two rods in a coupled configuration in accordance with the first embodiment.

[0037] Figure 6 is a top-down view of the two rods in an uncoupled configuration in accordance with the first embodiment.

[0038] Figure 7 is a side-on perspective view of the two rods in an uncoupled configuration in accordance with the first embodiment.

[0039] Figure 8 is a perspective view of the coupling assembly depicting a coupled configuration in accordance with a second embodiment.

[0040] Figure 9 is a top view of a coupling assembly depicting a coupled configuration in accordance with a second embodiment.

DESCRIPTION OF EMBODIMENTS

[0041] Referring to Figures 1 to 6, a first embodiment of the present invention is provided in the form of a rod assembly, specifically a sucker rod 100 comprising a male connecting end 10 and a female connecting end 20. A plurality of sucker rods 100, such as a first sucker rod 100A may be coupled with a second sucker rod 100B in series by connecting or mating a male connecting end 10 of the first sucker rod 100A with a female connecting end 20 of another of the sucker rods, such as the second sucker rod 100B. The male connecting end 10 comprises a male connector portion 12 that is substantially cylindrical in shape which is matingly received in cavity 22 thereby engaging the male connecting end 10 of sucker rod 100A with female connecting end 20 of sucker rod 100B. The male connector portion 12 is provided with a plurality of engaging ribs in the form of splines 14 running along a direction of the longitudinal axis of the rod 100. The cavity 22 in the female connecting end 20 is provided in the form of a hollow cylinder with grooves 24 that are adapted for receiving and retaining the plurality of splines 14 in an engaged or mated configuration (as shown particularly clearly in Figure 3). Providing the ribs or splines 14 that engage with the grooves or channels 24 in the said configuration allows the rotation of the coupled sucker rods 100A and 100B in both clockwise and anticlockwise direction without uncoupling the rods 100A and 100B during rotational operation in either direction. Furthermore, the scope of the present invention is in no way limited by the number of vertical splines 14 (and corresponding grooves 24) provided in the said rod or coupling assembly.

[0042] A locking mechanism 30 is also provided for preventing the male connecting end 10 from being withdrawn from the female connecting 20 during routine operation of the coupled rod strings comprising a series of coupled rods 100. The locking mechanism 30 comprises a stop in the form of an annular step 32 provided adjacent to the male connecting portion 12. A locking member in the form of a locking nut 34 is provided for deploying the locking mechanism. The locking nut 34 comprises female threads 36 that engage with male threads 26 provided on an outer peripherally located wall of the female connecting end 20. The locking nut 34 is freely movable along the spine of the rod 100 and can be rotated independently relative to the rod 100. In a typical operation, the male connecting portion 12 is received into the cavity 22 of the female connecting end 20 by aligning the splines 14 into the corresponding grooves 24. This mated configuration of the connected rods 100A and 100B is subsequently locked by deploying the locking mechanism 30 (as particularly evident in Figure 3). The locking nut 34 is pushed along the spine of the rod 100 until an underside portion 35 of the locking nut 34 abuts or contacts the step member 32. This results in the annular step 32 being positioned in between the female connecting end 20 and the locking nut 34. Furthermore, engagement of the female threads 36 on the locking nut 34 with the male threads 26 (on the outer wall of the female connecting end 20) by a tightening operation may be carried out by engaging the notch 37 provided on the head of the locking nut 34 for tightening and securing the coupling between rods 100A and 100B.

[0043] Referring to Figures 8 and 9 a second embodiment of the coupled rod assembly is illustrated. Like reference numerals depict like features which have been described in previous sections. A sucker rod 200 with a diameter of 1 inches and comprising a male connecting end 10 and a female connecting end 20 is provided. As described in previous sections, a plurality of sucker rods 200, such as a first sucker rod 200A may be coupled with a second sucker rod 200B in series by connecting or mating the male connecting end 10 of the first sucker rod 200A with a female connecting end 20 of another of the sucker rods, such as the second sucker rod 200B.

[0044] The male connecting end 10 comprises a male connector portion 12 that is substantially cylindrical in shape which is matingly received in cavity 22 thereby engaging the male connecting end 10 of sucker rod 100A with female connecting end 20 of sucker rod 100B. The male connector portion 12 is provided with a plurality of engaging splines 14 running along a direction of the longitudinal axis of the rod 200. The splines 14 are provided in the form of fourteen teeth like projections extending along the outer mating surface of the male connector portion. The major outer diameter (including the height of the splines or teeth) of the male connecting portion 12 is 1.25 inches. The minor outer diameter (without including the height of the splines or teeth) is 1.0625 inches.

[0045] The cavity 22 in the female connecting end 20 is provided in the form of a hollow cylinder with grooves 24 that are adapted for receiving and retaining the plurality of splines 14 in an engaged or mated configuration (as shown particularly clearly in Figure 9). Providing the ribs or splines 14 that engage with the grooves or channels 24 in the said configuration allows the rotation of the coupled sucker rods 200A and 200B in both clockwise and anticlockwise direction without uncoupling the rods 200A and 200B during rotational operation in either direction. Once again, we wish to clarify that the present invention is in no way limited by the number of splines provided on the male connecting portion 12 or by the number of grooves provided on the female connecting portion 22. Furthermore, the scope of the present invention is in no way limited by the number of vertical splines 14 (and corresponding grooves 24) provided in the said rod or coupling assembly.

[0046] The locking mechanism 30 prevents the male connecting end 10 from being withdrawn from the female connecting 20 during routine operation of the coupled rod strings comprising a series of coupled rods 200. The locking mechanism 30 comprises a stop in the form of an annular step 32 provided adjacent to the male connecting portion 12. A locking member in the form of a locking nut 34 is also provided for deploying the locking mechanism 30. The locking nut 34 comprises female threads 36 along an inner surface that engages with male threads 26 provided on an outer peripherally located wall of the female connecting end 20. The locking nut 34 is freely movable along the spine of the rod 200 and can be rotated independently relative to the rod 200.

[0047] In a typical operation, the male connecting portion 12 is received into the cavity 22 of the female connecting end 20 by aligning the splines 14 into the corresponding grooves 24. This mated configuration of the connected rods 200A and 200B is subsequently locked by deploying the locking mechanism 30 (as particularly evident in Figure 9). The locking nut 34 is pushed along the spine of the rod 200 until an underside portion 35 of the locking nut 34 abuts or contacts the step member 32. This results in the annular step 32 being positioned in between the female connecting end 20 and the locking nut 34.

[0048] A significant difference between the embodiments depicted in Figures 8 and 9 when compared with the embodiment depicted in Figures 1 to 6 relates to the provision of a tightening mechanism for deploying the locking nut 34 at the time of coupling rods 200A and 200B. Specifically, the locking nut 34 includes a notched portion 347 that is located at a head end of the locking nut 34. The provision of a notched portion 347 that includes a polygonal cross section allows the locking nut 34 to be easily engaged by a locking tool such as a wrench (not shown). The female connecting end 20 is also provided with a notched portion 247 for allowing the female connecting end 20 to be held in position while tightening the locking nut 34.

[0049] The present invention is no way limited to sucker rods and covers rod assemblies such as pony rods, polished rods and other such rods that may be utilised in a manner as described throughout the specification. The present invention in at least some embodiments also encompasses coupling assemblies for coupling a rod to a subsurface pump or a pumping apparatus.

[0050] In the present specification and claims (if any), the word 'comprising' and its derivatives including 'comprises' and 'comprise' include each of the stated integers but does not exclude the inclusion of one or more further integers.

[0051] Reference throughout this specification to 'one embodiment' or 'an embodiment' means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases 'in one embodiment' or 'in an embodiment' in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations.

[0052] In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims (if z appropriately interpreted by those skilled in the art.