[0002] IMPROVED STATOR ASSEMBLY FOR PROGRESSIVE CAVITY PUMPING SYSTEMS

[0003] CROSS REFERENCE TO RELATED APPLICATIONS

[0004]The present application claims the benefit of and priority to U.S. Provisional Patent Application Serial No. 61/861 ,802, filed August 2, 2013, and the contents of which are hereby incorporated by reference in its entirety.

[0005] STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR

DEVELOPMENT

[0006] Not applicable.

[0007] REFERENCE TO APPENDIX

[0008] Not applicable.

[0009] BACKGROUND OF THE INVENTION

[0010] Field of the Invention. The inventions disclosed and taught herein relate generally to pumping equipment; and more specifically related to an improved stator assembly for use with progressive cavity and similar pumps, and a downhole pump assembly including said improved stator.

[0011] Description of the Related Art.

[0012] A progressive cavity or eccentric screw pump is generally known in the art and is suitable for many applications, including oil production. As is well understood by those skilled in the art, a progressive cavity pump assembly includes a stator and rotor that engage with each other to define cavities for receiving the material to be pumped. In an oil production application, the assembly is suspended in a wellbore in communication with a reservoir. Fluid from the reservoir flows into the wellbore and enters the pump assembly at an entrance of the stator, entering a cavity defined cooperatively by the rotor and stator. As the rotor rotates relative to the stator, the defined cavities effectively "travel" along the axis of the assembly, carrying the fluid upwards. [0013] The capacity and efficiency of the progressive cavity pump assembly is determined at least in part by the correct engagement of the rotor with the stator. For instance, if the rotor is not fully extended through the stator, then the overall capacity of the pump assembly is reduced. However, in oilfield and similar applications, the positioning of the rotor in the stator must be accomplished remotely.

[0014] A prior art solution to the problem of aligning the rotor with the stator was to affix a tag plate or bar to the intake or suction end of the stator. The tag plate or bar provided an obstruction across the intake opening of the stator. When the rotor was lowered into the stator, the lower end of the rotor would pass through the stator and eventually contact the tag plate or bar. The contact could be detected by a weight indicator at the surface. Once contact had been achieved, the rotor could be retracted towards the surface by an appropriate amount, typically computed based on expected tension on the rod string. A disadvantage of the prior art tag plate, however, is that it could restrict slurries and solids from entering into the stator opening. It could also obstruct the passage of wireline tools that the operator wishes to lower into the wellbore, past the lower end of the stator. Moreover, the lower end of the rotor may strike or drag across the tag plate or bar during installation, potentially damaging the rotor or coating.

[0015] Another proposed solution is the use of a tag shoulder provided in a sub that is mounted to the tubing string above the stator, which cooperates with a stop mounted to the rod string on which the rotor is suspended, as described in Canadian Patent No. 2,567,989. As the rotor is lowered, the stop on the rod string comes into contact with the shoulder mounted on the tubing string, to land the rotor. Another proposed solution is a top-tag coupling assembly described in Canadian Patent No. 2,612,326, in which the rotor head, which is larger than the helical portion of the rotor, lands on a narrowing shoulder section of the tubing string collar or coupler, also located above the stator. However, because the shoulder is positioned in the tubing string or connector above the stator, these solutions present an additional obstacle to the rotor as it is lowered through the tubing string or connector above the stator. A metal shoulder may cause scratches or other damage to the rotor as it descends past the shoulder. [0016] The inventions disclosed and taught herein are directed to pumping equipment, and in particular to an improved stator assembly for use with progressive cavity and similar pumps, and a downhole pump assembly including said improved stator.

[0017] BRIEF SUMMARY OF THE INVENTION

[0018] The objects described above and other advantages and features of the invention are incorporated in the application as set forth herein, and the associated drawings, related to systems an improved stator assembly for use with progressive cavity and similar pumps, and a downhole pump assembly including said improved stator.

[0019] In accordance with a first embodiment of the present disclosure, a stator for use in a progressive cavity pump is disclosed. The stator typically includes a housing having a suction end and a discharge end, an elastomeric liner disposed within the housing and defining a passageway for receiving a rotor of the progressive cavity pump. The passageway typically comprises a reinforced component proximate to the discharge end of the housing. The reinforced component of the passageway defines an opening smaller in dimension than a head of the rotor. The reinforced component of the stator may define a shoulder adapted for contact with the rotor head. The reinforced component of the stator may comprise at least one pin, may be formed integrally within the housing, may be mounted on the interior of the housing, or may be mounted through the housing. The elastomeric liner is typically deformable to provide a compression fit between the stator and a rotor to define discrete cavities between the stator and rotor. The elastomeric liner may extend from the suction end of the stator and terminates before the discharge end of the stator. The reinforced component of the stator may be comprised of a material with greater resistance to deformity than the elastomeric liner.

[0020] In accordance with another embodiment of the present disclosure, a stator for use in a progressive cavity pump is disclosed. The stator typically comprises a housing comprising a wall and at least one reinforcing component extending from an interior face of the wall. The stator may further comprise an elastomeric liner disposed within the housing and extending over the at least one reinforcing component. The elastomeric liner may further define a passageway for a rotor of the progressive cavity pump. A component of the elastomeric liner may extend over the at least one reinforcing component defining a shoulder for engaging a rotor head of the rotor. The at least one reinforcing component is typically proximate to the discharge end of the housing. The reinforcing component may comprise of at least one pin, may be formed integrally with the housing, may be mounted on the interior of the housing, or may be mounted through the housing. The elastomeric liner may extend from the suction end of the stator and end before the discharge end of the stator.

[0021] In accordance with another embodiment of the present disclosure, a method of operating a progressive cavity pump is disclosed. The progressive cavity pump may comprise any stator includes those described herein. The stator typically comprises a housing having a suction end and a discharge end. The stator may comprise an elastomeric liner disposed within the housing and defining a passageway for receiving a rotor of the progressive cavity pump. The elastomeric liner may comprise at least one reinforced component proximate to the discharge end, the at least one reinforced component providing a landing surface to resist passage of a rotor head of the rotor through the passageway. The method typically comprises installing the stator in a wellbore, lowering the rotor for the progressive cavity pump on a rod string into the stator until a lower surface of the rotor head of the rotor contacts the shoulder of the stator, and on detecting said contact, raising the rotor on the rod string to a predefined position. The method may further comprise rotating the rotor in an eccentric rotation along the interior surface of the stator. The method may further include pumping material through the progressive cavity pump. The method may further include pumping material through an intake end of the progressive cavity pump and through an open cavity defined by the rotor and stator.

[0022] BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0023] The following figures form part of the present specification and are included to further demonstrate certain aspects of the present invention. The invention may be better understood by reference to one or more of these figures in combination with the detailed description of specific embodiments presented herein. [0024] FIG. 1 illustrates a perspective view of a segment of a downhole pump assembly including a collar, stator assembly, and rotor.

[0025] FIG. 2A illustrates a top view of the segment of the downhole pump assembly of FIG. 1 .

[0026] FIG. 2B illustrates a sectional view of the assembly of FIG. 1 in the plane 2B indicated in FIG. 2A.

[0027] FIG. 2C illustrates a plan sectioned view of the assembly of FIG. 1 in the plane 2C indicated in FIG. 2B.

[0028] While the inventions disclosed herein are susceptible to various modifications and alternative forms, only a few specific embodiments have been shown by way of example in the drawings and are described in detail below. The figures and detailed descriptions of these specific embodiments are not intended to limit the breadth or scope of the inventive concepts or the appended claims in any manner. Rather, the figures and detailed written descriptions are provided to illustrate the inventive concepts to a person of ordinary skill in the art and to enable such person to make and use the inventive concepts.

[0029] DETAILED DESCRIPTION

[0030] The Figures described above and the written description of specific structures and functions below are not presented to limit the scope of what Applicants have invented or the scope of the appended claims. Rather, the Figures and written description are provided to teach any person skilled in the art to make and use the inventions for which patent protection is sought. Those skilled in the art will appreciate that not all features of a commercial embodiment of the inventions are described or shown for the sake of clarity and understanding. Persons of skill in this art will also appreciate that the development of an actual commercial embodiment incorporating aspects of the present inventions will require numerous implementation-specific decisions to achieve the developer's ultimate goal for the commercial embodiment. Such implementation-specific decisions may include, and likely are not limited to, compliance with system-related, business-related, government-related and other constraints, which may vary by specific implementation, location and from time to time. While a developer's efforts might be complex and time-consuming in an absolute sense, such efforts would be, nevertheless, a routine undertaking for those of skill in this art having benefit of this disclosure. It must be understood that the inventions disclosed and taught herein are susceptible to numerous and various modifications and alternative forms. Lastly, the use of a singular term, such as, but not limited to, "a," is not intended as limiting of the number of items. Also, the use of relational terms, such as, but not limited to, "top," "bottom," "left," "right," "upper," "lower," "down," "up," "side," and the like are used in the written description for clarity in specific reference to the Figures and are not intended to limit the scope of the invention or the appended claims.

[0031]Applicants have created an improved stator assembly for use with progressive cavity and similar pumps, and a downhole pump assembly including said improved stator. The design and operation of progressive cavity pumps is generally known in the art. As will be understood by those skilled in the art, a progressive cavity pump assembly as contemplated herein includes a stator, typically cylindrical in shape but can embody alternate forms, with an interior surface defined to cooperate with a rotor so as to define one or more cavities between the interior surface of the stator and a surface of the rotor. Generally, an exterior surface of the rotor defines a helical shape and the interior surface of the stator defines a double helical passageway or bore. The typical shape is generally helical but variations are normal. When the rotor is engaged in the bore of the stator, the interior surface of the stator and exterior surface of the rotor contact to define cavities for receiving the material to be pumped. Typically, the rotor is manufactured of a rigid material such as an alloy steel or stainless steel that would typically include a wear resistant coating, while interior surface of the stator is provided by an elastomeric lining or insert in a metal stator housing. Being deformable, the elastomeric surface of the stator can provide for a compression fit between the stator and rotor so as to define discrete cavities. The selection of suitable materials for the stator and rotor components, as well as the other components of the entire pumping system, will be known to those in the art.

[0032] The material to be pumped enters an intake or suction end of the pump assembly, e.g., a suction end of the stator, and is typically received in an open cavity defined by the rotor and stator. The rotor is typically connected at a rotor head end, using couplings or other suitable connection means, on a drive shaft assembly connected to a drive system that moves the rotor in an eccentric rotation along the interior surface of the stator. As the rotor rotates, the defined cavities effectively "travel" along the axis of the assembly. The material in the cavities is thus carried along the axis of the stator to a discharge end of the stator.

[0033] In an oil production application, the material to be pumped is typically fluid, which can have liquid and gaseous components; however, those skilled in the art will appreciate that progressive cavity pumps, and the improvements discussed herein, can also be used in conjunction with slurries, solid matter, water, and gas. In an oil well application, the stator is typically suspended on a string of tubing within a wellbore in communication with a reservoir. The string of tubing itself may consist of an integral piece of tubing, or several segments screwed or otherwise joined together. The stator is fixed to the end of the tubing string by a collar. The interior diameters of the tubing string and the collar, as well as the stator itself, are dimensioned to admit passage of the rotor and any wireline tools that may be employed in the well. The drive shaft assembly on which the rotor is mounted may be a rod string, typically comprising segments of steel rods that are joined by screw couplings. The rotor, on its drive shaft, is lowered through the tubing string and into the stator.

[0034] The pump assembly can be located several thousand metres below the surface in an oilfield application. It can thus be appreciated that the actual mounting of the rotor within the stator occurs at a location remote from the operator, and that visual inspection of the pump assembly to ascertain that the rotor is correctly positioned within the stator is typically not possible. Generally, for optimum operation, the end of the rotor is expected to be substantially level with the suction end of the stator, and the rod string under tension; if the rotor ends some distance from the suction end, then the pumping capacity and efficiency of the pump assembly may be reduced. The position of the rotor within the pump assembly varies according to the load on the assembly. As fluid enters the assembly, its weight causes the rod string to stretch, thus altering the final position of the rotor.

[0035] Accordingly, the embodiments described herein provide an alternative alignment mechanism for a progressive cavity pump assembly that permits the operator to correctly position the rotor within the stator. In one example, tag pins are provided within the stator itself proximate to what may be considered the discharge end of the stator, which is the end opposing the suction end of the stator.

[0036] Turning now to the figures, FIG. 1 depicts a perspective view of a portion of a progressive cavity pump subassembly 100, comprising a stator 50 with a rotor 30 disposed within, and FIG. 2A illustrates a top view of the segment of the downhole pump assembly of FIG. 1 . It will be understood by those skilled in the art that the examples depicted in the accompanying figures are only representative of an actual progressive cavity pump subassembly 100 and are not to scale; for instance the rotor 30 and stator 50 can be considered to be segments of a full rotor and stator, respectively, truncated for ease of illustration. The stator 50 is coupled to the tubing string (not shown) at the discharge end 54 of the stator 50, either directly or by means of the collar 10 shown in the drawings. The collar 10 in turn is coupled to the tubing string (not shown) of the complete downhole assembly. Coupling may be accomplished using any suitable means known in the art. The elastomeric lining 55 in the stator 50 is not visible in FIG. 1 . Elastomeric lining 55 may be seen in FIGS. 2B and 2C, and is discussed in further detail below. However, as part of the housing 53, at least one reinforcing component, here shown as one of pins 60, provide reinforcement and/or an anchor for the elastomeric lining 55. Pins 60 may be more readily seen in FIG. 2B, and are discussed in further detail below.

[0037] FIG. 2B provides a cross-sectional view of the progressive cavity pump subassembly 100 of FIG. 1 . The collar 10 is coupled to the stator 50 at the discharge end 54 of the stator 50. The collar 10 is generally a cylindrical walled element. As mentioned above, the collar 10 is mounted to the tubing string (not shown). An inner diameter of the collar 10, as defined by interior surface 12, is large enough to permit passage of the rotor 30 therethrough. Fluid, or whatever material is being pumped, may pass from the rotor 30-stator 50 assembly into the collar 10 through the tubing to an outlet of the pumping system.

[0038] The stator 50 comprises a housing 53. Throughout a substantial part of the housing 53, an elastomeric liner, surface or wall 55 is provided. The elastomeric liner 55 in this example is a wall with a varying thickness profile that defines the interior surface 56 of the stator 50 which, as described above, provides the appropriate helical passageway 44 for the progressive cavity pump. The typical shape of passageway 44 is generally helical but variations are normal. The helically-shaped passageway 44 can extend to or near the suction end 52 of the stator 50, but may end before the discharge end 54. Accordingly, the elastomeric liner 55 does not extend all the way to the end 54 of the stator 50, but terminates before the end. It will be understood, however, in other collar-stator configurations, the elastomeric liner 55 may extend further along the interior of the stator 50. The elastomeric liner 55 is may be symmetrical at both the suction and discharge ends of the stator.

[0039] Within the elastomeric liner 55, one or more reinforcing components 60 are provided, in this case pins on opposite sides of the bore. The reinforcing components 60 extend at least from the interior face of the housing 53 into the elastomeric liner 55 and can be formed or manufactured of steel or similar material to that used for the housing 53 or collar 10. Generally, the reinforcing components 60 are formed of a material with greater resistance to deformity than the elastomeric liner 55. The reinforcing components 60 in the example illustrated in the drawings are in the form of rounded pins or protrusions extending through the housing 53 and into the interior of the housing 53. The pins 60 provide a reinforced, substantially level surface within the stator (i.e., in a plane substantially perpendicular to the axis of the stator). Here, the reinforcing components 60 are formed separately from the housing 53 and are inserted through boreholes or apertures 62 provided in the housing 53, and are secured in place, for instance by welding. Turning briefly to FIG. 2C, which illustrates a cross- sectional view of the progressive cavity pump subassembly 100 taken along plane 2C indicated in FIG. 2B, it can be seen that the exterior surface 61 of the reinforcing components 60 is substantially flush with the exterior surface of the stator housing 53.

[0040] Returning to FIG. 2B, the reinforcing components 60 form part of the stator structure and are located within the elastomeric liner 55 defining the interior surface of the stator 50, and in this example, the interior surface 56 of the stator 50 defined by the elastomeric liner 55 substantially maintains its helical configuration even at the reinforced sections 60 of the elastomeric liner 55, where the elastomeric liner 55 includes the reinforcing components 60. The elastomeric liner 55 extends over and incorporates the reinforcing components 60, generally conforming to the shape of the components 60, and terminates at the housing 53 above the reinforcing components 60.

[0041] In other examples, not shown in the figures, the reinforcing components 60 may be formed integrally with the housing 53 or are mounted on the interior of the housing 53 rather than through the housing 53. It will be appreciated by those skilled in the art that the rounded pin configuration of the reinforcing components 60 is not necessary, and that other shapes or configurations may be employed. It can be seen, though, that in this example, the reinforcing components 60 do not substantially interrupt the profile of the helical passageway 44 typically employed in progressive cavity pumps. This can be seen more readily in FIG. 2A, which is a top view of the progressive cavity pump subassembly 100, as well as in FIG. 2C. The elastomeric liner 55, in addition to defining the helical passageway 44 by its interior surface 56, also defines an opening 65 in its upper surface or shoulder 57. As is conventional in the art, the opening 65 is generally shaped to permit the required motion of the rotor 30 as it is moved and rotated on its drive shaft (not shown). The helical passageway 44 is defined by the interior surface of the elastomeric liner 55, and not the reinforcing components 60. The reinforcing components 60 thus do not unduly obstruct the passage of the rotor 30 or wireline tools into the stator 50. However, because the elastomeric liner 55 is now provided with reinforcement by the reinforcing components 60, the upper surface 57 can function as a landing surface or tag shoulder 57 that resists downward motion of the rotor head 34 without substantial deformity of the upper surface 57 or the helical passageway 44 defined by the elastomeric liner 55. Landing of the rotor head 34 on the reinforced stator upper surface 57 provides for proper alignment and positioning of the rotor 30 within the stator 50.

[0042] Returning to FIG. 2B, an appropriately dimensioned rotor 30 is shown inserted in the collar 10 and stator 50. The rotor 30 includes a rotor head 34 and a helical portion 40. The rotor head 34 is typically coupled to the rod string, not shown for clarity in the figures. The rotor head 34 is enlarged compared to the minor diameter of the helical passageway 44, and furthermore has a dimension greater than the distance between the reinforced portions 60 of the elastomeric liner 55. Thus, when the rotor 30, mounted on its rod string or drive shaft (not shown), is lowered as far as possible into the collar 10-stator 50 assembly, the lower surface 36 of the rotor head 34 will contact the upper surface or shoulder 57 defined by the elastomeric liner 55. The elastomeric liner 55, being reinforced by the reinforcing components 60 at or near the upper surface 57, is sufficiently rigid to function as a tag shoulder. Contact between the rotor head 34 and the reinforced elastomeric liner 55 can be detected using a weight indicator or other means known in the art. When this contact between the rotor head 34 and the stator 50 is detected, the rotor 30 can then be raised to the proper position as determined by the operator based on this reference point, and the rod string mounted to the drive system. In operation, a helix passageway 44 is formed by the cooperation of the interior surface 56 of the elastomeric liner 55 and the exterior surface 41 of the helical portion 40 of the rotor 30.

[0043] It will be appreciated from the foregoing that by reinforcing the elastomeric liner 55 of the stator 50 in this manner, it is not necessary to provide a separate tag plate or bar at the bottom of the stator 50, thus avoiding the prior art problems mentioned above. Furthermore, the reinforcement described herein effectively provides the stator 50 with an integral tag shoulder or surface 57 without the need for retrofitting or adapting the collar 10 to have an abutment or shelf to provide the tagging function, or installing a stop or other component on the rod string to cooperate with the adapted collar. Since the reinforcing components 60 are encased in the elastomeric liner 55, the risk of damage to the rotor 30 as it is lowered into the stator 50 is mitigated. The adaptation of the collar 10 or rod string (not shown) in this manner presents the possible risk of changing the static or dynamic characteristics of those components. [0044]Various embodiments of the present invention having been thus described in detail by way of example, it will be apparent to those skilled in the art that variations and modifications may be made without departing from the invention. The invention includes all such variations and modifications as fall within the scope of the appended claims. Throughout the specification, terms such as "may" and "can" are used interchangeably and use of any particular term should not be construed as limiting the scope or requiring experimentation to implement the claimed subject matter or embodiments described herein.

[0045] The proceeding examples are included to demonstrate preferred embodiments of the inventions. It should be appreciated by those of skill in the art that the techniques disclosed in the examples above represent techniques discovered by the inventors to function well in the practice of the inventions, and thus can be considered to constitute preferred modes for its practice. However, those of skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific embodiments which are disclosed and still obtain a like or similar result without departing from the scope of the inventions.

[0046] Other and further embodiments utilizing one or more aspects of the inventions described above can be devised without departing from the spirit of Applicants' invention. Further, the various methods and embodiments of the methods of manufacture and assembly of the system, as well as location specifications, can be included in combination with each other to produce variations of the disclosed methods and embodiments. Discussion of singular elements can include plural elements and vice-versa.

[0047] The order of steps can occur in a variety of sequences unless otherwise specifically limited. The various steps described herein can be combined with other steps, interlineated with the stated steps, and/or split into multiple steps. Similarly, elements have been described functionally and can be embodied as separate components or can be combined into components having multiple functions. [0048] The inventions have been described in the context of preferred and other embodiments and not every embodiment of the invention has been described. Obvious modifications and alterations to the described embodiments are available to those of ordinary skill in the art. The disclosed and undisclosed embodiments are not intended to limit or restrict the scope or applicability of the invention conceived of by the Applicants, but rather, in conformity with the patent laws, Applicants intend to fully protect all such modifications and improvements that come within the scope or range of equivalent of the following claims.