OVER MANDREL EXTRUSION FOR COMPOSITE PCP STATOR

Abstract

Techniques for forming a helical rubber hose are provided. Such techniques include modified crosshead extrusion techniques in which an elastomer is melted, fed into a crosshead assembly, and extruded on a helical mandrel fed through the crosshead assembly to form a hose. In techniques described herein, relative axial and rotational motion of the mandrel and a die plate at or on the outlet or output of the crosshead assembly are kinematically matched such that the distance of relative axial movement of the mandrel per one revolution equals one pitch of the mandrel.

Claims

1. A method of forming a hose, the method comprising: melting an elastomer; providing the melted elastomer to a crosshead assembly, wherein a die plate having an outlet port is mounted on an outlet of the crosshead assembly; moving a helical mandrel relative to the crosshead assembly and die plate outlet port while extruding the melted elastomer about the mandrel; and kinematically correlating relative axial and rotational movement between the mandrel and the die plate.

2. The method of claim 1, wherein the mandrel is rotationally fixed and the die plate is configured to rotate about a longitudinal axis along which the mandrel extends through the die plate.

3. The method of claim 2, wherein kinematically correlating relative axial and rotational movement between the mandrel and the die plate comprises axially moving the mandrel a distance equal to one pitch of the mandrel as the die plate rotates one revolution.

4. The method of claim 1, wherein the die plate is rotationally fixed and the mandrel is configured to rotate about its longitudinal axis.

5. The method of claim 4, wherein kinematically correlating relative axial and rotational movement between the mandrel and the die plate comprises rotating the mandrel about its longitudinal axis 360° as the mandrel travels axially a distance equal to one pitch of the mandrel.

6. The method of claim 1, wherein the mandrel is axially and rotationally fixed, and the die plate is configured to move axially and rotate about a longitudinal axis along which the mandrel extends through the die plate.

7. The method of claim 1, wherein the mandrel is axially fixed, the die plate is rotationally fixed, and the mandrel is configured to rotate about its longitudinal axis as the die plate moves axially.

8. The method of claim 1, wherein both the mandrel and the die plate are configured to rotate and move axially relative to each other.

9. The method of claim 1, wherein the elastomer is rubber.

10. The method of claim 1, wherein extruding the melted elastomer about the mandrel comprises extruding the melted elastomer through a gap between an outer diameter of the mandrel and an inner diameter of the die plate outlet port.

11. A helical hose formed by the method of claim 1.

12. A stator for a progressive cavity pump or positive displacement motor comprising the helical hose of claim 11.

13. A method for manufacturing a stator for a progressive cavity pump or positive displacement motor, the method comprising: forming a helical hose; inserting the helical hose into a stator tube; and filling a gap between an outer diameter of the helical hose and an inner diameter of the stator tube with a material.

14. The method of claim 13, wherein the material is a thermoset resin or plastic.

15. The method of claim 14, further comprising curing or vulcanizing the thermoset resin or plastic to solidify and bond the material to the helical hose.

16. The method of claim 13, wherein the helical hose is rubber.

17. The method of claim 13, wherein forming the helical hose comprises the method of claim 1.

18. The method of claim 13, wherein forming the helical hose comprises forming the helical hose about a mandrel, and the method further comprises removing the mandrel from the helical hose.

19. The method of claim 13, wherein forming the helical hose comprises extruding an elastomer about a mandrel using a crosshead assembly with a die plate while kinematically correlating relative axial and rotational movement between the mandrel and the die plate.

20. The method of claim 19, wherein kinematically correlating relative axial and rotational movement between the mandrel and the die plate comprises causing relative axial movement between the mandrel and the die plate a distance equal to one pitch of the mandrel while causing one revolution of relative rotational movement between the mandrel and the die plate.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0011] Certain embodiments, features, aspects, and advantages of the disclosure will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It should be understood that the accompanying figures illustrate the various implementations described herein and are not meant to limit the scope of various technologies described herein.

[0012] FIG. 1 illustrates an example PCP system.

[0013] FIG. 2 shows a transverse cross-section of a cPCP stator.

[0014] FIG. 3 shows a perspective 3D view of a portion of a rubbing lining of the cPCP stator.

[0015] FIG. 4 shows various aspects of a crosshead over mandrel extrusion technique.

[0016] FIG. 5A shows a partial longitudinal cross-section of a helical rubber hose formed on or about a helical mandrel.

[0017] FIG. 5B shows a partial perspective 3D view of the rubber hose and mandrel of FIG. 5A.

[0018] FIG. 6 shows an example technique for forming a helical rubber hose.

[0019] FIG. 7 shows another example technique for forming a helical rubber hose.

[0020] FIG. 8 shows an example ball transfer bearing.

DETAILED DESCRIPTION

[0021] In the following description, numerous details are set forth to provide an understanding of some embodiments of the present disclosure. It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various embodiments. Specific examples of components and arrangements are described below to simplify the disclosure. These are, of course, merely examples and are not intended to be limiting. However, it will be understood by those of ordinary skill in the art that the system and/or methodology may be practiced without these details and that numerous variations or modifications from the described embodiments are possible. This description is not to be taken in a limiting sense, but rather made merely for the purpose of describing general principles of the implementations. The scope of the described implementations should be ascertained with reference to the issued claims.

[0022] As used herein, the terms “connect”, “connection”, “connected”, “in connection with”, and “connecting” are used to mean “in direct connection with” or “in connection with via one or more elements”; and the term “set” is used to mean “one element” or “more than one element”. Further, the terms “couple”, “coupling”, “coupled”, “coupled together”, and “coupled with” are used to mean “directly coupled together” or “coupled together via one or more elements”. As used herein, the terms “up” and “down”; “upper” and “lower”; “top” and “bottom”; and other like terms indicating relative positions to a given point or element are utilized to more clearly describe some elements. Commonly, these terms relate to a reference point at the surface from which drilling operations are initiated as being the top point and the total depth being the lowest point, wherein the well (e.g., wellbore, borehole) is vertical, horizontal or slanted relative to the surface.

[0023] FIG. 1 illustrates an example PCP system 100. As shown, the PCP system 100 includes a pump (i.e., a PCP) 110, one or more sucker rods 120, and an electric motor 130. The PCP 110 includes a single helical rotor 112 that rotates inside a double helical stator 114 in use. The illustrated configuration includes a 1-lobe rotor and 2-lobe stator. However, other configurations are also possible, such as a 2-lobe rotor with 3-lobe stator or a 3-lobe rotor with a 4-lobe stator. During operation, fluid 106 is transferred from an intake at the bottom of the pump 110 to a discharge or outlet at the top of the pump 110 through a series of cavities 116 that form between the rotor 112 and stator 114 as the rotor 112 rotates within the stator 114.

[0024] In use, the PCP 110 is disposed downhole in a borehole lined with a well casing 102. The electric motor 130 is disposed at the surface of the well. The sucker rods 120 extend between and connect (e.g., physically and/or operatively connect) surface components of the system 100, such as the electric motor 130, and downhole components of the system 100, such as the PCP 110. Each sucker rod 120 can be threaded at one or both ends to enable threaded connections with other components, such as the PCP 110 (i.e., the rotor 112), surface component(s), and/or other sucker rods 120. In use, the motor 130 rotates or causes rotation of the sucker rods 120, which in turn rotate or cause rotation of the rotor 112. Production tubing 104 can be disposed in the borehole to convey pumped fluids 106 discharged from the outlet of the PCP 110 to the surface. In the illustrated configuration, the tubing 104 is disposed around or surrounds the sucker rods 120.

[0025] The present disclosure relates to extrusion techniques or technology. In some configurations, the present disclosure relates to manufacturing methods for producing a composite PCP stator, or cPCP stator. FIG. 2 shows a transverse cross-section of an example cPCP stator. As shown, the cPCP stator has an inner lining or layer 210, which may be formed of an elastomer such as a rubber, an outer tube 220, which may be metal, and a middle layer 230, which can be or include thermoset resin or plastic, between (e.g., radially between) the rubber lining 210 and the metal tube 220.

[0026] A method or process for manufacturing a cPCP stator can include: fabricating a hose (e.g., an elastomer hose, such as a rubber hose) that will become an inner lining 210 of the stator; placing the rubber hose over, around, or about a mandrel 350, e.g., a metallic mandrel, (or inserting the mandrel 350 in the hollow rubber hose); inserting the mandrel 350 with rubber hose into a metal stator tube; filling a gap between the rubber hose OD (outer diameter) and stator tube ID (inner diameter), for example, with thermoset resin or plastic; and curing (e.g., vulcanizing) the thermoset resin or plastic (or other material used to fill the gap) to solidify and bond the material to the rubber hose.

[0027] The present disclosure provides methods for fabricating a helically shaped hose, e.g., an elastomer hose such as a rubber hose, in an accurate and controllable manner. In some configurations, a crosshead extrusion technique allows a material, such as an elastomer or rubber, to be formed into a desired helical shape. The rubber can remain on the mandrel 350 during that process. The technique utilizes an axially movable mandrel 350 and involves kinematically matching rotation between the mandrel 350 OD (outer diameter), which forms the rubber hose 210 ID (inner diameter), and a die plate 360 that forms the rubber hose 210 OD. An axial movement of the mandrel 350 equivalent to a length of one pitch matches a single revolution relative to the die plate 360, which may be a rotatable or non-rotatable feature. In other words, as the mandrel 350 moves axially a distance equivalent to one pitch length, there is one revolution of relative movement between the die plate 360 and the mandrel 350.

[0028] Methods according to the present disclosure can be based on or share some features with a traditional crosshead over mandrel extrusion technique, for example as illustrated in FIG. 4. A material such as an elastomer (e.g., a synthetic or natural rubber) is preheated and melted in a high-pressure extrusion machine 370 (or extruder). The rubber melt is fed into a crosshead assembly 372, which may be coupled to or placed adjacent the extruder 370, e.g., coupled to or placed adjacent an outlet of the extruder 370.

[0029] Crosshead extrusion processes are often used to make cylindrical rubber rollers. A rigid mandrel (often made of metal) is pushed through the crosshead assembly 372. To form a cylindrical rubber roller, the mandrel is cylindrical. In the crosshead assembly 372, uncured rubber envelops the mandrel OD and is readied for extrusion. The mandrel is moved axially through a hollow die plate mounted on or at the crosshead assembly 372 outlet. Simultaneously, rubber melt is pushed through a gap between the mandrel OD and an ID of an outlet of the die plate. This process forms a uniform rubber layer enveloping the mandrel OD.

[0030] According to the present disclosure, this crosshead over mandrel extrusion technique is modified to form a helical rubber hose 210, for example as shown in FIG. 3. In techniques according to the present disclosure, the mandrel 350 is helical, as shown in FIGS. 5A-7. The mandrel 350 can thought of as or similar to a multi-lead or multi-start screw, in other words, having two or more starts. The example hose of FIG. 3 has two starts. However, more than two starts are also possible. One mandrel pitch (or lead) corresponds to, equals, or approximately or substantially equals one pitch of the helical rubber hose 210 formed by techniques according to the present disclosure, as shown in FIGS. 5A and 5B. In other words, if the mandrel 350 was threaded with an imaginary nut, the pitch could be defined as the axial distance the nut travels along the mandrel 350 with or during one revolution of the nut.

[0031] Techniques according to the present disclosure introduce a rotational degree of freedom to the mandrel 350 and/or the die plate 360 during the extrusion process. Techniques according to the present disclosure also include a kinematic link between axial movement of the mandrel 350 and relative rotational movement between the mandrel 350 and the die plate 360 (e.g., (1) rotation of the mandrel 350 relative to a non-rotatable die plate 360 or (2) rotation of the die plate 360 relative to a non-rotatable mandrel 350. In the case of (1) (rotation of the mandrel 350 relative to a non-rotatable die plate 360, for example as shown in FIG. 6), the mandrel 350 is rotated about its longitudinal axis 360° as the mandrel 350 travels (e.g., through the crosshead assembly 372 and die plate 360) an axial distance equal to one mandrel pitch. In the case of (2) (rotation of the die plate 360 relative to a non-rotatable mandrel 350, for example as shown in FIG. 7), the die plate 360 is rotated about its longitudinal axis (an axis extending through the die outlet port and along which the mandrel 350 extends and travels as the mandrel 350 moves through the crosshead assembly 372 and die plate 360 during extrusion) 360° as the mandrel 350 travels an axial distance equal to one mandrel pitch.

[0032] In techniques in which the mandrel 350 rotates relative to a stationary die plate 360, for example as shown in FIG. 6, guiding pins 362 can be included and used to provide or ensure the proper kinematic match or interaction between the mandrel 350 and die plate 360. The guiding pins 362 are anchored to a stationary unit or piece of equipment, for example, to the extruder 370 or to a separate assembly mounted to a floor. In the illustrated configuration, two guiding pins 362 are included. Tips of the pins 362 are in constant contact with the mandrel's flanks during extrusion, inducing friction forces on the mandrel 350 and causing motion of the mandrel 350. If the mandrel 350 has a relatively shallow pitch, the primary load(s) applied to the mandrel 350 during extrusion should move the mandrel 350 axially through the crosshead assembly 372. In such cases, the pins 362 can cause rotational motion of the mandrel 350. If the mandrel 350 has a relatively steep pitch, the primary load(s) applied to the mandrel 350 during extrusion should rotate the mandrel 350. In such cases, the pins 362 can cause the mandrel 350 to travel axially. In some configurations, the tips of the pins 362 can be designed as ball transfer bearings 364, for example as shown in FIG. 8. In some configurations, the pins 362 can be replaced with a customized roller aligned with the mandrel's helix.

[0033] In techniques in which the die plate 360 rotates relative to a non-rotatable mandrel 350, for example as shown in FIG. 7, the mandrel 350 is non-rotatable and is pushed or pulled axially through the crosshead assembly 372. The die plate 360 is mounted on a rotatable die at or on an outlet or output of the crosshead assembly 372. The RPM of the die is correlated to the axial velocity of the mandrel 350 such that one revolution of the die corresponds to an axial movement of the mandrel 350 equal to one pitch.

[0034] Other variations of techniques, for example, other kinematic schemes, according to the present disclosure are also possible. For example, the mandrel 350 can be axially fixed and non-rotatable, while the die plate 360 is axially moveable and rotatable, such that the die plate 360 rotates and moves axially relative to the stationary mandrel 350. As another example, the mandrel 350 can be rotatable, but axially fixed, while the die plate 360 is axially moveable but non-rotatable, such that the mandrel 350 rotates within the die plate 360 as the die plate 360 moves axially along or relative to the axially fixed mandrel 350. As another example, both the mandrel 350 and die plate 360 can be rotatable and axially moveable.

[0035] Extrusion or manufacturing techniques according to the present disclosure can also or alternatively be used to manufacture articles other than PCP stators. For example, techniques according to the present disclosure can be used to manufacture stators for positive displacement motors (PDM), for example to be used for drilling operations. As another example, techniques according to the present disclosure can be used, or adapted to be used, to manufacture rotors (for example, PCP and/or PDM rotors). Extrusion techniques according to the present disclosure can be used to cover such rotors with rubber or plastic layers. In general, techniques according to the present disclosure can be used to manufacture helical tubes, which may be disposed within or about other components of an article.

[0036] Language of degree used herein, such as the terms “approximately,” “about,” “generally,” and “substantially” as used herein represent a value, amount, or characteristic close to the stated value, amount, or characteristic that still performs a desired function or achieves a desired result. For example, the terms “approximately,” “about,” “generally,” and “substantially” may refer to an amount that is within less than 10% of, within less than 5% of, within less than 1% of, within less than 0.1% of, and/or within less than 0.01% of the stated amount. As another example, in certain embodiments, the terms “generally parallel” and “substantially parallel” or “generally perpendicular” and “substantially perpendicular” refer to a value, amount, or characteristic that departs from exactly parallel or perpendicular, respectively, by less than or equal to 15 degrees, 10 degrees, 5 degrees, 3 degrees, 1 degree, or 0.1 degree.

[0037] Although a few embodiments of the disclosure have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims. It is also contemplated that various combinations or sub-combinations of the specific features and aspects of the embodiments described may be made and still fall within the scope of the disclosure. It should be understood that various features and aspects of the disclosed embodiments can be combined with, or substituted for, one another in order to form varying modes of the embodiments of the disclosure. Thus, it is intended that the scope of the disclosure herein should not be limited by the particular embodiments described above.