Abstract:
The present invention recites a method of fabricating a stator for a downhole motor, the method comprising the steps of providing a stator tube having an interior surface and applying a bonding agent to the interior surface of the stator tube. Additionally, a mandrel is positioned within the stator tube, the mandrel having an outer geometry that is complimentary to a desired inner geometry for the stator. Furthermore, a reinforcing material is introduced into the stator tube to fill space between the mandrel and the interior surface of the stator tube and subsequently solidified to bond the reinforcing material to the interior surface of the stator tube, The mandrel is then removed from the bonded stator tube and reinforcing material such that a stator is fabricated.

Description:
BACKGROUND OF THE INVENTION 
     Downhole motors (colloquially known as “mud motors”) are powerful generators used in drilling operations to turn a drill bit, generate electricity, and the like. As suggested by the term “mud motor,” mud motors are often powered by drilling fluid (e.g., “mud”). Such drilling fluid is also used to lubricate the drill string and to carry away cuttings and, accordingly, often contains particulate matter such as borehole cuttings that can reduce the useful life of downhole motors. Accordingly, there is a need for new approaches for cost effectively manufacturing downhole motors and downhole motor components that are cost effective and facilitate quick replacement in the field. 
     SUMMARY OF THE INVENTION 
     The present invention generally relates to a method of fabricating a stator for a downhole motor wherein the method comprises the steps of providing a stator tube having an interior surface, applying a bonding agent to the interior surface of the stator tube, positioning a mandrel within the stator tube, the mandrel having an outer geometry that is complimentary to a desired inner geometry for the stator and introducing a reinforcing material into the stator tube to fill space between the mandrel and the interior surface of the stator tube. Additionally, the reinforcing material is solidified to bond the reinforcing material to the interior surface of the stator tube and then the mandrel is removed from the bonded stator tube and reinforcing material such that a stator is fabricated. 
     In accordance with one aspect of the present invention, the the stator tube comprises a material selected from the group consisting of: iron, steel, high speed steel, carbon steel, tungsten steel, brass, and copper. 
     Additionally, the bonding agent utilized in fabricating the stator may be a single-layer bonding agent or a multiple-layer bonding agent. 
     In accordance with one aspect of the present invention, the mandrel may comprise a material selected from the group consisting of: iron, steel, high speed steel, carbon steel, tungsten steel, brass, and copper. Additionally, the mandrel may be coated with a release agent having numerous forms including a solid, semi-solid or a liquid. 
     The reinforcing material of the present invention may take numerous forms as understood by one skilled in the art. For example, the reinforcing material may be a composite. In accordance with another aspect of the present invention, the reinforcing material may be a polymer. In accordance with a further aspect of the present invention, the reinforcing material may be a thermosetting plastic or a thermoplastic. 
     As understood by one skilled in the art, the reinforcing material of one aspect of the present invention may be selected from the group consisting of: epoxy resins, polyimides, polyketones, polyetheretherketones (PEEK), phenolic resins, and polyphenylene sulfides (PPS). 
     Additionally, the reinforcing material may be in various forms including a liquid, a paste, a slurry, a power, and/or a granular form. Furthermore, the reinforcing material may be cross-linked and/or may have a high degree of crystallinity. In accordance with aspects of the present invention, when solidifying the reinforcing material to bond the reinforcing material to the interior surface of the stator tube various techniques may be utilized. These techniques may include, but are not limited to the use of heat curing, radiation curing, steam curing, and cooling. 
     The present invention further claims a stator for a downhole motor, the stator comprising a stator tube including an inner surface and a solidified reinforcing material bonded to the inner surface, the solidified reinforcing material having an inner surface defining an internal helical cavity including a plurality of internal lobes. Additionally, the present invention recites a downhole motor comprising a stator wherein said stator comprises a stator tube including an inner surface and a solidified reinforcing material bonded to the inner surface, the solidified reinforcing material having an inner surface defining an internal helical cavity including a plurality of internal lobes and a rotor received within the stator. In accordance with the present invention, the rotor may be coated with an elastomer, wherein the elastomer may comprise one or more selected from the group consisting of: rubber, natural rubber (NR), synthetic polyisoprene (IR), butyl rubber, halogenated butyl rubber, polybutadiene (BR), nitrile rubber, nitrile butadiene rubber (NBR), hydrogenated nitrile butadiene rubber (HNBR), carboxylated hydrogenated nitrile butadiene rubber (XHNBR), chloroprene rubber (CR) Fluorocarbon rubber (FKM), and Perfluoroelastomers (FFKM) 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       For a fuller understanding of the nature and desired objects of the present invention, reference is made to the following detailed description taken in conjunction with the accompanying drawing figures wherein like reference characters denote corresponding parts throughout the several views and wherein: 
         FIG. 1  illustrates a wellsite system in which the present invention can be employed; 
         FIGS. 2A-2C  illustrate a Moineau-type positive displacement downhole motor having a 1:2 lobe profile according to one embodiment of the invention; 
         FIGS. 3A-3F  illustrate a Moineau-type positive displacement downhole motor having a 3:4 lobe profile according to one embodiment of the invention; 
       FIGS.  4  and  5 A- 5 D illustrate a method of producing a stator according to one embodiment of the invention; 
       FIGS.  6  and  7 A- 7 D illustrate a method of producing a stator insert according to one embodiment of invention; 
         FIG. 8  illustrates a stator tube and a stator insert having a splined geometry according to one embodiment of the invention; and 
         FIG. 9  illustrates an alternative method of producing a stator according to one embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the invention provide stators and stator inserts for downhole motors, methods for fabricating the same, and downhole motors incorporating the same. Various embodiments of the invention can be used in wellsite systems. 
     Wellsite System 
       FIG. 1  illustrates a wellsite system in which the present invention can be employed. The wellsite can be onshore or offshore. In this exemplary system, a borehole  11  is formed in subsurface formations by rotary drilling in a manner that is well known. Embodiments of the invention can also use directional drilling, as will be described hereinafter. 
     A drill string  12  is suspended within the borehole  11  and has a bottom hole assembly (BHA)  100  which includes a drill bit  105  at its lower end. The surface system includes platform and derrick assembly  10  positioned over the borehole  11 , the assembly  10  including a rotary table  16 , kelly  17 , hook  18  and rotary swivel  19 . The drill string  12  is rotated by the rotary table  16 , energized by means not shown, which engages the kelly  17  at the upper end of the drill string. The drill string  12  is suspended from a hook  18 , attached to a traveling block (also not shown), through the kelly  17  and a rotary swivel  19  which permits rotation of the drill string relative to the hook. As is well known, a top drive system could alternatively be used. 
     In the example of this embodiment, the surface system further includes drilling fluid or mud  26  stored in a pit  27  formed at the well site. A pump  29  delivers the drilling fluid  26  to the interior of the drill string  12  via a port in the swivel  19 , causing the drilling fluid to flow downwardly through the drill string  12  as indicated by the directional arrow  8 . The drilling fluid exits the drill string  12  via ports in the drill bit  105 , and then circulates upwardly through the annulus region between the outside of the drill string and the wall of the borehole, as indicated by the directional arrows  9 . In this well known manner, the drilling fluid lubricates the drill bit  105  and carries formation cuttings up to the surface as it is returned to the pit  27  for recirculation. 
     The bottom hole assembly  100  of the illustrated embodiment includes a logging-while-drilling (LWD) module  120 , a measuring-while-drilling (MWD) module  130 , a roto-steerable system and motor, and drill bit  105 . 
     The LWD module  120  is housed in a special type of drill collar, as is known in the art, and can contain one or a plurality of known types of logging tools. It will also be understood that more than one LWD and/or MWD module can be employed, e.g. as represented at  120 A. (References, throughout, to a module at the position of  120  can alternatively mean a module at the position of  120 A as well.) The LWD module includes capabilities for measuring, processing, and storing information, as well as for communicating with the surface equipment. In the present embodiment, the LWD module includes a pressure measuring device. 
     The MWD module  130  is also housed in a special type of drill collar, as is known in the art, and can contain one or more devices for measuring characteristics of the drill string and drill bit. The MWD tool further includes an apparatus (not shown) for generating electrical power to the downhole system. This may typically include a mud turbine generator (also known as a “mud motor”) powered by the flow of the drilling fluid, it being understood that other power and/or battery systems may be employed. In the present embodiment, the MWD module includes one or more of the following types of measuring devices: a weight-on-bit measuring device, a torque measuring device, a vibration measuring device, a shock measuring device, a stick slip measuring device, a direction measuring device, and an inclination measuring device. 
     A particularly advantageous use of the system hereof is in conjunction with controlled steering or “directional drilling.” In this embodiment, a roto-steerable subsystem  150  ( FIG. 1 ) is provided. Directional drilling is the intentional deviation of the wellbore from the path it would naturally take. In other words, directional drilling is the steering of the drill string so that it travels in a desired direction. 
     Directional drilling is, for example, advantageous in offshore drilling because it enables many wells to be drilled from a single platform. Directional drilling also enables horizontal drilling through a reservoir. Horizontal drilling enables a longer length of the wellbore to traverse the reservoir, which increases the production rate from the well. 
     A directional drilling system may also be used in vertical drilling operation as well. Often the drill bit will veer off of a planned drilling trajectory because of the unpredictable nature of the formations being penetrated or the varying forces that the drill bit experiences. When such a deviation occurs, a directional drilling system may be used to put the drill bit back on course. 
     A known method of directional drilling includes the use of a rotary steerable system (“RSS”). In an RSS, the drill string is rotated from the surface, and downhole devices cause the drill bit to drill in the desired direction. Rotating the drill string greatly reduces the occurrences of the drill string getting hung up or stuck during drilling. Rotary steerable drilling systems for drilling deviated boreholes into the earth may be generally classified as either “point-the-bit” systems or “push-the-bit” systems. 
     In the point-the-bit system, the axis of rotation of the drill bit is deviated from the local axis of the bottom hole assembly in the general direction of the new hole. The hole is propagated in accordance with the customary three-point geometry defined by upper and lower stabilizer touch points and the drill bit. The angle of deviation of the drill bit axis coupled with a finite distance between the drill bit and lower stabilizer results in the non-collinear condition required for a curve to be generated. There are many ways in which this may be achieved including a fixed bend at a point in the bottom hole assembly close to the lower stabilizer or a flexure of the drill bit drive shaft distributed between the upper and lower stabilizer. In its idealized form, the drill bit is not required to cut sideways because the bit axis is continually rotated in the direction of the curved hole. Examples of point-the-bit type rotary steerable systems and how they operate are described in U.S. Pat. Nos. 6,394,193; 6,364,034; 6,244,361; 6,158,529; 6,092,610; and 5,113,953; and U.S. Patent Application Publication Nos. 2002/0011359 and 2001/0052428. 
     In the push-the-bit rotary steerable system there is usually no specially identified mechanism to deviate the bit axis from the local bottom hole assembly axis; instead, the requisite non-collinear condition is achieved by causing either or both of the upper or lower stabilizers to apply an eccentric force or displacement in a direction that is preferentially orientated with respect to the direction of hole propagation. Again, there are many ways in which this may be achieved, including non-rotating (with respect to the hole) eccentric stabilizers (displacement based approaches) and eccentric actuators that apply force to the drill bit in the desired steering direction. Again, steering is achieved by creating non co-linearity between the drill bit and at least two other touch points. In its idealized form, the drill bit is required to cut side ways in order to generate a curved hole. Examples of push-the-bit type rotary steerable systems and how they operate are described in U.S. Pat. Nos. 6,089,332; 5,971,085; 5,803,185; 5,778,992; 5,706,905; 5,695,015; 5,685,379; 5,673,763; 5,603,385; 5,582,259; 5,553,679; 5,553,678; 5,520,255; and 5,265,682. 
     Downhole Motors 
     Referring now to  FIGS. 2A-2C , a Moineau-type positive displacement downhole motor  200  is depicted. Downhole motor  200  includes a rotor  202  received within a stator  204 . Rotor  202  can be a helical member fabricated from a rigid material such metals, resins, composites, and the like. Stator  204  can have an oblong, helical shape and be fabricated from elastomers that allow for the rotor  202  to rotate within the stator  204  as fluid flows between chambers  206  formed between the rotor  202  and the stator  204 . In some embodiments, stator  204  is received within stator tube  208  that can partially limit the deformation of the stator  204  as the rotor  202  rotates and can protect the exterior of stator  204  from wear. 
     Downhole motors  200  can be fabricated in a variety of configurations. Generally, when viewed as a latitudinal cross-section as depicted in  FIG. 1B , rotor  202  has n r  lobes and stator  204  has n s  lobes, wherein n s =n r +1. For example,  FIGS. 2A-2C  depict a downhole motor  200  with a 1:2 lobe profile, wherein rotor  202  has one lobe  210  and stator  204  has two lobes  212 .  FIGS. 3A-3F  depict a downhole motor  300  with a 3:4 lobe profile, wherein rotor  302  has three lobes  310  and stator  304  has four lobes  312 . Other exemplary lobe profiles include 5:6, 7:8, 9:10, and the like. 
     The rotation of rotor  302  is depicted in  FIGS. 3C-3F . 
     Downhole motors are further described in a number of publications such as U.S. Pat. Nos. 7,442,019; 7,396,220; 7,192,260; 7,093,401; 6,827,160; 6,543,554; 6,543,132; 6,527,512; 6,173,794; 5,911,284; 5,221,197; 5,135,059; 4,909,337; 4,646,856; and 2,464,011; U.S. Patent Application Publication Nos. 2009/0095528; 2008/0190669; and 2002/0122722; and William C. Lyons et al.,  Air  &amp;  Gas Drilling Manual: Applications for Oil  &amp;  Gas Recovery Wells  &amp;  Geothermal Fluids Recovery Wells  §11.2 (3d ed. 2009); G. Robello Samuel,  Downhole Drilling Tools: Theory  &amp;  Practice for Engineers  &amp;  Students  288-333 (2007);  Standard Handbook of Petroleum  &amp;  Natural Gas Engineering  4-276-4-299 (William C. Lyons &amp; Gary J. Plisga eds. 2006); and 1 Yakov A. Gelfgat et al.,  Advanced Drilling Solutions: Lessons from the FSU  154-72 (2003). 
     Methods of Producing Stators 
     Referring now to  FIG. 4  in the context of  FIGS. 5A-5D , a method  400  of producing a stator  500  is provided. Lateral slices without depth are depicted in  FIGS. 5A-5D  for ease of illustration and comprehension. 
     In step S 402 , a stator tube  502  is provided. As discussed herein, stator tube  502  can be a rigid material. For example, stator tube  502  can be fabricated from iron, steel, high speed steel, carbon steel, tungsten steel, brass, copper, and the like. 
     Optionally, in step S 404 , the interior surface of the stator tube  502  is prepared. In some embodiments, a worn stator insert is removed from the stator tube  502 . In other embodiments, the inner surface of the stator tube  502  is cleaned, degreased, sand blasted, shot blasted, and the like. 
     In step S 406 , a bonding agent  504  is applied to the interior surface of the stator tube  502 . The bonding agent  504  can be a single-layer bonding agent or a multiple-layer bonding agent. One skilled in the art will recognize that numerous suitable bonding agents existing, including but not limited to epoxy resin, phenolic resin, polyester resin or any number of suitable alternatives. 
     In step S 408 , a mandrel  506  is positioned within the stator tube  502 . Preferably the mandrel  506  is centered within the stator tube  502  such that the longitudinal axis of the mandrel  506  is coaxial with the longitudinal axis of the stator tube  502 . The mandrel  506  has an outer geometry that is complimentary to a desired inner geometry of the stator  500  to be produced. For example, mandrel  506  can have an oblong, helical shape and have n s  lobes (e.g., four lobes in the embodiment depicted in  FIG. 5A ). 
     In some embodiments, the mandrel  506  is coated with a release agent (not depicted) to promote removal of the mandrel  506 . Additionally or alternatively, one or more resilient layers  508  can be applied to the mandrel  506  (e.g., over the release agent) to strengthen the stator  500 . For the purpose of clarity, the term reinforcing/resilient layer will be used interchangeably within the present specification. For example, a resilient layer  508  can be formed from an elastomers such as rubber, natural rubber (NR), synthetic polyisoprene (IR), butyl rubber, halogenated butyl rubber, polybutadiene (BR), nitrile rubber, nitrile butadiene rubber (NBR), hydrogenated nitrile butadiene rubber (HNBR), carboxylated hydrogenated nitrile butadiene rubber (XHNBR), chloroprene rubber (CR), and the like. In still another embodiment, the resilient layer  508  can be reinforced with a fiber or textile such as poly-aramid synthetic fibers such as KEVLAR® fiber available from E.I. Du Pont de Nemours and Company of Wilmington, Del. 
     In some embodiments, a bonding agent (not depicted) is applied to the resilient layer  508 . The bonding agent can be a single-layer bonding agent or a multiple-layer bonding agent. 
     In step S 410 , a reinforcing material  510  is introduced into the stator tube  502 . Examples of suitable reinforcing materials  510  are discussed herein. 
     In step S 412 , the reinforcing material  510  is solidified as discussed herein. 
     In step S 414 , the mandrel  506  is removed from the solidified stator  500 . 
     Methods of Producing Stator Inserts 
     Referring now to  FIG. 6  in the context of  FIGS. 7A-7D , a method  600  of producing stator inserts is provided. Lateral slices without depth are depicted in  FIGS. 7A-7D  for ease of illustration and comprehension. 
     In step S 602 , a mandrel  702  is provided. The mandrel  702  has an outer geometry that is complimentary to a desired inner geometry of the stator insert to be produced. For example, mandrel  702  can have an oblong, helical shape and have n s  lobes (e.g., four lobes in the embodiment depicted in  FIG. 7A ). 
     In step S 604 , a flexible sleeve  704  is applied over mandrel  702 . The flexible sleeve  704  can be an elastomer. For example, the elastomers can be rubber, natural rubber (NR), synthetic polyisoprene (IR), butyl rubber, halogenated butyl rubber, polybutadiene (BR), nitrile rubber, nitrile butadiene rubber (NBR), hydrogenated nitrile butadiene rubber (HNBR), carboxylated hydrogenated nitrile butadiene rubber (XHNBR), chloroprene rubber (CR), Fluorocarbon rubber (FKM), Perfluoroelastomers (FFKM) and the like. In still another embodiment, the flexible sleeve  704  can be reinforced using a fiber or textile such as poly-aramid synthetic fibers such as KEVLAR® fiber available from E.I. Du Pont de Nemours and Company of Wilmington, Del. 
     In some embodiments, a lubricant or release agent (e.g., liquids, gels, and/or powders) are applied between the flexible sleeve  704  and mandrel  702  to facilitate insertion and removal of the mandrel  702 . Preferably, the lubricant/release layer is compatible with the mandrel  702  and the flexible sleeve  704 . One skilled in the art will recognize that this lubricant/release layer may take numerous forms, including but not limited to a permanent or semi-permanent layer having a solid or liquid form. 
     Optionally, in step S 606 , a vacuum is applied between the flexible sleeve and the mandrel to cause the flexible sleeve  704  to better conform to the geometry of the mandrel  702 . In some embodiments, a vacuum is not needed as the flexible material  704  conforms to the mandrel geometry without the need for physical manipulation. 
     In step S 608 , the assembled flexible sleeve  704  and mandrel  702  are placed within a mold  706 . Preferably the mandrel  702  is centered within the mold  706  such that the longitudinal axis of the mandrel  702  is coaxial with the longitudinal axis of the mold  706 . In some embodiments, inner geometry of the mold  706  is complimentary to the stator tube  708  into which the molded stator insert will be installed (less any allowances for adhesives  710 , expansion, contraction, and the like). For example, the stator insert can have a substantially circular outer profile and the stator tube  708  can have a substantially circular inner profile. 
     In another embodiment depicted in  FIG. 8 , the stator tube  808  can have a flexible sleeve  804 , the adhesive  710 , and a plurality of splines  812   a - 812   d ; and stator insert  814  can include a plurality of complimentary splines to provide mechanical retention of the stator insert  814  within the stator tube  808 . In accordance with an alternative embodiment, one skilled in the art will readily recognize that the inside and outside walls of the stator tube are not necessarily parallel. 
     In step S 610 , a reinforcing material  714  is introduced into the mold. Examples of suitable reinforcing materials  714  are discussed herein. 
     Optionally, a release agent and/or a lubricant can be applied to the interior surface of mold  706  prior to the introduction of the reinforcing material  714  in order to promote removal of the solidified stator insert from the mold  706 . 
     Additionally or alternatively, a bonding agent (not depicted) can be applied to the flexible sleeve  704  prior to the introduction of the reinforcing material  714  in order to promote bonding of the reinforcing material  714  with the flexible sleeve  704 . 
     In step S 612 , the reinforcing material  714  is solidified as discussed herein. 
     In step S 614 , the solidified reinforcing material  714  and the flexible sleeve  704  are removed from the mold  706 . In some embodiments, the exterior surface of the solidified stator insert is treated to promote better bonding with stator tube  708 . For example, the solidified stator insert can be cleaned, degreased, sand blasted, shot blasted, and the like. 
     In step S 616 , the mandrel  702  is optionally removed from the solidified stator insert prior to insertion of the stator into the stator tube  708  in step S 618 . In another embodiment, mandrel  702  is removed from the solidified stator insert after insertion into the stator tube  708 . 
     A variety of techniques can be used to prepare the stator tube  708  to receive the solidified stator insert. In some embodiments, a worn stator insert is removed from the stator tube  708 . In other embodiments, the inner surface of the stator tube  708  is cleaned, degreased, sand blasted, shot blasted, and the like. 
     In some embodiments, the stator insert is coupled to the inner surface of the stator tube  708 . The stator insert can be coupled to the stator tube  708  with an adhesive  710 . For example, the adhesive  710  can be applied to the outside of the stator insert and/or the inside of the stator tube  708 . Alternatively, the adhesive  710  can be flowed or injected, at pressure or under vacuum, between the stator insert and the stator tube  708  after the stator insert is inserted. A variety of adhesives  710  can be used including epoxies, poly(methyl methylacrylate), polyurethane-based adhesives, and the like. 
     Reinforcing Materials and Methods of Solidifying 
     The reinforcing materials  510 ,  714  discussed herein can be a variety of materials including composites, polymers, thermosetting plastic, thermoplastics, and the like. Exemplary polymers include epoxy resins, polyimides, polyketones, polyetheretherketones (PEEK), phenolic resins, polyphenylene sulfides (PPS), and the like. The reinforcing materials  510 ,  714  can be introduced in a variety of forms including a liquid, a paste, a slurry, a powder, a granular form, and the like. In accordance with aspects of the present invention, the reinforcing materials may include, but are not limited to numerous liquids, pastes or powders that may be solidified. In accordance with one aspect of the present invention, these may be ceramics or cements. 
     The reinforcing materials  510 ,  714  can be cross-linked. Additionally or alternatively, the reinforcing materials  510 ,  714  can have a high degree of crystallinity. 
     Solidifying of reinforcing materials  510 ,  714  may be accomplished by a variety of techniques including chemical additives, ultraviolet radiation, electron beams, heating, exposure to either a part or the full microwave spectrum, steam curing, cooling, and the like. Solidifying processes may vary between particular reinforcing materials  510 ,  714 , but can be ascertained from manufacturer&#39;s specifications and general chemistry principles. In some embodiments, the reinforcing material  510 ,  714  is solidified under pressure to promote bonding and/or increase mechanical properties with the resilient layers  508  or flexible sleeve  704 , to press the resilient layers  508  or flexible sleeve  704  against the geometry of mandrel  506 ,  702 , and to improve the mechanical properties of the reinforcing materials  510 ,  174 . For example, experiments reveal improvements of about 20% in T g , stiffness, and toughness when the reinforcing material is solidified under pressure. 
     Additional Methods of Producing Stators 
     Referring now to  FIG. 9  in the context of  FIGS. 5A-5D , a method  900  of producing a stator  500  is provided. Lateral slices without depth are depicted in  FIGS. 5A-5D  for ease of illustration and comprehension. 
     In step S 902 , a mandrel  506  is provided. The mandrel  506  can have an outer geometry that is complimentary to the desired inner geometry for the stator  500 . For example, mandrel  506  can have an oblong, helical shape and have n s  lobes (e.g., four lobes in the embodiment depicted in  FIG. 5A ). 
     Optionally, in step S 904 , the mandrel  506  can be coated with a release agent (not depicted) to promote removal of the mandrel  506  from the flexible sleeve  508 . 
     In step S 906 , a flexible sleeve  508  is applied over the mandrel  506 . The flexible sleeve  508  can be formed from an elastomers such as rubber, natural rubber (NR), synthetic polyisoprene (IR), butyl rubber, halogenated butyl rubber, polybutadiene (BR), nitrile rubber, nitrile butadiene rubber (NBR), hydrogenated nitrile butadiene rubber (HNBR), carboxylated hydrogenated nitrile butadiene rubber (XHNBR), chloroprene rubber (CR), Fluorocarbon rubber (FKM), Perfluoroelastomers (FFKM) and the like. In still another embodiment, the flexible sleeve  508  can be reinforced with a fiber or textile such as poly-aramid synthetic fibers such as KEVLAR® fiber available from E.I. Du Pont de Nemours and Company of Wilmington, Del. 
     Optionally, in step S 908 , a bonding agent (not depicted) is applied to the exterior surface of the flexible sleeve  508 . The bonding agent can be a single-layer bonding agent or a multiple-layer bonding agent. 
     In step S 910 , a stator tube  502  is provided. As discussed herein, stator tube  502  can be a rigid material. For example, stator tube  502  can be fabricated from iron, steel, high speed steel, carbon steel, tungsten steel, brass, copper, and the like. 
     Optionally, in step S 912 , the interior surface of the stator tube  502  is prepared. In some embodiments, a worn stator insert is removed from the stator tube  502 . In other embodiments, the inner surface of the stator tube  502  is cleaned, degreased, sand blasted, shot blasted, and the like. 
     In step S 914 , a bonding agent  504  is applied to the interior surface of the stator tube  502 . The bonding agent  504  can be a single-layer bonding agent or a multiple-layer bonding agent. In accordance with the present invention a variety of Bonding agents may be use, including but not limited to Hunstman CW47/HY33 or Chemosil 310. In step S 916 , the flexible sleeve  508  and mandrel  506  is positioned within the stator tube  502 . Preferably the mandrel  506  and flexible sleeve  508  is centered within the stator tube  502  such that the longitudinal axis of the mandrel  506  is coaxial with the longitudinal axis of the stator tube  502 . 
     In step S 918 , a reinforcing material  510  is introduced to fill the space between flexible sleeve  508  and the stator tube  502 . Examples of suitable reinforcing materials  510  are discussed herein. 
     In step S 920 , the reinforcing material  510  is solidified as discussed herein. 
     Optionally, in step S 922 , the mandrel  506  is removed from the stator  500 . 
     INCORPORATION BY REFERENCE 
     All patents, published patent applications, and other references disclosed herein are hereby expressly incorporated by reference in their entireties by reference. 
     EQUIVALENTS 
     Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents of the specific embodiments of the invention described herein. Such equivalents are intended to be encompassed by the following claims.