Patent Publication Number: US-10767440-B2

Title: Wiper dart with reinforced drive element

Description:
BACKGROUND 
     In the oil and gas industry, wellbores are commonly completed by cementing wellbore liner (e.g., casing, liner, etc.) into the drilled borehole. In some cementation operations, a wiper dart (alternately referred to as a dart, a wiper plug, a cementing plug, a drill pipe dart, and a drill pipe wiping dart) is pumped downhole to hydraulically force a cement slurry through the wellbore liner and out into the open wellbore. The cement slurry exits the wellbore liner and flows into an annulus defined between the wellbore liner and the wellbore wall where it eventually cures to provide a cement sheath that secures the wellbore liner within the wellbore. 
     Wiper darts are typically pumped downhole through a work string extended into the wellbore, including multiple lengths of drill pipe or other tubulars connected end to end. Wiper darts commonly have one or more wiper elements or “cups” that flare radially outward to sealingly engage the inner diameter of the work string. The wiper elements help generate a pressure differential across the wiper dart by preventing fluid flow across the wiper dart as it is pumped downhole. Moreover, the wiper elements also serve to “wipe” the inner wall of the work string and thereby substantially remove the cement slurry from the work string. 
     Wiper darts are often required to pass through varying inner diameters as they are pumped downhole. For instance, multiple tubing sizes are commonly used within the same work string, and each tubing size can exhibit a different inner diameter. Moreover, wiper darts are also often required to pass through minimum restrictions provided by various downhole tools, such as a cement head, safety valves, a crossover tool, diverter tools, liner hangers, liner plug assemblies, and other conventional wellbore cementing tools. Accordingly, not only does a wiper dart have to effectively seal and wipe a variety of inner diameters as it is pumped downhole, it must also successfully pass through various minimum restrictions while performing these vital functions. Such small inner diameters or restrictions are collectively referred to herein as “reduced diameter restrictions.” Due to the immense amount of friction caused by the wiper elements as they pass through reduced diameter restrictions, the wiper dart can become stuck and may not reach its final destination. As can be appreciated, retrieving a stuck wiper dart can be a costly and time-consuming operation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following figures are included to illustrate certain aspects of the present disclosure, and should not be viewed as exclusive embodiments. The subject matter disclosed is capable of considerable modifications, alterations, combinations, and equivalents in form and function, without departing from the scope of this disclosure. 
         FIG. 1  is a well system that may employ the principles of the present disclosure. 
         FIG. 2  is an isometric view of an example embodiment of the wiper dart of  FIG. 1 . 
         FIG. 3  is a cross-sectional side view of the wiper dart of  FIG. 2 . 
         FIG. 4  is a cross-sectional side view of the drive element of  FIGS. 2 and 3 . 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure is related to downhole tools used in the oil and gas industry and, more particularly, to wiper darts that include a reinforced drive element designed for operation through minimum and severe restrictions in a work string or wellbore liner. 
     Embodiments of the present disclosure describe a wiper dart that includes a drive element designed to help the wiper dart traverse reduced diameter sections encountered in a work string or a wellbore liner, which may help prevent the wiper dart from becoming stuck downhole. The wiper darts described herein include one or more wiper elements disposed about a mandrel, where each wiper element comprises a wiper cup that extends radially outward and rearwardly relative to the mandrel. Unlike traditional drive elements, which fail to include any form of rigid mechanical support to prevent extrusion, inversion, or bypass, the drive elements described herein include a rigid shoe and a cup coupled to the shoe. The cup extends radially outward and rearwardly from the shoe and exhibits a maximum diameter less than or equal to a maximum diameter of the wiper elements. In some embodiments, however, the cup may alternatively exhibit a maximum diameter greater than at least one of the wiper elements. Moreover, the shoe is designed to provide at least one of axial and radial support to the cup during operation. Preventing the wiper dart from becoming stuck in the work string or other portions of a wellbore is critical for cementing operations, for example. 
       FIG. 1  is a well system  100  that may employ the principles of the present disclosure, according to one or more embodiments. As depicted, the well system  100  includes a wellbore  102  that extends through various earth strata and has a substantially vertical section  104  that transitions into a substantially horizontal section  106 . The upper portion of the vertical section  104  may have a string of casing  108  cemented therein, and the horizontal section  106  may extend through a hydrocarbon-bearing subterranean formation  110 . A liner  112  is coupled to and otherwise “hung off” the distal end of the casing  108  at a liner hanger  114  and extends downhole from the casing  108  into the horizontal section  106 . The casing  108  and the liner  112  may each be referred to herein as “wellbore liners.” 
     A float shoe  116  is coupled to the distal end of the liner  112  and allows cement and other fluids to be discharged from the liner  112  into an annulus  118  defined between the liner  112  and the inner wall of the wellbore  102 . The float shoe  116  can be equipped with one or more floats or check valve devices that permit fluid flow out of the liner  112  while simultaneously preventing fluids from re-entering the liner  112  from the annulus  118 . 
     Fluids can be supplied to the liner  112  and the annulus  118  via a work string  120  that is insertable into the liner  112  at its uphole end. In some cementing applications, a liner wiper  122  (alternately referred to as a “cement plug”) may be releasably coupled to the lower end of the work string  120 . The liner wiper  122  has a flow passage  124  that extends therethrough to facilitate fluid communication between the work string  120  and the liner  112  once the work string  120  is properly coupled to the liner  112 . 
     In an example cementing operation, a cement slurry  126  is pumped down the work string  120  and into the liner  112  after passing through the flow passage  124  of the liner wiper  122 . After circulating through the liner  112 , the cement slurry  126  is discharged into the open wellbore  102  via the float shoe  116 . To promote the progression of the cement slurry  126  through the work string  120  and the liner  112 , a wiper dart  128  can be introduced into the work string  120  and pumped downhole. The wiper dart  128  may alternately be referred to as a pump down plug or a wiper plug. Generally, a pressurized fluid is supplied on its uphole side to hydraulically propel the wiper dart  128  through the work string  120 , which displaces the cement slurry  126  into the liner  112  and the annulus  118  as the wiper dart  128  progresses through the work string  120 . 
     The wiper dart  128  is configured to prevent fluid communication across the wiper dart  128  in both the uphole and downhole directions. To accomplish this, the wiper dart  128  includes one or more wiper elements  130  (two shown) extending from a central body to sealingly engage the inner wall of the work string  120 . The wiper elements  130  may be formed from any suitable material, such as a resilient elastomeric material, and may take any shape, such as the shape of a rearwardly extending cup. The sealed engagement of the wiper elements  130  against the inner diameter of the work string  120  allows the pressurized fluid to propel the wiper dart  128  downhole while simultaneously urging the cement slurry  126  and other fluids (e.g., a spacer fluid separating the cement slurry  126  and the wiper dart  128 ) in the downhole direction. As the wiper dart  128  advances within the work string  120 , the wiper elements  130  wipe the inner diameter of the work string  120  and thereby clean the work string  120  of residue cement slurry  126 . 
     The wiper dart  128  is configured to be received by and sealingly engage the liner wiper  122 , and thereby obstruct the flow passage  124 . Once the wiper dart  128  is received by the liner wiper  122 , increasing the fluid pressure within the work string  120  releases the liner wiper  122  and allows the liner wiper  122 , together with the wiper dart  128 , to be propelled downhole into the liner  112 . The liner wiper  122  includes wiping elements  132  configured to sealingly engage the inner wall of the liner  112  and operate similar to the wiping elements  130  of the wiper dart  128 , but with respect to the liner  112 . As the liner wiper  122  and the wiper dart  128  jointly advance within the liner  112 , the wiper elements  132  wipe (clean) the inner wall of the liner  112  and the cement slurry  126  (and/or other fluids) is pushed through the liner  112  and into the annulus  118  via the float shoe  116 . 
     Upon passing through a reduced diameter downhole tool or section of the work string  120 , the wiper elements  130  will radially contract to enable the wiper dart  128  to traverse such areas. Wrinkles may form about the outer periphery of the wiper elements  130  as they radially contract, which creates leak paths across the wiper dart  128  that decrease the ability of the wiper dart  128  to generate the pressure differential required to hydraulically propel the wiper dart  128  downhole. In other cases, upon passing through a reduced diameter downhole tool or section of the work string  120 , the hydraulic pressure may force the wiper elements  130  to invert in the downhole direction (i.e., turn itself inside out), which creates much larger leak paths across the wiper dart  128  and reduces its efficiency. 
     According to embodiments of the present disclosure, the wiper dart  128  may further include a drive element  134  used to help the wiper dart  128  pass through small inner diameters or restrictions within the work string  120  or other downhole tools included in the well system  100 . Such small inner diameters or restrictions within the work string  120  or downhole tools are collectively referred to herein as “reduced diameter restrictions.” The drive element  134  may be axially spaced from the wiper elements  130  along the body of the wiper dart  128  and may exhibit a smaller diameter as compared to the wiper elements  130 . Furthermore, the geometry of the drive element  134  may be designed to withstand increased hydraulic forces required to propel the wiper dart  128  through reduced diameter restrictions. The drive element  134  may be configured to combine the differential pressure capacity and rigid mechanical support of a packer cup, for example, with the flexibility of conventional wiper elements  130 . 
     While  FIG. 1  depicts the liner  112  as being extended into the horizontal section  106  of the wellbore  102 , those skilled in the art will readily recognize that the liner  112  is equally well suited for use solely or partially in the vertical section  106  or a deviated or slanted portion between vertical section  104  and the horizontal section  106 . The use of directional terms such as above, below, upper, lower, upward, downward, left, right, uphole, downhole and the like are used in relation to the illustrative embodiments as they are depicted in the figures, the upward direction being toward the top of the corresponding figure and the downward direction being toward the bottom of the corresponding figure, the uphole direction being toward the surface of the well and the downhole direction being toward the toe of the well. 
       FIG. 2  is an isometric view of an example embodiment of the wiper dart  128  of  FIG. 1 , according to one or more embodiments. As illustrated, the wiper dart  128  includes two wiper elements  130  axially spaced from each other and referred to in  FIG. 2  as a first wiper element  130   a  and a second wiper element  130   b . While two wiper elements  130   a,b  are depicted in  FIG. 2 , it will be appreciated that more or less than two wiper elements  130   a,b  may be included in the wiper dart  128 , without departing from the scope of the disclosure. As indicated above, the wiper elements  130   a,b  may be made of, for example, a resilient elastomeric material that allows the wiper elements  130   a,b  to flex radially inward upon encountering a reduced diameter restriction. 
     The wiper dart  128  also includes a nose assembly  202 , which may include a front cup  204 , a sealing section  206 , and a coupling member  208 . The front cup  204  may be positioned at the front or leading end of the nose assembly  202  and extends radially outward from the body of the wiper dart  128 . The front cup  204  may help maintain the wiper dart  128  generally centered within the work string  112  ( FIG. 1 ) or other downhole tubular as the wiper dart  128  advances downhole. Moreover, similar to the wiper elements  130   a,b , the front cup  204  may be made of a resilient elastomeric material that allows the front cup  204  to flex when needed. 
     The sealing section  206  may be configured to be received within and sealingly engage a receiving section of a downhole tool. In some embodiments, for example, the sealing section  206  may be configured to be received within and sealingly engage the flow passage  124  ( FIG. 1 ) of the liner wiper  122  ( FIG. 1 ), but could alternatively be configured to sealingly engage the receiving section of another type of downhole tool, without departing from the scope of the disclosure. To help facilitate a sealed engagement with the downhole tool, the sealing section  206  may be coated with an elastomeric compound and/or fitted with one or more seals. Once the sealing section  206  is properly received within a corresponding receiving section of a downhole tool, fluid communication through the downhole tool may be substantially prevented. 
     The coupling member  208  is depicted in  FIG. 2  as interposing the front cup  204  and the sealing section  106 , but could alternatively be placed at other locations along the length of the nose assembly  202 , without departing from the scope of the disclosure. The coupling member  208  may be configured to couple the wiper dart  128  to a downhole tool. Securing the wiper dart  128  to a downhole tool with the coupling member  208  allows the wiper dart  128  and the corresponding downhole tool to subsequently move as a single unit. In some embodiments, for example, the coupling member  208  may be configured to engage a receiving member provided by the liner wiper  122  ( FIG. 1 ) (e.g., within the flow passage  124 ) and thereby secure the wiper dart  128  to the liner wiper  122 . 
     The coupling member  208  may comprise any self-energized device designed to engage and latch into a corresponding receiving member of a downhole tool. In the illustrated embodiment, for example, the coupling member  208  may comprise a collet-type latch ring having a plurality of axially extending collet fingers  210  that protrude radially outward. The collet fingers  210  may be configured to locate and engage a corresponding collet profile provided by the receiving member of a downhole tool. In other embodiments, however, the coupling member  208  may comprise a “C” ring or snap ring that can be attached to the nose assembly  202  by expanding the ring over the outer diameter of the nose assembly  202  to lodge in a corresponding groove. Upon locating the receiving member of a downhole tool, the ring may snap or expand into engagement therewith and thereby secure the wiper dart  128  to the downhole tool. In yet other embodiments, the coupling member  208  may comprise one or more uniquely shaped keys (not shown) configured to selectively engage a matching uniquely shaped receiving profile in the receiving member of a downhole tool. 
     The drive element  134  is also depicted in  FIG. 2  as forming part of the wiper dart  128 . In the illustrated embodiment, the drive element  134  is positioned to axially interpose the wiper elements  130   a,b  and the nose assembly  202 . In other embodiments, however, the drive element  134  may be positioned at other locations along the axial length of the wiper dart  128 , such as between the wiper elements  130   a,b  or alternatively on the opposing uphole end of the wiper elements  130   a,b , without departing from the scope of the disclosure. 
       FIG. 3  is a cross-sectional side view of the wiper dart  128  of  FIG. 2 . As illustrated, the wiper dart  128  includes an elongate mandrel  302  having a first end  304   a  and a second end  304   b  opposite the first end  304   a . The nose assembly  202  may be secured to the mandrel  302  at the second end  304   b , such as by a threaded engagement, through the use of one or more mechanical fasteners (e.g., screws, bolts, snap rings, pins, etc.), or via an interference fit. 
     As illustrated, the sealing section  206  may exhibit a seal profile configured to mate with a corresponding profile of a receiving section of a downhole tool. More specifically, the sealing section  206  may include a first portion  306   a  and a second portion  306   b , where the first portion  306   a  exhibits a larger diameter than the second portion  306   b . One or both of the first and second portions  306   a,b  may be configured to be received by the profile provided by the receiving section of the downhole tool. In at least one embodiment, the flow passage  124  ( FIG. 1 ) of the liner wiper  122  of  FIG. 1  may provide a receiving profile configured to receive and seal the first and second portions  306   a,b.    
     The sealing section  206  may also include one or more seal elements  308  (two shown) configured to sealingly engage a receiving section of a downhole tool. In the illustrated embodiment, individual seal elements  308  may be positioned on each of the first and second portions  306   a,b , but could alternatively be positioned in other arrangements (e.g., more than one seal element  308  positioned on one or both of the first and second portions  306   a,b ), without departing from the scope of the disclosure. The seal elements  308  may be made of a variety of materials including, but not limited to, an elastomeric material, a rubber, a metal, a composite, a ceramic, any derivative thereof, and any combination thereof. In some embodiments, as illustrated, the seal elements  308  may comprise O-rings or the like. In other embodiments, however, the seal elements  308  may comprise a set of v-rings or CHEVRON® packing rings, or another appropriate seal configuration (e.g., seals that are round, v-shaped, u-shaped, square, oval, t-shaped, etc.), as generally known to those skilled in the art. One or more of the seal elements  308  may alternatively comprise a molded rubber or elastomeric seal, a metal-to-metal seal (e.g., O-ring, crush ring, crevice ring, up stop piston type, down stop piston type, etc.), or any combination of the foregoing. 
     As illustrated, the first and second wiper elements  130   a,b  each include or otherwise provide a wiper cup  310   a  and  310   b , respectively, formed in a generally frustoconical shape. Each wiper cup  310   a,b  extends radially outward and rearwardly and is, therefore, open toward the trailing end of the wiper dart  128 ; e.g., toward the uphole or back end. The first and second wiper elements  130   a,b  may be axially offset from each other along the length of the mandrel  302  and secured to the mandrel  302  by various means or devices. In some embodiments, for example, one or both of the wiper elements  130   a,b  may be coupled directly to the outer surface of the mandrel  302 , such as being molded directly to the outer surface of the mandrel  302  or being secured thereto using one or more mechanical fasteners (e.g., screws, bolts, snap rings, pins, etc.), or via a shrink or interference fit. 
     In other embodiments, however, one or both of the wiper elements  130   a,b  may be molded to or otherwise coupled to an insert  312  and the insert  312  may be sized to receive and otherwise extend over the mandrel  302 . In such embodiments, the insert  312  may be secured to the mandrel  302  through a shrink fit or alternatively (or addition thereto) with a threaded nut  314  coupled to the mandrel  302  at the first end  304   a.    
     The drive element  134  may define or otherwise provide a central orifice  316  configured to receive the mandrel  302  so that the drive element  134  may be translated along the mandrel  302  until positioned at a desired location. The drive element  134  may be secured to the mandrel  302  by various means or devices. In some embodiments, for example, drive element  134  may be coupled directly to the outer surface of the mandrel  302 , such as by using one or more mechanical fasteners (e.g., screws, bolts, snap rings, pins, etc.), a threaded engagement (e.g., the central orifice  316  and the mandrel  302  may be threaded), or via a shrink or interference fit. In other embodiments, however, drive element  134  may be restrained between the wiper elements  130   a,b  (e.g., the insert  312 ) and the nose assembly  202  (e.g., the sealing section  206 ) and held in place by threading the threaded nut  314  to the mandrel  302  at the first end  304   a.    
       FIG. 4  is a cross-sectional side view of the drive element  134  of  FIGS. 2 and 3 , according to one or more embodiments. As illustrated, the drive element  134  may include a shoe  402  and a cup  404  coupled to and extending from the shoe  402 . The shoe  402  comprises a generally annular body  406 , preferably made of a millable material. Examples of suitable materials for the body  406  include, but are not limited to, a metal (e.g., aluminum, steel, brass, etc.), a plastic, a high-strength thermoplastic, a phenolic, a composite material, a glass, and any combination thereof. The central orifice  316  is defined axially through the body  406  along a longitudinal axis  407  of the drive element  134  and exhibits a diameter D 1  that is large enough to receive the mandrel  302  ( FIG. 3 ). The body  406  exhibits a diameter D 2  that is small enough to allow the drive element  134  to pass through known reduced diameter restrictions that may be present downhole, but large enough to maximize the mechanical support of the cup  404 . 
     The cup  404  may be made of a variety of pliable or flexible materials including, but not limited to, an elastomer, a thermoplastic, a thermoset, and polyurethane. Examples of suitable elastomers that may be used for the cup  404  include, for example, nitrile butadiene (NBR) which is a copolymer of acrylonitrile and butadiene, carboxylated acrylonitrile butadiene (XNBR), butyl rubber, nitrile rubber, hydrogenated nitrile butadiene rubber (HNBR—also referred to as hydrogenated acrylonitrile butadiene rubber or highly saturated nitrile), carboxylated hydrogenated acrylonitrile butadiene (XHNBR), hydrogenated carboxylated acrylonitrile butadiene (HXNBR), halogenated butyl rubbers, styrene-butadiene rubber, ethylene propylene rubber, ethylene propylene diene rubber, epichlorohydrin rubber, polyacrylic rubber, silicone rubber, fluorosilicone rubber, chloroprene rubber, polysulfide rubber, ethylene propylene (EPR), ethylene propylene diene (EPDM), tetrafluoroethylene and propylene (FEPM), fluorocarbon (FKM), perfluoroelastomer (FEKM), natural polyisoprene, synthetic polyisoprene, polybutadiene, polychloroprene, neoprene, baypren, fluoroelastomers, perfluoroelastomers, polyether block amides, chlorosulfonated polyethylene, ethylene-vinyl acetate, thermoplastic elastomers, resilin, elastin, combinations thereof, and the like. Examples of suitable thermoplastics that may be used for the cup  404  include, for example, polyphenylene sulfide (PPS), polyetheretherketones (e.g., PEEK, PEK and PEKK), and polytetrafluoroethylene (PTFE). Examples of suitable thermosets that may be used for the cup  404  include, for example, epoxies and phenolics. 
     The cup  404  exhibits a generally frustoconical shape and provides a first or “leading” end  408   a  and a second or “trailing” end  408   b  opposite the leading end  408   a . The cup  404  further provides an inner cup surface  410   a  and an outer cup surface  410   b , where the inner cup surface generally defines the interior of the cup  404  and the outer cup surface  410   b  defines the exterior of the cup  404 . The cup  404  is coupled to the shoe  406  at the leading end  408   a  and extends radially outward and rearwardly therefrom toward the trailing end  408   b . Accordingly, similar to the wiper elements  130   a,b  ( FIG. 3 ), the drive element  134  generally opens toward the trailing end  408   b.    
     At least a portion of the leading end  408   a  may be received within a trough  410  defined in the shoe  406  and bonded thereto via one or more bonding techniques. In some embodiments, for instance, the trough  410  may be coated with a bonding agent and the shoe  406  may be subsequently placed in an injection-molding machine where the cup  404  is molded to the shoe  406 . As the material of the cup  404  cures, the bonding agent simultaneously cures to provide a bonded interface between the material of the shoe  406  and the material of the cup  404 . 
     In some embodiments, as illustrated, the outer cup surface  410   b  may be defined by a reinforced section  412   a  and an exposed section  412   b . The reinforced section  412   a  may be configured to provide structural reinforcement to the cup  404  to enable the drive element  134  to assume and resist axial and radial loading on the cup  404 . To accomplish this, the reinforced section  412   a  may be engaged against an end wall  414  provided by the shoe  406 . The reinforced section  412   a  may or may not be bonded to the end wall  414 . 
     The end wall  414  extends radially from the trough  410  at an angle  416  offset from the longitudinal axis  407 . In some embodiments, the angle  416  may be 90° (i.e., a vertical end wall  414 ). In other embodiments, however, and to allow the end wall  414  to provide an amount of radial support to the cup  404 , the angle  416  may range between about 60° and about 75° offset from the longitudinal axis  407 . In such embodiments, the end wall  414  applies a normal force on the cup  404 , which helps prevent the cup  404  from expanding radially outward during operation. The angle  416 , however, may alternatively be provided at any angle ranging between 1° and 90°, without departing from the scope of the disclosure. As will be appreciated, with an angled end wall  414 , the shoe  402  helps reduce flexibility of the cup  404  so that the drive element  134  can achieve the pressure differential required to propel the wiper dart  128  ( FIGS. 2-3 ) through the reduced diameter restrictions. 
     The exposed section  412   b  transitions from the reinforced section  412   a  and extends at an angle  418  offset from the longitudinal axis  407 . In some embodiments, the angles  416 ,  418  may be the same. In other embodiments, however, the angles  416 ,  418  may be dissimilar. The angle  418  may range between about 10° and about 45°, but is preferably less than 30° and greater than 0°. 
     The angle  418  of the outer cup surface  410   b  defines the angle of impingement for the cup  404  as the wiper dart  128  ( FIGS. 2-3 ) moves downhole. The angle  418  may be designed such that a maximum outer diameter D 3  of the drive element  134  is less than or equal to the maximum outer diameter of any of the wiper elements  130   a,b  ( FIGS. 2-3 ). Accordingly, the angle of impingement for the drive element  134  may be less than the respective angles of impingement of the wiper elements  130   a,b . As will be appreciated, a lower angle  418  will allow the wiper dart  128  ( FIGS. 2-3 ) to more easily pass through the reduced diameter restrictions. Moreover, a lower angle  418  will also make the cup  404  less susceptible to inverting, which translates into providing the drive element  134  with a higher differential pressure capability during operation. 
     It should be noted, however, that embodiments are also contemplated herein where the maximum outer diameter D 3  of the drive element  134  is greater than at least one of the wiper elements  130   a,b  ( FIGS. 2-3 ), without departing from the scope of the disclosure. In such embodiments, the structural support of the shoe  402  still serves its purpose in reducing the flexibility of the cup  404 , which enables the drive element  134  to achieve the pressure differential required to propel the wiper dart  128  ( FIGS. 2-3 ) through the reduced diameter restrictions. 
     The inner cup surface  410   a  extends at an angle  420  offset from the longitudinal axis  407 . In some embodiments, the angles  418 ,  420  may be the same. In other embodiments, however, the angles  418 ,  420  may be dissimilar. The angle  420  may range between about 10° and about 45°, but is preferably less than 30° and greater than 0°. In at least one embodiment, the angle  420  of the inner cup surface  410   a  may be greater than the angle  418  of the outer cup surface  410   b . This results in a more firm cup  404  that tapers to a thinner cup  404  dimension from the leading end  408   a  toward the trailing end  408   b.    
     To facilitate a better understanding of the present disclosure, the following example of a representative embodiment is given. In no way should the following example be read to limit or define the scope of the disclosure. 
     The above-described wiper dart  128  may be introduced into the work string  120  and conveyed downhole. The drive element  134  may be specifically designed for the minimum and most severe restrictions in the work string  120 . Commonly, multiple pipe (tubular) sizes are used within the same work string. Consequently, the work string  120  in this example includes one or more 6⅝″ pipes, one or more 5½″ pipes, and one or more 5″ pipes. There are typically two diameters per pipe size due to the internal upset of each connection and, therefore, these pipe sizes may exhibit inner diameters of 6.065″, 5.187″, 4.670″, 3.500″, 4.276″, and 3.687″. 
     Not only does the wiper dart  128  have to effectively seal and wipe each of these minimum diameters, it must also successfully pass through the minimum restriction of various downhole tools, such as a cement head, safety valves, a crossover tool, diverter tools, liner hangers, liner plug assemblies, and other conventional wellbore cementing tools. The minimum restrictions of such downhole tools can be less than 2″ in some cases. 
     In the present example, the diameter D 2  ( FIG. 4 ) of the body  406  ( FIG. 4 ) of the shoe  402  ( FIG. 4 ) may be 2.220″. As a result, the minimum restriction for which the wiper dart  128  is designed is 2.250″ due to the hard shoulder of the shoe  402 . Testing undertaken by the inventors has showed that the drive element  134  is able to withstand more than 1,000 psi in a 2.50 inner diameter reduced diameter restriction. This is possible due, in part, to the angle  418  ( FIG. 4 ) of the outer cup surface  410   b  ( FIG. 4 ), which was about 20°, and the rigid mechanical support of the shoe  402  at the end wall  414  ( FIG. 4 ). As will be appreciated, a shallow angle  418  may prove advantageous in leveraging trigonometric principles (i.e., the shallower the angle  418  relative to the longitudinal axis  407 , the ratio of applied pressure directed radially will increase), which results in a greater effective radial seal. The greater effective radial seal may enable an increased axial force on the effective piston diameter in order to overcome drag that can result from interference between the outer diameter of the wiper elements  130   a,b  and the inner diameter of the restriction. 
     Accordingly, the drive element  134  may prove advantageous in combining the differential pressure capacity and rigid mechanical support of a packer cup, for example, with the flexibility of conventional wiper elements  130   a,b . Whereas conventional wiper elements  130   a,b  exhibit a 50-100 psi differential pressure capacity, the presently disclosed embodiments of the drive element  134  may exhibit a differential pressure capacity of 1000 psi or more. 
     Embodiments disclosed herein include: 
     A. A wiper dart that includes one or more wiper elements disposed about a mandrel, each wiper element comprising a wiper cup that extends radially outward and rearwardly relative to the mandrel, a nose assembly coupled to the mandrel, and a drive element disposed about the mandrel and including a shoe and a cup coupled to the shoe, wherein the cup extends radially outward and rearwardly from the shoe and exhibits a maximum diameter less than or equal to a maximum diameter of the one or more wiper elements, and wherein the shoe provides at least one of axial and radial support to the cup. 
     B. A well system that includes a work string extended within a wellbore and coupled to a wellbore liner, and a wiper dart conveyed into the work string to hydraulically force a fluid through the work string and into the wellbore liner, the wiper dart including one or more wiper elements disposed about a mandrel and each comprising a wiper cup that extends radially outward and rearwardly relative to the mandrel to sealingly engage an inner wall of the work string, a nose assembly coupled to the mandrel, and a drive element disposed about the mandrel and including a shoe and a cup coupled to the shoe, wherein the cup extends radially outward and rearwardly from the shoe and exhibits a maximum diameter less than or equal to a maximum diameter of the one or more wiper elements, and wherein the shoe provides at least one of axial and radial support to the cup. 
     C. A method that includes pumping a fluid into a work string extended within a wellbore and coupled to a wellbore liner, pumping a wiper dart into the work string, the wiper dart including one or more wiper elements disposed about a mandrel, a nose assembly coupled to the mandrel, and a drive element disposed about the mandrel and including a shoe and a cup coupled to the shoe, wherein the cup exhibits a maximum diameter less than or equal to a maximum diameter of the one or more wiper elements, engaging an inner wall of the work string with the one or more sealing elements as the wiper dart advances downhole and thereby hydraulically forcing the fluid into the wellbore liner, propelling the wiper dart through a reduced diameter section defined in the work string with the drive element, and providing at least one of axial and radial support to the cup with the shoe as the wiper drive element propels the wiper dart through the reduced diameter section. 
     Each of embodiments A, B, and C may have one or more of the following additional elements in any combination: Element 1: wherein the drive element axially interposes the one or more wiper elements and the nose assembly. Element 2: further comprising a central orifice defined axially through the shoe to receive the mandrel. Element 3: wherein the cup comprises a flexible material selected from the group consisting of an elastomer, a thermoplastic, a thermoset, polyurethane, and any combination thereof. Element 4: wherein the shoe comprises a material selected from the group consisting of a metal, a plastic, a high-strength thermoplastic, a phenolic, a composite material, a glass, and any combination thereof. Element 5: wherein the shoe defines a trough and the cup is bonded to the shoe at the trough. Element 6: wherein the cup provides an inner cup surface and an outer cup surface and wherein the outer cup surface provides a reinforced section that engages an end wall defined by the shoe. Element 7: wherein the end wall extends at an angle offset from a longitudinal axis of the drive element and less than 90° to provide radial support to the cup. Element 8: wherein the cup provides an inner cup surface that extends at a first angle relative to a longitudinal axis of the drive element and an outer cup surface that extends at a second angle relative to the longitudinal axis and dissimilar to the first angle. 
     Element 9: wherein a portion of the wellbore is lined with casing and the wellbore liner comprises a liner coupled to and extending from the casing. Element 10: further comprising a downhole tool releasably coupled to a lower end of the work string to receive the wiper dart. Element 11: wherein the drive element interposes the one or more wiper elements and the nose assembly. Element 12: wherein the shoe defines a trough and the cup is bonded to the shoe at the trough. Element 13: wherein the cup provides an inner cup surface and an outer cup surface and wherein the outer cup surface provides a reinforced section that engages an end wall defined by the shoe. Element 14: wherein the end wall extends at an angle offset from a longitudinal axis of the drive element and less than 90° to provide radial support to the cup. 
     Element 15: wherein the shoe defines a trough and the cup is bonded to the shoe at the trough, the method further comprising providing axial support to the cup with the cup bonded to the shoe at the trough. Element 16: wherein the cup provides an inner cup surface and an outer cup surface and the outer cup surface provides a reinforced section, the method further comprising providing axial support to the cup by engaging the reinforced section against an end wall defined by the shoe. Element 17: wherein the end wall extends at an angle offset from a longitudinal axis of the drive element and less than 90°, the method further comprising providing radial support to the cup by engaging the reinforced section against an end wall defined by the shoe. 
     By way of non-limiting example, exemplary combinations applicable to A, B, and C include: Element 6 with Element 7; Element 13 with Element 14; and Element 16 with Element 17. 
     Therefore, the disclosed systems and methods are well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the teachings of the present disclosure may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered, combined, or modified and all such variations are considered within the scope of the present disclosure. The systems and methods illustratively disclosed herein may suitably be practiced in the absence of any element that is not specifically disclosed herein and/or any optional element disclosed herein. While compositions and methods are described in terms of “comprising,” “containing,” or “including” various components or steps, the compositions and methods can also “consist essentially of” or “consist of” the various components and steps. All numbers and ranges disclosed above may vary by some amount. Whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range is specifically disclosed. In particular, every range of values (of the form, “from about a to about b,” or, equivalently, “from approximately a to b,” or, equivalently, “from approximately a-b”) disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. Moreover, the indefinite articles “a” or “an,” as used in the claims, are defined herein to mean one or more than one of the elements that it introduces. If there is any conflict in the usages of a word or term in this specification and one or more patent or other documents that may be incorporated herein by reference, the definitions that are consistent with this specification should be adopted. 
     As used herein, the phrase “at least one of” preceding a series of items, with the terms “and” or “or” to separate any of the items, modifies the list as a whole, rather than each member of the list (i.e., each item). The phrase “at least one of” allows a meaning that includes at least one of any one of the items, and/or at least one of any combination of the items, and/or at least one of each of the items. By way of example, the phrases “at least one of A, B, and C” or “at least one of A, B, or C” each refer to only A, only B, or only C; any combination of A, B, and C; and/or at least one of each of A, B, and C.