Patent Publication Number: US-2022230804-A1

Title: Reinforced mcei transducer for downhole communication

Description:
RELATED APPLICATIONS 
     This application presents a modification of U.S. Pat. No. 7,091,810, to Hall et al., entitled Element of an Inductive Coupler, issued Aug. 15, 2006, incorporated herein by this reference. Except in reference to  FIGS. 1 and 2 , this disclosure is largely taken from said &#39;810 reference. 
    
    
     BACKGROUND 
     This invention relates to elements for use in inductive couplers for downhole components. U.S. Pat. No. 6,670,880, which is herein incorporated by reference, discloses a downhole transmission system through a string of downhole components. A first transmission element is located in the one end of each downhole component, which includes a first magnetically conducting, electrically-insulating trough, and a first electrically conductive coil lying therein. A second data transmission element is located in the other end, with a similar arrangement comprising a second magnetically conducting, electrically insulating trough and a second electrically conductive coil. The transmission system further comprises an electrical conductor in electrical communication with and running between each first and second coil in the downhole component. The string of downhole components is cooperatively arranged such that the troughs are in magnetic communication with each other and transmit signals through induction. 
     SUMMARY OF THE INVENTION 
     This application presents an annular magnetically conductive electrically insulating (MCEI) transducer, sometimes referred to as an inductive coupler, for use in downhole tools such as may be found in the drillstring and tools within the drillstring. The inductive coupler may comprise an annular MCEI trough. The annular trough may present a generally U shaped cross section or it may present a prismatic cross section. The annular trough may comprise an interior wall separated from an exterior wall. The interior and exterior wall may be joined by top and bottom surfaces. The MCEI trough may comprise one or more annular mechanical reinforcements. The mechanical reinforcements may comprise a variety of annular structures. The annular structures may be embedded within the space separating the respective walls of the MCEI trough. The annular structure may be radially embedded within the annular MCEI trough. 
     The annular structure may comprise one or more annular rods, bars, tubes, slit tubes, or wires, or combinations thereof, arranged within the walls of the MCEI trough. Also, the annular structure may comprise an annular mesh and mesh segments. The annular mesh and mesh segments may comprise a metal or nonmetal. The mesh may be embedded within the walls of the MCEI trough or the mesh may encapsulate the exterior of the MCEI trough. Furthermore, the annular structure may comprise a natural or synthetic fabric. Natural fabrics may include a cotton, silk, wool fabric, or rubber fabric, or a combination of natural fabrics. Synthetic fabrics may include a carbon fabric, a glass fabric, or a polymeric fabric, or a combination of synthetic fabrics. Also, the annular structure may comprise a metal fabric. The presence of the annular structure within the MCEI trough may strengthen the trough and add resilience to the otherwise brittle ferrite trough. 
     The annular MCEI trough may comprises a continuous ring or a single piece annular trough. An advantage of the single piece trough may be to reduce the leakage of the transmitted signal across the coupled transducers. Or it may be to prevent outside interference with the transmitted signal. Without the annular reinforcements as proposed herein, the single piece trough may be susceptible breakage under the stresses associated with the downhole environment. Nevertheless, the MCEI trough may comprise two or more trough segments. It may be preferred that the fewer trough segments the better for efficient communication downhole. The annular reinforcements proposed in this disclosure may enable a single piece annular trough or a trough comprising the fewest number of trough segments. Whether the annular MCEI trough may be comprised of a single piece or trough segments, the annular trough may comprise at least a portion of the annular reinforcement structures. 
     The annular reinforcement structures may comprise non-MCEI trough fibers, that is the fibers may be magnetically conductive but not electrically insulating, or vice versa. On the other hand, the MCEI trough may comprises annular reinforcements comprising MCEI fibers. 
     The annular reinforced MCEI trough may comprise one or more perforations as described in pending U.S. patent application Ser. No. 17/665,533, to Fox, entitled Downhole Transmission System with Perforated MCEI Segments, filed Feb. 5, 2022, incorporated herein by this reference. An electrically conducting wire coil may be disposed within the annular reinforced MCEI trough. Perforations in the MCEI trough may provide an exit passageway for the wire coil to exit the trough. 
     The reinforced MCEI trough may be molded within an annular polymeric block. Such a configuration is disclosed in pending U.S. patent application Ser. No. 17/559,619, to Fox, entitled Inductive Coupler for Downhole Transmission Line, filed Dec. 22, 2021, incorporated herein by this reference. The annular polymeric block may be disposed within an annular groove within a drillstring tool. furthermore, the annular polymeric block may itself comprise the annular reinforcement structures disclosed herein. 
     The following portion of the summary is taken from the &#39;810 reference. An element for an inductive coupler in a downhole component comprises a magnetically conductive trough, which is disposed in a recess in an annular housing. The circular or annular trough comprises an outer generally U-shaped surface, an inner generally U-shaped surface, and two generally planar surfaces joining the inner and outer surfaces. The element further comprises pressure relief grooves in at least one of the surfaces of the circular or annular trough. Preferably, the pressure relief grooves are in the outer generally U-shaped surface of the element. The grooves are provided to control the cracking of the magnetically conductive trough. Material, such as ferrite, may crack during the assembly of an inductive coupler. Control crack parallel to a magnetic field is believed to not adversely affect signal transmission between transmission elements. 
     In the preferred embodiment, an electrically conductive coil is disposed in a trough formed by the inner generally U-shaped surface. As a signal travels around the coil, the magnetically conductive material magnifies the magnetic field created by the electrical signal. The magnified magnetic field may influence a generally circular or annular magnetically conductive trough in an adjacent inductive coupler of an adjacent downhole component. The adjacent generally circular or annular magnetically conductive trough may influence an electrically conducting coil disposed within its trough and an electrical current may be generated. 
     Disclosed are pressure relief grooves which are scored lines. Preferably the pressure relief grooves are parallel to the magnetic field generated by the magnetically conductive material. In one aspect of the present invention, the element comprises cracks. The cracks may be generally parallel to a magnetic field generated by the magnetically conductive material. It is believed that pressure felt by the element may crack along scored lines. It is also believed that cracks parallel to the magnetic field do not adversely affect the strength of the magnetic field. It is believed that a crack normal to the magnetic field creates a gap with a similar magnetic resistivity as of air, which may weaken the strength of the magnetic field. 
     The magnetically conductive material may be selected from the group consisting of soft iron, ferrite, a nickel iron alloy, a silicon iron alloy, a cobalt iron alloy, and a mu-metal. In the preferred embodiment the magnetically conductive material is ferrite. Preferably, the magnetically conducting material is also electrically insulating. In one embodiment of the present invention, the generally circular or annular trough of magnetically conductive material is segmented. In another embodiment of the present invention, the generally circular or annular trough of magnetically conductive material is an open-ended ring. 
     The element may further comprise an electrically insulating filler material. Preferably, the filler material is selected from a group consisting of epoxy, natural rubber, fiberglass, carbon fiber composite, a polymer, polyurethane, silicon, a fluorinated polymer, grease, polytetrafluoroethyene and perfluoroalkoxy, or a combination thereof. 
     The annular housing may be a metal ring. In one embodiment the annular housing is a steel ring. In another embodiment, the annular housing is a stainless steel ring. Preferably, the annular housing is disposed in a groove formed in the end of the downhole component. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a diagram of a sectioned portion of an annular ferrite trough of the present invention. 
         FIG. 2  is a diagram of a sectioned portion of an annular ferrite trough of the present invention. 
       (Prior Art)  FIG. 3  is a cross sectional view of an embodiment of a downhole tool string. 
       (Prior Art)  FIG. 4  is a perspective cross sectional view of an embodiment of downhole components. 
       (Prior Art)  FIG. 5  is a perspective view of an embodiment of an inductive coupler. 
       (Prior Art)  FIG. 6  is a cross-sectional view of an embodiment of a magnetic transmission circuit. 
       (Prior Art)  FIG. 7  is a partial perspective view of an embodiment of an element. 
       (Prior Art)  FIG. 8  is a partial perspective view of an embodiment of an element. 
       (Prior Art)  FIG. 9  is a partial perspective view of an embodiment of an element. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following detailed description is in reference to  FIGS. 1 and 2 . This application presents an annular magnetically conductive electrically insulating (MCEI) transducer, sometimes referred to as an inductive coupler, for use in downhole tools such as may be found in the drillstring and tools within the drillstring. The inductive coupler may comprise an annular MCEI trough, a portion of which is shown at  200 . The annular trough  200  may present a generally U shaped cross section or it may present a prismatic cross section. The annular trough  200  may comprise an interior wall  240  separated from an exterior wall  205 . The interior and exterior  240 / 205  walls may be joined by top and bottom surfaces. The MCEI trough may comprise one or more annular mechanical reinforcements. The mechanical reinforcements may comprise a variety of annular structures. The annular structures may be embedded within the radial space separating the respective walls  240 / 205  of the MCEI trough  200 . The annular structure may be radially embedded within the annular MCEI trough  200 . 
     The annular structure may comprise one or more annular rods  210 , bars  210 , tubes  210 , slit tubes  250 , or wires  225 , or combinations thereof, arranged within radial space or between the walls of the MCEI trough  200 . Also, the annular structure may comprise an annular mesh  225  and mesh segments  225 , as seen through cut away  235 . The annular mesh  225  and mesh segments  225  may comprise a metal or nonmetal. The mesh  225  may be embedded radially within the walls  240 / 205  of the MCEI trough  200  or the mesh  225  may encapsulate the exterior  205  of the MCEI trough  200 . Furthermore, the annular structure may comprise a natural or synthetic fabric. Natural fabrics may include a cotton, silk, wool fabric, or rubber fabric, or a combination of natural fabrics. Synthetic fabrics may include a carbon fabric, a glass fabric, or a polymeric fabric, or a combination of synthetic fabrics. Also, the annular structure may comprise a metal fabric. The presence of the annular structures  230 ,  220 , and  250 , as may be seen exposed on the ends of the trough  200 , within the MCEI trough  200  may strengthen the trough and add resilience to the otherwise brittle ferrite trough. 
     The annular MCEI trough  200  may comprises a continuous ring or a single piece annular trough. An advantage of the single piece trough may be to reduce the leakage of the transmitted signal across the coupled transducers. Or it may be to prevent outside interference with the transmitted signal. Without the annular reinforcements as proposed herein, the single piece trough may be susceptible breakage under the stresses associated drillstring tools and with the downhole environment. Nevertheless, the MCEI trough  200  may comprise two or more trough segments. As shown in (Prior Art)  FIGS. 7-9 . It may be preferred that the fewer trough segments the better for efficient communication downhole. The annular reinforcements proposed in this disclosure may enable a single piece annular trough or a trough comprising the fewest number of trough segments. Whether the annular MCEI trough  200  may be comprised of a single piece or trough segments, the annular trough may comprise at least a portion of the annular reinforcement structures. 
     The annular reinforcement structures may comprise non-MCEI trough fibers, that is the fibers may be magnetically conductive but not electrically insulating, or vice versa. On the other hand, the MCEI trough may comprises annular reinforcements comprising MCEI fibers. For example, reinforcing fabrics may comprise MCEI fibers. 
     The annular reinforced MCEI trough  200  may comprise one or more perforations as described in pending U.S. patent application Ser. No. 17/665,533, to Fox, entitled Downhole Transmission System with Perforated MCEI Segments, filed Feb. 5, 2022, incorporated herein by this reference. An electrically conducting wire coil may be disposed within the annular channel  215  of the reinforced MCEI trough. Perforations in the MCEI trough&#39;s channel wall  245  may provide an exit passageway for the wire coil to exit the trough. 
     The reinforced MCEI trough may be molded within an annular polymeric block. Such a block configuration is disclosed in pending U.S. patent application Ser. No. 17/559,619, to Fox, entitled Inductive Coupler for Downhole Transmission Line, filed Dec. 22, 2021, incorporated herein by this reference. The annular polymeric block may be disposed within an annular groove within a drillstring tool. Furthermore, the annular polymeric block may itself comprise the annular reinforcement structures disclosed herein. 
     The following portion of the detailed description is taken from the &#39;810 reference. Except as modified by  FIGS. 1 and 2  and related text, the following description applies to the present invention. 
     (Prior Art)  FIG. 3  shows an embodiment of a downhole tool string  31  suspended in a well bore by a derrick  32 . Surface equipment  33 , such as a computer, connects to a data swivel  34 . The data swivel  34  is adapted to transmit data to and from an integrated transmission network while the downhole tool string  31  is rotating. The integrated transmission network comprises the transmission systems of the individual components  35 ,  36 ,  57  of the downhole tool string  31 . Preferably the downhole component is a pipe  36 ,  57 . Alternatively the downhole component is a tool  35 . Tools  35  may be located in the bottom hole assembly  37  or along the length of the downhole tool string  31 . The tools  35  on a bottom hole assembly  37  may be sensors, drill bits, motors, hammers, and steering elements. The tools  35  located along the downhole tool string  31  may be links, jars, seismic sources, seismic receivers, sensors, and other tools that aid in the operations of the downhole tool string  31 . Different sensors are useful downhole such as pressure sensors, temperature sensors, inclinometers, thermocouplers, accelerometers, and imaging devices. Preferably the downhole tool string  31  is a drill string. In other embodiments the downhole tool string  31  is part of a production well. 
     The downhole tool string  31  is made up of components, as shown in (Prior Art)  FIG. 4 . The components may be pipes  36 ,  57  or some of the above mentioned tools  35 . The components comprise inductive couplers  85  (shown in (Prior Art)  FIG. 5 ) located in the secondary shoulder  39  of the pin end  40  and the secondary shoulder  41  of the box end  42  of the component  36 . The inductive couplers  85  may comprise an element  38 ,  47  comprising an annular housing  43 . In one embodiment the elements  38 ,  47  may comprises a plurality of generally linear, magnetically conductive segments, each of which segments includes an outer generally U-shaped surface  88 , an inner generally U-shaped surface  80 , and planar surfaces  79  (shown in (Prior Art)  FIG. 7 ). The surfaces  79 ,  80 ,  88  together define a generally linear trough  89  from one end to the other end of each segment. The segments are arranged within the housing recess  86  so as to form a generally circular or annular trough  55 . 
     Preferably the element  38 ,  47  is disposed in an annular groove  62  formed in the secondary shoulders  39 ,  41 . Preferably the annular housing  43  is a metal ring. The annular housing  43  may be a steel ring. In other embodiment the annular housing  43  is a stainless steel ring. The elements  38 ,  47 , in a single downhole component, are connected by an electrical conductor  44 . Preferably the electrical conductor  44  is a coaxial cable. In other embodiments the electrical conductor  44  is a pair of twisted wires. In some embodiments, the electrical conductor  44  is a tri-axial cable. 
     The circular or annular trough  55  may house an electrically conductive coil  45  encapsulated by the magnetically conductive material. Preferably, the magnetically conductive material is an easily magnetized and easily de-magnetized material selected from the group consisting of soft iron, ferrite, a nickel iron alloy, a silicon iron alloy, a cobalt iron alloy and a mu-metal. More preferably the magnetically conductive material is made of ferrite. The coil  45  comprises one loop of insulated wire. Alternatively, the coil  45  may comprise at least two loops of insulated wire. The wire may be made of copper and is insulated with an insulating layer  73  of a varnish, an enamel, or a polymer. When the components  36 ,  57  of the downhole tool string  31  up are made, the magnetically conductive trough  38 ,  47  line up adjacent each other and allow data transmission between the components  36 ,  57 . A threaded portion  48  located between the primary shoulder  49  and secondary shoulder  39  of the pin end  40  and a threaded portion  50  located between the primary shoulder  51  and secondary shoulder  41  of the box end  42  provide a means of attachment for the downhole components  36 ,  57 . 
     (Prior Art)  FIG. 5  shows a partial perspective of an element comprising an open-ended ring  74  of magnetically conductive material. Pressure relief grooves  70  are scored into the magnetically conductive material. Also illustrated is a connection between the electrical conductor  44  and the electrical conducting coil  45 . In the preferred embodiment, a signal travels along the electrical conductor  44  of the downhole component  36 . The signal passes from the electrical conductor  44  to a lead wire  52  of the coil  45 . The inductive coupler  85  comprises an anti-rotation device  53 , which keeps the annular housing  43  from rotating about the axis of the lead wire  52 . In the preferred embodiment the lead wire  52  may enter the annular housing  43  through a hole  75  in the annular housing  43 , where there is a void  54  of magnetically conductive material. The coil  45  is housed within the magnetically conductive circular or annular trough  55  and is grounded to the annular housing  43  in the void  54  in the magnetically conductive trough. Preferably, the grounded portion  56  of the coil  45  is brazed to the annular housing  43 . In some embodiments of the present invention, the element  38 ,  47  disposed in a groove  62  formed by the secondary shoulders  39 ,  41  of both the pin end  40  and also in the box end  42  of the downhole component  36 . The open-ended ring  74  may be complete when it is installed into the annular housing  43 ; however, due to strain felt by the element  38 ,  47  while it is being installed, the magnetically conductive material may crack during installation. 
     The elements  38 ,  47  comprise an electrically insulating filler material  60  which holds the circular or annular trough  55  in place. Preferably the filler material  60  is selected from the group consisting of epoxy, natural rubber, fiberglass, carbon fiber composite, a polymer, polyurethane, silicon, a fluorinated polymer, grease, polytetrafluoroethylene and perfluoroalkoxy, or a combination thereof. Polytetrafluoroethylene and perfluoroalkoxy are the more preferred filler materials  60 . 
     It is important that the electrically-insulating filler material  60  will withstand the elevated pressures and temperatures in downhole conditions. Consequently, it is preferred to treat the filler material  60  to make sure that it does not contain any air pockets. Preferably the filler material  60  is centrifuged to remove all bubbles that might be introduced during mixing. One such treatment method involves subjecting the filler material  60  in a centrifuge. A most preferred form of this method subjects the filler material  60  to a centrifuge at between 2500 to 5000 rpm for about 0.5 to 3 minutes. 
     (Prior Art)  FIG. 6  shows an embodiment of a magnetic transmission circuit  61  formed by cooperating magnetic fields from the element  38  and the adjacent element  47 . As the signal travels along the coil  45 , the magnetic field from the electrical current is magnified by the magnetically conductive material. The magnified magnetic field influences the magnetically conductive material in the adjacent element  47  in the adjacent downhole component  57 . The electrically conducting coils  45 ,  59  may be arranged in a manner to allow the magnetic fields to generate the magnetic transmission circuit  61 . The magnetic transmission circuit  61  may be allowed by disposing one coil  45  in a clockwise direction in the circular or annular trough  55  of magnetically conducting material and disposing an adjacent coil  59  in a counterclockwise direction in an adjacent circular or annular trough  76  of magnetically conductive material. The coil  59  in the adjacent element  47  is influenced by the magnetic transmission circuit  61  to generate an electrical current and that signal is passed to the electrical conductor  58  in the adjacent downhole component  57 . 
     A partial perspective view of an embodiment of the element is shown in (Prior Art)  FIG. 7 . The coil  45  is encapsulated by an open-ended ring  74  of magnetically conductive material within the generally circular or annular trough  55  formed by the inner generally U-shaped surface  80 . A pressure relief groove  70  is formed in the outer generally U-shaped surface  88 . In some embodiments the pressure relief groove  70  may be formed in the inner generally U-shaped surface  80  or in at least one of the planar surfaces  79 . In the preferred embodiment the pressure relief groove  70  is a scored line. 
     It is believed that a crack normal to the magnetic field may adversely affect the magnetic transmission circuit  61 . It is believed that the crack may have a similar magnetic resistance as air. It is further believed that an area in the magnetic transmission circuit  61  which has a similar magnetic resistance as air may weaken the strength of the entire magnetic transmission circuit  61 . A pressure relief groove  70  is believed to control the cracking along the groove  70 . It is preferred that pressure relief grooves  70  are parallel to the direction of the magnetic fields. It is believed that cracks controlled by the pressure relief grooves that are formed parallel to the direction of the magnetic fields may not adversely affect the magnetic transmission circuit  61 . (Prior Art)  FIG. 8  shows an embodiment of an element  38  with a partial crack  71  controlled by the pressure relief groove  70 . (Prior Art)  FIG. 9  shows an embodiment of an element  38  with a crack  72  that separates the magnetically conductive material. 
     A preferred method of forming an element  38 ,  47  of magnetically conductive material begins with providing a mold having a trough conforming to the final dimensions of the circular or annular trough  55 . A two-part, heat-curable epoxy formulation is mixed in a centrifuge cup, to which the magnetically conductive material and a length of fiberglass rope are added. The parts are centrifuged for up to 30 minutes to cause all bubbles induced by mixing to rise out of the viscous liquid, and to cause the liquid to penetrate and seal any porosity in the magnetically conductive material. The fiberglass rope is then laid in the bottom of the mold, which is either made from a material, which does not bind to epoxy, such as polymerized tetrafluroethane or which is coated with a mold release agent. The magnetically conductive material is then placed on top of the fiberglass rope, to fill the mold. Any excess epoxy is wiped out of the groove. The planar surfaces  79  of the magnetically conductive material may be precisely aligned by holding it in position with magnets placed around the circular or annular trough in the mold. After the epoxy is cured, either at room temperature or in an oven, the circular or annular tough  46  is removed from the mold. Preferably, lines are scored into the outer generally U-shaped surface, before the element  38 ,  47  is place in the annular housing  43  or into the annular groove  62  formed in the end of the downhole component  36 ,  57 . 
     The description above and the attached figures are meant to illustrate specific embodiments of the present invention and not limit its scope. Those having ordinary skill in the art will appreciate that other embodiments will fall within the scope and spirit of the invention as defined in the appended claims.