Patent Publication Number: US-2023163659-A1

Title: Field attachable and pressure testable coupling for metal-to-metal motor lead extensions

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to electric submersible pumping systems and more particularly to systems and methods for securely connecting and testing multiple motor lead extensions. 
     BACKGROUND 
     Submersible pumping systems are often deployed into wells to recover petroleum fluids from subterranean reservoirs. Typically, a submersible pumping system includes a number of components, including an electric motor coupled to one or more high performance pump assemblies. Production tubing is connected to the pump assemblies to deliver the petroleum fluids from the subterranean reservoir to a storage facility on the surface. 
     The motor is typically an oil-filled, high capacity electric motor that can vary in length from a few feet to nearly one hundred feet, and may be rated up to hundreds of horsepower. Typically, electricity is generated on the surface and supplied to the motor through a heavy-duty power cable. The power cable typically includes several separate conductors that are individually insulated within the power cable. Power cables are often constructed in round or flat configurations. 
     In many applications, power is conducted from the power cable to the motor via a “motor lead extension” or “motor lead cable.” The motor lead extension typically includes one or more “leads” that are configured for connection to a mating receptacle on the motor. The leads from the motor lead extension are often retained within a motor-connector that is commonly referred to as a “pothead.” The pothead relieves the stress or strain realized between the motor and the leads from the motor lead extension. Motor lead extensions are often constructed in a “flat” configuration for use in the limited space between downhole equipment and the well casing. 
     Power and motor lead cables typically include a conductor, insulation surrounding the conductor, a barrier covering the insulation, a lead-based sheathing that encases the barrier and a durable external armor that surrounds the sheathing. As an alternative to lead-based sheathing, manufacturers have attempted to use alloy-based capillary tubing as protective jacket around the insulated conductors. Conventional capillary tubing is produced as a seamless extruded tube through which the conductor and insulation layers must be pulled. The frictional interface between the insulated conductor and conventional capillary tubing frustrates efforts to encapsulate longer conductors within the closed capillary tubing. This prevents the use of capillary tubing sheathing for all but the shortest motor lead cables. 
     In applications where longer motor lead extensions are needed, two motor lead extensions can be spliced together using overlapping layers of tape. Many operators will not permit the use of taped splice connections, particularly where the taped splice would be located beneath a packer or other zonal isolation device in the well. In these situations, the total length of the motor lead extension is limited by the maximum length of a single motor lead extension. Accordingly, there is a need for an improved system for making and deploying motor lead extensions that provides well operators with a range of longer motor lead extensions. It is to these and other deficiencies in the prior art that exemplary embodiments of the present invention are directed. 
     SUMMARY OF THE INVENTION 
     In one aspect, embodiments of the present disclosure are directed to a pumping system for use in recovering wellbore fluids from a wellbore. The pumping system includes an electrical power source, a motor drive connected to the power source, a power cable connected to the motor drive, a submersible electric motor, and a pump driven by the electric motor. The pumping system further includes a motor lead coupler that joins together an upper motor lead extension and a lower motor lead extension. The upper motor lead extension has an upper end and a lower end, where the upper end of the upper motor lead extension is connected to the power cable and the lower end of the upper motor lead extension is connected to the motor lead coupler. The lower motor lead extension has an upper end and a lower end, where the lower end of the lower motor lead extension is connected to the motor and the upper end of the lower motor lead extension is connected to the motor lead coupler. 
     In another aspect, embodiments of the present disclosure are directed to a motor lead coupler for connecting a first motor lead extension to a second motor lead extension, where the first motor lead extension includes a first plurality of leads and the second motor lead extension includes a second plurality of leads. The motor lead coupler includes a body, a first plurality of receivers on a first end of the body, a second plurality of receivers on a second end of the body, and a plurality of intermediate terminals. Each of the first plurality of receivers is configured to receive a corresponding one of the first plurality of leads, and each of the second plurality of receivers is configured to receive a corresponding one of the second plurality of leads. Each of the intermediate terminals is connected between a corresponding pair of the first plurality of receivers and the second plurality of receivers. 
     In yet another aspect, embodiments of the present disclosure are directed to a method for connecting an upper motor lead extension to a lower motor lead extension with a motor lead coupler, wherein each of the upper motor lead extension and the lower motor lead extension includes a plurality of motor leads that have a conductor, an insulator surrounding the conductor, and a metal tube surrounding the insulator. The method includes the steps of removing a portion of the metal tube from an end of each of the plurality of leads to expose a portion of the insulator, removing a portion of the exposed insulator from the end of each of the plurality of leads to expose a conductor tip, placing a metal compression nut over the metal tube of each lead, and placing a metal ferrule over the metal tube of each lead such that the ferrule is between the compression nut and the conductor tip. 
     The method continues with the steps of inserting the conductor tip, the exposed portion of the insulator, and a portion of the metal tube of each lead into a corresponding one of a plurality of receivers within the motor lead coupler. The method further includes the step of securing each lead within the corresponding one of the plurality of receivers by tightening the compression nut into the receiver to form a metal-to-metal seal between the motor lead coupler, the ferrule, and the metal tube. In some embodiments, the method further includes the step of conducting a pressure test on the connection between each lead and the motor lead coupler by connecting a source of pressurized fluid to a pressure test port adjacent to each of the plurality of receivers on the motor lead coupler. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    depicts the installation of upper and lower motor lead extensions connected by a motor lead coupling constructed in accordance with exemplary embodiments. 
         FIG.  2    is a perspective view of the motor lead coupling of  FIG.  1   . 
         FIG.  3    is a cross-sectional and exploded view of the motor lead coupling of  FIG.  2   . 
         FIG.  4    is a cross-sectional view of the motor lead coupling of  FIG.  3    in which the upper and lower motor leads are connected through the coupling. 
     
    
    
     WRITTEN DESCRIPTION 
     In accordance with an exemplary embodiment of the present invention,  FIG.  1    shows a front view of a downhole pumping system  100  attached to production tubing  102 . The downhole pumping system  100  and production tubing  102  are disposed in a wellbore  104 , which is drilled for the production of a fluid such as water or petroleum from a subterranean geologic formation  106 . 
     The wellbore  104  includes a casing  108 , which has perforations  110  that permit the exchange of fluids between the wellbore  104  and the geologic formation  106 . One or more packers  112  or other zonal isolation devices can be used to separate various segments or stages within the wellbore  104 . Although the downhole pumping system  100  is depicted in a vertical well, it will be appreciated that the downhole pumping system  100  can also be used in horizontal, deviated, and other non-vertical wells. Accordingly, the terms “upper” and “lower” should not be construed as limiting the disclosed embodiments to use in vertical wells. The terms “upper” and “lower” are simply intended to provide references to components that are closer to the wellhead  114  (“upper”) or closer to the perforations  110  and terminal end of the wellbore  104  (“lower”). 
     The production tubing  102  connects the pumping system  100  to a wellhead  114  located on the surface. Although the pumping system  100  is primarily designed to pump petroleum products, it will be understood that the present invention can also be used to move other fluids. It will also be understood that, although each of the components of the pumping system  100  are primarily disclosed in a submersible application, some or all of these components can also be used in surface pumping operations. 
     The pumping system  100  includes a pump  116 , a motor  118  and a seal section  120 . The motor  118  is an electric motor that receives its power from a surface-based supply through a power cable  122  and a plurality of motor lead extensions  124 . In many embodiments, the power cable  122  and motor lead extensions  124  are configured to supply the motor  118  with three-phase electricity from a surface-based variable speed (or variable frequency) drive  200 , which receives electricity from a power source  202 . 
     The motor  118  converts the electrical energy into mechanical energy, which is transmitted to the pump  116  by one or more shafts. The pump  116  then transfers a portion of this mechanical energy to fluids within the wellbore  104 , causing the wellbore fluids to move through the production tubing  102  to the surface. In some embodiments, the pump  116  is a turbomachine that uses one or more impellers and diffusers to convert mechanical energy into pressure head. In other embodiments, the pump  116  is a progressive cavity (PC) or positive displacement pump that moves wellbore fluids with one or more screws or pistons. 
     The seal section  120  shields the motor  118  from mechanical thrust produced by the pump  116 . The seal section  120  is also configured to prevent the introduction of contaminants from the wellbore  104  into the motor  118 . Although only one pump  116 , seal section  120  and motor  118  are shown, it will be understood that the downhole pumping system  100  could include additional pumps  116 , seal sections  120  or motors  118 . 
     As depicted in  FIG.  1   , there are two motor lead extensions  124 : an upper (or first) motor lead extension  124   a  and a lower (or second) motor lead extension  124   b . The upper motor lead extension  124   a  is connected to the power cable  122  with a power-to-motor connector  126 , which may be located above or below the packer  112  (the connector  126  is located above the packer  112  in the embodiment depicted in  FIG.  1   ). 
     The upper motor lead extension  124   a  is connected to the lower motor lead extension  124   b  with a motor lead coupler  128 . As shown in  FIG.  1   , the motor lead coupler  128  is positioned below the packer  112  in the portion of the wellbore  104  that is more commonly exposed to wellbore fluids produced from the formation  106 . As explained below, the motor lead coupler  128  provides a secure coupling device that can be easily assembled in the field as the pumping system  100  is being deployed in the wellbore  104 . Moreover, the motor lead coupler  128  is configured for post-assembly pressure testing to ensure that the motor lead coupler  128  will provide a leak-resistant connection between two adjacent motor lead extensions  124 . Although a single motor lead coupler  128  is depicted between upper and lower motor lead extensions  124   a ,  124   b  in  FIG.  1   , it will be appreciated that additional motor lead couplers  128  can be used as necessary to connect additional motor lead extensions  124  between the power cable  122  and the motor  118 . 
     Turning to  FIG.  2   , shown therein is a perspective view of one embodiment of the motor lead coupler  128 . The motor lead coupler  128  includes a durable, corrosion-resistant body  130  that can be manufactured from Inconel or another metal alloy. The motor lead coupler  128  is generally configured to provide a sealed and electrically isolated connection between individual leads  132  from the upper and lower motor lead extensions  124   a ,  124   b . The leads  132  each include a conductor  134  that is surrounded by an insulator  136 , that is in turn encapsulated within an exterior metal tube  138 . The conductor  134  can be a solid or stranded copper conductor. The insulator  136  can include one or more layers of electrically isolating and chemically resistant polymers. The metal tube  138  can be a capillary tube constructed from a corrosion-resistant metal alloy, such as Inconel. 
     Although the motor lead coupler  128  depicted in  FIG.  2    is configured to provide a connection between three sets of individual leads  132  between the upper and lower motor lead extensions  124   a ,  124   b , it will be appreciated that in other embodiments, a plurality of separate motor lead couplers  128  are used to connect the corresponding leads  132  of the upper and lower motor lead extensions  124   a ,  124   b . For example, it may be desirable to use three separate “single lead” motor lead couplers  128  for connecting the three leads  132  commonly found in the upper and lower motor lead extensions  124   a ,  124   b . 
     Referring now also to  FIGS.  3  and  4   , shown therein are exploded and assembled cross-sectional views, respectively, of a portion of the motor lead coupler  128  illustrating the connections made between leads  132  from the upper and lower motor lead extensions  124   a ,  124   b . It will be appreciated that in most applications, the motor lead coupler  128  will include three sets of various components depicted in  FIGS.  3  and  4   . That is, for each pair of leads  132  within the upper and lower motor lead extensions  124   a ,  124   b , the motor lead coupler  128  includes an upper receiver  140   a , a lower receiver  140   b , and a central channel  142 . As explained below, the upper receiver  140   a  and lower receiver  140   b  of the motor lead coupler  128  are generally configured to resemble the pothead connection on the motor  118  such that the upper and lower motor lead cables  124   a ,  124   b  can be configured for connection to the motor lead coupler  128  in the field with minimal modification. 
     As best illustrated in  FIG.  3   , the upper receiver  140   a  and lower receiver  140   b  include openings  144   a ,  144   b , respectively, that extend toward one another from opposite ends of the body  130  of the motor lead coupler  128 . The central channel  142  has a smaller diameter than the upper and lower openings  144   a ,  144   b , which may include upper and lower receiver threads  146   a ,  146   b . The motor lead coupler  128  includes an intermediate terminal  148  positioned within the central channel  142 . The intermediate terminal  148  provides a conductive connector between the corresponding leads  132  of the upper and lower motor lead extensions  124   a ,  124   b . In some embodiments, the motor lead coupler  128  includes an insulator tube  150  within at least a portion of the central channel  142 . In other embodiments, the entire length of the central channel  142  is shielded by the insulator tube  150 . The insulator tube  150  electrically isolates the components inside the central channel  142  from the body  130  of the motor lead coupler  128 . 
     In some embodiments, the motor lead coupler  128  further includes a pothead insulator  152  inside the insulator tube  150 . The pothead insulator  152  provides an additional layer of electrical insulation for the upper end of the lower motor lead extension  124   b . As depicted in  FIG.  4   , the pothead insulator  152  can be located within the insulator tube  150  of the central channel  142  in a position to receive the uninsulated portion of the conductor  134 . 
     In some embodiments, the motor lead coupler  128  also includes upper and lower pressure test ports  166   a ,  166   b , which provide a mechanism for connecting a pressure test kit (not shown) to the upper and lower receivers  140   a ,  140   b  on the motor lead coupler  128 . In these embodiments, each lead  132  of the upper and lower motor lead extensions  124   a ,  124   b  further includes one or more compliant seals  164  for enabling the pressure testing function of the pressure test ports  166   a ,  166   b . As depicted in  FIGS.  3  and  4   , the leads  132  include an outer seal  164   a  and an inner seal  164   b . The outer seal  164   a  seals between the outside of the compression nuts  154  and the corresponding receivers  140 . The inner seal  164   b  seals between the inside of the compression nuts  154  and the outside of the metal tube  138 . In the embodiment depicted in  FIGS.  3  and  4   , the inner seal  164   b  is positioned inboard and adjacent to the upper and lower ferrules  146   a ,  146   b . 
     The upper motor lead cable  124   a  extends between the power-to-motor cable connector  126  and the motor lead coupler  128 . The lower motor lead cable  124   b  extends from the motor lead coupler  128  to the motor  118 . The lower end of the upper motor lead cable  124   a  and the upper end of the lower motor lead cable  124   b  are each initially configured to be connected into the conventional pothead connection on the motor  118 . Likewise, the upper and lower receivers  140   a ,  140   b  each are configured to match the general form of the pothead connector on the motor  118 . 
     As best illustrated in  FIG.  2   , the lower end of the upper motor lead extension  124   a  has been prepared by cutting back a portion of the metal tube  138  to reveal a length of exposed insulator  136  around the conductor  134 . An upper compression nut  154   a  and upper ferrule  156   a  are installed around the metal tube  138  of each lead  132  of the upper motor lead extension  124   a . The upper ferrule  156   a  and upper compression nut  154   a  are manufactured from a suitable corrosion-resistant metal. The upper compression nut  154   a  includes threads  158   a  that mate with corresponding receiver threads  146   a  in the upper receiver  140   a . When each lead  132  of the upper motor lead extension  124   a  is inserted into the corresponding upper receiver  140   a  of the motor lead coupler  128 , the upper compression nut  154   a  can be threaded into the receiver threads  146   a  of the upper receiver  140   a  and tightened to a specified extent. This compresses and deforms the upper ferrule  156   a  within the narrowing upper receiver  140   a  to create a sealed, metal-to-metal connection between the metal tube  138  of the lead  132  and the interior of the motor lead coupler  128 . 
     In some embodiments, the upper end of the lower motor lead extension  124   b  is prepared in the same way as the lower end of the upper motor lead extension  124   a . In those embodiments, the lower receiver  140   b  is configured to match the upper receiver  140   a . In other embodiments, the upper end of the lower motor lead extension  124   b  includes a longer length of exposed insulator  136 . In most applications, the lowermost motor lead extension  124   b  is provided with excess length, which permits the use of a longer section of insulator  136 . In this way, the upper end of the lower motor lead extension  124   b  has been prepared by cutting back a portion of the metal tube  138  to reveal a longer length of exposed insulator  136  around the conductor  134 . In these embodiments, it may not be necessary to install the cylindrical pothead insulator  152  to cover the exposed insulator  136  of the lower motor lead extension  124   b . The longer section of the insulator  136  provide sufficient protection within the motor lead coupler  128 , which has been configured to accommodate the longer exposed insulator  136  by lengthening the lower receiver  140   b . 
     A lower upper compression nut  154   b  and lower ferrule  156   b  are installed around the metal tube  138  of each lead  132  of the lower motor lead extension  124   b . The lower ferrule  156   b  and lower compression nut  154   b  are manufactured from a suitable corrosion-resistant metal. The lower compression nut  154   b  includes threads  158   b  that mate with corresponding receiver threads  146   b  in the lower receiver  140   b . When each lead  132  of the lower motor lead extension  124   b  is inserted into the corresponding lower receiver  140   b  of the motor lead coupler  128 , the lower compression nut  154   b  can be threaded into the receiver threads  146   b  of the lower receiver  140   b  and tightened to a specified extent. This compresses and deforms the lower ferrule  156   b  within the narrowing lower receiver  140   b  to create a sealed, metal-to-metal connection between the metal tube  138  of the lead  132  and the interior of the motor lead coupler  128 . 
     In some embodiments, the insulator  136  is cut back from the distal end of each lead  132  to reveal an uninsulated, exposed conductor tip  160 . The conductor tip  160  is configured to be captured within the intermediate terminal  148 . In other embodiments, a lead terminal  162  is attached to the conductor tip  160 . The lead terminal  162  can be configured for a mating engagement with the corresponding side of the intermediate terminal  148 . For example, in some embodiments, the lead terminal  162  is configured as a socket that receives a post from the intermediate terminal  148 . In other embodiments, the lead terminal  162  is configured as a post that is received within a socket of the intermediate terminal  148 . 
     It will be appreciated that the leads  132  of the upper motor lead extension  124   a  can be configured differently than the leads  132  of the lower motor lead extension  124   b . In exemplary embodiments, the upper motor lead extension  124  can be configured for use without modification in the field where the upper receivers  140   a  of the motor lead coupler  128  are configured to match a standard motor pothead connection. This permits the use of an “off-the-shelf” motor lead extension  124  for the upper motor lead extension  124 . Because the standard motor lead extension used for the lower motor lead extension  124   b  is typically configured for connection between the power cable  122  and the motor  118 , the upper end of the lower motor lead extension  124   b  will typically require minor modification before it can be connected to the motor lead coupler  128 . 
     Thus, in an exemplary method of assembly and installation, the lower end of the lower motor lead extension  124   b  is connected to the motor  118  using the standard pothead connection. The lower motor lead extension  124   b  is then banded to the pumping system  100  or production tubing  102  to support the weight of the lower motor lead extension  124   b . The upper (free) end of the lower motor lead extension  124   b  can be prepared as set forth above and connected to the motor lead coupler  128 . Each lead  132  of the lower motor lead extension  124   b  is secured within a corresponding lower receiver  140   b  of the motor lead coupler  128 . The motor lead coupler  128  is designed to securely accept each lead  132  of the lower motor lead extension  124   b  with minimal modification to the lower motor lead extension  124   b , which can easily be performed in the field before the pumping system  100  is deployed into the wellbore  104 . 
     Once the lower motor lead extension  124   b  has been secured to the motor lead coupler  128 , the lower end of the upper motor lead extension  124   a  can be similarly attached to the motor lead coupler  128  by securing each lead  132  into a corresponding one of the upper receivers  140   a . In exemplary embodiments, the upper receivers  140   a  are configured to match the standard pothead connection on the motor  118  such that no field modification to the lower end of the upper motor lead extension  124   a  is necessary. The upper end of the upper motor lead extension  124   a  can then be connected to the power cable  122  using the conventional power-to-motor connector  126 , or by tape-splicing the upper motor lead cable  124   a  to the power cable  122 . 
     The motor lead coupler  128  provides a mechanism for connecting two motor lead extensions  128  with a robust metal-to-metal seal. To confirm that the upper and lower motor lead extensions  124   a ,  124   b  have been properly secured within the motor lead coupler  128 , the installer can perform a pressure test by connecting the field pressure test kit to the upper and lower pressure test ports  166   a ,  166   b . As illustrated in  FIGS.  3  and  4   , the upper and lower pressure test ports  166   a ,  166   b  are located inboard of the upper and lower compression nuts  154   a ,  154   b , ferrules  156   a ,  156   b , and seals  164   a ,  164   b . Although a wide variety of pressure tests can be conducted, in one embodiment a standard leak test is performed by connecting an external source of fluid pressure to each of the upper and lower pressure test ports  166   a ,  166   b . 
     Once the test pressure has been applied through the pressure test ports  166   a ,  166   b , the pressure can be monitored for a test period. If the pressure remains substantially the same throughout the test period, this indicates that each of the leads  132  has been properly sealed within the corresponding receiver  140  of the motor lead coupler  128 . If the pressure begins to fall during the test period, this indicates that one or more of the sealing features between the lead  132  and the motor lead coupler  128  is unsatisfactory and requires attention. In some pressure tests, the pressure applied to the pressure test ports  166   a ,  166   b  is increased and decreased in a cyclic manner to test the resiliency of the connections between the leads  132  and the motor lead coupler  128  over multiple pressure cycles. The ability to easily pressure test the connection made by the motor lead coupler  128  between the upper and lower motor lead extensions  124   a ,  124   b  presents a significant advantage over prior art methods of tape-splicing motor lead extensions together. 
     It is to be understood that even though numerous characteristics and advantages of various embodiments of the present invention have been set forth in the foregoing description, together with details of the structure and functions of various embodiments of the invention, this disclosure is illustrative only, and changes may be made in detail, especially in matters of structure and arrangement of parts within the principles of the present invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. Where a particular reference numeral has been modified with “a” or “b” to represent similar components in different portions of a system (e.g., upper widget 999a and lower widget 999b), use of the reference numeral alone designates both of the similar components (e.g., upper and lower widgets 999). It will be appreciated by those skilled in the art that the teachings of the present invention can be applied to other systems without departing from the scope and spirit of the present invention.