Patent Grant
8382508
This invention relates in general to electrical submersible pump assemblies for subterranean well production, in particular, to a connector for connecting a power cable to a motor lead of the pump assembly.
Submersible pumping systems are often used in hydrocarbon producing wells for pumping fluids from within the well bore to the surface. These fluids are generally liquids and include produced liquid hydrocarbon as well as water. One type of system used in this application employs a electrical submersible pumping system (ESP). A common type of ESP comprises a centrifugal pump suspended on a string of tubing within a casing of the well. The pump is driven by a downhole electrical motor, normally a three-phase AC type. A power line extends from a power source at the surface alongside the tubing to the motor to supply power.
Typically the power line is made up of two sections, a motor lead and a power cable. The motor lead has a plug on its lower end that secures to a receptacle known as a “pothead” at the upper end of the electrical motor. The other end of the motor lead is connected to a power cable with a splice, or other type of connector.
In some wells, the well environment may be quite harsh with high temperatures and pressures and corrosive well fluids. However, current splicing media or materials used in the existing art may not be capable of withstanding the harsh environments in some wells. If these materials degrade, well fluids could enter the connection and a short could result that would require the pump assembly to be pulled and replaced. For these same reasons, it would be desirable for a connection to have minimal elastomeric, epoxy and potable materials.
In addition, the high temperature of the well will cause the components of the connector to expand. This expansion may damage the connector and the connection by creating sufficient forces to the components of the splice connection to deform and damage them. A connector splice that can withstand the thermal expansion forces resulting from a high temperature environment would be desirable.
Current art connectors may require that the connection be made in a shop environment and once the connection is made, it could not be disconnected or reconnected. It would be desirable for a connector to have the capability to be connected on site and to allow a connector to be disconnected and reconnected at the site, as needed or desired.
Conventional connection designs may be bulky and have large profiles. However, there are some situations in which the target wells have size limitations that prevent the use of these conventional designs. Therefore, it would be beneficial to have a connector design that is operable to work in harsh conditions and overcome the other shortcomings discussed above while maintaining a small profile.
Embodiments of this application include devices that couple multi phase high voltage power cable to individual tube encapsulated, high voltage motor lead cables. The philosophy behind the device is that it can connect multi phase cable conductors multiple times, in a low profile manner that eliminates phase to phase shorts, along with providing multiple sealing barriers between the well annulus and connection.
The device can be manufactured in a controlled environment and factory acceptance tested before field installation, allowing for a superior field connection. The multi phase power cable will be prepped with individual connectors for each phase. Then a series of factory acceptance testing, both mechanical and electrical, will be performed to ensure integrity. Likewise, the tube encapsulate motor lead will be prepped with individual connectors. Then a series of factory acceptance testing, both mechanical and electrical will be performed to ensure integrity. Once the equipment has arrived in the field, both components can be connected quickly, elevating the use of a splice.
In one embodiment of the current application, an electrical power assembly for supplying power to a motor has a motor lead having one end for connection to the motor and having a plurality of individual metal sheathed conductors, a power cable having one end for connection to a power source and having a plurality of individual metal sheathed conductors, and a splice connector for joining each of the conductors of the motor lead to one of the conductors of the power cable. The splice connector includes a tubular metal fastener body with a motor lead end and a power cable end, a tapered motor lead shoulder adjacent to the motor lead end and a tapered power cable shoulder adjacent to the power cable end. There may be fastener body threads on the power cable end and on the motor lead end of the fastener body. The splice connector also has a metal nut assembly fixed to one of the power cable conductors having threads that engage the fastener body threads on the power cable end, the metal nut assembly having a tapered shoulder in metal-to-metal sealing engagement with the power cable shoulder of the fastener body. A metal coupler is fixed to one of the motor lead conductors and has threads that engage the fastener body threads on the motor lead end. The metal coupler has a tapered shoulder in metal-to-metal sealing engagement with the motor lead shoulder of the fastener body, thereby sealing an interior of the fastener body. An electrical contact on the conductor of the power cable and the conductor of the motor lead mate with each other in the interior of the fastener body.
In some embodiments, the assembly includes an elastomeric seal disposed between the nut assembly and the fastener body, the elastomeric seal having a plurality of expansion relief voids operable to collapse and relieve stresses exerted by the seal when the seal undergoes thermal expansion. The elastomeric seal may be located within the interior of the fastener body axially between the tapered shoulders. The elastomeric seal may have a conical shoulder that engages a conical shoulder of the fastener body and a flat shoulder facing the nut assembly and wherein the relief voids extend into the flat shoulder.
In other embodiments, the assembly may include an access port through a wall of the fastener body and a closure member for opening and closing the access port. The fastener body may be filled with a dielectric fluid which is pumped through the access port when the access port is open.
In other embodiments, the assembly may include a plurality of the splice connectors, each independently connecting one motor lead conductor to one power cable conductor. The threads at the power cable end and the motor lead end may be internal. The tapered shoulders adjacent the power cable end and the motor lead end may be within the interior of the fastener body.
In alternative embodiments, an electrical power assembly for supplying power to a motor includes a motor lead having one end for connection to the motor and having a plurality of individual conductors, a power cable having one end for connection to a power source and having a plurality of individual conductors and a splice connector for joining each of the conductors of the motor lead to one of the conductors of the power cable. The splice connector may include a tubular metal fastener body with a motor lead end and a power cable end and fastener body threads on the power cable end and on the motor lead end of the fastener body. The splice connector may also include a metal nut assembly fixed to one of the power cable conductors having threads that engage the fastener body threads on the power cable end. An electrical contact on the conductor of the power cable and the conductor of the motor lead, may mate with each other in the interior of the fastener body. An elastomeric seal may be disposed between the nut assembly and the fastener body, the elastomeric seal including a plurality of expansion relief ports operable to collapse and relieve stresses exerted by the seal when the seal undergoes thermal expansion.
In some embodiments, the elastomeric seal comprises a flat end face, a cylindrical band adjacent to the end face, and a tapered conical portion opposite the end face. The relief ports may be open to the end face and are shorter in length than a length of the cylindrical band. An outside surface of the tapered conical portion may mate with a tapered shoulder of the fastener body.
In yet other embodiments, an electric submersible pumping system includes a pump, an electric motor coupled to the pump, a motor lead connected to the motor and having a plurality of motor lead conductors, a power cable having a plurality of power cable conductors and a splice connector for connecting each of the power cable conductors to one of the motor lead conductors. Each of the splice connectors may include a tubular metal fastener body with a motor lead end and a power cable end and a tapered motor lead shoulder in the interior of the fastener body adjacent to the motor lead end and a tapered power cable shoulder in the interior of the fastener body adjacent to the power cable end. There may be fastener body threads on the power cable end and on the motor lead end of the fastener body. Each of the splice connectors may also include a metal nut assembly having threads that engage the fastener body threads on the power cable end, the metal nut assembly having a tapered shoulder in metal-to-metal sealing engagement with the power cable shoulder of the fastener body. A metal coupler may have threads that engage the fastener body threads on the motor lead end. The metal coupler may also have a tapered shoulder in metal-to-metal sealing engagement with the motor lead shoulder of the fastener body, thereby sealing an interior of the fastener body. An electrical contact on the conductor of the power cable and the conductor of the motor lead, may mate with each other in the interior of the fastener body.
In yet other embodiments, an electrical power assembly for supplying power to a motor includes a motor lead for connection to the motor and having a plurality of individual metal sheathed conductors, a power cable for connection to a power source and having a plurality of individual metal sheathed conductors and a tubular fastener body. The fastener body may include contacts for electrically connecting the one of the motor lead conductors to the one of the power cable conductors within the interior of the fastener body, and seals at a motor end and a power cable end of the fastener body for sealing of the one of the motor lead conductors and one of the power cable conductors to the fastener body, the seals defining a sealed interior within the fastener body containing a dielectric fluid. An access port through a wall of the fastener body may be operable to allow dielectric fluids to enter therethrough into the interior of the fastener body and there may be a closure member for opening and closing the access port. The closure member may be a screw.
In other embodiments, a mechanical connector includes a tubular metal fastener body with a first end and a second end and a tapered first shoulder adjacent to the first end and a tapered second shoulder adjacent to the second end and fastener body threads on the first end and on the second end of the fastener body. A metal nut assembly may be operable to connect to a conductor of a first cable, the nut assembly having threads that engage the fastener body threads on first end. The metal nut assembly may have a tapered shoulder in metal-to-metal sealing engagement with the first shoulder of the fastener body. A metal coupler may be operable to connect to a conductor of a second cable, the coupler having threads that engage the fastener body threads on the second end. The metal coupler may have a tapered shoulder in metal-to-metal sealing engagement with the second shoulder of the fastener body, thereby sealing an interior of the fastener body. An electrical contact on the first conductor of the first cable and the conductor of the second cable, may mate with each other in the interior of the fastener body.
In some embodiments, the connector may have an elastomeric seal disposed between the nut assembly and the fastener body. The elastomeric seal may have a flat end face, a cylindrical band adjacent to the end face, a tapered conical portion opposite the end face, and a plurality of expansion relief ports operable to collapse and relieve stresses exerted by the seal when the seal undergoes thermal expansion. The relief ports may be open to the end face and are shorter in length than a length of the cylindrical band. The connector may have an access port through a wall of the fastener body and a closure member for opening and closing the access port. The interior of the fastener body may filled with a dielectric fluid which may be pumped through the access port when the access port is open.
Some of the features and benefits of the present invention having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which:
In this embodiment, power cable 20 extends alongside production tubing 14, terminating in a splice or connector 21 that electrically couples cable 20 to a second power cable, or motor lead 23. Power cable 20 may be a high voltage, multi phase power cable, such as a three phase power cable. On the lower end of power cable 20, motor lead 23 connects to a pothead connector 22 that electrically connects and secures motor lead 23 to motor housing 24 of electric motor 16. The motor lead 23 extends upward beyond the pump, for example from 10 to 80 ft. The motor lead 23 could exceed 80 ft or be shorter than 10 ft depending on the application. The motor lead 23 may be flat and smaller in dimension than the power cable so that it can pass between the pump assembly and the casing.
Turning to
Each phase conductor 26 of power cable 20 comprises an outer metal tubing sheath 36 as its outermost layer. Cable tubing 36 is a tubular with a central axis and may be formed of ferrous metals including carbon steel, stainless steel tubular or non-ferrous metals, like Monel. A layer of cable insulation 38 is located within and co-axial to cable tubing 36. Cable insulation 38 forms a tubular with a central opening which contains cable wire 40. Cable wire 40 is a solid cylindrical member which is co-axial with both cable insulation 38 and cable tubing 36. In alternative embodiment, cable wire 40 could be a series of smaller braided wires to comprise a single wire member or phase.
Each conductor 28 of the motor lead 23 (
In the embodiment shown in
Turning to
As is seen in
A circumferential recess 62 is formed within the region of lesser wall thickness 60 of nut assembly 48. An elastomeric seal ring 64 is located within recess 62. Seal ring 64 creates a back-up seal between nut assembly 48 and fastener body 96. Threads on an exterior surface of nut assembly 48 may engage threads on an internal surface of the upper end of fastener body 96 to retain nut assembly 48 within fastener body 96. In alternative embodiments, other known forms of connection may be used to retain nut assembly 48 within fastener body 96. Cable tubing 36 terminates within nut assembly 48, while cable insulation 38 and cable wire 40 extend through the entire length of nut assembly 48.
Abutting the lower end 66 of nut assembly 48 is a first side of a metal thrust washer 68. Thrust washer 68 protects an elastomeric main seal 70 from rotational motion of nut assembly 48 and transfers the axial forces of nut assembly 48 Cable insulation 38 and cable wire 40 extend through the internal bore of main seal 70. As can be seen in
A number of expansion relief voids 78 are located within the cylindrical band 72. The voids 78 are open to end face 76 and are shorter in length than the length of cylindrical band 72. When exposed to high temperatures, main seal 70 will tend to expand. When the main seal 70 tends to expand it deforms against thrust washer 68 and upward facing shoulder 132, causing the material of main seal 70 to extend into or collapse into voids 78. This will reduce both the axial and the outward forces that main seal 70 would otherwise apply to the components that are in proximity to main seal 70. This will allow the nut assembly 48 to be used successfully in a broader range of high temperature well conditions.
Returning to
Turning now to the end of splice connector 32 closest to motor lead 23 (
As can be seen in
Threads on an exterior surface of coupler nut 98 may engage threads on an internal surface of the lower end of fastener body 96 to retain coupler nut 98 within fastener body 96. In alternative embodiments, other known forms of connection may be used to retain coupler nut 98 within fastener body 96. Housing coupler 92 comprises at least one, and as shown in
Returning to
Surrounding the male pin 120, and the lead insulation 44 is a pin or male insulator 122. Male insulator 122 is inside of fastener body 96 and creates an electrically insulating barrier between male pin 120 and fastener body 96. Male insulator may be formed of, for example, a high temperature polymer, thermoplastic or other known appropriate insulating material. Male insulator 122 may be attached to male pin 120 with a circular clip or other known retaining means. Male insulator 122 is a tubular member with a larger outer diameter and larger inner diameter at a lower end to accommodate the lead wire 46, lead insulation 44 and wire pocket 124. At its upper end, male insulator 122 has a smaller inner diameter surrounding the pin member 126 and a smaller outer diameter to fit within a lower end of female insulator 82. Male insulator 122 terminates before an upper end of pin member 126 such that pin member 126 may be disposed directly into wire pocket 84 of female pin 80. An electrical connection between the cable wire 40 and the lead wire 46 is made by way of the cable wire 40 being connected to the female pin 80, which is in contact with the male pin 120, which in turn is connected to the lead wire 46.
Fastener body 96 extends from the nut assembly 48 at its upper end, to coupler nut 98 at its lower end. As discussed above, there are metal-to-metal seals at both the upper end and lower end of fastener body 96. In some embodiments, air that is trapped within the confines of fastener body 96 may be vacuumed out by way of an access port 128 through the fastener body. To do so, a screw 130 in port 128 could be removed from the fastener body to open port 128. A dielectric fluid, such as dielectric motor oil, dielectric grease, or other suitable substance, may be pumped through port 128 to displace any air and fill any voids within fastener body 96. Screw 130 would then be replaced back in port 128 to close and seal port 128.
In operation, each phase conductor 26 the power cable 20 will be prepared and fitted with certain components of an individual splice connector 32. Likewise, each phase conductor 28 of the motor lead 23 will be prepared and fitted with certain components of an individual splice connector 32. Before and after the mating of the components of each splice connector 32, a series of factory acceptance tests, both mechanical and electrical may then be performed to ensure integrity of each splice connector 32. The splice connector 32 may then be disconnected and the motor lead 23 and power cable 20 relocated to its field of service. Once the motor lead 23, power cable 20 and related equipment has arrived in the field, the components of each splice connector 32 can be quickly and easily reconnected before the ESP assembly is lowered into the well by traditional means. Because each phase conductor 26 of power cable 20 mates independently by a separate splice connector 32 to each phase conductor 28 of the motor lead 23, the possibility of phase to phase shorts will be significantly reduced.
In addition, if the ESP needs to be returned to the surface for service or repair, the components of each splice connector 32 can be easily disconnected from each other, allowing the power cable 20 to be separated from the motor lead 23. When the ESP is ready to be returned to the well, the components of splice connector 32 can be easily reconnected to each other, creating an electrical connection between the power cable 20 and the motor lead 23.
During a disconnection procedure, looking at
Although the present invention has been described in detail, it should be understood that various changes, substitutions, and alterations can be made hereupon without departing from the principle and scope of the invention. Accordingly, the scope of the present invention should be determined by the following claims and their appropriate legal equivalents.
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