Patent Grant
9825400
Field of the Invention
The invention relates generally to downhole electric equipment, and more particularly to systems and methods for improving the reliability and ease of installation of electrical connections between power cables and downhole electric equipment such as electric submersible pumps (ESP's).
Related Art
Electric submersible pump (ESP) systems are commonly positioned within subterranean wells and used to pump fluids from the wells. Power suitable to drive the ESP systems is produced at the surface of the wells and is delivered to the ESP systems via power cables that extend into the wells. The power cables are typically spliced to motor lead extensions (heavy gauge conductive wires), which are in turn connected to the motor of the ESP using a “pothead” connector.
Conventionally, a motor lead extension extends along the exterior of the ESP from near the top of the ESP to the motor. At the top of the motor, the motor lead extension is curved inward so that the pothead connector at the end of the motor lead extension can be coupled to the motor head. The motor head is normally configured to accept the pothead connector at an angle with respect to the axis of the system in order to facilitate the connection of the pothead to the motor head. The connection is angled to accommodate the position of the pothead as the stiff motor lead extension is curved inward toward the connection on the motor head.
Although the angled connection of the pothead to the motor head relieves the problem of the motor lead extension affecting the orientation of the pothead, it can cause several other problems. For instance, the motor lead extension and pothead have some weight and therefore tend to hang straight down. Consequently, it is necessary for the installer to manually reorient the pothead to the angle of the motor head interface. As noted above, the motor lead extension is very stiff, and it may be difficult to accurately position the pothead to correctly engage the motor head.
Another, related problem is that, because the pothead connector is angled with respect to the axis of the motor, the connector extends outward, radially, beyond the outer diameter of the motor and into the annulus between the motor and the casing of the well. Further, the motor lead extension, which is aligned with the pothead connector, also extends outward beyond the outer diameter of the motor and into the annulus between the motor and the casing. As a result of the pothead and the motor lead extension extending beyond the outer diameter of the motor, the equipment designer must either reduce the size of the motor to accommodate this, or risk of damage to the pothead or motor lead extension when the motor is installed in the narrow annulus in the well.
Yet another problem is that the connection between the pothead and the motor head may be damaged in the process of trying to align and secure these components. More specifically, the insulation block (“i-block”) that is positioned in the motor head to provide insulation between the conductors at the pothead interface may be very brittle, and an attempt to secure a misaligned pothead to the motor may crack the i-block. The i-block may then fail to provide the necessary electrical isolation of the conductors, which can result in shorting of the conductors and failure of the motor.
Another problem with conventional pothead connectors is that the interface between the connector and the motor housing provides only a small area for sealing. Typically, a relatively small, annular seal is positioned around a portion of the pothead connector that plugs into the motor housing. Also, conventional pothead connectors are typically secured to the motor housing by a pair of bolts on opposite sides of the plug-in portion of the connector. As the pothead connector becomes more slender and as the spacing of the bolts increases, the deflection of the connector housing increases, resulting in reduced contact pressure on the sealing surface of the connector. The use of only two bolts in the conventional design may also require increasingly large bolts to provide the desired preload, but the amount of space for these bolts is decreasing as motor diameters are reduced.
This disclosure is directed to systems and methods for connecting power cables to downhole equipment such as ESPs using side-exit (radial) connections. In one particular embodiment, a system includes an electric drive coupled by a power cable to a piece of downhole equipment such as an ESP. The electric drive is positioned at the surface of a well with the power cable coupled to it. The power cable extends into the well bore and is coupled to the downhole equipment which is positioned in the well bore. The power cable has a connector with a first set of radially oriented terminals (the terminals are perpendicular to the conductors of the power cable). These terminals engage a second set of terminals that are installed in the downhole equipment. The radial orientation of the terminals of the connector and downhole equipment allow the power cable to remain axially oriented, thereby facilitating engagement of the terminals and requiring less annular space in the well bore.
In one embodiment, the connector and the downhole equipment have complementary sealing surfaces between which a fluid tight seal is formed. A gasket may be positioned between the sealing surfaces to improve the seal. The sealing surfaces may be substantially flat and may be axially oriented, allowing for a much greater sealing area than conventional pothead connectors. This also allows the connector to be secured to the equipment housing with more (e.g., three or more) bolts or other fasteners than conventional potheads, thereby reducing deflection and improving contact pressure across the sealing surfaces. The connector may be positioned within a recess in the housing of the downhole equipment in order to reduce the amount of annular space required by the connector.
An alternative embodiment comprises a method for electrically coupling a power cable to a piece of downhole equipment such as an ESP. In this method, a power cable is provided, where the lower end of the power cable has a side-exit (radial) connector. This connector has a set of terminals that are oriented perpendicularly to the power cable so that they face radially inward toward the ESP. The ESP has a complementary set of terminals that are configured to be electrically coupled to (e.g., mate with) the terminals of the connector. The terminals of the ESP face generally radially outward. The power cable, which is oriented parallel to the axis of the ESP (and the well bore) is positioned with the connector radially outward from the terminals of the ESP. The connector is then moved radially inward toward the ESP to engage its terminals with those of the ESP. When the terminals have been engaged with each other, the connector is secured to the ESP's housing, forming a seal between the two. A gasket or the like may be positioned between the connector and the ESP housing to provide a better seal.
Numerous other embodiments are also possible.
Other objects and advantages of the invention may become apparent upon reading the following detailed description and upon reference to the accompanying drawings.
While the invention is subject to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and the accompanying detailed description. It should be understood, however, that the drawings and detailed description are not intended to limit the invention to the particular embodiment which is described. This disclosure is instead intended to cover all modifications, equivalents and alternatives falling within the scope of the present invention as defined by the appended claims. Further, the drawings may not be to scale, and may exaggerate one or more components in order to facilitate an understanding of the various features described herein.
One or more embodiments of the invention are described below. It should be noted that these and any other embodiments described below are exemplary and are intended to be illustrative of the invention rather than limiting.
As described herein, various embodiments of the invention comprise systems and methods for coupling the power cable of an ESP system to the motor of the system in a manner that reduces or eliminates one or more of the problems described above. This is accomplished by utilizing a side-exit (radial) configuration of the connector pins that extend through the housing of the motor head, in conjunction with a connector at the end of the motor lead extension that is configured to engage the connector pins radially (i.e., horizontally as the connector and motor leads are suspended vertically).
Referring to
In this embodiment, ESP 120 includes a motor section 121, seal section 122, and pump section 123. ESP 120 may include various other components which will not be described in detail here because they are well known in the art and are not important to a discussion of the invention. Motor section 121 is operated to drive pump section 123, thereby pumping the oil or other fluid through the tubing string and out of the well. Drive system 110 produces power (e.g., three-phase AC power) that is suitable to drive motor section 121. This output power is provided to motor section 121 via power cable 112.
Power cable 112 includes a primary cable that extends downward along the tubing string from the drive unit at the surface of the well to a point near the ESP. At this point (typically 10-50 feet above the ESP), the primary cable is connected (e.g., spliced) to a motor lead extension. The motor lead extension runs from the primary cable to the motor, and is connected to the motor by a connector 113. In a conventional system, connector 113 is a “pothead” that is positioned at the top of the motor and is oriented at an angle of around 10-15 degrees with respect to the axis of the motor in order to accommodate the gradual curve of the stiff conductors that extend from the motor lead extensions, essentially straight through the pothead, and then into the motor. In the present systems, however, the connection between the motor lead extensions and the conductors within the motor form relatively sharp angles, thereby reducing or eliminating problems associated with bend the motor leads. For example, the present systems may use a side-exit connector which has conductive pins that are connected at right angles to the motor lead extensions and internal motor leads. This may also be referred to as a radial connection because the terminals that connect the motor lead extensions to the internal wiring of the motor extend radially through the interface between the connector and the motor head.
For the purposes of this disclosure, the terms “axis” will be used to refer to the longitudinal axis of the well bore. The ESP and cable are considered to be substantially coaxial with the well bore. The term “axial” and similar terms will be used to refer to directions substantially parallel to the axis of the well bore. The term “radial” and similar terms will be used to refer to directions substantially perpendicular to the axis of the well bore. Radial directions do not necessarily intersect the axis of the well bore.
Before describing exemplary embodiments of the present invention, it may be helpful to illustrate a conventional pothead connection. Referring to
The electrical conductor of the motor lead is encased in a layer of electrical insulation. A layer of polymeric or metallic material of low permeability may cover the insulating layer, and a protective metal layer may be provided to prevent damage to the motor lead when the motor is installed in the well. The conductor of the motor lead passes through the top of the pothead connector, and the end of the conductor is connected within the body of the pothead connector to a conductive female terminal 222 positioned at a lower end of the connector. Insulating engineered material 223 provides mechanical strength and electrical insulation to keep the conductors in position and electrically isolated. A polymeric seal is made against the insulating engineered material and the insulation of the conductor. Female terminal 222 is configured to mate with a male terminal 231 of motor head 230. An insulating block (“i-block”) insulates the male terminal from the housing of motor head 230. Male terminal 231 is electrically coupled to the internal wiring 233 of the motor. A seal 228 is provided between a lower portion of pothead connector 220 and motor head 230.
It can be seen from
In the embodiment of
In the embodiment of
Connector 310 is configured to engage the connector pins radially (horizontally or left-to-right in the figures) while the motor lead extensions are extended axially (vertically or top-to-bottom in the figures). As noted above, this configuration eliminates the need to manually reposition the connector from an axial orientation in order to engage the connector pins. In one embodiment, the pins are configured to mate with corresponding sockets in the connector. In other embodiments, the pins may be positioned in the motor and designed to engage corresponding terminals of the connector in a face-to-face configuration, or in some other manner. After connector 310 engages the connector pins, the connector is secured to the motor head. The connector may be secured using a variety of means, such as screws, nuts and studs, clamping bands, and the like.
Referring to
Each of the motor lead extensions (e.g., 320) extends (vertically in the figure) into an MLE insulator block 306, which is nested within the portion of connector 310 that is secured to the motor housing. MLE insulator block 306 has a nose 307 that extends laterally (horizontally in the figure) from the body of the MLE insulator block. Nose 307 is shaped to fit within the pocket formed by opening 305 in insulator block 303. Holes (e.g., 308) are formed in nose 307 to accommodate the connector pins (e.g., 304) that extend outward from the insulator block 303 in the motor head. When MLE insulator block 306 is mated with motor head insulator block 303, the connector pins extend through the holes to electrically couple the motor leads (e.g., 302) to the motor lead extensions (e.g., 320). An insulating plate 309 may be positioned between the nose of MLE insulator block 306 and motor head insulator block 303 to increase the tracking path in the connection.
When connector 310 is secured to motor head 300, the assembly is more compact than a system with a conventional pothead connection. As shown in
Referring to
The connector pins in this embodiment are installed with electrical insulators that electrically isolate the connector pins from the motor head and from each other. The electrical insulators are designed to extend through the motor head to increase the tracking path between the connector pins and other conductive components such as the motor head housing. Connector 410 is configured to engage the radially extending connector pins while it and the motor lead extensions are axially oriented. Since the weight of the motor lead extensions and connector normally maintains the connector in this orientation, this facilitates proper engagement of connector 410 with the connector pins in motor head 400.
As in the embodiment of
The embodiment of
Referring to
In this embodiment, electrical insulators are installed around the connector pins in a manner similar to the previously described embodiments. The connector configuration in this embodiment would, however, maintain the axial alignment of the conductors, rather than making the right angles of the side-exit configurations of
Referring to
This side of pothead connector 610 has a flat surface 617 that abuts a corresponding flat surface of motor head 600 (within recess 605) when the pothead connector is installed on the motor head. The sealing surfaces of motor head 600 and pothead connector 610 in this embodiment are substantially parallel to the axis of the motor. A portion of the recess extends upward to accommodate motor lead extensions 620 and allows the pothead connector and motor lead extensions to lie flat against the motor, which reduces the amount of annular space occupied by the system. A gasket 616 is positioned on surface 617 to provide a seal between pothead connector 610 and motor head 600. Pothead connector 610 is wide enough to allow placement of multiple bolt holes (e.g., 612) around the connector (between opening 618 and the outer edges of the connector), so that multiple fasteners (e.g., bolts 611) can be used to secure the connector to motor head 600.
The embodiment of
As noted above, the specific embodiments described herein are exemplary, and many variations of the described features may be incorporated into other embodiments that fall within the scope of the claims. For instance, rather than using gaskets to seal the connector against the motor, other sealing means, such as o-rings, rubber boots, etc., can be used as alternatives to, or in combination with gaskets. Alternative embodiments may also use different types of fasteners to secure the connector to the motor. For example, clamps, straps/banding, tack welding, threaded or quick-connect fasteners may be used. In still another variation, the components may use snap-together construction which requires no fasteners at all.
The benefits and advantages which may be provided by the present invention have been described above with regard to specific embodiments. These benefits and advantages, and any elements or limitations that may cause them to occur or to become more pronounced are not to be construed as critical, required, or essential features of any or all of the described embodiments. As used herein, the terms “comprises,” “comprising,” or any other variations thereof, are intended to be interpreted as non-exclusively including the elements or limitations which follow those terms. Accordingly, a system, method, or other embodiment that comprises a set of elements is not limited to only those elements, and may include other elements not expressly listed or inherent to the described embodiment.
While the present invention has been described with reference to particular embodiments, it should be understood that the embodiments are illustrative and that the scope of the invention is not limited to these embodiments. Many variations, modifications, additions and improvements to the embodiments described above are possible. It is contemplated that these variations, modifications, additions and improvements fall within the scope of the invention as detailed within the descriptions herein.
This application claims the benefit of U.S. Provisional Patent Application 62/027,481, filed Jul. 22, 2014 by Clingman et al, which is incorporated by reference as if set forth herein in its entirety.
| Number | Name | Date | Kind |
|---|---|---|---|
| 5186644 | Pawlicki | Feb 1993 | A |
| 5595496 | Konda | Jan 1997 | A |
| 6666708 | Saito | Dec 2003 | B2 |
| 20130040480 | Frey | Feb 2013 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20160024854 A1 | Jan 2016 | US |
| Number | Date | Country | |
|---|---|---|---|
| 62027481 | Jul 2014 | US |
