This invention relates in general to a subterranean connector for use in a wellbore. More particularly, the present invention is directed to a high temperature pothead connector used to provide power to a submersible motor. Yet more particularly, the present invention provides a pothead connector that is capable of withstanding extreme conditions, such as high temperatures and pressures, as well as highly corrosive environments.
A common type of electrical submersible pump 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 motor lead has three conductors that are insulated and located within a single elastomeric jacket that is extruded around the assembled insulated conductors. Metallic outer armor may wrap around the jacket of the motor lead to avoid damage to the motor lead while running the pump assembly into the well. The motor lead extends upward beyond the pump, for example from 10 to 80 ft. The total of the motor lead and pothead is known as the motor lead extension (MLE). The lead could exceed 80 ft or be shorter than 10 ft depending on the application. A splice connects the motor lead to the power cable. The motor lead is flat and smaller in dimension than the power cable so that it can pass between the pump assembly and the casing.
The power cable comprises three conductors, each having one or more layers of insulation. An elastomeric jacket is usually extruded over the assembled conductors. In some cases, the insulated conductors are encased in lead. The insulated conductors are arranged either in a flat side-by-side configuration, or in a round configuration spaced 120 degrees apart from each other relative to a longitudinal axis of the power cable. A metallic armor is typically wrapped around the jacket to form the exterior of the power cable.
In some wells, the formation temperature is quite hot. Also, the motor generates heat. At least one of the insulation layers of each conductor may be formed of a polymer that is resistant to high temperature degradation. However, current high temperature polymer materials may not be capable of withstanding the high temperatures and harsh environments in some wells. If the insulation degrades, a short could result that would require the pump assembly to be pulled and replaced. Conventional pothead designs that are capable of withstanding these extreme conditions are generally bulkier and have large profiles. However, there are some situations in which the target wells have size limitations that prevent the use of these conventional pothead designs. Therefore, it would be beneficial to have a pothead design that is operable to work in harsh conditions while maintaining a small profile.
The present invention is directed to a device and method that satisfies at least one of these needs. One embodiment of the present invention provides for a pothead assembly having a compression plate, a plurality of ferrules, a pothead housing and a single compression collar. The compression plate has a plurality of holes formed therethrough, with each hole adapted to receive a metal wire protector containing an insulated wire. Each ferrule surrounds one of the metal wire protectors and engages one of the holes of the compression plate. The pothead housing has a base portion, with the base portion having a plurality of passages formed therein that register with the holes in the compression plate, wherein each passage receives one of the insulated wires. The single compression collar is in operable engagement with the pothead housing and all of the ferrules. The compression plate is located between at least a portion of the compression collar and the base portion of the pothead housing such that advancing the compression collar toward the base portion compresses each ferrule such that each ferrule is operable to circumferentially engage and seal around one of the metal wire protectors. In one embodiment, the holes are located radially about the compression plate's centerpoint. In another embodiment, the assembly includes a plurality of insulated wires, wherein each insulated wire is contained within one of the metal wire protectors. In an additional embodiment, the compression plate has a lower face, and the base portion includes a backside face, wherein one of the faces is convex and the other face is concave. For example, if the lower face is concave, then the backside face would be convex. Advantageously, in some embodiments of the present invention, the ferrules can be compressed simultaneously.
In an additional embodiment of the present invention, the pothead assembly also includes a lower insulator, a plurality of female receptacles, a plurality of retaining sleeves, a retainer, a compression gasket, a boot and a terminal pin isolation seal that radially surrounds the prong receptacle insulators. The lower insulator includes a lower end and an upper end, with the upper end having a plurality of insulator passages formed therein and the lower end having a plurality of prong receptacle insulators. The insulator passages are aligned with the base passages. The female receptacles are partially disposed within the insulator passages, while the retaining sleeves are disposed within the insulator passages and abut the female receptacles. The retainer has a back portion that is operable to threadedly engage the pothead housing. The compression gasket contacts the pothead housing and is operable to expand radially outward once the pothead assembly is connected to a downhole electric motor. The boot radially surrounds the retainer and abuts the compression gasket and is operable to provide additional sealing protection.
In a further embodiment, the present invention can include a first and second alignment bore. The first alignment bore extends into the lower insulator from its back surface and the second alignment bore extends into the base portion's front surface. An indexing pin is disposed within the first and second alignment bores and is operable to properly align components within the pothead assembly. In another embodiment, the retainer is made from a non-conductive material, which can include polyetheretherketone. In yet another embodiment of the present invention, the retainer can include a recess on a front edge of the retainer. This recess is formed to cooperate with a tool, such as a spanner wrench, in order to apply the necessary torque to engage the retainer with the pothead housing.
In a further embodiment, the pothead assembly includes the compression plate, a plurality of conical ferrules, the pothead housing, and the compression collar. The compression plate includes a lower face and a plurality of holes formed therethrough, with each of the holes being operable to receive an insulated wire contained within a metal wire protector. The holes are spaced circumferentially about the compression plate's center. Each of the conical ferrules is operable to receive one of the metal wire protectors. The pothead housing has a lower end and an upper end, with the lower end having a flange that is operable to engage a downhole electric motor. The upper end includes a base portion and a backside face. Both the base portion and the backside face have a plurality of passages formed therethrough, with each of the passages being operable to receive one of the ferrules and one of the insulated wires. The compression collar has an axis and is engageable with the pothead housing, with the compression plate located therebetween. Each of the passages in the backside face has a conical portion that mates with one of the ferrules, such that when the compression collar is engaged with the upper end of the pothead housing, the compression collar exerts an axial force on the compression plate, causing the compression plate to exert an axial force on the ferrules, which in turn causes the ferrules to move inwardly into the conical portions of the passages of the backside face and deform circumferentially about the metal wire protectors to form a metal to metal seal. In one embodiment, the seal formed around each metal wire protector is done without the use of a weld joint.
In one embodiment, a portion of the inner periphery of the compression collar is threaded for engaging threads of the pothead housing, and an upper end of the compression collar includes an annular lip, the annular lip being operable to exert an axial force on the compression plate as the threads are tightened.
The present invention also includes a method for creating a metal to metal seal within a pothead without the use of a weld joint. In one embodiment of the present invention, the method includes inserting a plurality of metal wire protectors through a plurality of ferrules and through a plurality of passages of a pothead assembly and engaging a single compression collar with a pothead housing such that a compression plate exerts a compressive force on the ferrules against the pothead housing and simultaneously compresses all the ferrules about the metal wire protectors to form a metal to metal seal.
Pothead connector [22] further includes compression collar [42] and compression plate [44]. In one embodiment, both compression collar [42] and compression plate [44] are made of high strength, corrosive resistant metallic material. As discussed in more detail below, compression plate [44] and compression collar [42] stabilize thin-walled tubing [36] (and thus wire [30]) within pothead connector [22]. As shown in
Each thin-walled tubing [36] has its own ferrule [38]. Each ferrule is a conical metal sleeve, having a larger diameter on the upper side. In one embodiment, each ferrule [38] engages thin-walled tubing [36] by a compression force (e.g. crimping). In a farther embodiment, each ferrule [38] is crimped onto thin-walled tubing [36] with equal crimping force. Additionally, the ferrule/tube seating depth is equivalent for each ferrule. In another embodiment, each ferrule [38] sealingly engages and deforms thin-walled tubing [36] upon rotation of compression collar [42] onto pothead housing [46].
As shown, pothead housing [46] comprises base portion [49] formed to coaxially reside within annular skirt [41]. A housing skirt [51], which is generally annular, extends from base portion's [49] outer periphery towards the lower end of pothead connector [22]. In one embodiment, base portion [49] includes a backside face [57] (
In one embodiment, compression plate [44] slides up against the back side of each ferrule [38], and compression collar [42] is slipped over compression plate [44]. Compression plate [44] has bore holes [66] (
Lower insulator [52] also includes passages aligned with the passages formed in base portion [49]. A portion of wire [30] and insulating layer [32] extend longitudinally past thin-walled tubing [36] within pothead housing [46] and into the passage of lower insulator [52]. A retaining sleeve [48] is provided in the lower insulator passage that radially surrounds insulating layer [32]. Preferably, retaining sleeve [48] is made of a non-conductive engineered thermoplastic. More preferably, retaining sleeve [48] is made of polyetheretherketone (PEEK). A portion of wire [30] further extends longitudinally past insulating layer [32]. The portion of wire [30] is not insulated and is threaded on its outer surface. In the embodiment shown, each female receptacle [50] has a generally tubular configuration and includes a wire connection [53] on its upper end and a prong receptacle insulator [55] on its lower end. A flange extends radially outward from the outer surface of wire connection [53] proximate to female receptacle [50] open end. Each, female receptacle [50] is disposed in pothead connector [22] with its wire connection [53] in the lower portion of lower insulator [52]. Threads are formed on the inner circumference of wire connection [53] so that wire [30] may be threadedly connected to female receptacle [50] via wire connection [53]. Lower insulator [52] is then pushed over each female receptacle [50] and retaining sleeve [48]. The lower insulator passage has a reduced diameter proximate to lower insulator [52] lower end that forms a shoulder mating with the flange. In a preferred embodiment, lower insulator [52] is made of a non-conductive engineered thermoplastic. In a more preferred embodiment, lower insulator [52] is made of PEEK.
The lower portion of lower insulator [52] has an outer diameter reduced from the upper portion, defining a shoulder on the insulator's outer surface where its outer diameter is reduced. An annular gap resides between the lower portion of lower insulator [52] and the inner diameter of housing skirt [51]. Threaded retainer [54], which is threaded on its outside periphery, is formed for insertion into the annular gap between lower insulator [52] and housing skirt [51] and threadedly connects with pothead housing [46]. Threaded retainer [54] has at least one recess [60] on its lower edge formed to cooperate with a spanner wrench to apply the necessary torque to connect threaded retainer [54] to pothead housing [46].
When threaded retainer [54] is connected within pothead housing [46], its upper terminal end engages the shoulder on lower insulator [52] thereby securing lower insulator [52] within pothead housing [46] and pothead connector [22]. Threaded retainer [54] helps to align and seal the non-conductive material of pothead connector [22]. A first alignment bore [61] is formed downward from the upper surface of lower insulator [52]. A second alignment bore [63] is formed upward from the lower surface of base portion [49]. In one embodiment, indexing pin [58] is disposed within the second alignment bore and during assembly lower insulator [52] is oriented to receive indexing pin [58] therein. Indexing pin [58] thus aligns and properly orients components within pothead connector [22]. A cylindrical ring or seal boot [56] radially surrounds threaded retainer [54] and is adjacent pothead housing [46]. The configuration as shown in
While the invention has been shown or described in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention. Additionally, the present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed.
This patent application claims priority to U.S. Provisional Patent Application Ser. No. 61/047,469 filed on Apr. 24, 2008, which is incorporated by reference in its entirety.
Number | Date | Country | |
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61047469 | Apr 2008 | US |