Stator coil retention system for unvarnished stators

A downhole electric motor device has a longitudinally extending tubular housing; a stator part deployed within the tubular housing; a stator coil winding looped through the stator part with an end turn having an apex; and a connecting device connecting between at least one of the coil windings and an end of the housing adjacent to an end of the stator part, thereby supporting the coil winding.

TECHNICAL FIELD

The present application relates generally to enhancements in downhole electrical motors, and in particular to supporting and restraining the movement of stator coils located within the motor housing.

BACKGROUND

Electrical motors are often placed downhole in an oil or gas field to perform a variety of functions. These functions can include artificial lift, whereby the motor drives a pump that is used to bring downhole fluids to the surface. A typical motor can be 6 inches in diameter and 30 feet long. The wire used in the windings can be ⅛ inch magnet wire. The magnet wire can be over 1000 feet long. The magnet wire is wound through the lamination stack many times to create a stator coil for each phase of the motor. The stator coils in a three phase AC motor can weigh in excess of 600 pounds.

Some designs for downhole motors use stator coils that are wrapped in polyimide tape and treated with varnish. The varnishing process provides mechanical stiffness, insulation, protects the stator coils from vibration damage, protects the coils from water, and holds the stator coils in place. The varnish itself has an upper limit operating temperature approaching 400° F. The varnish can be used in conjunction with epoxy, increasing the effective operating temperature to 550° F. At or above those temperatures the varnish will generally melt, causing the motor to be inoperable.

It is beneficial if artificial lift equipment can operate in higher temperature environments. In a steam assisted gravity drainage system a small borehole injects steam into the formation and another larger borehole below the small borehole collects the resulting production fluids. The steam is used to lower the viscosity of the well fluids and promote production of formation fluids that normally would not be possible. However, the temperature requirements for such operation can be in excess of 550° F. Therefore, a varnished stator coil can become a limiting factor when artificial lift equipment is deployed downhole in such an environment. Absent the varnish, issues can develop relating to inadequate support of the weight of the stator windings.

Accordingly, there exists a need for an apparatus and a method to retain unvarnished stator coils inside a motor housing.

SUMMARY

Embodiments in the present application relate to a downhole electric motor device comprising: a longitudinally extending tubular housing; a stator part deployed within the tubular housing; a stator coil winding looped through the stator part with an end turn having an apex; and a connecting device connecting between at least one of the coil windings and an end of the housing adjacent to an end of the stator part, thereby supporting the coil winding

Other or alternative embodiments having fewer or additional features will be apparent from the following description, from the drawings, and from the claims.

It is to be noted, however, that the appended drawings illustrate only typical embodiments and are therefore not to be considered limiting of claim scope, for the embodiments may admit to other equally effective embodiments.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to provide an understanding of the various embodiments. However, it will be understood by those skilled in the art that those embodiments presented may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.

In the specification and appended claims, the terms “connect”, “connection”, “connected”, “in connection with”, and “connecting” are used to mean “in direct connection with” or “in connection with via another element”; and the term “set” is used to mean “one element” or “more than one element”. As used herein, the terms “up” and “down”, “upper” and “lower”, “upwardly” and “downwardly”, “upstream” and “downstream”; “above” and “below”; and other like terms indicating relative positions above or below a given point or element are used in this description to more clearly described some embodiments. However, when applied to equipment and methods for use in wells that are deviated or horizontal, such terms may refer to a left to right, right to left, or other relationship as appropriate. Moreover, the term “sealing mechanism” includes: packers, bridge plugs, downhole valves, sliding sleeves, baffle-plug combinations, polished bore receptacle (PBR) seals, and all other methods and devices for temporarily blocking the flow of fluids through the wellbore. Furthermore, the term “treatment fluid” includes fluid delivered to a formation to stimulate production including, but not limited to, fracing fluid, acid, gel, foam or other stimulating fluid.

The present application generally relates to a well system that utilizes a submersible motor. By way of example, a submersible motor may be used in an electric submersible pumping system to produce or otherwise move desired fluids. An embodiment can include a submersible motor constructed with unvarnished stator coils with a support device to be utilized in order to support the stator coil windings within the motor housing.

In the embodiment illustrated inFIG. 1, an electric submersible pumping system34is designed for deployment in a well40within a geological formation42containing desirable production fluids, such as hydrocarbon based fluids. A wellbore44typically is drilled into formation42and, at least in some applications, is lined with a wellbore casing46. The wellbore casing46is perforated to form a plurality of openings (perforations)48through which production fluids can flow from formation42into wellbore44. In other applications, the submersible pumping system34can be used to deliver treatment fluids downhole and out through perforations48into the surrounding reservoir.

The electric submersible pumping system34may be deployed into wellbore44with a suitable conveyance system50that can be constructed in a variety of forms and configurations depending on the application. For example, conveyance system50may comprise a tubing52, such as production tubing or coiled tubing. The conveyance system50is connected to submersible pump36or to another appropriate component of electric submersible pumping system34by a connector54. In the embodiment illustrated, a power cable56is routed downhole along conveyance system50and electric submersible pumping system34to submersible motor32. The power cable56provides electrical power to submersible motor32so the submersible motor can, in turn, power submersible pump36. In operation, the submersible pump36draws well fluid into the electric submersible pumping system34via a pump intake58and pumps the fluid to a collection location through, for example, tubing52.

By way of example, submersible motor32may comprise a three-phase, induction motor in which stator coils76provide the motor field. The submersible motor may be constructed without varnish, and the stator coils76have end turns77aand77bthat are supported with a support device, as described in greater detail below.

Referring generally toFIG. 2, one embodiment of submersible motor32is illustrated. In this embodiment, submersible motor32comprises an outer housing60, such as a tubular housing. A stator62, having a stator bore64, is positioned within the housing60such that the stator bore64is generally aligned with housing60in an axial direction. A rotor66is rotatably positioned within stator bore64and coupled to a drive shaft68. During operation, the rotating rotor66causes drive shaft68to rotate, and this rotation is used to drive submersible pump36.

By way of example, stator62is formed with a plurality of laminations70, such as steel laminations with insulation between each lamination. The stack of steel laminations may be insulated by suitable end laminations72aand72bdisposed at opposed axial ends of the lamination stack70. In many applications, the laminations are perforated in a manner that creates generally axial slots to receive insulated magnet wire conductors74that form the motor stator coil76. At axial ends of the lamination stack, the insulated wire conductors74of the stator coils76are looped into end turns77aand77b. The end turns77aand77benable the insulated wire conductors74to be directed back through the lamination stack via axial slots according to a desired winding pattern. The insulated wire conductors74that form end turns77aand77bcan be grouped together with each group secured by a suitable wrap80or other type of covering. Electrical power is supplied to winding76via appropriate lead wires82. Submersible motor32is a three-phase motor comprising stator coils77for all three phases, as well as associated end turns77aand77bfor each stator coil74.

By way of example, an embodiment of the invention might include using a support device84aand84b. The support device84aand84bcan be flat in shape and have slots102as depicted inFIG. 3Athat provide connecting points. After each of the three stator coils76required for an AC motor32have been threaded, taped80, and coated with an epoxy, the support devices84aand84bare threaded into place at both ends of the housing60. Then, each of the end turns77aand77bare connected with the adjacent support devices84aand84bwith a connecting device86aand86bin order to connect between the stator coils76and the support device84aand84b. For example, the connecting device can be fiberglass tape. Furthermore, the connecting device86aand86bcan help prevent axial and radial movement of the stator coils76.

By way of example, the support devices84aand84bcould be configured with various types of slot configurations as illustrated inFIG. 3.FIG. 3Adepicts a support device101located within a housing. The slots102can be a pattern optimized to support the weight of the stator coil76as well as other design considerations. The slots103for support device104are smaller and would be able to support more stator coil76weight. The support device105is easier to manufacture because the slots106can be formed from a simple drilling process.

Another embodiment of the invention utilizes a support device188with a wave shaped profile to minimize stator coil76movement. For comparison reasonsFIG. 4Adepicts an inner panoramic of the previous embodiments whileFIG. 4Bdepicts the inner panoramic of the current embodiment. After each of the three stator coils177of an AC motor are threaded, taped, and coated with an epoxy, the wave shaped support device188is screwed into place. Then, each of the three end turns are connected (e.g., tied) to the wave shaped support device188with the connecting device186, e.g., a sufficient amount of fiberglass tape186, in order to suspend the stator coils177from the support device188. Next, a wave shaped support device188on the opposite side of the housing60is screwed into place and again the end turns190on the opposite side are connected with the connecting device186and can prevent axial and radial movement of the stator coils177. The profile of the wave shaped support device188is such that the restraining mechanism, in this case fiberglass tape86, has tension forces that are normal to the point of the end turn190where the fiberglass tape86is in contact. That will prevent the fiberglass tape186from sliding in the direction of the apex of the end turn190. As a result, the forces on the fiberglass tape86will be evenly distributed and less prone to failure.

Another embodiment might include using a conical structure in conjunction with fiberglass tape214aand214bto prevent the axial and radial movement of the stator coil276. Conical structures92aand92bare inserted as depicted inFIG. 5and will keep the stator coils276in place against the motor housing260. Then, the end turns210aand210bare fastened to the support device212aand212bwith fiberglass tape214aand214b, respectively. The conical structures92aand92breduces the stress on the fiberglass tape214aand214brespectively. The conical structures92aand92balso allow mechanically weaker materials with improved characteristics such as thermal resistance to be used as the connecting device.

Alternatively, the support device84aand84bcan be composed of a suitable metal other than stainless steel, such as a suitable polymer, plastic compound, a metal with an insulation coating, and/or composite compound. The support device84aand84bcan be either a conductive or non-conductive metal depending on the distance from the end turns and other design considerations such as the insulation on the end turns and the type of fastening mechanism material.

Alternatively, the connecting device86aand86bcan be composed of Nylon, Teflon, or other suitable materials or equivalent material or combinations known in the art.

Alternatively, the support device84aand84bcan be mounted on a shoulder within the housing60instead of threading into place. The support device84aand84bcan also be threaded into place and stopped with a shoulder.

Alternatively, the support device84aand84bcan utilize some other type of contact point other than slots or holes that is known in the art.

The embodiments described above provide examples of submersible motors and support devices that can be used to improve the run life of a variety of well systems. It should be noted, however, that the fastening mechanism can be used to prevent the radial inward collapse of end coils in many types of motors and in a wide variety of well related applications. Additionally, the material used to create the fastening mechanism, the number of fastening mechanism components used in an individual motor, and the configuration of those components can be adjusted as needed for a given application. Though multiple stator coils76are noted most often, one or more end coils are contemplated. Also, though stator coils76and associated parts and description and most often contemplated with respect to both ends of a motor/stator device, it is contemplated that separate features are equally applicable to only one end thereof.

Accordingly, although only a few embodiments of the present invention have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this application. Such modifications are intended to be included within the scope as defined in the claims.