Patent Description:
<CIT> discloses an electric submersible pumping system to pump fluids from a wellbore. <CIT> discloses an underwater canned pump with a magnetic thrust bearing comprising platters that remain stationary with respect to a shaft and thrust discs connected to the shaft and interleaved with the platters, the thrust discs producing repulsive magnetic forces when approaching the platters.

Submersible pumping systems are often deployed into wells to recover petroleum fluids from subterranean reservoirs. The submersible pumping system includes one or more fluid filled electric motors coupled to one or more high performance pumps. When energized, the motor provides torque to the pump through a series of connected shafts. When rotated, the pump pushes wellbore fluids to the surface through production tubing in accordance with well-known fluid mechanics.

During operation, thrust generated by the pump is carried through the shaft to other components within the pumping system. Because the components within the pumping system are often closely positioned with very small tolerances, axial movement created by thrust from the motor or pump may cause adjacent components to come into contact. This contact may accelerate wear or cause immediate damage to the components within the pumping system.

In the past, designers have employed interference-based thrust bearings to carry the thrust created within the pumping system. Typical thrust bearings include a stationary portion affixed to a housing, a rotating portion affixed to the rotating shaft, and a pad positioned between these two portions. The pad resists axial motion between the stationary and rotating portions of the thrust bearing.

Although widely adopted, the use of traditional thrust bearings may be undesirable in certain applications. Because traditional thrust bearings require contact between the rotating and stationary portions of the thrust bearing, the components within the thrust bearing must be installed within prescribed tolerances. Additionally, as the thrust pads wear over time, the tolerances between adjacent components may change and the thrust bearing may become less effective at limiting axial movement along the shaft. There is, therefore, a need for an improved thrust bearing design that overcomes these and other deficiencies in the prior art.

In accordance with an embodiment of the present invention, <FIG> shows an elevational view of a pumping system <NUM> attached to production tubing <NUM>. The pumping system <NUM> and production tubing <NUM> are disposed in a wellbore <NUM>, which is drilled for the production of a fluid such as water or petroleum. As used herein, the term "petroleum" refers broadly to all mineral hydrocarbons, such as crude oil, gas and combinations of oil and gas.

The pumping system <NUM> includes a pump <NUM>, a motor <NUM>, a seal section <NUM> and a thrust chamber <NUM>. The production tubing <NUM> connects the pumping system <NUM> to a wellhead <NUM> located on the surface. Although the pumping system <NUM> is primarily designed to pump petroleum products, it will be understood that the pumping system <NUM> can also be used to move other fluids. It will also be understood that, although each of the components of the pumping system <NUM> are primarily disclosed in a submersible application, some or all of these components can also be used in surface pumping operations. Furthermore, although the pumping system <NUM> is depicted in a vertical deployment in <FIG>, the pumping system <NUM> can also be used in non-vertical applications, including in horizontal and non-vertical wellbores <NUM>. Accordingly, references to "upper" and "lower" within this disclosure are merely used to describe the relative positions of components within the pumping system <NUM> and should not be construed as an indication that the pumping system <NUM> must be deployed in a vertical orientation.

The motor <NUM> receives power from a surface-based facility through power cable <NUM>. Generally, the motor <NUM> is configured to drive the pump <NUM>. In some embodiments, the pump <NUM> is a progressive cavity pump or positive displacement pump. In other embodiments, the pump <NUM> is a turbomachine that uses one or more impellers and diffusers to convert mechanical energy into pressure head. The pump <NUM> includes a pump intake <NUM> that allows fluids from the wellbore <NUM> to be drawn into the pump <NUM>. The pump <NUM> forces the wellbore fluids to the surface through the production tubing <NUM>.

The seal section <NUM> provides several functions, including transmitting torque between the motor <NUM> and pump <NUM>, restricting the flow of wellbore fluids into the motor <NUM> and accommodating the expansion and contraction of motor lubricant as the motor <NUM> moves through thermal cycles during operation and pressure equalization. The seal section <NUM> includes one or more internal fluid isolation mechanisms that provide a positive barrier between the clean lubricants in the motor <NUM> and the contaminated fluids in the wellbore <NUM>. The seal section <NUM> may include some combination of labyrinth chambers, seal bags, pistons, bellows and other fluid isolation mechanisms. These fluid isolation mechanisms may be placed in series or in parallel within the seal section <NUM>.

In the embodiment depicted in <FIG>, the seal section <NUM> is positioned above the motor <NUM> and below the pump <NUM>. The thrust chamber <NUM> is positioned between the motor <NUM> and the seal section <NUM>. It will be understood that the thrust chamber <NUM> may be integrated within the housing of the seal section <NUM> or the motor <NUM>, or configured as a separate component within the pumping system <NUM> (as depicted in <FIG>). The thrust chamber <NUM> should be positioned within the pumping system <NUM> so that it can control the axial displacement of shafts used to transfer torque from the motor <NUM> to the pump <NUM>.

Turning to <FIG>, shown therein is a cross-sectional view of the thrust chamber <NUM>. The thrust chamber <NUM> includes a housing <NUM>, a head <NUM>, a base <NUM> and a shaft <NUM>. The head <NUM> and base <NUM> are configured for secure engagement with the housing <NUM>. The head <NUM> is configured to connect the thrust chamber <NUM> to an adjacent downstream component, such as the seal section <NUM>. The base <NUM> is configured to connect the thrust chamber <NUM> to an adjacent upstream component, such as the motor <NUM>. The shaft <NUM> transfers torque from the motor <NUM> to the seal section <NUM> and pump <NUM>. The housing <NUM>, head <NUM> and base <NUM> may be filled with a liquid lubricant during assembly.

The thrust chamber <NUM> includes a magnetic thrust bearing <NUM>. The magnetic thrust bearing <NUM> generally includes one or more thrust discs <NUM> and one or more stationary platters <NUM>. The thrust discs <NUM> and platters <NUM> are interleaved within the magnetic thrust bearing <NUM> in an alternating pattern. The thrust discs <NUM> are secured to the shaft <NUM> through a keyed, pinned or press-fit connection and configured for rotation within the thrust chamber <NUM>. The platters <NUM> are secured in a stationary position within the housing <NUM>. As illustrated in <FIG>, there are three thrust discs <NUM> interleaved between four platters <NUM>.

Turning to <FIG>, shown therein are front and rear views, respectively, of a thrust disc <NUM>. The thrust disc <NUM> includes a plurality of magnets <NUM> arranged about the thrust disc <NUM>. In the embodiment depicted in <FIG>, the magnets <NUM> are secured to both faces 136a, 136b of the thrust disc <NUM>. In other embodiments, the magnets <NUM> are only secured to one face <NUM> of the thrust disc <NUM>. Turning to <FIG>, shown therein are front and rear views, respectively, of a platter <NUM>. The platter <NUM> also includes a plurality of magnets <NUM> arranged about the platter <NUM>. The magnets <NUM> may be secured to both faces 138a, 138b of the platter <NUM> or to only one face <NUM> of the platter <NUM>. As used herein, the term "thrust disc magnets" will refer to magnets <NUM> attached to, or embedded within, the thrust discs <NUM>. The term "platter magnets" will refer to magnets <NUM> attached to, or embedded within, the platters <NUM>.

The platter <NUM> further includes a central aperture <NUM> through which the shaft <NUM> extends without contacting the platter <NUM>. Although eight magnets <NUM> are shown on the thrust disc <NUM> and platter <NUM> of <FIG>, it will be appreciated that the use of greater or fewer numbers of magnets <NUM> on the thrust discs <NUM> and platters <NUM> falls within the scope of the invention. Moreover, it will be appreciated that the size, shape, configuration and number of magnets <NUM> may differ between the thrust discs <NUM> and platters <NUM> within the magnetic thrust bearing <NUM>.

Turning to <FIG>, shown there is a side perspective view of an exemplary embodiment of the magnet <NUM>. Each magnet <NUM> is a permanent magnet that produces magnetic fields with poles extending in substantially opposite axial directions. Suitable magnetic materials include nickel-plated rare-earth magnets, such as neodymium and alloys of neodymium, iron and boron. Although the magnets <NUM> may be cylindrical (as shown in <FIG>), the magnets <NUM> may also be bar, box-type or ring magnets.

The magnets <NUM> can be secured to the thrust discs <NUM> and platters <NUM> with threaded fasteners, adhesive, clamps, brackets or other locking mechanisms. In some embodiments, the thrust disc <NUM> and platter <NUM> may include recessed magnet pockets (not shown) that are sized and shaped such that the magnets <NUM> are recessed, flush or only slightly protruding from the faces <NUM> of the thrust discs <NUM> and faces <NUM> of the platters <NUM>. In other embodiments, the thrust discs <NUM> and platters <NUM> include bores through which the magnets <NUM> extend from one side to the other.

In yet other embodiments, the thrust discs <NUM> and platters <NUM> are constructed from magnetic materials or materials impregnated with magnetic particles and produce magnetic fields without the need for the magnets <NUM>. In each case, the magnets <NUM> are oriented on the faces <NUM>, <NUM> of the thrust discs <NUM> and platters <NUM> such that the poles of the magnetic fields produced by the magnets <NUM> are commonly aligned. For example, all of the magnets <NUM> on face 136a of thrust disc <NUM> are oriented such that the north magnetic pole of each magnet <NUM> extends away from the face 136a of the thrust disc <NUM>.

<FIG> provides a side view of a portion of the magnetic thrust bearing <NUM> within the housing <NUM>. The thrust discs <NUM> and platters <NUM> are arranged in an alternating, interleaved fashion within the magnetic thrust bearing <NUM>. A small gap <NUM> is provided between each pair of thrust discs <NUM> and platters <NUM>. Each thrust disc <NUM> and platter <NUM> is oriented within the magnetic thrust bearing <NUM> to produce a repelling magnetic force with an adjacent thrust disc <NUM> or platter <NUM>. This repulsive force is produced by matching the polarity of the magnetic fields produced by adjacent thrust discs <NUM> and platters <NUM>. The magnitude of the repulsive magnetic force increases as the distance between adjacent thrust discs <NUM> and platters <NUM> decreases. In this way, axial movement of the thrust discs <NUM> and shaft <NUM> is restricted by the repulsive force produced by the magnets <NUM> on the adjacent stationary platters <NUM>.

Although a repulsive force is useful in opposing the approximation of the thrust discs <NUM> and platters <NUM>, it may also be useful in certain applications to configure the magnetic thrust bearing <NUM> so that it produces an attractive force between the discs <NUM> and platters <NUM>. For example, it may be useful in certain applications to offset the weight carried by the shaft <NUM> through the housing <NUM> with an attractive force produced between a disc <NUM> and a platter <NUM>. The attractive magnetic force can be produced by orienting the magnets <NUM> on discs <NUM> and platters <NUM> with opposite magnetic poles on juxtaposing sides of the magnets <NUM>. It will be appreciated that the magnetic thrust bearing <NUM> may include a first set of discs <NUM> and platters <NUM> that are configured to produce an attractive force and a second set of discs <NUM> and platters <NUM> that are configured to produce a repulsive force. To avoid cancelling the forces produced by these respective sets of discs <NUM> and platters <NUM>, it may be useful to set the platters <NUM> and discs <NUM> at different distances within these sets so that, for example, the attractive forces are effective before the counteracting repulsive forces become prevalent.

The magnetic thrust bearing <NUM> presents significant advantages over prior art thrust bearings. In particular, the thrust discs <NUM> and platters <NUM> of the magnetic thrust bearing <NUM> are designed to oppose lateral movement of the shaft <NUM> without the frictional losses that arise from conventional contact-based thrust bearings. Additionally, the efficacy of the magnetic thrust bearing <NUM> does not diminish over time and the magnets <NUM> can be reused after the useful life of the pumping system <NUM> has expired.

Claim 1:
A magnetic thrust bearing (<NUM>) for use in a pumping system that includes a pump (<NUM>) driven by a motor (<NUM>) through a shaft (<NUM>), the magnetic thrust bearing (<NUM>) comprising:
platters (<NUM>) that remain stationary with respect to the shaft (<NUM>), wherein each of the platters (<NUM>) includes a plurality of platter magnets (<NUM>) and characterized in that each of the platter magnets (<NUM>) extends from one side of the platter (<NUM>) to the other side of the platter; and
thrust discs (<NUM>) connected to the shaft (<NUM>) and alternatingly interleaved with the platters (<NUM>), wherein each of the thrust discs (<NUM>) includes a plurality of thrust disc magnets (<NUM>) configured to produce repulsive magnetic forces as the thrust discs (<NUM>) approach the platters (<NUM>) and wherein each of the thrust disc magnets (<NUM>) extends from one side of the thrust disc (<NUM>) to the other side of the thrust disc.