Patent Application
20200362871
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it may be understood that these statements are to read in this light, and not as admissions of prior alt
Wells are drilled to extract oil and/or gas from subterranean reserves. These resources are extracted from the wellbore through a wellhead that couples to the end of the wellbore. The flow of oil and/or gas out of the well is typically controlled by one or more valves on the wellhead. After flowing through the wellhead, the flow of oil and/or gas may be directed to a compressor that pumps the oil and/or gas to the surface, in a subsea environment, and/or pumps the fluid flow to another location, such as a refinery. Unfortunately, the vertically oriented shafts of these pumps or compressors may not be preloaded. In other words, the vertically oriented shafts may not have a force acting substantially perpendicular to their longitudinal axis that loads and stabilizes the shaft. These pumps or compressors with unloaded vertically oriented shafts may therefore experience rotor whirl or other rotor dynamic effects. Over time, rotor whirl may wear these vertically oriented pumps or compressors, which may result in reduced performance and/or increased maintenance.
In one embodiment, a vertical rotating system that includes a first vertical shaft that rotates. The first vertical shaft is oriented such that the gravitational force is substantially parallel to the first vertical shaft. A radial bearing extends about a first portion of the first vertical shaft. A first impeller sectioned couples to the first vertical shaft and rotates in a first direction to pump a first fluid. A first stator surrounds the first vertical shaft. The first stator defines a first groove that extends about a second portion of the first vertical shaft. The first groove receives a second fluid. A pressure of the second fluid drives the first vertical shaft away from the first groove.
In another embodiment, a vertical rotating system that includes a first vertical shaft that rotates about a central axis of the first vertical shaft. The first vertical shaft is oriented such that the gravitational force is substantially parallel to the first vertical shaft. A first impeller section couples to the first vertical shaft and rotates in a first direction. A stator surrounds the first vertical shaft. A plurality of bearing pads that extend circumferentially about the first vertical shaft. The plurality of bearing pads couple to the stator with a respective pivot connector of a plurality of pivot connectors. The plurality of bearing pads direct a force created by rotation of the first vertical shaft in a fluid to load the first vertical shaft.
In another embodiment, a contra-rotating compressor that includes a first vertical shaft that rotates about a first central axis of the first vertical shaft. The first vertical shaft is oriented such that the gravitational force is substantially parallel to the first vertical shaft. A first impeller section couples to the first vertical shaft and rotates in a first direction. A second vertical shaft rotates about a second central axis of the second vertical shaft. The second vertical shaft is oriented such that the gravitational force is substantially parallel to the second vertical shaft. A second impeller section rotates in a second direction that is opposite the first direction. The first and second impeller sections are axially aligned. A bearing system loads the first vertical shaft and/or the second vertical shaft.
These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
Reference will now be made in detail to specific embodiments illustrated in the accompanying drawings and figures. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to one of ordinary skill in the art that embodiments may be practiced without these specific details. In other instances, well-known methods, procedures, and components, have not been described in detail so as not to unnecessarily obscure aspects of the embodiments.
It will also be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first object could be termed a second object, and, similarly, a second object could be termed a first object, without departing from the scope of the present disclosure.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description and the appended claims, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term “and/or” as used herein refers to and encompasses any and possible combinations of one or more of the associated listed items. It will be further understood that the terms “includes,” “including,” “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, operations, elements, components, and/or groups thereof. Further, as used herein, the term “if” may be construed to mean “when” or “upon” or “in response to determining” or “in response to detecting,” depending on the context.
The discussion below relates to vertically oriented compressors, such as contra-rotating wet gas compressors. Contra-rotating wet gas compressors include inner and outer impeller sections that couple to separate shafts that rotate in opposite directions. The impeller sections are arranged so that alternating impeller sections rotate in opposite directions. This may enable the compressor to operate without static diffusers between the rotating impeller sections. Each impeller section includes impeller blades that rotate with the impeller sections. As the impeller blades rotate they transfer mechanical energy to the fluid (e.g., oil and/or gas), which compresses and drives the fluid through the contra-rotating wet gas compressor.
Each of these impeller sections couples to and is driven by a vertically oriented shaft. As these vertically oriented shafts rotate, the shafts may experience rotor dynamic effects, such as rotor whirl. In order to block and/or reduce these rotor dynamic effects these vertically oriented compressors include a bearing system. The bearing system creates a force (e.g., load) on the vertically oriented shafts that is perpendicular to or substantially perpendicular to the longitudinal axis of the vertically oriented shafts). In operation, the force drives the vertically oriented shafts toward a bearing, which blocks and/or reduces movement of the vertically oriented shafts as they rotate. In other words, the force generated by the bearing system blocks and/or reduces undesirable rotor dynamic effects, such as rotor whirl. As will be explained below, the bearing system may use a pressurized fluid to create the force on a vertically oriented shaft or the bearing system may use a series of bearing pads to generate and focus a force toward a vertically oriented shaft. In the discussion below, the term vertically oriented shaft is intended to describe shafts that are parallel to or substantially parallel to gravity vectors.
The subsea station 14 is connected to one or more flow lines, such as flow line 24. As illustrated, the flow line 24 couples to a platform 26, enabling oil and/or gas to flow from the wells 18 to the platform 26. In some embodiments, the flow lines 24 may extend from the subsea station 14 to another facility such as a floating production, storage and offloading unit (FPSO), or a shore-based facility. The flow lines 24 can also be used to supply fluids, as well as include control and data lines for use with the subsea equipment. In operation, the compressor module 22 pumps oil and/or natural gas from the subsea station 14 to the platform 26 through the flow line 24. In some embodiments, the compressor module 22 may also be located downhole, or in a subsea location such as on the sea floor in a Christmas tree at a wellhead 16.
It should be understood that the compressor module 22 may be configured for other subsea fluid processing functions, such as a subsea pumping module, a seawater injection module, and/or a subsea separator module. It should also be understood that the compressor module 22 may pump single-phase liquids, single-phase gases, or multiphase fluids.
In order to block and/or reduce undesirable rotor dynamic effects, such as rotor whirl, the compressor 48 includes one or more bearing systems 74 that load the vertically oriented shafts 56 and 60. For example, the compressor 48 may include two or more bearing systems 74 that create loads at different positions along the length of the shafts 56 and 60. By loading the shafts 56 and 60 at different points, the bearing systems 74 may further reduce and/or block undesirable rotor dynamic effects of the shafts 56 and 60.
The vertically oriented shaft 56 couples to the plurality of inner impeller sections 58 within the compressor section 54. As the vertically oriented shaft 56 rotates in counterclockwise direction 66, the vertically oriented shaft 56 rotates the inner impeller section 58 in counterclockwise direction 66. The rotation of the inner impeller section 58 rotates a plurality of impeller blades/airfoils 100 coupled to each inner impeller section 58. It is these impeller blades/airfoils 100 that drive and compress the fluid.
As explained above, the shaft 56, 60 is vertically oriented. That is, the shaft 56, 60 may be parallel to or substantially parallel to gravity vectors, such as gravity vector 126. The vertical orientation of the shaft 56, 60 may enable undesirable rotor dynamic effects (e.g., rotor whirl) as the shaft 56, 60 rotates. To reduce and/or block these undesirable rotor dynamic effects, the bearing system 74 directs a pressurized fluid into contact with the shaft 56, 60. The force of the fluid on the shaft 56, 60 blocks and/or reduces movement of the shaft 56, 60 that is perpendicular or substantially perpendicular to a longitudinal axis 127 of the cavity 122 (e.g., rotor whirl).
In order to direct the fluid into contact with the shaft 56, 60, the stator 120 defines a conduit 128 that receives the pressurized fluid. In some embodiments, the pressurized fluid may be a pressurized fluid (e.g., oil) used in the motors 50, 52. In other embodiments, the pressurized fluid may be the same fluid pressurized by the compressor 48. For example, a portion of the pressurized fluid exiting the outlet 72 of the compressor 48 may be directed to the stator 120 where it enters the conduit 128.
After flowing through the conduit 128, the fluid enters a chamber 130 that extends about the shaft 56, 60. The chamber 130 does not extend about the entire circumference of the shaft 56, 60 in order to create force in a specific direction. For example, the chamber 130 may extend between 1-270 degrees, 10-150 degrees, 50-100 degrees about the circumference of the shaft 56, 60. As the pressure of the fluid builds in the chamber 130, the fluid exerts a force that drives the shaft 56, 60 in direction 132. This force then controls the position of the shaft 56, 60 within the stator 120. After entering the chamber 130, some of the fluid may exit the chamber 130 and flow into one or more secondary chambers 134. The secondary chambers 134 may be on one or both sides of the chamber 130 along the axis of the shaft 56, 60. The secondary chambers 134 may extend completely about the shaft 56, 60. As the secondary chamber 134 receives the pressurized fluid, it creates a pressure pocket that encompasses the shaft 56, 60 equalizing the forces acting on the shaft 56, 60 over the length 136 of the secondary chamber 134. By including the secondary chamber 134 the bearing system 74 may provide a stabilizing force that may block excess movement of the shaft 56, 60 in direction 132 created by the pressure of the fluid in the chamber 130.
In operation, the shafts 56, 60 rotate within the stator 120, which drives rotation of the compressor section 54. As the shaft 56, 60 rotates (e.g. rotates in counterclockwise direction 151) the fluid in the cavity 122 adheres to the outer surface of the shaft 56, 60. The fluid is then dragged between the shaft 56, 60 and the bearing pads 152. The force of the fluid contacting the bearing pads 152 (i.e., contacting a face of the bearing pads 152 that faces the shaft 56, 60) drives rotation of the bearing pads 152 about the pivot connector 154. As illustrated in
Returning to
While the bearing system 150 includes two bearing pads 152 (i.e., bearing pads labeled 170) that are smaller/shorter than the remaining bearing pads 152, it should be understood that the number of smaller/shorter bearing pads to larger/longer bearing pads may change. For example, the bearing system 150 may include one shorter/smaller bearing pad and the remaining may be longer/larger bearing pads. In some embodiments, there may be more than two sizes of bearing pads. For example, the bearing system 150 may include two small bearing pads, two medium bearing pads, and one large bearing pad arranged within the stator 120 in order to load the shaft 56, 60 in a desired manner. It should also be understood that the number of bearing pads 152 may also vary depending the embodiments. For example, the bearing system 150 may include 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more bearing pads.
As illustrated, some of the bearing pads 202 include pivot connectors 204 that are spaced a distance 206 from a first outermost edge 208 (e.g., counter-clockwise edge). These bearing pads 202 will be labeled with the number 207. The remaining bearing pads 202 couple to the pivot connectors 204 at a distance 210 from the first outermost edge 208. These bearing pads 202 will be labeled with the number 209. The distance 210 is greater than the distance 206, which places the pivot connectors 204 closer to or at the center of the bearing pads 209. In this position, the bearing pads 209 will rotate less about the pivot connectors 204. Less rotation of the bearing pads 209 reduces the difference in the dimensions of the gap 212 between the first outermost edge 208 and the second outermost edge 211 of the bearing pads 202 and the shaft 56, 60. A more uniform gap 212 reduces the pressure gradient and therefore the force generated by the bearing pads 209 in direction 214. In contrast, the bearing pads 207 rotate more than the bearing pads 209 because the distance 206 from the first outermost edge 208 is less. The increased rotation of the bearing pads 207 increases the difference in the dimensions of the gap 212 between the first outermost edge 208 and the second outermost edge 211. A less uniform gap 212 increases the pressure gradient and therefore the force in directions 216 of the bearing pads 207. The difference in the forces created by the bearing pads 207 and 209 biases the shaft 56, 60 towards the bearing pads 209, which loads the shaft 56, 60.
As explained above, the bearing system 200 illustrates two sets of bearing pads (i.e., 207 and 209) with pivot connectors 204 at different distances from the first outermost edge 208. In some embodiments, each bearing pad 202 may couple to a respective pivot connector 204 at a distance that differs from the other bearing pads 202. In still other embodiments, there may be more than two groups of bearing pads with the same distances between the first outer most edges 208 and the pivot connectors 204. It should also be understood that bearing system 200 may include 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more bearing pads 202.
While three bearing system configurations have been discussed above, it should be understood that varying combinations of these configurations may also be possible. Specifically, a bearing system may include one or more of the configurations discussed above in order to bias or load a vertically oriented shaft to reduce and/or block undesirable rotor dynamic effects (e.g., rotor whirl). Specifically, the bearing system may include one or more of the following options: (1) varying the size of the bearing pads; (2) varying the position of the pivot connectors with respect to the bearing pads; and (3) varing the spacing between the bearing pads.
As used herein, the terms “inner” and “outer”; “up” and “down”; “upper” and “lower”; “upward” and “downward”; “above” and “below”; “inward” and “outward”; and other like terms as used herein refer to relative positions to one another and are not intended to denote a particular direction or spatial orientation. The terms “couple,” “coupled,” “connect,” “connection,” “connected,” “in connection with,” and “connecting” refer to “in direct connection with” or “in connection with via one or more intermediate elements or members.”
The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. Moreover, the order in which the elements of the methods described herein are illustrate and described may be re-arranged, and/or two or more elements may occur simultaneously. The embodiments were chosen and described in order to best explain the principals of the invention and its practical applications, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.
