Patent Publication Number: US-2022220819-A1

Title: Downhole plug deployment

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of the filing date of U.S. provisional application No. 63/137,545 filed on 14 Jan. 2021. The entire disclosure of the prior application is incorporated herein by this reference. 
    
    
     BACKGROUND 
     This disclosure relates generally to equipment utilized and operations performed in conjunction with a subterranean well and, in one example described below, more particularly provides for plug deployment downhole. 
     It can be advantageous to be able to control fluid flow in a well. For example, well tools can be activated or deactivated by deploying a plug into a tubular string from the surface. Plugs can be used to operate valves or prevent flow through flow passages when desired. 
     Therefore, it will be appreciated that improvements are continually needed in the art of controlling fluid flow in a well. The present disclosure provides such improvements, which may be utilized in a wide variety of different well operations and with a wide variety of different well systems. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a representative partially cross-sectional view of an example of a well system and associated method which can embody principles of this disclosure. 
         FIGS. 2A  &amp; B are representative partially cross-sectional views of examples of vibratory tools that may be used with the  FIG. 1  system and method. 
         FIG. 3  is a representative cross-sectional and perspective view of an example of a plug release tool that can embody the principles of this disclosure. 
         FIG. 4  is a representative cross-sectional view of the plug release tool, taken along line  4 - 4  of  FIG. 3 . 
         FIG. 5  is a representative cross-sectional view of the plug release tool, taken along line  5 - 5  of  FIG. 4 . 
         FIG. 6  is a representative cross-sectional and perspective view of the plug release tool with an example of a plug. 
         FIG. 7  is a representative cut-away view of the plug. 
         FIG. 8  is a representative cross-sectional and perspective view of the plug release tool with another example of the plug. 
         FIG. 9  is a representative cut-away view of the  FIG. 8  plug. 
         FIG. 10  is a representative cross-sectional and perspective view of another example of the plug release tool with another example of the plug. 
         FIG. 11  is a representative cross-sectional and perspective view of a portion of the  FIG. 10  plug release tool. 
         FIG. 12  is a representative cross-sectional view of an example of an insert section of the  FIG. 10  plug release tool. 
         FIG. 13  is a representative end view of the insert section. 
         FIG. 14  is a representative cross-sectional view of the insert section with another example of the plug. 
     
    
    
     DETAILED DESCRIPTION 
     Representatively illustrated in  FIG. 1  is a system  10  for use with a subterranean well and an associated method which can embody principles of this disclosure. However, it should be clearly understood that the system  10  and method are merely one example of an application of the principles of this disclosure in practice, and a wide variety of other examples are possible. Therefore, the scope of this disclosure is not limited at all to the details of the system  10  and method described herein and/or depicted in the drawings. 
     In the  FIG. 1  example, a drill string  62  has been deployed into a wellbore  60 , in order to drill the wellbore further into the earth. For this purpose, the drill string  62  includes a drill bit  64  connected at its distal end. The drill bit  64  is part of a tool string  68  or bottom hole assembly (BHA). Note that it is not necessary in keeping with the principles of this disclosure for a BHA to be positioned at a bottom of a hole, wellbore or any other specific position in a well. 
     In addition, it is not necessary for a drilling operation to be performed. The drill string  62  could be another type of tubular string, such as a completion string, a workover string, etc. The scope of this disclosure is not limited to any particular well operation or function performed with a tubular string in a well. 
     As depicted in  FIG. 1 , a vibratory tool  22  is connected in the drill string  62  as part of the BHA  68 . The vibratory tool  22  is used in this example to assist in deploying the drill string  62  into a generally horizontal section of the wellbore  60 . When operational, the vibratory tool  22  produces vibrations, for example, due to pressure fluctuations, accelerations of mass, impacts, or other stimulus caused by the vibratory tool. The vibrations produced by the vibratory tool  22  reduce friction between the drill string  62  and the wellbore  60 , thereby enabling the drill string to displace more readily along the wellbore. 
     A downhole plug release tool  12  is also connected in the drill string  62  as part of the BHA  68 . The plug release tool  12  is used to release a plug (such as, a ball, a dart, etc.) downhole, so that the plug can engage the vibratory tool  22  to thereby operate the vibratory tool. In this example, the engagement of the plug with the vibratory tool  22  may be used to activate or deactivate the vibratory tool, that is, to cause the vibrations to be produced by the vibratory tool, or to cause the vibrations to cease. 
     In other examples, the vibratory tool  22  may not be used. For example, the release of the plug  14  could instead be used to operate a drill motor  66 , a stabilizer, a reamer, or another type of well tool. The scope of this disclosure is not limited to use of the plug release tool  12  to operate any particular type of well tool, or to cause any particular function to be performed in the well. The plug release tool  12  may be used to activate or deactivate any type of well tool. 
     As depicted in  FIG. 1 , the vibratory tool  22  is positioned in a generally horizontal section of the wellbore  60 . It is desired in this example for the vibratory tool  22  to produce vibrations when the BHA  68  is in the generally horizontal section of the wellbore  60 , since this is when the friction between the drill string  62  and the wellbore is greatest, and vibrations may be undesirable when the BHA  68  is in a generally vertical section of the wellbore. 
     Note that it is not necessary for the BHA  68  or any other portion of a tubular string to be positioned in a generally horizontal or otherwise inclined section of a wellbore, or for the wellbore to even include a generally horizontal section, when a well tool is operated using the plug release tool  12 . The plug release tool  12  could be used to operate a well tool in a vertical section of a wellbore in keeping with the scope of this disclosure. 
     In some examples it may be desired to cease operation of the vibratory tool  22  when the drill motor  66  and drill bit  64  are being used to drill into the earth. For example, the vibrations produced by the vibratory tool  22  might otherwise be too energetic when sufficient fluid is flowed through the drill string  62  to operate the drill motor  66 . In such examples, it may be desired to cease production of the vibrations after the BHA  68  is positioned in the generally horizontal section of the wellbore  60  but before commencing drilling. 
     Referring now to  FIGS. 2A  &amp; B, two examples of how the plug release tool  12  may be used to operate the vibratory tool  22  are representatively illustrated. However, as mentioned above, it should be clearly understood that the scope of this disclosure is not limited to operating a vibratory tool using the plug release tool  12 , or to operating the vibratory tool  22  in any particular manner. 
     In the  FIG. 2A  example, the plug release tool  12  is used to release a plug  14  into a fluid passage  16  of the plug release tool. Fluid flow  18  through the passage  16  conveys the plug  14  into a fluid passage  20  of the vibratory tool  22 . The plug  14  may be released in the plug release tool  12  in response to any type of stimulus including, for example, passage of a predetermined time period, exposure to well fluid, degrading (e.g., dissolution, corrosion, melting, oxidation, hydration, etc.) of a layer of the plug, a change in orientation of the plug release tool, and/or a variation in the fluid flow  18  through the plug release tool, or a combination of any of these. The scope of this disclosure is not limited to any particular stimulus or cause for release of the plug  14 . 
     The fluid passage  20  splits in the vibratory tool  22  into an operational flow passage  24  and a bypass flow passage  26 . Sufficient fluid flow through the operational flow passage  24  will cause a predetermined pressure differential across a vibratory device  28  and thereby cause the vibratory device to produce vibrations. 
     The vibratory tool  22  and vibratory device  28  in the  FIG. 2A  example may be similar to those described in U.S. Pat. No. 9,957,765, which is incorporated herein by this reference in its entirety for all purposes. Other types of vibratory tools and vibratory devices may be used in keeping with the scope of this disclosure. 
     When the bypass flow passage  26  is open, the predetermined pressure differential is not produced across the vibratory device  28 , because the fluid flow  18  is permitted to pass through the bypass flow passage instead of, or in addition to, the operational flow passage  24 . However, when the plug  14  sealingly engages a seat  30  in the bypass flow passage  26  (a screen, filter or other exclusion device  32  prevents the plug from being conveyed into the operational flow passage  24 ), the bypass flow passage is closed and the fluid flow  18  through the bypass flow passage is prevented. 
     The predetermined pressure differential across the vibratory device  28  is, thus, achieved and the vibrations are produced. In this manner, the vibratory tool  22  can be operated to begin producing the vibrations downhole when desired (such as, when the BHA  68  is in the generally horizontal section of the wellbore  60  in the  FIG. 1  system  10 ). 
     In the  FIG. 2B  example, the vibratory device  28  is initially able to produce vibrations downhole in response to the fluid flow  18 . The bypass flow passage  26  is closed and the predetermined pressure differential can be produced across the vibratory device  28 . The vibratory tool  22  can be operated to cease production of the vibrations when desired. 
     The fluid flow  18  through the bypass flow passage  26  is initially prevented by a sliding sleeve  34 . The sliding sleeve  34  may be retained in this initial position by releasable means, such as, a shear pin, snap ring, collets, etc. (not shown). 
     When the plug  14  is released by the plug release tool  12 , the plug can be conveyed by the fluid flow  18  into sealing engagement with the seat  30 , which is formed in the sliding sleeve  34  in this example. This sealing engagement prevents the fluid flow  18  from passing through the operational flow passage  24  and, thus, causes the vibrations to cease being produced by the vibratory device  28 . In addition, the sleeve  34  will displace to a position in which the fluid flow  18  is permitted to pass through the bypass flow passage  26 . 
     The vibratory tool  22  and vibratory device  28  in the  FIG. 2B  example may be similar to those described in U.S. Pat. No. 9,181,767, which is incorporated herein by this reference in its entirety for all purposes. Other types of vibratory tools and vibratory devices may be used in keeping with the scope of this disclosure. 
     In  FIGS. 3-5 , an example of the downhole plug release tool  12  is representatively illustrated. In this example, the plug  14  is released from the plug release tool  12  in response to a combination of a change in orientation of the plug release tool and a change in the fluid flow  18  through the plug release tool. 
     As depicted in  FIG. 3 , the plug release tool  12  is in an inclined or generally horizontal orientation. The plug  14  is engaged with a seat  36  formed in an insert  38  secured in an outer housing  40 . Multiple flow passages  42 ,  44  extend longitudinally through the insert  38  and form portions of the flow passage  16 , which extends longitudinally through the outer housing  40 . 
     The flow passage  42  is centrally located in the insert  38 . The fluid flow  18  causes a pressure differential to be created across the plug  14  when it is engaged with the seat  36 . In this manner, the plug  14  is maintained in engagement with the seat  36 , even though the plug release tool  12  is in an inclined or horizontal orientation. 
     When the plug release tool  12  is initially deployed into the wellbore  60  as part of the BHA  68  in the  FIG. 1  system  10 , the plug release tool is in a generally vertical orientation, and the plug  14  is engaged with the seat  36 , thereby closing off the flow passage  42 . Thereafter, the fluid flow  18  through the drill string  62  will maintain the plug  14  engaged with the seat  36  (due to a pressure differential created across the plug by the fluid flow), even after the orientation of the tool  12  changes to inclined or horizontal. 
     When it is desired to release the plug  14 , for example, to operate the vibratory tool  22 , the fluid flow  18  is ceased, so that the pressure differential across the plug is relieved. If, at this point, the plug release tool  12  is in a horizontal or sufficiently inclined orientation, the plug  14  will fall away from the seat  36  by action of gravity. The plug release tool  12  may be positioned in a horizontal or sufficiently inclined orientation before or after the fluid flow  18  is ceased. 
     In  FIG. 4 , a cross-sectional view of the plug release tool  12  is representatively illustrated. In this view, the plug  14  is not depicted, and it can be seen that there are six of the flow passages  44  circumferentially distributed about the central flow passage  42 . One of the flow passages  44  is in a lowermost position, directly below the central flow passage  42 . However, it is not necessary for the lowermost flow passage  44  to be positioned directly below the central flow passage  42 . 
     The number of flow passages  44  can be varied as desired. Preferably, there are enough of the flow passages  44  to ensure that at least one of them will be appropriately positioned, when the plug release tool  12  is in a sufficiently inclined or horizontal orientation, so that the plug  14  can be conveyed through the lowermost flow passage by the fluid flow  18 . 
     In  FIG. 5 , the plug release tool  12  is representatively illustrated after the plug  14  has fallen away from the seat  36 . The plug  14  can now be conveyed by the fluid flow  18  through the lowermost flow passage  44 . 
     Note that, in this example, the plug  14  is too large in diameter to pass through the flow passage  42 , but the plug is not too large to pass through the flow passages  44 . In the event that the plug  14  should fail to fall away from the seat  36  after the fluid flow  18  is ceased and the plug release tool  12  is in a sufficiently inclined or horizontal orientation, another plug could be deployed into the flow passage  16  (such as, deployed from surface), and this other plug could be conveyed through the lowermost (or other) flow passage  44  by the fluid flow  18  and into the vibratory tool  22  (or other well tool) to operate the well tool. 
     In  FIGS. 6 &amp; 7  another example of the plug release tool  12  is representatively illustrated. In this example, the plug  14  has at least one outer layer that initially prevents it from passing through the flow passages  44 . In this manner, the plug  14  cannot inadvertently fall away from the seat  36  and pass through one of the flow passages  44  before it is intended to operate the vibratory tool  22  (or other well tool). 
     As depicted in  FIG. 6  it may be seen that, with the outer layer on the plug  14 , the plug is too large to pass through any of the flow passages  44 . However, if the outer layer is degraded or dispersed downhole, so that an outer diameter of the plug  14  is decreased in this example, the plug will be able to pass through one of the flow passages  44 . 
     As depicted in  FIG. 7 , the outer layer  46  covers an inner core  48  of the plug  14 . The inner core  48  may be made of a suitably strong and tough material (such as, steel, tungsten carbide, etc.). However, the scope of this disclosure is not limited to use of any particular material for the inner core  48 . 
     The outer layer  46  may be made of any material that will degrade or disperse downhole as desired. For example, the outer layer material may degrade in response to exposure to well fluid (either naturally occurring or later introduced), or in response to passage of a predetermined period of time. The outer layer material may dissolve, corrode, oxidize or hydrate in well fluid. The outer layer material may melt when exposed to downhole temperature. The outer layer material may comprise a eutectic material, magnesium, a dissolvable plastic, ploy-glycolic acid, poly-lactic acid, anhydrous boron, paraffin or wax, etc. The scope of this disclosure is not limited to any particular material of the outer layer  46 . 
     The plug release tool  12  of  FIGS. 6 &amp; 7  operates in a similar manner to the plug release tool of  FIGS. 3-5 , except that the plug  14  cannot pass through the flow passages  44  until the outer layer  46  is degraded or dispersed. Note that, in this example, the plug  14  is initially too large in diameter to pass through the flow passages  42 ,  44 , but when the outer layer  46  is degraded or dispersed the plug is not too large to pass through the flow passages  44 . In the event that the plug  14  should fail to fall away from the seat  36  after the fluid flow  18  is ceased and the plug release tool  12  is in a sufficiently inclined or horizontal orientation, another plug could be deployed into the flow passage  16  (such as, deployed from surface), and this other plug could be conveyed through the lowermost (or other) flow passage  44  by the fluid flow  18  and into the vibratory tool  22  (or other well tool) to operate the well tool. 
     In  FIGS. 8 &amp; 9  another example of the plug release tool  12  is representatively illustrated. In this example, the plug  14  has multiple outer layers that initially prevent it from passing through the flow passages  44 . In this manner, the plug  14  cannot inadvertently fall away from the seat  36  and pass through one of the flow passages  44  before it is intended to operate the vibratory tool  22  (or other well tool). 
     As depicted in  FIG. 8  it may be seen that, with the multiple outer layers on the plug  14 , the plug is too large to pass through any of the flow passages  42 ,  44 . However, if the outer layers are degraded or dispersed downhole, so that an outer diameter of the plug  14  is decreased in this example, the plug will be able to pass through one of the flow passages  44 . 
     As depicted in  FIG. 9 , a layer  50  covers an inner core  48  of the plug  14 . The layer  50  may be made of any material that will degrade or disperse downhole as desired. For example, any of the materials described above for the outer layer  46  may be used for the material of the layer  50 . The scope of this disclosure is not limited to any particular material of the layer  50 . 
     An outer layer  52  covers the layer  50  of the plug  14 . The outer layer  52  may be made of any material that will degrade or disperse downhole as desired. For example, any of the materials described above for the layers  46 ,  50  may be used for the material of the layer  52 . The scope of this disclosure is not limited to any particular material of the layer  52 . 
     In one example, the outer layer  52  could be made of a material that degrades or disperses in response to exposure to elevated well temperature (such as, a eutectic, paraffin or wax material). In this manner, the outer layer  52  would not degrade at or near the surface, but would melt or otherwise degrade and, thus, permit exposure of the layer  50  to well fluids, when the plug release tool  12  is sufficiently deep in the well and the fluid flow  18  is established to prevent inadvertent dislodgment of the plug  14  from the seat  36 . 
     In this example, the layer  50  could be made of a material that dissolves, corrodes, oxidizes, hydrates or otherwise degrades or disperses in response to contact with well fluid. The layer  50  is prevented from contacting the well fluid until the outer layer  52  is degraded or dispersed. After the layer  50  is degraded or dispersed, the outer diameter of the plug  14  is small enough to allow the plug to pass through one of the flow passages  44  with the fluid flow  18 . 
     The plug release tool  12  of  FIGS. 8 &amp; 9  operates in a similar manner to the plug release tool of  FIGS. 3-7 , except that the plug  14  cannot pass through the flow passages  44  until both of the layers  50 ,  52  are degraded or dispersed. Note that, in this example, the plug  14  is initially too large in diameter to pass through the flow passages  42 ,  44 , but when the layers  50 ,  52  are degraded or dispersed the plug is not too large to pass through the flow passages  44 . 
     In the event that the plug  14  should fail to fall away from the seat  36  after the fluid flow  18  is ceased and the plug release tool  12  is in a sufficiently inclined or horizontal orientation, another plug could be deployed into the flow passage  16  (such as, deployed from surface), and this other plug could be conveyed through the lowermost (or other) flow passage  44  by the fluid flow  18  and into the vibratory tool  22  (or other well tool) to operate the well tool. 
     In  FIGS. 10-13 , another example of the downhole plug release tool  12  is representatively illustrated. In this example, the plug  14  is not retained by the fluid flow  18  against the seat  36  until it is desired to release the plug. Instead, the plug  14  is retained by a retainer structure  54  that degrades or disperses downhole in order to release the plug  14 . 
     The plug  14  and the retainer structure  54  are secured in the insert  38  by means of a threaded member  56 . In other examples, the plug  14  and retainer structure  54  could be secured in the insert  38  without use of the threaded member  56 , the retainer structure and the threaded member could be integrated as a single element, etc. The scope of this disclosure is not limited to any particular details of any of the plug release tool  12  examples as described herein or depicted in the drawings. 
     The retainer structure  54  is made of a material that degrades or disperses in the well environment as desired. For example, any of the materials described above for use in the layers  46 ,  50 ,  52  may be used in the retainer structure  54 . 
     Thus, the plug  14  is initially retained in the insert  38  by the retainer structure  54  until the material of the retainer structure degrades or disperses in the well. This allows the plug  14  to fall by action of gravity (when the plug release tool  12  is in a sufficiently inclined or horizontal orientation) to a position in which the fluid flow  18  can convey the plug through one of the flow passages  44 , and then through the remainder of the flow passage  16  to the vibratory tool  22  (or other well tool). 
     As in the  FIGS. 3-9  examples, the  FIGS. 10-13  example of the plug release tool  12  needs to be in a sufficiently inclined or horizontal orientation, in order for the plug  14  to fall and be released for conveyance with the fluid flow  18  to the vibratory tool  22  (or other well tool). However, in the  FIGS. 10-13  example, the fluid flow  18  does not need to be ceased in order to allow the plug  14  to fall. 
     As in the  FIGS. 6-9  examples, the  FIGS. 10-13  example of the plug release tool  12  requires a material to be degraded or dispersed, in order for the plug  14  to be released for conveyance with the fluid flow  18  to the vibratory tool  22  (or other well tool). However, in the  FIGS. 10-13  example, a material needs to be degraded or dispersed in order for the plug  14  to fall in the insert  38 , but no material of the plug  14  itself is degraded or dispersed. Instead, a material retaining the plug  14  is degraded or dispersed. The plug  14  itself is small enough to pass through the flow passages  44  any time it is released from the retainer structure  54 . 
     Note that radially extending passages  58  are formed in the insert  38  to enable the plug  14  to fall when the retainer structure  54  is degraded or dispersed. In the event that the plug  14  should fail to fall from the insert  38  when the retainer structure  54  is degraded and the plug release tool  12  is in a sufficiently inclined or horizontal orientation, another plug could be deployed into the flow passage  16  (such as, deployed from surface), and this other plug could be conveyed through the lowermost (or other) flow passage  44  by the fluid flow  18  and into the vibratory tool  22  (or other well tool) to operate the well tool. 
     In  FIG. 14 , another example of the plug release tool  12  is representatively illustrated, although only the plug  14 , insert  38 , retainer structure  54  and threaded member  56  are depicted. The remainder of the  FIG. 14  plug release tool  12  is the same as or similar to the  FIGS. 10-13  example. 
     As depicted in  FIG. 14 , the retainer structure  54  is elongated as compared to the  FIGS. 10-13  example. The  FIG. 14  elongated retainer structure  54  positions the plug  14  so that it is more closely aligned with the radial passages  58  in the insert  38 . In this manner, the plug  14  will more readily fall through one of the radial passages  58  when the retainer structure  54  is degraded or dispersed. As a result, the plug  14  can fall in the insert  38 , so that it can be conveyed with the fluid flow  18  to the vibratory tool  22  (or other well tool) at less inclined (more vertical) orientations. 
     It may now be fully appreciated that the above disclosure provides significant advancements to the art of deploying plugs in a well. In examples described above, a plug  4  can be deployed from the plug release tool  12  when desired to activate or deactivate a well tool, such as, the vibratory tool  22 . 
     A downhole plug release tool  12 , system  10  and method are provided to the art. In one example, a plug  14  is released from the plug release tool  12  downhole, and the plug is then engaged with a well tool to thereby operate the well tool. 
     The operation of the well tool may comprise activating or deactivating a vibratory device  22 . The operation of the well tool may comprise opening or closing a bypass passage  26  of the well tool. The operation of the well tool may comprise activating or deactivating a drill motor  66 , reamer, stabilizer or other well tool. 
     The plug  14  may be released in response to passage of a predetermined time period, exposure to well fluid, degrading (e.g., dissolution, corrosion, melting, oxidation, hydration, etc.) of a layer  46 ,  50 ,  52  of the plug or a structure  54  retaining the plug, a change in orientation of the plug release tool  12 , and/or a variation in fluid flow  18  through the plug release tool. 
     The plug  14  may comprise one or more outer layers  46 ,  50 ,  52 . The plug  14  may be released when the one or more outer layers  46 ,  50 ,  52  is degraded, so that the plug is smaller than a passage  44  for fluid flow  18  through the plug release tool  12 . 
     The plug  14  may comprise a layer  52  that degrades when exposed to downhole temperature, and another layer  50  that degrades when exposed to well fluid. The layer  50  that degrades when exposed to well fluid may be disposed inside the layer  52  that degrades when exposed to downhole temperature. 
     The above disclosure also provides a method of deploying a plug  14  in a subterranean well. In one example, the method can comprise: positioning a tool string  68  in the well, the tool string  68  including a plug release tool  12  and a well tool (e.g., the vibratory tool  22 , a stabilizer, etc.); then releasing the plug  14  from the plug release tool  12 ; and then operating the well tool in response to releasing the plug  14 . 
     The positioning step can include maintaining a fluid flow  18  through the plug release tool  12 , thereby maintaining the plug  14  engaged with a seat  36  of the plug release tool  12 . The seat  36  may be encircled by multiple flow passages  44  in the plug release tool  12 . 
     The releasing step can include ceasing the fluid flow  18 , thereby permitting the plug  14  to disengage from the seat  36 . The method can include resuming the fluid flow  18  after the step of ceasing the fluid flow  18 , thereby displacing the plug  14  through one of the flow passages  44  to the well tool. 
     The step of maintaining the fluid flow  18  may be performed at least partially while the tool string  68  is in a vertical section of a wellbore  60 . The step of ceasing the fluid flow  18  may be performed while the tool string  68  is in an inclined section of the wellbore  60 . 
     The releasing step can include degrading a layer  46 ,  50 ,  52  of the plug  14  in the plug release tool  12 . The degrading step can include reducing a diameter of the plug  14 , thereby permitting the plug  14  to displace through a flow passage  44  of the plug release tool  12 . 
     The releasing step can include degrading first and second layers  50 ,  52  of the plug  14 . The first layer  50  may degrade in response to contact with a well fluid and the second layer  52  may degrade in response to exposure to elevated temperature in the well. 
     The positioning step can include a retainer structure  54  of the plug release tool  12  preventing displacement of the plug  14  through a flow passage  44  of the plug release tool  12 . The releasing step can include degrading the retainer structure  54 . 
     The operating step can include activating or deactivating the well tool. The well tool may comprise a vibratory tool  22 , and the operating step may include the vibratory tool  22  producing vibrations, or preventing the vibratory tool  22  from producing vibrations. 
     Also described above is a plug release tool  12  for use in a subterranean well. In one example, the plug release tool  12  can comprise: an outer housing  40 ; and an insert  38  secured in the outer housing  40 . The insert  38  can comprise multiple longitudinally extending flow passages  42 ,  44  formed through the insert  38 . 
     The plug release tool  12  may include a plug seat  36  formed in the insert  38 . The flow passages  42 ,  44  may comprise a first flow passage  42  and multiple second flow passages  44 . The plug seat  36  may encircle the first flow passage  42 , and the second flow passages  44  may be circumferentially distributed about the first flow passage  42 . 
     Each of the second flow passages  44  may have a diameter greater than a diameter of the first flow passage  42 . The plug release tool  12  may include a plug  14 . The first flow passage  42  may have a diameter less than a diameter of the plug  14 , and each of the second flow passages  44  may have a diameter greater than the plug  14  diameter. 
     The plug release tool  12  may include a retainer structure  54  and a plug  14 . The retainer structure  54  may releasably secure the plug  14  in the insert  38 . 
     The retainer structure  54  may be degradable downhole. The flow passages  44  may be circumferentially distributed about the retainer structure  54 . 
     The plug release tool  12  may include a plug  14 . The plug  14  may comprise an inner core  48  and at least one layer  46 ,  50 ,  52  surrounding the inner core  48 . 
     The flow passages  42 ,  44  may comprise a first flow passage  42  and multiple second flow passages  44 . The first flow passage  42  may have a diameter less than a diameter of the inner core  48 , and each of the second flow passages  44  may have a diameter greater than a diameter of the inner core  48 . 
     The “at least one” layer  46 ,  50 ,  52  may be degradable downhole. The “at least one” layer  46 ,  50 ,  52  may comprise first and second layers  50 ,  52 . The first layer  50  may be degradable in response to contact with a well fluid, and the second layer  52  may be degradable in response to exposure to elevated downhole temperature. 
     Although various examples have been described above, with each example having certain features, it should be understood that it is not necessary for a particular feature of one example to be used exclusively with that example. Instead, any of the features described above and/or depicted in the drawings can be combined with any of the examples, in addition to or in substitution for any of the other features of those examples. One example&#39;s features are not mutually exclusive to another example&#39;s features. Instead, the scope of this disclosure encompasses any combination of any of the features. 
     Although each example described above includes a certain combination of features, it should be understood that it is not necessary for all features of an example to be used. Instead, any of the features described above can be used, without any other particular feature or features also being used. 
     It should be understood that the various embodiments described herein may be utilized in various orientations, such as inclined, inverted, horizontal, vertical, etc., and in various configurations, without departing from the principles of this disclosure. The embodiments are described merely as examples of useful applications of the principles of the disclosure, which is not limited to any specific details of these embodiments. 
     In the above description of the representative examples, directional terms (such as “above,” “below,” “upper,” “lower,” “upward,” “downward,” etc.) are used for convenience in referring to the accompanying drawings. However, it should be clearly understood that the scope of this disclosure is not limited to any particular directions described herein. 
     The terms “including,” “includes,” “comprising,” “comprises,” and similar terms are used in a non-limiting sense in this specification. For example, if a system, method, apparatus, device, etc., is described as “including” a certain feature or element, the system, method, apparatus, device, etc., can include that feature or element, and can also include other features or elements. Similarly, the term “comprises” is considered to mean “comprises, but is not limited to.” 
     Of course, a person skilled in the art would, upon a careful consideration of the above description of representative embodiments of the disclosure, readily appreciate that many modifications, additions, substitutions, deletions, and other changes may be made to the specific embodiments, and such changes are contemplated by the principles of this disclosure. For example, structures disclosed as being separately formed can, in other examples, be integrally formed and vice versa. Accordingly, the foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the invention being limited solely by the appended claims and their equivalents.