WO2015073001A1

WO2015073001A1 - System and methodology for using a degradable object in tubing

Info

Publication number: WO2015073001A1
Application number: PCT/US2013/070053
Authority: WO
Inventors: Mitchel Stretch
Original assignee: Schlumberger Canada Ltd; Services Petroliers Schlumberger SA; Schlumberger Technology BV; Schlumberger Technology Corp; Schlumberger Holdings Ltd; Prad Research and Development Ltd
Current assignee: Schlumberger Canada Ltd; Services Petroliers Schlumberger SA; Schlumberger Technology BV; Schlumberger Technology Corp; Schlumberger Holdings Ltd; Prad Research and Development Ltd
Priority date: 2013-11-14
Filing date: 2013-11-14
Publication date: 2015-05-21
Anticipated expiration: 2016-05-14

Abstract

A methodology and system facilitate performance of an operation in tubing, such as wellbore tubing. A seat is placed in the tubing so that an object may be delivered along an interior of the tubing for engagement with the seat. The object is designed with a non-degradable component, e.g. wiper, mounted on a degradable core. In many applications, fluid may be used to move the object along the interior of the tubing and into engagement with the seat. As the object moves along the interior, the wiper is used to wipe, e.g. scrape, material from an inside surface of the tubing. After the object engages the seat, pressure may be applied along the interior of the tubing to actuate a desired tool. Upon completion of the procedure, the core may be degraded, e.g. dissolved, and thus removed from the tubing.

Description

SYSTEM AND METHODOLOGY FOR USING A DEGRADABLE OBJECT IN

TUBING

BACKGROUND

[0001] In a variety of well-related applications, objects are delivered downhole to actuate tools and/or to enable a variety of well services. For example, darts may be pumped downhole along an interior of a tubing string deployed in a wellbore. The dart is moved until it engages and seals against a corresponding seat. After the dart seals against the seat, fluid may be pressurized in the interior of the tubing string above the seat. The pressurized fluid is used to actuate a desired tool. Following actuation, the dart is removed by a suitable removal process, such as milling, to provide a passageway to a lower portion of the wellbore. The passageway may be used for cementing operations, well treatment operations, and/or a variety of additional or other well-related procedures.

SUMMARY

[0002] In general, the present disclosure provides a methodology and system for performing an operation in tubing, such as a wellbore tubing. A seat is placed in the tubing so that an object may be delivered along an interior of the tubing for engagement with the seat. The object is designed with a non-degradable component, e.g. wiper, mounted on a degradable core. In many applications, fluid may be used to move the object along the interior of the tubing and into engagement with the seat. As the object moves along the interior, the non-degradable component may be used to wipe, e.g.

scrape, material from an inside surface of the tubing. After the object engages the seat, pressure may be applied along the interior of the tubing to actuate a desired tool. Upon completion of the procedure, the core may be degraded, e.g. dissolved, and thus removed from the tubing. Additionally, the non-degradable component (e.g. wiper) of the object can in some cases be expanded into a recess in the tool holding the seat. If the seat is not degradable, it can also expand into the recess. Once the non-degradable component and seat are expanded into the recess, the inner diameter of the tool is such that it is as large or larger than the inner diameter of the tubing, providing full-bore unrestricted access to the lower section of the well without the need for a milling operation.

[0003] Modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Certain embodiments of the disclosure will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It should be understood, however, that the accompanying figures illustrate various implementations described herein and are not meant to limit the scope of various technologies described herein, and:

[0005] Figure 1 is a schematic representation of an example of a well system having a tubing string deployed in a wellbore with an object deployed through an interior of the tubing string for tool actuation, according to an embodiment of the disclosure;

[0006] Figure 2 is a cross-sectional illustration of an example of an object deployed along an interior of a tubing, according to an embodiment of the disclosure;

[0007] Figure 3 is an illustration similar to that of Figure 2 but showing the object in a different operational position, according to an embodiment of the disclosure;

[0008] Figure 4 is an illustration similar to that of Figure 3 but with a portion of the object degraded and removed, according to an embodiment of the disclosure;

[0009] Figure 5 is a cross-sectional illustration of another example of an object deployed along an interior of a tubing, according to an embodiment of the disclosure; [0010] Figure 6 is an illustration similar to that of Figure 5 but showing the object in a different operational position, according to an embodiment of the disclosure;

[0011] Figure 7 is an illustration similar to that of Figure 6 but showing the outer non-degradable section of the object expanded into a recess in the tubing, according to an embodiment of the disclosure;

[0012] Figure 8 is an illustration similar to that of Figure 7 but with a portion of the object degraded and removed along with a degradable seat, providing unrestricted access through the inner diameter of the tubing, according to an embodiment of the disclosure;

[0013] Figure 9 is a cross-sectional illustration of another example of an object deployed along an interior of a tubing, according to an embodiment of the disclosure;

[0014] Figure 10 is an illustration similar to that of Figure 9 but showing the object in a different operational position, according to an embodiment of the disclosure;

[0015] Figure 11 is an illustration similar to that of Figure 10 but showing the object in a different operational position, according to an embodiment of the disclosure;

[0016] Figure 12 is an illustration similar to that of Figure 11 but with a portion of the object degraded and removed, according to an embodiment of the disclosure;

[0017] Figure 13 is a cross-sectional illustration of another example of an object deployed along an interior of a tubing, according to an embodiment of the disclosure;

[0018] Figure 14 is an illustration similar to that of Figure 13 but showing the object in a different operational position, according to an embodiment of the disclosure; [0019] Figure 15 is an illustration similar to that of Figure 14 but showing the outer non-degradable section of the object expanded into a recess in the tubing, according to an embodiment of the disclosure;

[0020] Figure 16 is an illustration similar to that of Figure 15 but with a portion of the object degraded and removed along with a degradable seat, providing unrestricted access through the inner diameter of the tubing, according to an embodiment of the disclosure;

[0021] Figure 17 is a cross-sectional illustration of another example of an object deployed along an interior of a tubing, according to an embodiment of the disclosure;

[0022] Figure 18 is an illustration similar to that of Figure 17 but showing the object in a different operational position, according to an embodiment of the disclosure;

[0023] Figure 19 is an illustration similar to that of Figure 18 but showing the outer non-degradable section of the object expanded into a first recess in the tubing, according to an embodiment of the disclosure;

[0024] Figure 20 is an illustration similar to that of Figure 19 but showing the outer non-degradable section of the object and an object seat expanded into a second, deeper recess in the tubing, according to an embodiment of the disclosure;

[0025] Figure 21 is an illustration similar to that of Figure 20 but with a portion of the object degraded and removed, providing unrestricted access through the inner diameter of the tubing, according to an embodiment of the disclosure;

[0026] Figure 22 is a cross-sectional illustration of another example of an object deployed along an interior of a tubing, according to an embodiment of the disclosure; [0027] Figure 23 is an illustration similar to that of Figure 22 but showing the object in a different operational position, according to an embodiment of the disclosure;

[0028] Figure 24 is an illustration similar to that of Figure 23 but showing the outer non-degradable section of the object expanded into a first recess in the tubing, according to an embodiment of the disclosure;

[0029] Figure 25 is an illustration similar to that of Figure 24 but showing the outer non-degradable section of the object and an object seat expanded into a second, deeper recess in the tubing, according to an embodiment of the disclosure; and

[0030] Figure 26 is an illustration similar to that of Figure 25 but with a portion of the object degraded and removed, providing unrestricted access through the inner diameter of the tubing, according to an embodiment of the disclosure.

DETAILED DESCRIPTION

[0031] In the following description, numerous details are set forth to provide an understanding of some embodiments of the present disclosure. However, it will be understood by those of ordinary skill in the art that the system and/or methodology may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.

[0032] The present disclosure generally relates to a system and methodology for performing an operation in tubing, such as a wellbore tubing. In wellbore applications, an object, e.g. a dart, is moved along an interior of a tubing string located within a wellbore. The object is moved into engagement with a corresponding seat, and pressure may be applied uphole from the seated object to cause actuation of a tool. The object may be used to actuate many types of tools and/or to facilitate other operations in well applications and other applications utilizing tubing. [0033] According to an embodiment, a seat member comprises a seat which is placed in the tubing so that an object may be delivered along an interior of the tubing for engagement with the seat. The object is designed with a non-degradable component, e.g. wiper, mounted on a degradable core. By way of example, the degradable core may be formed from a dissolvable material, such as a material which dissolves when exposed to well fluids. The well fluids may be hydrocarbon-based fluids or other fluids, e.g. acids, pumped downhole to dissolve the core. In many applications, fluid may be used to move the object along the interior of the tubing and into engagement with the seat. In an example, as the object moves along the interior the wiper removes, e.g. scrapes or cleans, material from an inside surface of the tubing. After the object engages the seat, pressure may be applied along the interior of the tubing to actuate a desired tool. Upon

completion of the procedure, the core may be degraded, e.g. dissolved, and thus removed from the tubing.

[0034] The object may be used in many types of tubing and in many applications to, for example: wipe an interior surface of the tubing; to actuate a tool; and to

subsequently present a flow passage via degradation of the object core. For example, the object may comprise a dart having a degradable, e.g. dissolvable, core. In this example, the dart is deployed through a tubing string to wipe cement or other debris or fluids from the tubing along an upper portion of the wellbore. The core may then be removed, e.g. dissolved, to provide flow access to a lower portion of the wellbore. Prior to degradation of the core, the dart also may be moved, e.g. pumped, into engagement with a seat for actuation of a tool. It should be noted that the object, e.g. dart, may be moved along vertical and deviated, e.g. horizontal, sections of the wellbore. Thus, use of the terms upper and lower refer to portions of the wellbore uphole and downhole, respectively, of a reference point such as the seat. In a horizontal portion of the wellbore, for example, upper refers to the region between the reference point and the surface while lower refers to the wellbore on an opposite side of such reference point.

[0035] The degradable core of the object, e.g dart, is coupled with a non- degradable component, such as a non-degradable wiper. This allows non-degradable, e.g. non-dissolvable, materials to be used as the wiping, e.g. scraping or cleaning, component of the object while still providing unrestricted access to a lower portion of the wellbore after tool actuation. Once the object, e.g. dart, lands in the seat and actuates the desired tool the core degrades. The non-degradable component may be formed as an expandable component which expands outwardly into a recess to provide full-bore access to the lower portion of the wellbore. By way of example, the non-degradable portion may be a wiper formed from a non-dissolvable material, such as rubber, steel, or other materials that are beneficial to wiping, e.g. scraping or cleaning, the wellbore.

[0036] In some examples, the object may be formed with different types of degradable materials. For example, the core may be formed from two types of material which dissolve at different rates. In some applications, the non-degradable component, e.g. wiper, may be formed from a component which may be degraded more slowly or at a different time than the core. For example, the wiper or other non-degradable component can be formed from a dissolvable material which dissolves at a slower rate than the core.

[0037] Referring generally to Figure 1, a schematic representation is provided to illustrate a system for performing an operation in a wellbore. However, the technique may be used in a variety of well and non-well related tubing systems. In the illustrated example, a tubing string 30 comprises tubing 32 deployed in a wellbore 34. Wellbore 34 extends from surface equipment 36, e.g. a wellhead, down through a subterranean formation 38. Surface equipment 36 is located at a surface location 40 which may be a land surface or a seabed. The wellbore 34 may be a generally vertical wellbore, but the wellbore also may comprise deviated, e.g. horizontal, sections.

[0038] In the embodiment illustrated, a seat member 42 is deployed along tubing

32 and comprises a seat 44. The seat 44 may be positioned along an interior 46 of the tubing 32. In this example, the wellbore 34 is divided into an upper portion 48 located above, i.e. uphole, of seat 44 and a lower portion 50 located below, i.e. downhole, of seat 44. The tubing string 30 also may comprise a tool or tools 52 which are located and designed to facilitate a variety of well-related operations, such as service operations. In some applications, for example, tool 52 may comprise a valve or valves designed to facilitate a cementing operation, gravel packing operation, or other well service operation. However, a variety of additional or other tools may be located along the tubing string 30. In this example, tool 52 may be actuated by applying pressure along the interior 46 of the upper portion 48 of wellbore 34.

[0039] To enable pressurization of interior 46 and/or to facilitate other

procedures, an object 54 may be moved along interior 46 from surface location 40 toward seat 44. In a variety of applications, the object 54 may be pumped down along interior 46 via a fluid and moved into engagement with seat 44. Upon engaging seat 44, object 54 is designed to form a sufficient seal to enable pressurization of the fluid in interior 46 of upper portion 48. The pressurization may be used to actuate tool 52 and/or to perform other downhole operations.

[0040] In the example illustrated, object 54 may be in the form of a dart.

However, object 54 also may be constructed as another suitable shape for moving along interior 46 of tubing 32 and engaging seat 44. The object 54 also may comprise a degradable portion and a non-degradable portion. For example, object 54 may comprise a degradable core 56, formed of a degradable material, and a non-degradable structure 58, formed of a non-degradable material and mounted on degradable core 56. In the illustrated example, the non-degradable structure 58 is in the form of a wiper designed to wipe, e.g. scrape or clean, an interior surface 60 defining interior 46 of tubing 32 as the object 54 is moved along interior 46 in the direction of arrow 62.

[0041] In some applications, the degradable material of core 56 is formed from a dissolvable material which readily dissolves in the presence of a wellbore fluid, such as a hydrocarbon fluid present in the wellbore, a delivery or actuating fluid which delivers object 54 downhole, or another type of fluid, e.g. acid, pumped downhole along interior 46 of tubing 32. However, the degradable material also may comprise a frangible material or other type of material which may be selectively degraded and removed after use of object 54 at seat 44. The degradable core 56 may be designed to degrade in reaction to a variety of inputs. The non-degradable structure 58, e.g. wiper, may be formed from a non-dissolvable material or a slower dissolving material, such as rubber, steel, or other suitable material for a given application. The non-degradable structure 58 does not degrade (or it degrades more slowly) when exposed to the given input which causes degradation of the core 56.

[0042] In an operational example, the object 54 is pumped down along interior 46 and the non-dissolvable wiper scrapes and cleans interior surface 60 of debris until object 54 engages seat 44. At this stage, the fluid in interior 46 of upper portion 48 is subjected to increased pressure so as to actuate tool 52. The increased pressure may be created by surface pumps. Subsequently, the core 56 is removed and allowed to dissolve or is simply degraded to enable removal. Upon removal of core 56, interior 46 becomes a flowthrough passage to lower portion 50 of wellbore 34.

[0043] Referring generally to Figure 2, a more detailed example of an

embodiment of object 54 is illustrated as deployed within tubing 32. In this example, the non-degradable component 58 is in the form of a wiper 64 mounted on the degradable core 56. By way of example, degradable core 56 may be constructed from a dissolvable material and wiper 64 may be constructed from a non-dissolvable material. The wiper 64 is mounted on core 56 via a mounting feature 66, such as an annular recess formed along an exterior of the degradable core 56. The core 56 and annular recess 66 are sized to maintain wiper 64 in contact with interior surface 60 as the object 54 is pumped or otherwise moved along interior 46 of tubing 32.

[0044] In the embodiment illustrated, the object 54 is moved along interior 46 as wiper 64 wipes along interior surface 60 until the object 54 engages seat member 42. By way of example, the degradable core 56 may comprise an engagement surface 68 oriented and constructed for sealing or substantial sealing with seat 44. Once the object 54 is engaged with seat 44, as illustrated in Figure 3, pressure may be increased in interior 46 of upper portion 48 to actuate tool 52 or to perform another operation.

Following the operation, e.g. tool actuation, the degradable core 56 is removed to provide a flow passageway connecting the interior 46 of upper portion 48 with the lower portion 50 of wellbore 34, as indicated by arrow 70 in Figure 4. The degradable core 56 may be removed via degradation, e.g. dissolving the core 56 in a suitable fluid. In some applications, however, the degradable core 56 may be removed by other techniques and subsequently dissolved or otherwise degraded.

[0045] The wiper 64 may be used in a wellbore application to wipe the interior surface 60 of the upper wellbore portion 48 of cement, debris, fluids, and/or other materials. In many applications, the cement, debris, fluids, or other material are pushed out of an open valve where the upper and lower wellbore meet or simply out of the end of the tubing string 30. In this type of example, tool 52 may be in the form of an open valve, and object 54 is used to close the valve by pushing on seat 44 to transition the seat member 42 which, in turn, transitions a valve sleeve of the tool/valve 52. In other applications, however, the seat 44 may be an affixed seat to allow pressurization for actuation of other types of tools 52. Subsequently, the degradable core 56 is removed, e.g. dissolved or otherwise removed, to provide access to the lower wellbore portion 50 below tool 52 and seat 44.

[0046] Referring generally to Figures 5-8, another embodiment is illustrated in which the non-degradable component 58, e.g. wiper 64, is spring biased in a radially outward direction. This allows the non-degradable component 58/wiper 64 to be expanded outwardly so as to provide full-bore, unrestricted access to the lower portion 50 of wellbore 34. By way of example, the spring bias may be created by compressing a naturally resilient material into annular recess 66 or by providing an outward bias via a spring member 72 positioned between degradable core 56 and non-degradable component 58.

[0047] In operation, the object 54 is again pumped or otherwise moved along interior 46, as illustrated in Figure 5. During movement, the wiper 64 may be used to wipe interior surface 60 of tubing 32. Once the object 54 engages seat 44, pressure may be increased along interior 46 to actuate tool 52, as illustrated in Figure 6. In the example illustrated, seat member 42 is connected with a sleeve 74 of tool 52. As pressure is increased in interior 46 above seat 44, the seat member 42 and seat 44 are transitioned or moved along the inside of tubing 32 to actuate the tool 52, as illustrated in Figure 7.

[0048] Once the object 54 has shifted the seat 44 a sufficient distance, the spring bias acts to expand the wiper 64 (or other non-degradable component 58) into a cavity 76. By way of example, cavity 76 may be in the form of an annular recess formed into interior surface 60 along the inside of tubing 32. The degradable core 56 may then be removed and degraded, as illustrated in Figure 8. Additionally, seat member 42 may be formed from a degradable material to enable removal of the seat member after actuation of tool 52. By expanding the non-degradable component 58 into cavity 76 and by dissolving or otherwise degrading seat member 42, a full-bore, unrestricted passageway to lower wellbore portion 50 can be established, as indicated by arrow 78. In some applications, the core 56 and seat member 42 may be removed by dissolving their component material in a suitable fluid.

[0049] Referring generally to Figures 9-12, another embodiment is illustrated in which tool 52 comprises a valve 80. In operation, the object 54 is again pumped or otherwise moved along interior 46, as illustrated in Figure 9. During movement, the wiper 64 may be used to wipe interio surface 60 of tubing 32. In this example, seat member 42 may comprise an object receiving cavity 82 sized to receive object 54 therein, as illustrated in Figure 10. The seat 44 is disposed within object receiving cavity 82, as illustrated. In this particular example, valve 80 is initially in an open position in which valve ports 84 are aligned with tubing ports 86 to enable flow of fluid between interior 46 and a wellbore annulus 88 surrounding tubing 32. The valve ports 84 may be located in a valve sleeve 90 slidably positioned along the interior of tubing 32.

[0050] Once the object 54 engages seat 44, pressure may be increased along interior 46 to actuate tool 52, as illustrated in Figure 11. In the example illustrated, seat member 42 is engaged with valve sleeve 90 of tool 52. As pressure is increased in interior 46 above seat 44, the seat member 42 and seat 44 are transitioned or moved along the inside of tubing 32 which, in turn, shifts valve sleeve 90 along the inside of tubing 32. Valve sleeve 90 is shifted to move valve ports 84 out of alignment with tubing ports 86 which effectively actuates tool 52 by closing valve 80.

[0051] After using object 54 to move seat 44 and thus shift valve sleeve 90, the degradable core 56 may be removed, as illustrated in Figure 12. Closure of valve 80 prevents fluid flow between interior 46 and the surrounding annulus 88. Additionally, removal of degradable core 56 by, for example, dissolving the core, allows free flow of fluid from interior 46 of upper wellbore portion 48 to lower wellbore portion 50. Valve 80 may be used in cementing operations or a variety of other operations in which controlled flows of fluid are established between different wellbore regions.

[0052] Referring generally to Figures 13-16, another embodiment is illustrated in which tool 52 again comprises valve 80. However, this embodiment also utilizes cavity 76, expandable component 58, and a degradable seat member 42. Valve 80 may be used in a variety of applications, such as providing a flow path when a lower wellbore region is plugged. In operation, object 54 is again pumped or otherwise moved along interior 46, as illustrated in Figure 13. During movement, the non-degradable component/wiper 64 may be used to wipe interior surface 60 of tubing 32.

[0053] In this example, the object 54 is moved into engagement with seat 44, as illustrated in Figure 14. The pressure is then increased along interior 46 to actuate tool 52 which in this example comprises valve 80. Valve 80 is shifted to another operational position, e.g. a closed position as illustrated in Figure 15. After the object 54 has shifted the seat 44 a sufficient distance, the spring bias acting on wiper 64 expands the wiper (or other non-degradable component 58) into cavity 76. By way of example, cavity 76 may again be in the form of an annular recess formed into interior surface 60 along the inside of tubing 32.

[0054] Following expansion of wiper 64 into cavity 76, the degradable core 56 may be removed/degraded, as illustrated in Figure 16. In this example, seat member 42 also is formed from a degradable material to enable removal of the seat member 42 after actuation of tool 52/valve 80. By expanding the non-degradable component 58 into cavity 76 and by dissolving or otherwise degrading seat member 42, a full-bore, unrestricted passageway to lower wellbore portion 50 can be established. In some applications, the degradable core 56 and seat member 42 may be removed by dissolving their component material in a suitable fluid.

[0055] Referring generally to Figures 17-21, another embodiment is illustrated in which both the non-degradable component 58, e.g. wiper 64, and the seat member 42 are spring biased in a radially outward direction. This allows the non-degradable component 58 and the seat member 42 to be expanded outwardly, thus providing full-bore, unrestricted access to the lower portion 50 of wellbore 34. To create the radially outward spring bias, the non-degradable component 58 and seat member 42 each may be constructed from a naturally resilient material which is compressed inwardly and fitted within interior surface 60 of tubing 32. In other applications, separate spring members may be located within the non-degradable component 58 and seat member 42 to provide the radially outwardly directed spring bias.

[0056] In operation, the object 54 is again pumped or otherwise moved along interior 46, as illustrated in Figure 17. The non-degradable component 58 may be in the form of wiper 64 which is employed to wipe inside surface 60 of tubing 32. Once the object 54 engages seat 44, pressure may be increased along interior 46 to actuate tool 52, as illustrated in Figure 18. In the example illustrated, seat member 42 is initially secured to the surrounding tubing 32 via a shear member 92, such as a shear ring or shear pins. Additionally, the seat member 42 is engaged with sleeve 74 of tool 52. As pressure is increased in interior 46 above seat 44, the shear member 92 is sheared. This allows the seat member 42 and seat 44 to be transitioned or moved along the inside of tubing 32 to actuate the tool 52 via movement of sleeve 74, as illustrated in Figure 19.

[0057] Once the object 54 has shifted the seat member 42/seat 44 a sufficient distance, the spring bias described above acts to expand both the wiper 64 (or other non- degradable component 58) and the seat member 42 into cavity 76, as illustrated in Figure 20. By way of example, cavity 76 may again be in the form of an annular recess formed into interior surface 60 along the inside of tubing 32. In this example, however, the cavity 76 has a first portion for receiving component 58 and a second portion for receiving the seat member 42. This allows the degradable core 56 to be

removed/degraded, as illustrated in Figure 21. In some applications, the degradable core 56 may be removed by dissolving the core 56 with a suitable fluid. By expanding the non-degradable component 58 and the seat member 42 into cavity 76, a full-bore, unrestricted passageway to lower wellbore portion 50 can be established.

[0058] Referring generally to Figures 22-26, another embodiment is illustrated which is similar to the previous embodiment in that both the non-degradable component 58, e.g. wiper 64, and the seat member 42 are spring biased in a radially outward direction. This allows the non-degradable component 58 and the seat member 42 to be expanded outwardly and to provide full-bore, unrestricted access to the lower portion 50 of wellbore 34. To create the radially outward spring bias, the component 58 and seat member 42 each may similarly be constructed from a naturally resilient material which is compressed inwardly and fitted within interior surface 60 of tubing 32. In other applications, separate spring members may be located within the non-degradable component 58 and seat member 42 to provide the radially outwardly directed spring bias.

[0059] However, the embodiment illustrated in Figures 22-26 employs tool 52 in the form of valve 80. This embodiment again utilizes cavity 76, expandable component 58, and expandable seat member 42. Valve 80 may be used in a variety of applications, such as providing a flow path when a lower wellbore region is plugged. In operation, the object 54 is pumped or otherwise moved along interior 46, as illustrated in Figure 22. Component 58 may be in the form of wiper 64 so that during movement, the non- degradable component/wiper 64 may be used to wipe inside surface 60 of tubing 32.

[0060] In this example, the object 54 is moved into engagement with seat 44, as illustrated in Figure 23. Seat member 42 may be initially secured to the surrounding tubing 32 via shear member 92, e.g. a shear ring or shear pins. Additionally, the seat member 42 is engaged with the valve sleeve 90 of valve 80. As pressure is increased in interior 46 above seat 44, the shear member 92 is sheared. This allows the seat member 42 and seat 44 to be transitioned or moved along the inside of tubing 32 to actuate the valve 80 via movement of valve sleeve 90, as illustrated in Figure 24. Depending on the specific application, the valve 80 may be shifted between various operational

configurations. In the specific example illustrated, the valve 80 is initially in an open position in which valve ports 84 are aligned with tubing ports 86 to enable flow between interior 46 and the surrounding annulus 88. The valve 80 is then transitioned to a closed position.

[0061] After the object 54 has shifted the seat 44 a sufficient distance, the spring bias acting on wiper 64 and seat member 42 expands both the wiper (or other non- degradable component 58) and the seat member 42 into cavity 76. By way of example, cavity 76 may again be in the form of an annular recess formed into interior surface 60 along the inside of tubing 32. The annular recess 76 may have a first portion for receiving the wiper 64 and a second portion for receiving the seat member 42.

[0062] Following expansion of wiper 64 and the seat member 42 into cavity 76, the degradable core 56 may be removed/degraded, as illustrated in Figure 25. In some applications, expansion of the wiper 64/component 58 and seat member 42 allows the degradable core 56 to be removed and then degraded. In other applications, the degradable core 56 may be removed via degradation, e.g. by dissolving the core 56 with a suitable fluid. By expanding the non-degradable component 58 and the seat member 42 into cavity 76, a full-bore, unrestricted passageway to lower wellbore portion 50 can be established, as illustrated in Figure 26.

[0063] The specific arrangement of system components for a given well application or non-well tubing application may vary. For example, a variety of components may be employed in the tubing string and the tubing string may have a variety of sizes, configurations, and lengths. Additionally, the object moved along the interior of the tubing string may have many forms and configurations depending on the environment, the seat structure, the material selected, and the tools to be actuated. Both the degradable and non-degradable components of the object may vary in materials and configurations depending on the technique selected for degradation, the naturally occurring fluids, and the fluids available to be pumped down through the tubing string. The object may be designed to enable release of the core through degradation or to mechanically release the core followed by core degradation. Similarly, many types of valves and other tools may be used in the tubing string and actuated via deployment of the object through the interior of the tubing string.

[0064] Although a few embodiments of the disclosure 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 disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims.

Claims

CLAIMS claimed is:

A method for performing an operation in a wellbore, comprising:

placing a seat in a tubing proximate a lower end of an upper portion of the wellbore;

providing an object with a non-dissolvable wiper mounted on a dissolvable core;

using fluid to move the object along an interior of the tubing to wipe an interior surface of the tubing via the wiper until the object engages the seat;

applying pressure against the object in the interior of the tubing to actuate a tool; and

dissolving the core to provide access to a lower portion of the wellbore.

The method as recited in claim 1 , wherein placing the seat comprises placing a dissolvable seat.

The method as recited in claim 1 , wherein placing the seat comprises placing an expandable seat along the tubing; and wherein the method further comprises expanding the expandable seat into a recess of the tubing.

The method as recited in claim 1, wherein providing an object comprises providing the object with the non-dissolvable wiper in the form of an expandable, non-dissolvable wiper; and wherein the method further comprises enabling expansion of the expandable, non-dissolvable wiper into a wiper recess formed in the tubing.

The method as recited in claim 1, wherein applying pressure against the object comprises applying pressure to actuate a valve.

6. The method as recited in claim 1, wherein applying pressure against the object comprises applying pressure to shift the seat and thus close a valve.

7. The method as recited in claim 1 , wherein providing an object with a non- dissolvable wiper comprises mounting a rubber, non-dissolvable wiper on the dissolvable core.

8. The method as recited in claim 1 , wherein providing an object with a non- dissolvable wiper comprises mounting a steel, non-dissolvable wiper on the dissolvable core.

9. The method as recited in claim 1, further comprising expanding the non- dissolvable wiper to provide full-bore access to the lower portion of the wellbore following removal of the dissolvable core.

10. A system for use in a tubing, comprising:

a core formed of a degradable material which degrades when exposed to a given input; and

a wiper mounted on the core, the wiper being formed of a material which is non-degradable when exposed to the given input, the wiper having a diameter sized to wipe along an interior surface of a corresponding tubing as the core and the wiper are pumped along an interior of the corresponding tubing.

11. The system as recited in claim 10, wherein the core is formed from sections which dissolve at different rates when exposed to the given input, the input being in the form of a fluid suitable for dissolving the core.

12. The system as recited in claim 10, wherein the core is dissolvable in a well fluid.

13. The system as recited in claim 10, wherein the wiper is formed from a rubber material.

14. The system as recited in claim 10, wherein the wiper is formed from a steel material.

15. The system as recited in claim 10, wherein the wiper is radially expandable to create a larger through-opening upon removal of the core.

16. A system, comprising :

a tubing string deployed in a wellbore and having an interior defined by an interior surface of the tubing string;

a seat member deployed along the tubing string to present a seat along the interior of the tubing string;

a tool deployed along the tubing string; and

an object having a core formed from a degradable material and a wiper formed from a non-degradable material and mounted to the core, the wiper being sized to wipe along the interior surface as the object moves along the interior of the tubing string until engaging the seat, the object and the seat being sufficiently sealed upon engagement to enable actuation of the tool via increased pressure in the tubing string uphole of the object.

17. The system as recited in claim 16, wherein the object comprises a dart in which the core is dissolvable in a well fluid.

18. The system as recited in claim 16, wherein the tool comprises a valve actuatable by shifting the seat upon application of sufficient pressure in the interior of the tubing string.

19. The system as recited in claim 16, wherein the seat is dissolvable and the wiper is expandable to provide full-bore access to a lower portion of the wellbore after removal of the core.