US20180291700A1

US20180291700A1 - Downhole plug assembly

Info

Publication number: US20180291700A1
Application number: US15/484,322
Authority: US
Inventors: Huilin Tu; Kyle Tse; John R. Whitsitt; Gregoire Jacob
Original assignee: Schlumberger Technology Corp
Current assignee: Schlumberger Technology Corp
Priority date: 2017-04-11
Filing date: 2017-04-11
Publication date: 2018-10-11
Also published as: WO2018191204A1

Abstract

An apparatus includes a body member and a ring member. The body member has a through passageway, and the body member includes an outer engagement surface. The ring member has a contracted state and an expanded state, and the ring member includes an inner engagement surface and an outer surface. The seal member is adapted to axially move with respect to the body member in response to the application of an axial force such that the outer engagement surface of the body member physically engages the inner engagement surface of the ring member to radially expand the ring member to transition the ring member to the expanded state and cause the outer surface of the ring member to contact an inner wall of a tubing string. The physical engagement of the inner engagement surface of the ring member with the outer engagement surface of the body member forms a seal between the ring member and the body member. The contact of the outer surface of the ring member with the tubing string forms a seal between the ring member and the tubing string and secures the ring member to the tubing string. The inner engagement surface and the outer engagement surface are adapted to physically interact to retain the ring member in the expanded state when the axial force is removed.

Description

BACKGROUND

For purposes of preparing a well for the production of oil or gas, at least one perforating gun may be deployed into the well via a conveyance mechanism, such as a wireline, slickline or a coiled tubing string. The shaped charges of the perforating gun(s) are fired when the gun(s) are appropriately positioned to perforate a casing of the well and form perforating tunnels into the surrounding formation. Additional operations may be performed in the well to increase the well's permeability, such as well stimulation operations and operations that involve hydraulic fracturing. The above-described perforating and stimulation operations may be performed in multiple stages of the well.
The above-described operations may be performed by actuating one or more downhole tools (perforating guns, sleeve valves, and so forth) and by forming one or more fluid-diverting fluid barriers downhole in the well.

SUMMARY

The summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.
In accordance with an example implementation, a technique includes running a plug assembly inside a tubing string of a well; and setting the plug assembly. Setting the plug assembly includes axially, moving a seal member of the plug assembly with respect to a body member of the plug assembly to cause an outer engagement surface of the body member to physically engage an inner engagement surface of a ring member of the plug assembly to radially expand the ring member to transition the ring member to an expanded state and cause an outer surface of the ring member to contact an inner wall of the tubing string; using the physical engagement of the inner engagement surface of the ring member with the outer engagement surface of the body member to form a seal between the ring member and the body member; using contact of the outer surface of the ring member with the tubing string to form a seal between the ring member and the tubing string and secure the ring member to the tubing string; and using a physical interaction between the inner engagement surface and the outer engagement surface to retain the ring member in the expanded state when the axial force is removed.
In accordance with another example implementation, a system that is usable with a well includes a tubing string, an untethered object and a plug assembly. The plug assembly includes a body member and a ring member. The body member has a through passageway, and the body member includes an outer engagement surface and a seat that is adapted to catch the untethered object to form a fluid barrier in the tubing string. The ring member has a contracted state and an expanded state; and the ring member includes an inner engagement surface and an outer surface. The seal member is adapted to axially move with respect to the body member in response to the application of an axial force such that the outer engagement surface of the body member physically engages the inner engagement surface of the ring member to radially expand the ring member to transition the ring member to the expanded state and cause the outer surface of the ring member to contact an inner wall of the tubing string. The physical engagement of the inner engagement surface of the ring member with the outer engagement surface of the body member forms a seal between the ring member and the body member. The contact of the outer surface of the ring member with the tubing string forms a seal between the ring member and the tubing string and secures the ring member to the tubing string. The inner engagement surface and the outer engagement surface are adapted to physically interact to retain the ring member in the expanded state when the axial force is removed.
In accordance with yet another example implementation, an apparatus includes a body member and a ring member. The body member has a through passageway, and the body member includes an outer engagement surface. The ring member has a contracted state and an expanded state, and the ring member includes an inner engagement surface and an outer surface. The seal member is adapted to axially move with respect to the body member in response to the application of an axial force such that the outer engagement surface of the body member physically engages the inner engagement surface of the ring member to radially expand the ring member to transition the ring member to the expanded state and cause the outer surface of the ring member to contact an inner wall of a tubing string. The physical engagement of the inner engagement surface of the ring member with the outer engagement surface of the body member forms a seal between the ring member and the body member. The contact of the outer surface of the ring member with the tubing string forms a seal between the ring member and the tubing string and secures the ring member to the tubing string. The inner engagement surface and the outer engagement surface are adapted to physically interact to retain the ring member in the expanded state when the axial force is removed.
Advantages and other features will become apparent from the following drawings, description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are schematic diagrams of a well illustrating the use of a plug assembly in connection with a well stimulation operation according to an example implementation.

FIGS. 2 and 5 are perspective views of plug assemblies according to example implementations.

FIG. 3A is a cross-sectional view of a portion of a well illustrating the running of the plug assembly of FIG. 2 into a tubing string according to an example implementation.

FIG. 3B is a cross-sectional view of the portion of the well illustrating the setting of the plug assembly in the tubing string according to an example implementation.

FIG. 3C is a cross-sectional view of the portion of the well illustrating a fluid barrier formed in the tubing string using the plug assembly according to an example implementation.

FIG. 4 is an illustration of physical interaction of ratchet teeth of a seal member with ratchet teeth of a plug assembly of a body member of the plug assembly according to an example implementation.

FIG. 6A is a cross-sectional view of a portion of the well illustrating the running of the plug assembly of FIG. 5 into a tubing string according to an example implementation.

FIG. 6B is a cross-sectional view of the portion of the well illustrating the setting of the plug assembly in the tubing string according to an example implementation.

FIG. 6C is a cross-sectional view of the portion of the well illustrating a fluid barrier formed from the plug assembly of FIG. 5 according to an example implementation.

FIG. 7 is an illustration of physical interaction of an engagement surface of a seal member of a plug assembly with an engagement surface of a body member of the plug assembly according to an example implementation.

FIG. 8 is a flow diagram illustrating a technique to form a fluid barrier in a tubing string according to an example implementation.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth but implementations may be practiced without these specific details. Well-known circuits, structures and techniques have not been shown in detail to avoid obscuring an understanding of this description. “An implementation,” “example implementation,” “various implementations” and the like indicate implementation(s) so described may include particular features, structures, or characteristics, but not every implementation necessarily includes the particular features, structures, or characteristics. Some implementations may have some, all, or none of the features described for other implementations. “First”, “second”, “third” and the like describe a common object and indicate different instances of like objects are being referred to. Such adjectives do not imply objects so described must be in a given sequence, either temporally, spatially, in ranking, or in any other manner. “Coupled”, “connected”, and their derivatives are not synonyms. “Connected” may indicate elements are in direct physical or electrical contact with each other and “coupled” may indicate elements co-operate or interact with each other, but they may or may not be in direct physical or electrical contact. Also, while similar or same numbers may be used to designate same or similar parts in different figures, doing so does not mean all figures including similar or same numbers constitute a single or same implementation. Although terms of directional or orientation, such as “up,” “down,” “upper,” “lower,” “uphole,” “downhole,” and the like, may be used herein for purposes of simplifying the discussion of certain implementations, it is understood that these orientations and directions may not be used in accordance with further example implementations.
In accordance with example implementations, a plug assembly may be run into a tubing string (a casing string, for example) of a well for purposes of forming a fluid barrier at a target downhole location. For example, the plug assembly may be run downhole inside the tubing string on a conveyance mechanism (a coiled tubing string or a wireline, as examples), and when the plug assembly is at the target location, a setting tool may be actuated for purposes for causing the plug assembly to radially expand to engage the wall of the tubing string to anchor the plug assembly in place. Moreover, in the setting of the plug assembly, a fluid seal may be formed between the plug assembly and the tubing string wall. The plug assembly may have a through passageway that may be blocked to form a fluid obstruction, or barrier, by deploying an untethered object (an activation ball, for example) inside the tubing string passageway such that the untethered object travels down through the tubing string passageway to land in an internal seat of the plug assembly.
The fluid barrier may be used in connection with a well stimulation operation. For example, in accordance with some implementations, the fluid barrier may be used to divert fluid to the surrounding formation in a hydraulic fracturing operation.
In accordance with example implementations, the plug assembly includes a sealing member, or ring, which is radially expanded downhole inside the tubing string for purposes of securing, or anchoring, the plug assembly to the tubing string wall and forming a seal for the plug assembly between the sealing ring and the tubing string wall. In accordance with example implementations, the sealing ring has both an inner profile and an outer profile, which do not significantly change (other than having increased corresponding diameters) when the sealing ring is transitioned from its radially contracted state to its radially expanded state. The preservation of these profiles allows an inner engagement surface of the sealing member to be used to both anchor and seal against a body member of the plug assembly.
More specifically, in accordance with example implementations, the plug assembly has a tapered inner engagement surface that is constructed to physically engage an outer engagement surface of the body member for purposes of radially expanding the sealing ring. Moreover, the engagement of these surfaces locks, or anchors, the positions of the sealing ring and body member with respect to each other, forms a fluid seal between these elements and in general, secures the plug assembly in place in the tubing string.
In accordance with various example implementations that are described herein, the tapered engagement surfaces of the sealing ring and body member of the plug assembly may be smooth surfaces; surfaces having ratchet teeth; surfaces having smooth portions and portions having ratchet teeth; and so forth.
As a more specific example, FIG. 1A depicts a well 100 in accordance with some implementations. The well 100 includes a laterally extending wellbore 120, which traverses one or more hydrocarbon-bearing formations. For the specific implementation depicted in FIG. 1A, the wellbore 120 is lined and supported by a tubing string 130. The tubing string 130 may be cemented to the wellbore 120 (i.e., the tubing string 130 may be a casing); or the tubing string 130 may be anchored or secured, to the surrounding formation(s) by one or multiple packers (i.e., the tubing string 130 may be installed in an “open hole wellbore”). For the specific example of FIG. 1A, the tubing string 130 is a casing that has been run into the wellbore 120, and a cementing operation has been performed to place cement 140 in the annular region between the exterior of the casing and the wall of the wellbore 120.
It is noted that although FIG. 1A depicts a laterally extending wellbore, the technique systems that are disclosed herein may likewise apply to vertically extending wellbores. Moreover, in accordance with example implementations, the well 100 may contain multiple wellbores, which contain tubing strings that are similar to the tubing string 130 of FIG. 1A. The well 100 may be a subsea well or may be a terrestrial well depending on the particular implementation. Additionally, the well 100 may be an injection well or may be a production well, depending on the particular implementation. Thus, many implementations are contemplated, which are within the scope of the appended claims.
As depicted in FIG. 1A, the tubing string 130 extends from a heel end 141 of a lateral segment 121 of the wellbore 120 to a toe end 143 of the segment 121. The lateral segment 121 may be associated with multiple stages, which may be isolated and stimulated separately.
For the specific example depicted in FIG. 1A, a plug assembly 150 has been set and thus, anchored, or secured, to the tubing string 130 at a target downhole location. For this example, the plug assembly 150 is located in a zone, or stage, of the well 100 to be fractured. In this manner, as shown in FIG. 1A, hydraulic communication with the surrounding formation may have been enhanced through, for example, a perforating operation that formed perforations 134 that extend through the surrounding tubing string wall and into the surrounding formation. Hydraulic communication may be enhanced using other techniques (abrasive jetting operations, for example). The plug assembly 150 may be set at the lower end of the zone to be fractured, as illustrated in FIG. 1A.
Referring to FIG. 1B, an untethered object (an activation sphere, or ball 170, as an example), may be deployed inside the central passageway of the tubing string 130 to land in a seat 154 of the plug assembly 150 for purposes of sealing a through passageway of the set plug assembly to form a fluid barrier inside the tubing string 130. In this regard, after the fluid barrier is formed, a well stimulation operation may be performed that relies on the fluid barrier. For example, a hydraulic fracturing operation may be performed in which a fracturing fluid is pumped into the tubing string 130, and the fluid barrier diverts the fluid into the surrounding formation.
In the context of this application, an “untethered object” refers to an object that is communicated downhole through the passage of a tubing string along at least part of its path without the use of a conveyance line (a slickline, a wireline, a coiled tubing string, and so forth). As examples, the untethered object may be a ball (or sphere), a dart or a bar. Regardless of its particular form, the untethered object travels through the passageway of the tubing string to land in the object catching seat of the plug assembly to form a corresponding fluid obstruction, or barrier.
Referring to FIG. 2, in accordance with example implementations, the plug assembly 150 includes a sealing member, or ring 220, which has two states: a radially retracted state for purposes of running the plug assembly 150 downhole inside a tubing string; and a radially expanded state for purposes of anchoring and sealing the plug assembly 150 to the tubing string wall. As depicted in FIG. 2, in accordance with example implementations, the sealing ring 220 may be a slotted metal sealing ring similar to a slotted metal sealing ring that is described in U.S. Patent Publication No. US 2016/0333661, entitled, “METAL SEALING DEVICE,” which has a publication date of Nov. 17, 2016, and is hereby incorporated by reference in its entirety. Sealing rings other than a slotted metal sealing ring may be used, in accordance with further example implementations.
The plug assembly 150 further includes a tubular body member 230. In general, the body member 230 has an outer, tapered surface (not depicted in FIG. 2), which engages an inner tapered surface (not depicted in FIG. 2) of the sealing ring 220 for purposes of radially expanding the sealing ring 220. Moreover, the contacting tapered services both secure, or anchor, the sealing ring 220 to the body 230 to lock, or secure, the sealing ring 220 in its radially expanded state and form a fluid seal between the sealing ring 220 and the body member 230.
As depicted in FIG. 2, in accordance with some implementations, the plug assembly 150 may be run downhole inside the tubing string 130 on a setting tool, which includes a setting sleeve 210 and an inner mandrel. More specifically, when the plug assembly 150 is at the target downhole location in which a fluid barrier is to be formed, an actuator (not shown in FIG. 2) produces an axial force along a longitudinal axis 201 to shear, shear screws 214 (which confine movement of the setting sleeve 210 when the plug assembly 150 is being run downhole) to allow the setting sleeve 210 to move axially along the longitudinal axis 201 and force the sealing ring 220 against the body member 230 to transition the sealing sleeve 220 into its regularly expanded state.
Among the other features of the plug assembly 150, in accordance with some implementations, the plug assembly 150 may include one or multiple slips 256 for purposes of enhancing the anchoring of the plug assembly 150 to the tubing wall, one or more corresponding slip bases 260 for purposes of forcing the slips 256 against the tubing wall in response to the axial movement of the setting sleeve 210, and a shear ring 254 for purposes of confining movement of the slip base(s) 260 during the running of the plug assembly 150 downhole. Moreover, as depicted in FIG. 2, in accordance with some implementations, the setting tool may include a lower body member 250 for purposes of providing a downhole stop against which the setting sleeve 220 acts to radially expand the sealing ring 220.
FIG. 3A is a cross-sectional view depicting the running of the plug assembly 150 downhole inside the tubing string 130. As shown, in this state, the plug assembly 150 has an overall radially contracted outer diameter to allow the plug assembly 150 to freely pass through the central passageway of the tubing string 130. When the plug assembly 150 is at the targeted downhole location inside the tubing string 130, the setting tool may then be remotely activated (via a wireline-communicated command, for example), which causes the setting tool to apply an axial force to the setting sleeve 210 to set the plug assembly, as depicted in FIG. 3B. In this manner, as shown in FIG. 3B, the setting sleeve 210 translates along the longitudinal axis 201 and contacts the uphole end of the sealing ring 220 to cause an inner tapered surface 312 of the sealing ring 220 to slide against a tapered outer surface 312 of the body member 230. Axial movement of the sealing ring 220, in turn, causes the sealing ring 220 to radially expand, due to the interaction of the tapered surfaces 310 and 312. Continued movement of the setting sleeve continues until, as depicted in FIG. 3B, an internal annular shoulder of the setting sleeve 210 contacts an uphole end of the inner mandrel of the setting tool to cause the mandrel to move the lower body member 250 to sheer pins 252 to release the setting tool from the plug assembly 150. Before the setting tool is released, however, the movement of the inner mandrel engages an inner surface of the body member 230 to cause the body member 230 to act against the slip bodies 260 to radially expand the slips 256.
FIG. 3C depicts the plug assembly 150 after removal of the setting tool and after deployment of an untethered object (such as an activation ball 330), which lands in an internal, annular seat of the body member 230 to form a fluid seal in the interior passageway of the plug assembly 150. Moreover, with this internal fluid seal and the corresponding fluid seals formed between the body member 230 and seal ring 220, and the seal between the sealing ring 220 and the tubing string wall, a fluid barrier is formed inside the tubing string 130.
Referring to FIG. 4, in accordance with example implementations, the inner surface 310 of the sealing ring 220 may include annularly extending ratchet teeth 412, which are constructed to engage corresponding ratchet teeth 414 of the outer engagement surface 312 of the body member 230. In this manner, the axial force produced by the setting tool slides the ratchet teeth 412 with respect to the ratchet teeth 414 so that when the axial force is removed (due to the release of the setting tool), the interaction between the ratchet teeth 412 and 414 secures, or anchors, the sealing ring 220 relative to the body member 230. Moreover, in accordance with some implementations, the engagement of the ratchet teeth 412 and 414 form a fluid seal between the sealing ring 220 and the body member 230.
In accordance with some implementations, the tapered surface of the sealing ring 220 may be at an angle between 5 to 10 degrees of the longitudinal axis 210, and in accordance with some implementations, the angle may be approximately 7 degrees. Moreover, in accordance with example implementations, the tapered surface of the body member 230 may have the same taper angle as the taper angle for the sealing ring 220.
In accordance with further example implementations, a plug assembly may have a sealing ring and body member, which have corresponding tapered surfaces without ratchet teeth. More specifically, referring to FIG. 5, in accordance with further example implementations, a plug assembly 500 may be deployed downhole and include a sealing ring 520, which has an interior, tapered and smooth surface (not depicted in FIG. 5) that is constructed to physically engage a corresponding exterior tapered and smooth surface (not depicted in FIG. 5) of a body member 530. In general, some elements of the plug assembly 500 are similar to the plug assembly 150 (FIG. 2), with different reference numerals, such as reference numerals 520 and 530, being used to denote different elements for the plug assembly 500.
Referring to FIG. 6A, similar to the plug assembly 150, the plug assembly 500 may be run downhole inside the tubing string 150 in a radially contracted state and radially expanded, as depicted in FIG. 6B, for purposes of setting the plug assembly 500. In this manner, as shown in FIG. 6B, the setting of the plug assembly 500 includes axially moving the setting sleeve 210 to cause the sealing ring 520 to regularly expand due to the physical interaction between a smooth tapered interior surface 610 of the sealing ring 520 with a relatively smooth exterior tapered surface 612 of the body member 530.
The tapered surfaces 610 and 612, in turn, perform dual functions, in accordance with example implementations: the tapered surfaces 610 and 612 form a fluid seal between the sealing ring 520 and body member 530; and the tapered surfaces 610 and 612 secure, or lock, the sealing ring 520 to the body member 530 due to a frictional contact force, which resists axial separation of these elements when the setting tool removes the axially applied force to leave the plug assembly 150 set inside the well, as depicted in FIG. 6C. Moreover, as depicted in FIG. 6C, an untethered object such as the activation ball 330, may be deployed inside the tubing string 130 to land in a seat of the body member 530 for purposes of forming a fluid barrier inside the tubing string 130.
In accordance with example implementations, the smooth, tapered surfaces 610 and 612 may each have a tapered angle with respect to the longitudinal axis 201 between 5 to 10 degrees (an angle of 7 degrees, for example).
Other variations are contemplated, which are within the scope of the appended claims. For example, as described above, the plug assembly 150 (FIG. 2) includes a tapered surface having a ratcheting profile, and the plug assembly 500 (FIG. 5) includes smooth tapered surfaces. However, in accordance with further example implementations, a plug assembly may have a combination of surfaces. More specifically, referring to FIG. 7, in accordance with some implementations, a plug assembly may have a sealing ring 720 and a body member 730, which have tapered surfaces that each have ratchet teeth and smooth portions. In this regard, as shown in FIG. 7, in accordance with some implementations, the ratchet teeth may be located on the smaller inner diameter portions, and the smooth portions may be located on the larger inner diameter portions of the sealing ring 720 and body member 730.
Due to this relationship, when the setting tool sleeve 210 forces the sealing ring 720 into the position depicted in FIG. 7, the ratchet teeth engage to lock the position of the sealing ring 720 with respect to the body member 730, and the smooth surfaces engage each other to form a fluid seal between the sealing ring 720 and body member 730. In accordance with some implementations, the inner surface of the sealing ring 720 and the outer surface of the body member 730 may have a tapered angle with respect to the longitudinal axis 201 between 5 to 10 degrees (a tapered angle of 7 degrees, for example).
Referring to FIG. 8, thus, in accordance with example implementations, a technique 800 to form a fluid barrier inside a tubing string in a well includes running (block 804) a plug assembly inside the tubing string; setting (block 808) the plug assembly in response to the application of an axial force; and using (block 812) a physical engagement of an inner engagement surface of a sealing ring of the plug assembly with an outer engagement surface of a body member of the plug assembly to form a seal between the sealing ring and the body member. The technique includes using (block 816) contact of the outer surface of the ring member with the tubing string to form a seal between the sealing ring and the tubing string and secure the sealing ring to the tubing string; and using (block 820) physical interaction between the inner engagement surface and the outer engagement surface to retain the ring member in the expanded state when the axial force is removed.
The plug assembly may be constructed from one or multiple degradable or dissolvable materials, in accordance with example implementations. In this manner, although, in accordance with some implementations, the plug assembly may be removed through a milling operation, in accordance with further example implementations, one or more components of the plug assembly may include degradable, or dissolvable, materials to create a temporary fluid barrier so that the segment, or zone, inside the tubing string above the plug assembly may be fractured over a relatively short window of time (a window of one to twelve hours, for example). After these component(s) dissolve, the fluid barrier is thus removed, thereby allowing the through passageway of the plug assembly to allow fluid flow from zones below the plug assembly and access through the region of the tubing string in which the fluid barrier was previously formed.
In accordance with some implementations, the untethered object (an activation ball, for example) may be formed from one or multiple degradable, or dissolvable materials.
Thus, in accordance with example implementations, the plug assembly and/or untethered object may include one or multiple materials, which degrade, or dissolve, after the fracturing operation has been completed. The degradable material(s) of the plug assembly may ideally degrade over a relatively longer time window (a time window of several days, weeks or months, as examples) as compared to the time window over which the untethered object degrades. Thus, a relatively fast dissolving untethered object, such as an activation ball, may be deployed to seal the through passageway of the plug assembly, thereby isolating the zone above the plug assembly from other zones below the plug assembly. After a well stimulation the relies on the fluid barrier is over, the untethered object dissolves at a relatively fast rate, and then the plug assembly may dissolve, at a relatively slower rate to completely remove the restriction created by the plug assembly.
In accordance with example implementations, the dissolvable or degradable material may be the same as one or more of the alloys that are discussed in the following patents and patent applications, which have an assignee in common with the present application: U.S. Pat. No. 7,775,279, entitled, “DEBRIS-FREE PERFORATING APPARATUS AND TECHNIQUE,” which issued on Aug. 17, 2010; U.S. Pat. No. 8,211,247, entitled, “DEGRADABLE COMPOSITIONS, APPARATUS COMPOSITIONS COMPRISING SAME, AND A METHOD OF USE,” which issued on Jul. 3, 2012; PCT Application Pub. No. WO 2016/085798, entitled, “SHAPING DEGRADABLE MATERIAL,” having a publication date of Jun. 2, 2016; PCT Application Pub. No. WO 2016/085804, entitled, “SEVERE PLASTIC DEFORMATION OF DEGRADABLE MATERIAL,” having a publication date of Jun. 2, 2016; PCT Application Pub. No. WO 2016/085806, entitled, “BLENDING OF WATER REACTIVE POWDERS,” having a publication date of Jun. 2, 2016; PCT Application Pub. No. WO 2015/184041, entitled, “DEGRADABLE POWDER BLEND,” having a publication date of Dec. 3, 2015; and PCT Application Pub. No. WO 2015/184043, entitled, “DEGRADABLE HEAT TREATABLE COMPONENTS,” having a publication date of Dec. 3, 2015.
While the present techniques have been described with respect to a number of embodiments, it will be appreciated that numerous modifications and variations may be applicable therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the scope of the present techniques.

Claims

What is claimed is:

1. A method comprising:

running a plug assembly inside a tubing string of a well; and

setting the plug assembly, wherein setting the plug assembly comprises:

axially, moving a seal member of the plug assembly with respect to a body member of the plug assembly to cause an outer engagement surface of the body member to physically engage an inner engagement surface of a ring member of the plug assembly to radially expand the ring member to transition the ring member to an expanded state and cause an outer surface of the ring member to contact an inner wall of the tubing string;

using the physical engagement of the inner engagement surface of the ring member with the outer engagement surface of the body member to form a seal between the ring member and the body member;

using contact of the outer surface of the ring member with the tubing string to form a seal between the ring member and the tubing string and secure the ring member to the tubing string; and

using a physical interaction between the inner engagement surface and the outer engagement surface to retain the ring member in the expanded state when the axial force is removed.

2. The method of claim 1, wherein using the physical engagement of the inner engagement surface of the ring member with the outer engagement surface of the body member to form the seal comprises forming the seal between tapered surfaces.

3. The method of claim 1, wherein using the inner engagement surface and the outer engagement surface to retain the ring member in the expanded state comprises using the physical interaction of tapered surfaces.

4. The method of claim 1, wherein using the physical interaction of the inner engagement surface and the outer engagement surface to retain the ring member in the expanded state comprises engaging ratchet teeth of the ring member and the body member.

5. A system usable with a well comprising:

a tubing string; and

an untethered object; and

a plug assembly, comprising:

a body member having a through passageway, the body member comprising an outer engagement surface and a seat adapted to catch the untethered object to form a fluid barrier in the tubing string; and

a ring member having a contracted state and an expanded state, the ring member comprising an inner engagement surface and an outer surface,

wherein:

the seal member is adapted to axially move with respect to the body member in response to the application of an axial force such that the outer engagement surface of the body member physically engages the inner engagement surface of the ring member to radially expand the ring member to transition the ring member to the expanded state and cause the outer surface of the ring member to contact an inner wall of the tubing string;

the physical engagement of the inner engagement surface of the ring member with the outer engagement surface of the body member forms a seal between the ring member and the body member;

the contact of the outer surface of the ring member with the tubing string forms a seal between the ring member and the tubing string and secures the ring member to the tubing string; and

the inner engagement surface and the outer engagement surface are adapted to physically interact to retain the ring member in the expanded state when the axial force is removed.

6. The system of claim 5, wherein the inner engagement surface of the ring member comprises a tapered surface, the ring circumscribes a longitudinal axis, and the tapered surface is inclined with respect to the axis by an angle between 5 and 10 degrees.

7. The system of claim 5, wherein the inner engagement surface of the ring member comprises a ratchet profile.

8. The system of claim 5, wherein:

the inner engagement surface of the ring member comprises a first tapered surface;

the outer engagement surface of the body member comprises a second tapered surface; and

the first and second tapered surfaces are adapted to form the seal between the ring member and the body member.

9. The system of claim 5, wherein:

the first and second tapered surfaces are adapted to produce a friction force to retain the ring member in the expanded state when the axial force is removed.

10. The system of claim 5, wherein:

the inner engagement surface of the ring member comprises a first tapered surface and first ratchet teeth;

the outer engagement surface of the body member comprises a second tapered surface and second ratchet teeth;

the first and second tapered surfaces are adapted to form the seal between the ring member and the body member; and

the first and second ratchet teeth are adapted to lock an axial position of the seal member relative to the body member to retain the ring member in the expanded state when the axial force is removed.

11. An apparatus comprising:

a body member having a through passageway, the body member comprising an outer engagement surface; and

wherein:

the seal member is adapted to axially move with respect to the body member in response to the application of an axial force such that the outer engagement surface of the body member physically engages the inner engagement surface of the ring member to radially expand the ring member to transition the ring member to the expanded state and cause the outer surface of the ring member to contact an inner wall of a tubing string;

12. The apparatus of claim 11, wherein the body member comprises a slotted metal ring.

13. The apparatus of claim 11, wherein the inner engagement surface of the ring member comprises a tapered surface.

14. The apparatus of claim 13, wherein the ring member circumscribes a longitudinal axis and the tapered surface is inclined with respect to the axis by an angle between 5 and 10 degrees.

15. The apparatus of claim 11, wherein the inner engagement surface of the ring member comprises a ratchet profile.

16. The apparatus of claim 11, wherein:

17. The apparatus of claim 11, wherein:

18. The apparatus of claim 11, wherein:

19. The apparatus of claim 18, wherein:

the first ratchet teeth of the inner engagement surface of the ring member is associated with a first range of inner diameters of the ring member;

the first tapered surface of the inner engagement surface of the ring member is associated with a second range of inner diameters of the ring member; and

the diameters of the first range of inner diameters are larger than the diameters of the second range of inner diameters.

20. The apparatus of claim 11, wherein the body member comprises a seat to circumscribe the through passageway, and the seat is adapted to catch an object to form a fluid barrier in the well.

21. The apparatus of claim 11, wherein the at least one of the seal members or the body member comprises a degradable material constructed to degrade in a time interval less than one month in a downhole environment of the well.